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Optimal Depth for Nasopharyngeal Temperature Probe Positioning
Abstract
Background:
The nasopharynx is considered 1 of the 4 generally reliable core temperature measurement sites. But curiously, there is no consensus on how far past the nares to insert the probe. Insertion depth is likely to influence the accuracy of nasopharyngeal temperature measurements because probes near the nares will be cooled by ambient air; similarly, probes inserted too far may approach the airway and be cooled by ventilation gases. We thus determined the range of nasopharyngeal probe insertion depths that best approximate reference core temperature measured in the distal esophagus.
Methods:
In 36 adults undergoing noncardiac surgery with endotracheal intubation, we inserted a nasopharyngeal thermometer 20 cm past the nares and an esophageal temperature probe 40 cm from the incisors. The nasopharyngeal probe was withdrawn sequentially 2 cm at a time at 5-minute intervals. Pairs of nasopharyngeal and reference distal esophageal temperatures were then compared and summarized by Bland and Altman methods.
Results:
All nasopharyngeal probe insertion depths between 10 and 20 cm past the nares provided temperatures similar to reference distal esophageal temperatures. At those depths, the bias was typically approximately -0.1°C, with SD of approximately ±0.15°C; the limits of agreement thus were easily within our a priori specified clinically acceptable range of -0.5°C and 0.5°C.
Conclusions:
Any nasopharyngeal probe insertion depth between 10 and 20 cm well represents core temperature in adults having noncardiac surgery.
... Moreover, surgical patients are exposed to cold environments [2]. Thus, patients undergoing general anesthesia develop hypothermia easily and have a risk of complications such as coagulation disorder, infection, heart complications, or delayed wound healing [1,[3][4][5][6]. Therefore, avoiding hypothermia is very important for preventing complications in patients undergoing surgery [2,3,7]. ...
... Thus, patients undergoing general anesthesia develop hypothermia easily and have a risk of complications such as coagulation disorder, infection, heart complications, or delayed wound healing [1,[3][4][5][6]. Therefore, avoiding hypothermia is very important for preventing complications in patients undergoing surgery [2,3,7]. Although it is essential to use various methods to prevent intraoperative hypothermia, accurate monitoring of core body temperature is also necessary [3,4]. ...
... Therefore, avoiding hypothermia is very important for preventing complications in patients undergoing surgery [2,3,7]. Although it is essential to use various methods to prevent intraoperative hypothermia, accurate monitoring of core body temperature is also necessary [3,4]. Core body temperatures can be monitored at multiple locations, such as the tympanic membrane (TM), pulmonary artery, esophagus, and nasopharynx [3][4][5]. ...
Monitoring core temperature is crucial for maintaining normothermia during general anesthesia. Insertion of a gastric decompression tube (GDT) may be required during laparoscopic surgery. Recently, a newly designed GDT with a thermistor for monitoring esophageal temperature has been introduced. The purpose of the present study was to evaluate the optimal insertion depth of a GDT with a thermistor. Forty-eight patients undergoing elective laparoscopic surgery in the Trendelenburg position were included in the study. The GDT was inserted to a depth of nose–earlobe–xiphoid distance (NEX) + 12 cm and withdrawn sequentially, 2 cm at a time, at 5-min intervals. Temperatures of the GDT thermistor were compared with the core temperature of the tympanic membrane (TM) using Bland and Altman analysis. The correlation between optimal insertion depth of the GDT and anatomical distance (cricoid cartilage to the carina, CCD; carina to the left hemidiaphragm, CLHD) was evaluated, and a mathematical model to predict the optimal insertion depth of the GDT with a thermistor was calculated. Temperatures of TM and GDT thermistor at NEX + 4 cm showed good agreement and strong correlation, but better agreement and stronger correlation were seen at the actual location with the most minor temperature differences. The optimal insertion depth of the GDT was estimated as −15.524 + 0.414 × CCD − 0.145 × CLHD and showed a strong correlation with the actual GDT insertion depth (correlation coefficient 0.797, adjusted R2 = 0.636). The mathematical formula using CCD and CLHD would be helpful in determining the optimal insertion depth of a GDT with a thermistor.
... Nasopharyngeal probes need to be inserted between 10 and 20 cm past the nares to accurately estimate core temperature in adults-which is further than generally appreciated ( fig. 2). 29 Tympanic membrane probes are more difficult to insert than generally appreciated because the aural canal is several centimeters long and is not straight. The difficulty is that patients and clinicians inserting thermistors or thermocouples often mistake the bend in the canal for the tympanic membrane and thus do not insert the probes far enough to reach the membrane itself. ...
... Nasopharyngeal temperatures were accurate at insertion depths between 10 and 20 cm, defined by being within ±0.5°C of esophageal temperature. reprinted with permission from Wang et al.29 ...
The esophagus and nasopharynx are usually the best temperature monitoring sites during general anesthesia. Alternatives suitable for neuraxial anesthesia and postoperative care include oral and axillary temperatures, along with zero-heat flux forehead temperature.
... All intravenous fluids (including transfused fluid and blood) were warmed to 42°C via a fluid warmer (Smiths Medical ASD Inc., Rockland, MA) in both groups. Nasopharyngeal temperature was monitored continuously during the operation with the probe inserted at least 10 cm (16). ...
Background
Elderly patients having esophagectomies often become hypothermic which may promote complications. We tested the hypothesis that aggressive warming to a core temperature of 37°C reduces postoperative pulmonary complications (PPCs) in elderly patients having esophageal cancer resections.
Methods
This study was a pre-defined sub-study of a multi-center, parallel group, superiority trial (PROTECT). Patients aged >65 years and having elective radical resection of esophageal cancer in a single center were randomly allocated into either aggressive warming group (target intraoperative core temperatures of 37°C) or routine thermal management group (target intraoperative core temperatures of 35.5°C). The primary endpoint was the incidence of PPCs. Secondary endpoints included duration of chest tube drainage and other postoperative complications.
Results
A total of 300 patients were included in the primary analysis. PPCs occurred in 27 (18%) of 150 patients in the aggressive warming group and 31 (21%) of 150 patients in the routine thermal management group. The relative risk (RR) of aggressive versus routine thermal management was 0.9 (95% CI: 0.5, 1.4; p = 0.56). The duration of chest drainage in patients assigned to aggressive warming was shorter than that assigned to routine thermal management: 4 (3, 5) days vs. 5 (4, 7) days; hazard ratio (HR) 1.4 [95% CI: 1.1, 1.7]; p = 0.001. Fewer aggressively warmed patients needed chest drainage for more than 5 days: 30/150 (20%) vs. 51/150 (34%); RR:0.6 (95% CI: 0.4, 0.9; p = 0.03). The incidence of other postoperative complications were similar between the two groups.
Conclusion
Aggressive warming does not reduce the incidence of PPCs in elderly patients receiving esophagectomy. The duration of chest drainage was reduced by aggressive warming. But as a secondary analysis of a planned sub-group study, these results should be considered exploratory.
Clinical trial registration
https://www.chictr.org.cn/showproj.aspx?proj=37099 , ChiCTR1900022257.
... Intraoperative hypothermia was associated with a longer postoperative extubation time, prolonged PACU, ICU, and hospital stay, and a higher rate of postoperative bleeding and transfusion, as shown clearly in our study. Intraoperative core temperature is commonly monitored with an esophageal or nasopharyngeal temperature probe by inserting the probe into the lower third of the esophagus or nasopharynx cavity (33,34). Other methods of core temperature measurement were tympanic membrane temperature or rectal temperature measurement (16,35). ...
Objective:
The incidence of intraoperative hypothermia remains high in pediatric patients during anesthesia and surgery even though core body temperature monitoring and warming systems have been greatly improved in recent years. We analyzed the risk factors and outcomes of intraoperative hypothermia in neonates and infants undergoing general anesthesia and surgery.
Methods:
The data on the incidence of intraoperative hypothermia, other clinical characteristics, and outcomes from electronic records of 1,091 patients (501 neonates and 590 infants between 28 days and 1 year old), who received general anesthesia and surgery, were harvested and analyzed. Intraoperative hypothermia was defined as a core temperature below 36°C during surgery.
Results:
The incidence of intraoperative hypothermia in neonates was 82.83%, which was extremely higher than in infants (38.31%, p < 0.001)-the same as the lowest body temperature (35.05 ± 0.69°C vs. 35.40 ± 0.68°C, p < 0.001) and the hypothermia duration (86.6 ± 44.5 min vs. 75.0 ± 52.4 min, p < 0.001). Intraoperative hypothermia was associated with prolonged PACU, ICU, hospital stay, postoperative bleeding, and transfusion in either age group. Intraoperative hypothermia in infants was also related to prolonged postoperative extubation time and surgical site infection. After univariate and multivariate analyses, the age (OR = 0.902, p < 0.001), weight (OR = 0.480, p = 0.013), prematurity (OR = 2.793, p = 0.036), surgery time of more than 60 min (OR = 3.743, p < 0.001), prewarming (OR = 0.081, p < 0.001), received >20 mL/kg fluid (OR = 2.938, p = 0.004), and emergency surgery (OR = 2.142, p = 0.019) were associated with hypothermia in neonates. Similar to neonates, age (OR = 0.991, p < 0.001), weight (OR = 0.783, p = 0.019), surgery time >60 min (OR = 2.140, p = 0.017), pre-warming (OR = 0.017, p < 0.001), and receive >20 mL/kg fluid (OR = 3.074, p = 0.001) were relevant factors to intraoperative hypothermia in infants along with the ASA grade (OR = 4.135, p < 0.001).
Conclusion:
The incidence of intraoperative hypothermia was still high, especially in neonates, with a few detrimental complications. Neonates and infants each have their different risk factors associated with intraoperative hypothermia, but younger age, lower weight, longer surgery time, received more fluid, and no prewarming management were the common risk factors.
... postoperative complications [2][3][4]. Body temperature is monitored at various locations, such as the esophagus and nasopharynx [5]. In addition, the rectal and bladder temperatures reasonably estimate the core temperature. ...
Background
Body temperature is a vital sign, and temperature monitoring during liver transplantation is important. Tracheal temperature can be measured via an endotracheal tube with a temperature sensor on the cuff of the tube. This study aimed to investigate the accuracy and trending ability of tracheal temperature measurement compared to those of the core temperature measured at the esophagus and pulmonary artery (PA) in living donor liver transplant recipients.
Methods
Twenty-two patients who underwent living donor liver transplantation (LDLT) were enrolled. Patients were intubated using an endotracheal tube with a temperature sensor placed on the inner surface of the tube cuff. Tracheal, esophageal, and PA temperatures were recorded at five time points corresponding to the different phases of liver transplantation. The tracheal and esophageal, tracheal and PA, and esophageal and PA temperatures were compared using Bland–Altman analysis, four-quadrant plot/concordance analysis, and polar plot analysis.
Results
Bland–Altman analysis showed an overall mean bias (95% limits of agreement) between tracheal and esophageal temperatures of -0.10 °C (-0.37 °C to 0.18 °C), with a percentage error of 0.27%; between tracheal and PA temperatures, -0.05 °C (-0.91 °C to 0.20 °C), with a percentage error of -0.15%; and between esophageal and PA temperatures, 0.04 °C (-0.27 °C to 0.35 °C), with a percentage error of 0.12%. The concordance rates between tracheal and esophageal temperatures, tracheal and PA temperatures, and esophageal and PA temperatures were 96.2%, 96.2%, and 94.94%, respectively. The polar plot analysis showed a mean angular bias (radial limits of agreement) of 4° (26°), -3° (13°), and 2° (21°).
Conclusions
Monitoring core temperature at the inner surface of the endotracheal tube cuff is accurate in all phases of LDLT with good trending ability; thus, it can be an excellent alternative for monitoring during LDLTs.
... The highest temperature in the same ear was recorded after at least three consecutive measurements. In contrast, immediately after induction of general anaesthesia to extubation, the patient's core temperature was measured in the nasopharynx by inserting a 12 Fr thermistor probe (L000412, Gonimed Co., South Korea) at a depth of 10-20 cm from the nares [11]. The patient's temperature was recorded on arrival in the pre-anaesthesia holding area (baseline), on arrival in the operating room, every 15 min immediately after induction of anaesthesia to the end of surgery, and every 15 min from PACU admission for 1 h by the same anaesthesiology resident. ...
Background: Short-term prewarming effectively reduces intraoperative hypothermia in adult patients. However, few data exist regarding its efficacy in elderly patients. Elderly people have a reduced ability to regulate their body temperature, which affects the efficacy of prewarming. This study aimed to compare the clinical efficacy of short-term pre-warming in elderly patients with that in adult patients.
Methods: We enrolled 25 adult (20-50 years) and 25 elderly (> 65 years) patients scheduled for ureteroscopic stone surgery under general anaesthesia. All patients received preanaesthetic forced-air warming for 20 min. The core temperature was measured using an infrared tympanic thermometer during awakening and nasopharyngeal thermistors during anaesthesia. Incidence and severity of intraoperative hypothermia (< 36°C) was compared. Postoperative shivering and number of patients requiring active warming in the post-anaesthesia care unit were also assessed.
Results: Intraoperative hypothermia was more frequent in elderly than in adult patients (58.3% vs. 12.0%; relative risk 2.6; 95% confidence interval 1.5 to 4.6; effect size h = 1.010; p = 0.001). The severity of intraoperative hypothermia showed a significant intergroup difference (p = 0.002). Postoperative shivering was more frequent in elderly than in adult patients (33.3% vs. 8.0%, p = 0.037). A greater number of elderly patients in the post-anaesthesia care unit required active warming (33.3% vs. 8.0%, p = 0.037).
Conclusions: The effects of short-term prewarming on the prevention of hypothermia and maintenance of perioperative normothermia are not the same in the elderly and adult patients.
... Unfortunately, intraoperative temperature readings usually contain a number of artifacts. Mechanistically, these artifacts may be a result of temperature probes that are suboptimally placed, temperature probes that accidentally fall out of a patient's oral cavity or nasal orifice, low readings resulting from the probe warming up from room temperature to a patient's core temperature, or readings associated with the repositioning of temperature probes [8,9]. Although some studies have proposed temperature artifact-reducing algorithms, their validation remains lacking, and the most widely cited algorithm relies on equal time intervals across measurements-a condition that is frequently violated within many large data sets [10]. ...
Background
The automated acquisition of intraoperative patient temperature data via temperature probes leads to the possibility of producing a number of artifacts related to probe positioning that may impact these probes’ utility for observational research.
Objective
We sought to compare the performance of two de novo algorithms for filtering such artifacts.
Methods
In this observational retrospective study, the intraoperative temperature data of adults who received general anesthesia for noncardiac surgery were extracted from the Multicenter Perioperative Outcomes Group registry. Two algorithms were developed and then compared to the reference standard—anesthesiologists’ manual artifact detection process. Algorithm 1 (a slope-based algorithm) was based on the linear curve fit of 3 adjacent temperature data points. Algorithm 2 (an interval-based algorithm) assessed for time gaps between contiguous temperature recordings. Sensitivity and specificity values for artifact detection were calculated for each algorithm, as were mean temperatures and areas under the curve for hypothermia (temperatures below 36 C) for each patient, after artifact removal via each methodology.
Results
A total of 27,683 temperature readings from 200 anesthetic records were analyzed. The overall agreement among the anesthesiologists was 92.1%. Both algorithms had high specificity but moderate sensitivity (specificity: 99.02% for algorithm 1 vs 99.54% for algorithm 2; sensitivity: 49.13% for algorithm 1 vs 37.72% for algorithm 2; F-score: 0.65 for algorithm 1 vs 0.55 for algorithm 2). The areas under the curve for time × hypothermic temperature and the mean temperatures recorded for each case after artifact removal were similar between the algorithms and the anesthesiologists.
Conclusions
The tested algorithms provide an automated way to filter intraoperative temperature artifacts that closely approximates manual sorting by anesthesiologists. Our study provides evidence demonstrating the efficacy of highly generalizable artifact reduction algorithms that can be readily used by observational studies that rely on automated intraoperative data acquisition.
... A reasonable compromise for a universally valid positioning for both intubated and spontaneously breathing children could be to place the probe tip within the corridor of the NCP and the end of soft palate. This would prevent both inaccurate measurement because of a too proximal placement in the nasal cavity 11,19 and irritation of glottic structures because of a too distal position in the hypopharynx. ...
Background:
Core temperature monitoring is indispensable to prevent children from perioperative thermal perturbations. Although nasopharyngeal measurements are commonly used in anesthesia and considered to reflect core temperature accurately, standardized target depths for probe insertion are unknown in children.
Aims:
Our primary goal was to determine a target depth of nasopharyngeal temperature probe insertion in children by measuring distances on magnetic resonance imaging (MRI). Secondary aims were to correlate these measurements with biometric variables and facial landmark-distances to derive formulas estimating target depth.
Methods:
We conducted a prospective observational study in children ≤12 years undergoing cranial MRI with anesthesia. We documented patient characteristics and measured the landmark-distances nostril-mandible, nostril-tragus, and philtrum-tragus on patient's faces. On MRI, the target point for the probe tip was considered to be the site of the nasopharyngeal mucosa with the closest proximity to the internal carotid artery. After its determination in the transverse axis and triangulation to the sagittal axis, we measured the distance to the nostril. This distance, defined as target insertion depth, was correlated with the patient characteristics and used for univariate and multiple linear regression analysis.
Results:
One hundred twenty children with a mean age of 4.5 years were included. The target insertion depth ranged from 61.8 mm in infants to 89.8 mm in 12-year-old children. Height correlated best (ρ = 0.685, 95%-CI: [0.57-0.77]). The best-fit estimation in millimeters, "40.8 + height [cm] × 0.32,″ would lead to a placement in the target position in 67% of cases. A simplified approach by categories of 50-80, 80-110, 110-130, and >130 cm height with target insertion depths of 60, 70, 80, and 85 mm, respectively, achieved similar probabilities.
Conclusions:
Height-based formulas could be a valuable proxy for the insertion depth of nasopharyngeal temperature probes. Further clinical trials are necessary to investigate their measurement accuracy.
... Second, it could not be confirmed whether the nasopharyngeal upper or middle mucosa was the optimal probe location. Nonoptimally positioned nasopharyngeal temperature probes to achieve significantly different core temperature values from those obtained with optimally positioned probes [21]. Finally, it could not be determined whether all patients in the PACU whose core body temperature was recorded using an infrared TM thermometer had not undergone otoscopy to rule out ear fragments. ...
Previous studies reported the impact of intrinsic and extrinsic factors on intraoperative hypothermia. However, no clinical study to date has considered the effects of both the phase of the menstrual cycle (an intrinsic factor) and the fresh gas flow rate (FGF) during anesthesia (an extrinsic factor) on the core body temperature and intraoperative hypothermia. This study is aimed at investigatig the effect of the menstrual cycle phase on intraoperative hypothermia when considering the FGF in patients who underwent laparoscopic gynecologic surgery. This study included 667 women aged 19-65 years with menstruation cycles and menopause. The patients were divided into the follicular, luteal, and menopause groups. The primary outcome was the correlations of hormonal status with intraoperative hypothermia. Secondary outcomes included the incidence of intraoperative hypothermia, time to onset of hypothermia, incidence of shivering after anesthesia, and frequency of antishivering drug use in the three groups and risk factors for hypothermia. Overall, the hypothermia incidence was the lowest and the time to onset of hypothermia was the longest in the luteal phase group. At a high FGF, the incidence of hypothermia in the luteal phase group was lower than that in the other two groups ( P < 0.05 ). At a low FGF, the time to onset of hypothermia in the luteal phase group was longer than that in the other two groups ( P < 0.05 ). The female hormonal status had weak positive correlations with hypothermia at low and high FGF rates. A high FGF in univariate and multivariate analyses, follicular phase and menopause in multivariate analysis, and estradiol and progesterone levels in univariate analysis were risk factors for hypothermia. When considering the FGF, the luteal phase is associated with better outcomes concerning intraoperative hypothermia.
... After anesthesia induction, a nasopharyngeal temperature probe (Philips) was lubricated and inserted into the nasal cavity to continuously monitor the core temperature. According to relevant studies 16,17 and our experience in clinical practice, the depth of the nasopharyngeal temperature probe was 10-15 cm. ...
Background
Whether intraoperative temperature management can help patients recover quickly in the postanesthesia care unit (PACU) still remains to be investigated. This study aimed to investigate the effect of intraoperative temperature management on the quality of postoperative recovery of patients who underwent pulmonary lobectomy in the PACU.
Methods
Totally, 98 patients aged 45–60 years with a body mass index of 20–25 kg/m² who underwent elective thoracoscopic lobectomy were enrolled. Patients were categorized into two groups using a random number table: the conventional group received routine intervention to maintain normothermia (Group C, n = 49) and the aggressive group received integrated interventions (Group A, n = 49). In Group C, normothermic fluid was infused intravenously, the heating blanket was turned on when the intraoperative temperature was <35.0 °C, and the warming was stopped when the temperature reached 36.5 °C. In Group A, the fluid heated to 37 °C was infused intravenously, and the heating blanket was used intraoperatively. When the body temperature was >37 °C, the heating blanket was turned off, and when the body temperature was <36.5 °C, the heating blanket was turned on to continue heating.
Results
Steward awakening scores at 1 min and 5 min after extubation and PaO2 levels at 15 min after extubation were higher in Group A than in Group C (P < 0.05); incidence of chills, nausea, and vomiting in the PACU was lower in Group A than in Group C (P < 0.05); and length of stay in the PACU was shorter in Group A than in Group C (P < 0.05).
Conclusion
Aggressive intraoperative temperature management of patients undergoing thoracoscopic lobectomy can improve the quality of postoperative recovery in the PACU through a safe and smooth transition compared with routine insulation measures.
... The nasopharyngeal probe should be inserted through the middle or inferior meatus in the nasal cavity. Any nasopharyngeal temperature probe insertion depth between 10 and 20 cm corresponds well to the T c in adults [21][22][23]. Similar to tympanic membrane temperature measurement, this technique may give false low values in patients with unstable circulation and can lead to errors in the temperature measurements as a result of imprecise probe location or obstructed nasal canals. ...
Core temperature reflects the temperature of the internal organs. Proper temperature measurement is essential to diagnose and treat temperature impairment in patients. However, an accurate approach has yet to be established. Depending on the method used, the obtained values may vary and differ from the actual core temperature. There is an ongoing debate regarding the most appropriate anatomical site for core temperature measurement. Although the measurement of body core temperature through a pulmonary artery catheter is commonly cited as the gold standard, the esophageal temperature measurement appears to be a reasonable and functional alternative in the clinical setting. This article provides an integrative review of invasive and noninvasive body temperature measurements and their relations to core temperature.
... However, these devices each are subject to several limitations. They cannot be used in awake patients, the insertion depth is likely to influence the accuracy of the temperature measurements and placement of the transesophageal echocardiography probe may interfere with nasopharyngeal or esophageal temperature monitoring [13]. Other options include bladder, rectal, sublingual, axilla and tympanic membrane thermometers. ...
We evaluated the disposable non-invasive SpotOn™ thermometer relying on the zero-heat-flux technology. We tested the hypothesis that this technology may accurately estimate the core temperature. The primary objective was to compare cutaneous temperature measurements from this device with blood temperatures measured with the pulmonary artery catheter. Secondary objective was to compare measurements from the zero-heat-flux thermometer indirectly with other routinely used thermometers (nasopharyngeal, bladder, rectal). We included 40 patients electively scheduled for either off-pump coronary artery bypass surgery or pulmonary thromboendarterectomy. Temperatures were measured using zero-heat-flux (SpotOn™), pulmonary artery catheter, nasopharyngeal, rectal, and bladder thermometers. Agreement was assessed using the Bland and Altman random effects method for repeated measures data, and Lin’s concordance correlation coefficient. Accuracy was estimated (defined as <0.5° difference with the gold standard), with a 95% confidence interval considering the multiple pairs of measurements per patient. 17 850 sets of temperature measurements were analyzed from 40 patients. The mean overall difference between zero-heat-flux and pulmonary artery catheter thermometer was -0.06 °C (95% limits of agreement of ± 0.89 °C). In addition, 14 968 sets of temperature measurements were analyzed from 34 patients with all thermometers in situ. Results from the zero-heat-flux thermometer showed better agreement with the pulmonary artery catheter than the other secondary core thermometers assessed. In conclusion, the SpotOn™ thermometer reliably assessed core temperature during cardiac surgery. It could be considered an alternative for other secondary thermometers in the assessment of core temperature during general anesthesia.
... The temperature of adjacent devices, like endotracheal tubes, airway gases, gastric tubes, may influence measurements obtained with nasopharyngeal probes. A depth of 10-20 cm past the nares is the correct position for these devices in order to provide results comparable to those obtained with oesophageal probes [81,82]. ...
Unintentional hypothermia (core temperature < 36 °C) is a common side effect in patients undergoing surgery. Several patient-centred and external factors, e.g., drugs, comorbidities, trauma, environmental temperature, type of anaesthesia, as well as extent and duration of surgery, influence core temperature. Perioperative hypothermia has negative effects on coagulation, blood loss and transfusion requirements, metabolization of drugs, surgical site infections, and discharge from the post-anaesthesia care unit. Therefore, active temperature management is required in the pre-, intra-, and postoperative period to diminish the risks of perioperative hypothermia. Temperature measurement should be done with accurate and continuous probes. Perioperative temperature management includes a bundle of warming tools adapted to individual needs and local circumstances. Warming blankets and mattresses as well as the administration of properly warmed infusions via dedicated devices are important for this purpose. Temperature management should follow checklists and be individualized to the patient’s requirements and the local possibilities.
... Although the best single estimate of core temperature is considered the pulmonary artery [58], its approach is completely invasive, and hence not suitable for children undergoing non-cardiac surgery. A more commonly used alternative is an oesophageal temperature probe [61,62]. Inserting the probe deep enough to reach the lower third of the oesophagus is important to accurately estimate core temperature [63]. ...
Background:
First described by paediatric anaesthesiologists, perioperative hypothermia is one of the earliest reported side effects of general anaesthesia. Deviations from normothermia are associated with numerous complications and adverse outcomes, with infants and small children at the highest risk. Nowadays, maintenance of normothermia is an important quality metric in paediatric anaesthesia.
Methods:
This review is based on our collection of publications regarding perioperative hypothermia and was supplemented with pertinent publications from a MEDLINE literature search.
Results:
We provide an overview on perioperative hypothermia in the paediatric patient, including definition, history, incidence, development, monitoring, risk factors, and adverse events, and provide management recommendations for its prevention. We also summarize the side effects and complications of perioperative temperature management.
Conclusions:
Perioperative hypothermia is still common in paediatric patients and may be attributed to their vulnerable physiology, but also may result from insufficient perioperative warming. An effective perioperative warming strategy incorporates the maintenance of normothermia during transportation, active warming before induction of anaesthesia, active warming during anaesthesia and surgery, and accurate measurement of core temperature. Perioperative temperature management must also prevent hyperthermia in children.
... To calibrate before the experimentation, two single-use disposable temperature probes to be used in each subject can be simultaneously exposed to ambient room environment to record the differences in their baseline recordings if any so that these differences can be accounted for while recording the temperatures during the experimentation. After calibration, the first temperature probe for continuously recording nasopharyngeal temperature can be placed across one nostril at appropriate depth in upper nasopharyngeal cavity at fossa of Rosenmuller under fiberscope guidance from the contralateral nostril [5][6][7][8][9]. Thereafter after removing the fiberscope, the second temperature probe can be affixed freely hanging in front of that contralateral nostril to assess the ambient temperature just outside the nostril. ...
... Previous work has shown a close agreement between the nasal technique used in this study and distal esophageal temperature measurements [8]. Within 10 min of T 0 , the blunt tipped nasal temperature probe was inserted 8 cm into one naris [8][9][10]. This provided a minimum of 5 min for thermal equilibration of the temperature probe before the first measurement (T 15 ), 15 min after T 0 . ...
Background:
While much effort has been devoted to correcting intraoperative hypothermia, less attention has been directed to preventing redistribution hypothermia. In this study, we compared three different anesthetic induction techniques to standard IV propofol inductions (control) in their effect on reducing redistribution hypothermia.
Methods:
Elective, afebrile patients, age 18 to 55 years, were randomly assigned to one of four groups (n = 50 each). Group "INH/100" was induced with 8% sevoflurane in 100% oxygen, Group "INH/50" with 8% sevoflurane in 50% oxygen and 50% nitrous oxide, Group "PROP" with 2.2 mg/kg propofol, and Group "Phnl/PROP" with 2.2 mg/kg propofol immediately preceded by 160 mcg phenylephrine. Patients were maintained with sevoflurane in 50% nitrous oxide and 50% oxygen in addition to opioid narcotic. Forced air warming was used. Core temperatures were recorded every 15 min after induction for 1 h.
Results:
Compared to control group PROP, the mean temperatures in groups INH/100, INH/50, and Phnl/PROP were higher 15, 30, 45 and 60 min after induction (p < 0.001 for all comparisons), averaging between 0.39 °C and 0.54 °C higher. In group PROP, 60% of patients had at least one temperature below 36.0 °C in the first hour whereas only 16% did in each of groups INH/100, INH/50, and Phnl/PROP (p < 0.0001 in each group compared to PROP).
Conclusions:
In this effectiveness trial, inhalation inductions with sevoflurane or with prophylactic phenylephrine bolus prior to propofol induction reduced the magnitude of redistribution hypothermia by an average of 0.4 to 0.5 °C in patients aged 18 to 55 years.
Trial registration:
Retrospectively registered on clinical-trials.gov as NCT02331108 , November 20, 2014.
... Measuring temperature at this site is common clinical practice. The nasopharyngeal probe is relatively robust to variations in positioning, at any depth 10-20 cm past the nares [28], and there is good evidence that it provides an accurate and precise measure of body temperature [1,29,30]. On the other hand, temperature measurements in the nasal cavity may not reflect core temperature [31]; Lee et al. reported that fewer than half of nasopharyngeal temperature probes placed blindly were optimally positioned [32] and van Zundert et al. advocate for direct laryngoscopy during insertion, which ensures that the probe is in the oropharynx or the esophagus [33]. ...
General anesthesia impairs thermoregulation and contributes to perioperative hypothermia; core body temperature monitoring is recommended during surgical procedures lasting > 30 min. Zero-heat-flux core body temperature measurement systems enable continuous non-invasive perioperative monitoring. During a previous trial evaluating the benefits of preoperative forced-air warming, intraoperative temperatures were measured with both a zero-heat-flux sensor and a standard naso-/oropharyngeal temperature probe. The aim of this secondary analysis is to evaluate their agreement. ASA I–III patients, scheduled for elective, non-cardiac surgery under general anesthesia, were enrolled. A zero-heat-flux sensor was placed on the participant’s forehead preoperatively. Following induction of anesthesia, a “clinical” temperature probe was placed in the nasopharynx or oropharynx at the anesthesiologist’s discretion. Temperature measurements from both sensors were recorded every 10 s. Agreement was analyzed using the Bland–Altman method, corrected for repeated measurements, and Lin’s concordance correlation coefficient, and compared with existing studies. Data were collected in 194 patients with a median (interquartile range) age of 60 (49–69) years, during surgical procedures lasting 120 (89–185) min. The zero-heat-flux measurements had a mean bias of − 0.05 °C (zero-heat-flux lower) with 95% limits of agreement within − 0.68 to + 0.58 °C. Lin’s concordance correlation coefficient was 0.823. The zero-heat-flux sensor demonstrated moderate agreement with the naso-/oropharyngeal temperature probe, which was not fully within the generally accepted ± 0.5 °C limit. This is consistent with previous studies. The zero-heat-flux system offers clinical utility for non-invasive and continuous core body temperature monitoring throughout the perioperative period using a single sensor.
... In addition, knowing the distance from the nares to epiglottis is also useful for blind nasotracheal intubation, [3] fiber-optic nasal intubation with a preinserted endotracheal tube, [4] and temperature sensor placement. [5] In this study, we measured the distance from the nares to epiglottis and examined the relationships of the optimal insertion length (defined as the nares-to-epiglottis distance minus 1 cm) with patient characteristics and various external facial measurements. After data analysis, we aimed to introduce an easy and convenient method to correctly predict the optimal insertion depth of a nasopharyngeal airway, and thereby facilitating the selection of a nasopharyngeal airway of an appropriate size. ...
The nasopharyngeal airway is an important equipment in airway management, a correct placement is crucial for its effectiveness. We measured the nares-to-epiglottis distance (NED) and examined the correlations of the optimal insertion length (NED-1) with patient characteristics and various external facial measurements. We aimed to develop a simple method for estimating the optimal insertion length and to help select an appropriate nasopharyngeal airway.
Two hundred patients of ASA grade I & II aged >20 years undergoing elective surgery under general anesthesia were enrolled. We measured nares-to-ear tragus distance (NTD), nares-to-mandibular angle distance (NMD), philtrum-to-ear tragus distance (PTD), and philtrum-to-mandibular angle distance (PMD). The NED was measured by fiber-optic bronchoscope. All measurements were obtained in centimeters. NED-1 (cm) was defined as the optimal insertion length. The patient's sex, age, body weight, body height, and body mass index were recorded.
The NED-1 significantly correlated with body weight, body height, NTD, NMD, PTD, and PMD. Backward stepwise multiple linear regression analysis yielded the formula for predicting NED-1: 0.331 − 0.018 × BW + 0.061 × BH + 1.080 × NMD – 1.256 × PMD + 0.697 × PTD (r = 0.640, P < .001). The regression lines of the optimal insertion length versus PTD showed the best fit to the equality line. The measurements of PTD showed the minimal differences from NED-1 and with the most patients showing <1 cm differences from NED-1.
The optimal insertion depth of nasopharyngeal airway can easily be predicted by the distance from philtrum-to-ear tragus, and a nasopharyngeal airway of an appropriate size can be selected accordingly.
... Following induction of anaesthesia and intubation, the OTP (CareFusion General Purpose Temperature Probe, Disposable, 12Fr, Carefusion Finland 320 Oy, Kuortaneenkatu 200510, Helsinki, Finland) was inserted orally under direct vision with laryngoscopy. The tip was then advanced 40 cm distal to the incisors [9] and fixed in position with adhesive tape. The self adhesive ZFT electrode was attached above the right supraorbital ridge after cleaning with a 2% chlorhexidine/ alcohol wipe, according to the manufacturer's instructions. ...
Accurately monitoring peri-operative core temperature is a cornerstone of good practice. Relatively invasive devices such as oesophageal temperature probes and pulmonary artery catheters facilitate this, but are inappropriate for many patients. There remains a need for accurate monitors of core temperature that can be used in awake patients. This study compared the accuracy of two core temperature thermometers that can be used for this purpose: the 3M Bair Hugger™ Temperature Monitoring System Zero Flux Thermometer and the CorTempR™ Wireless Ingestible Temperature Sensor. Readings were compared with the oesophageal probe, the current intraoperative standard. Thirty patients undergoing elective surgical procedures under general anaesthesia were recruited. The ingestible sensor was ingested prior to induction of anaethesia, and post induction, the zero-flux electrode attached above the right eyebrow and oesophageal probe inserted. During surgery, the temperature on each device was recorded every minute. Measurements were compared using Bland–Altman analysis. The ingestible sensor experienced interference from use of diathermy and fluoroscopy in the operating theatre, rendering 39% of its readings unusable. These were removed from analysis. With remaining readings the bias compared with oesophageal probe was + 0.42 °C, with 95% limits of agreement − 2.4 °C to 3.2 °C. 75.4% of readings were within ± 0.5 °C of the OTP reading. The bias for the zero flux electrode compared to oesophageal probe was + 0.02 °C with 95% limits of agreement − 0.5 °C to 0.5 °C. 97.7% of readings were within ± 0.5 °C of the oesophageal probe. The study findings suggest the zero-flux thermometer is sufficiently accurate for clinical use, whereas the ingestible sensor is not.
Trial registration The study was registered at http://www.clinicaltrials.gov, NCT Number: NCT02121574.
... [15][16][17] Several studies are available in literature which describe the optimal depth of insertion of nasopharyngeal temperature probe. [18][19][20] There has been no study to define the exact site of temperature probe placement in the nasopharynx. We hypothesized that placing the temperature probe at the level of fossa of Rosenmuller will reflect core temperature as it is in close relationship with septal branch of sphenopalatine artery, which in turn is a branch of external carotid artery and the parapharyngeal branch of internal carotid artery. ...
Introduction:
Monitoring body temperature and maintaining normothermia are now essentially the standard-of-care during anesthesia. This study was designed to compare the temperature measured by nasopharyngeal temperature probes inserted by landmark method and fiberscope-guided method with esophageal temperature. We hypothesized that placing the temperature probe at the level of fossa of Rosenmuller will reflect core temperature as it is in close relationship to the brain.
Subjects and methods:
Sixty-five patients aged 18-60 years were enrolled in this cross-sectional study. Two methods were used in our study to place the temperature probes. In landmark-based method, we inserted temperature probe through nostril for a depth equal to philtrum-tragus distance. In fiberscope-guided method, the temperature probe was inserted into nostril and its tip was positioned at fossa of Rosenmuller under fiberscope guidance.
Results:
The nasopharyngeal temperatures were recorded at seven time intervals along with esophageal temperature. Mean temperatures were calculated at three different sites. The degree of agreement between two methods at seven time intervals was also calculated. Both methods had good correlation with esophageal temperature. Depth of insertion of temperature probes was documented. There was difference in depth of insertion of temperature probe of around 4.26 cm between two methods, probe length from philtrum to tragus (D1) being longer than distance from fossa of Rosenmuller to nares (D2).
Conclusions:
Nasopharyngeal temperature measured at fossa of Rosenmuller with probe inserted by fiberscope-guided method and that measured by landmark-based method with probe inserted according to philtrum-tragus distance shows good correlation with esophageal temperature.
... Сенсор вводят через ноздри и проводят в нижнюю носовую пазуху над твёрдым нёбом. Продвижение температурного датчика в пределах 10-20 см вглубь от ноздрей считают оптимальным, достаточным для точного определения центральной температуры [14]. ...
Центральная температура тела человека служит важнейшим показателем, мониторируемым в клинической практике анестезиологии и интенсивной терапии. Современные анестетики влияют на процессы регуляции центральной температуры и приводят к её снижению в периоперационном периоде. Непреднамеренная интраоперационная гипотермия сопровождает многие операции, проводимые под общей и регионарной анестезией. Она значительно увеличивает риск кардиальных и инфекционных послеоперационных осложнений, на её фоне возрастают послеоперационная кровопотеря и потребность в гемотрансфузии. Пациенты в условиях гипотермии медленнее просыпаются, их пробуждение чаще сопровождается мышечной дрожью. Периоперационная гипотермия приводит к увеличению сроков госпитализации и внутрибольничной летальности. В связи с этим предотвращение непреднамеренной периоперационной гипотермии - важная часть анестезиологического обеспечения больного во всех областях хирургии. Поддержание нормотермии во время операции служит важной составляющей всех программ ранней послеоперационной активизации больных.
... It should be noted that some of these forms of measurement are not indicated for intraoperative surgical patients due to the specific needs of subjects subjected to anestheticsurgical procedures who are often exposed to intubation, manipulation of organs and spaces or to specific positions to ensure the success of the surgery (8)(9) . ...
OBJECTIVE
To verify the correlation between temperature measurements performed using an infrared tympanic thermometer and an esophageal thermometer during the intraoperative period.
METHOD
A longitudinal study of repeated measures was performed including subjects aged 18 years or older undergoing elective oncologic surgery of the digestive system, with anesthesia duration of at least 1 hour. Temperature measurements were performed simultaneously by a calibrated esophageal thermometer and by a calibrated infrared tympanic thermometer, with laboratory reading precision of ±0.2ºC. The operating room temperature remained between 19 and 21ºC.
RESULTS
The study included 51 patients, mostly men (51%), white (80.4%). All patients were kept warm by a forced-air heating system, for an average of 264.14 minutes (SD = 87.7). The two temperature measurements showed no different behavior over time (p = 0.2205), however, tympanic measurements were consistently 1.24°C lower (p<0.0001).
CONCLUSION
The tympanic thermometer presented reliable results but reflected lower temperatures than the esophageal thermometer.
... The temperature measured in the nasal cavity was significantly lower than that in the upper nasopharynx, oropharynx, or esophagus, and the temperature difference was constant. Wang et al. [12] also reported that an insertion depth between 10 and 20 cm provides a good indication of core temperature. These studies revealed that the temperature probe should be placed at least 10 cm deep when measuring the core temperature in the nasopharynx. ...
Recently, endotracheal tubes with an embedded temperature sensor in the inner surface of the tube cuff (temperature tracheal tubes) have been developed. We sought to assess whether temperature tracheal tubes show a good agreement with esophageal temperature probes during surgery.
We enrolled 40 patients who underwent laparoscopic surgery in an observational study. The tracheas of all patients were intubated with a temperature tracheal tube, and an esophageal temperature probe was inserted into the esophagus. Tracheal and esophageal temperatures were recorded at 15-min intervals until the end of surgery. Temperatures from both devices were analyzed using Bland–Altman analysis, four-quadrant plots, and polar plots.
We analyzed 261 data points from 36 patients. Temperatures ranges were 34.2 °C to 36.6 °C for the tracheal temperature tube and 34.7 °C to 37.2 °C for the esophageal temperature probe. Bland–Altman analysis showed an acceptable agreement between the two devices, with an overall mean bias (95% limit of agreement) of −0.3 °C (−0.8 °C to 0.1 °C) and a percentage error of 3%; the trending ability (temperature changes over time) between the two devices showed a concordance rate of 94% in four-quadrant plot (cut-off ≥ 92%), but this was higher than the acceptable mean angular bias of 177° (cut-off < ± 5°) and radial limits of agreement of 52° (cut-off < ± 30°) in the polar plot. Bronchoscopy during extubation and patient interviews at six hours postoperatively revealed no serious injuries related to the use of the temperature tracheal tube.
The temperature tracheal tube showed an acceptable overall mean bias of −0.3 °C and a percentage error of 3%, but incompatible trending ability with the esophageal temperature probe.
cris.nih.go.kr (KCT0007265); 22 April 2022.
No study has compared tracheal and esophageal temperatures when a breathing circuit with a heated wire humidifier was used. This study aimed to investigate the correlation between tracheal and esophageal temperatures in patients using a breathing circuit with heated wire humidifiers. Tracheal temperatures measured by the cuff sensor correlated well with esophageal temperatures while using a heated wire humidifier breathing circuit in patients with anesthesia duration of > 2 hours. Thirty-eight patients who underwent general anesthesia for > 2 hours were enrolled. Tracheal and esophageal temperatures were recorded at 5-minute intervals, starting from the insertion of the esophageal temperature probe to the end of anesthesia. The temperatures were compared by Bland-Altman analysis, calculating the proportion of tracheal temperature measurements within ± 0.25°C of esophageal temperatures, and linear mixed-effects model. Univariate analysis was performed to assess whether any variables influenced the proportion of differences within ± 0.25°C.
Results
After excluding 4 patients with an anesthesia duration of < 2 hours, data from 34 patients (1163 sets of tracheal and esophageal temperatures) were analyzed. Concordance correlation coefficient was 0.78. The overall mean bias (95% limits of agreement) between the tracheal and esophageal temperatures was −0.16°C (−0.65°C to 0.34°C). The percentage of temperature differences within ± 0.25°C was 73.5% ± 32.3, with a median of 89.4% [0,100]. The linear mixed-effects model revealed that the estimated intercept was 0.17°C with a 95% confidence interval (CI) of 0.13°C to 0.22°C. The duration of anesthesia and the number of temperature measurements were associated with higher concordance between the tracheal and esophageal temperatures in univariate analysis.
This study explored the risk factors and established a prediction model for intraoperative hypothermia (IOH) in patients undergoing robotic surgery. We conducted a retrospective survey of patients undergoing elective robotic surgery at the China-Japan Union Hospital of Jilin University during June 2020–October 2021 using institutional medical records. Intraoperative core temperatures and potential influencing factors were collected, and regression analyses were used to assess the risk factors for IOH and establish a prediction model for the incidence of IOH. Overall, 833 patients who underwent robotic surgery were included in the final analysis; IOH was observed in 344 patients (incidence, 0.41; 95% confidence interval [CI] 0.38–0.45). A higher body mass index (BMI) and baseline core temperature were protective factors for IOH. A final prediction model for IOH was developed based on the determining factors with an area under the receiver operating characteristic curve of 0.85 under fivefold cross validation (95% CI 0.83–0.88). Accordingly, a lower BMI and baseline core temperature, thoracic surgeries, morning surgeries, and surgeries with longer durations were risk factors for IOH during robotic surgeries. Our prediction model has an excellent discrimination ability for predicting IOH in robotic surgeries.
Background:
The effect of ambient temperature, with and without active warming, on intraoperative core temperature remains poorly characterized. The authors determined the effect of ambient temperature on core temperature changes with and without forced-air warming.
Methods:
In this unblinded three-by-two factorial trial, 292 adults were randomized to ambient temperatures 19°, 21°, or 23°C, and to passive insulation or forced-air warming. The primary outcome was core temperature change between 1 and 3 h after induction. Linear mixed-effects models assessed the effects of ambient temperature, warming method, and their interaction.
Results:
A 1°C increase in ambient temperature attenuated the negative slope of core temperature change 1 to 3 h after anesthesia induction by 0.03 (98.3% CI, 0.01 to 0.06) °Ccore/(h°Cambient) (P < 0.001), for patients who received passive insulation, but not for those warmed with forced-air (-0.01 [98.3% CI, -0.03 to 0.01] °Ccore/[h°Cambient]; P = 0.40). Final core temperature at the end of surgery increased 0.13°C (98.3% CI, 0.07 to 0.20; P < 0.01) per degree increase in ambient temperature with passive insulation, but was unaffected by ambient temperature during forced-air warming (0.02 [98.3% CI, -0.04 to 0.09] °Ccore/°Cambient; P = 0.40). After an average of 3.4 h of surgery, core temperature was 36.3° ± 0.5°C in each of the forced-air groups, and ranged from 35.6° to 36.1°C in passively insulated patients.
Conclusions:
Ambient intraoperative temperature has a negligible effect on core temperature when patients are warmed with forced air. The effect is larger when patients are passively insulated, but the magnitude remains small. Ambient temperature can thus be set to comfortable levels for staff in patients who are actively warmed.
Background:
Core temperature can be accurately measured from the esophagus or nasopharynx during general anesthesia, but neither site is suitable for neuraxial anesthesia. We therefore determined the precision and accuracy of a novel wireless axillary thermometer, the iThermonitor, to determine its suitability for use during neuraxial anesthesia and in other patients who are not intubated.
Methods:
We enrolled 80 adults having upper abdominal surgery with endotracheal intubation. Intraoperative core temperature was measured in distal esophagus and was estimated at the axilla with a wireless iThermonitor WT701 (Raiing Medical, Boston MA) at 5-minute intervals. Pairs of axillary and reference distal esophageal temperatures were compared and summarized using linear regression and repeated-measured Bland-Altman methods. We a priori determined that the iThermonitor would have clinically acceptable accuracy if most estimates were within ±0.5°C of the esophageal reference, and suitable precision if the limits of agreement were within ±0.5°C.
Results:
There were 3339 sets of paired temperatures. Axillary and esophageal temperatures were similar, with a mean difference (esophageal minus axillary) of only 0.14°C ± 0.26°C (standard deviation). The Bland-Altman 95% limits of agreement were reasonably narrow, with the estimated upper limit at 0.66°C and the lower limit at -0.38°C, thus ±0.52°C, indicating good agreement across the range of mean temperatures from 34.9°C to 38.1°C. The absolute difference was within 0.5°C in 91% of the measurements (95% confidence interval, 88%-93%).
Conclusions:
Axillary temperature, as recorded by the iThermonitor WT701, well represents core temperature in adults having noncardiac surgery and thus appears suitable for clinical use.
The literature survey 2016 is based on 592 papers found in Scopus and 35 additional publications detected in the journal "Thermology international "with the keywords "thermography" OR "infrared imaging" OR "thermology" OR "temperature measurement" OR "thermometry" AND "published in 2016" and restricted to "medicine". The papers were analysed with respect to the origin of authors, the language and the publication source. Although the search was restricted to medicine, only 158 papers were related to thermal applications in humans. Similar as in the surveys of previous years, a detailed description is provided of publications related to Raynaud's phenomenon, Complex Regional Pain Syndrome and Breast diseases. Most of the publication activity in breast thermography was in 2016 in Asia and many authors of these papers are not qualified as medical doctors.
Background:
Although the nasopharynx is a commonly used temperature-monitoring site during general anesthesia, it is unknown whether the position of nasopharyngeal temperature probes placed blindly by anesthesia practitioners is optimal. The purposes of this study were (1) to determine where the nasopharyngeal mucosa is in closest proximity to the internal carotid artery (ICA) and (2) to evaluate the tip position of nasopharyngeal temperature probes that were placed by anesthesiology residents and nurse anesthetists.
Methods:
In the first phase of the study, we reviewed enhanced axial computed tomography images of 100 patients to determine where the nasopharyngeal mucosa was in closest proximity to the left or the right ICA. The distance from this point to the nares was then measured in the sagittal image. In the second phase of the study, nasendoscopy was used to evaluate the positioning of nasopharyngeal temperature probes placed by anesthesiology residents (244 patients) or nurse anesthetists (116 patients). Malpositioned probes were repositioned to an optimal location, and the temperature differences were recorded.
Results:
In the computed tomography images, the mucosa in closest proximity to the ICA was in the upper, mid-, and lower nasopharynx in 60%, 38%, and 2% of patients, respectively. The average distances between the ICA and the nasopharyngeal mucosa in the upper portion were significantly shorter than those in the lower portion (female: 9.4 vs 16.8 mm, P < 0.001; male: 12.4 vs 18.8 mm, P < 0.001). The average distances (95% prediction interval) from the nares to the upper portion of the nasopharynx through the inferior meatus were 9.1 (8.1-10.2) cm in females and 9.7 (8.6-10.8) cm in males. Temperature probes were correctly positioned in the upper or mid-nasopharynx by residents and nurses in 43% (95% confidence interval [CI], 37%-49%) and 41% (95% CI, 36%-50%), respectively. When the probe was inadvertently placed in the nasal cavity, the median (95% CI) temperature difference from the upper nasopharynx was 0.2°C (0.15°C-0.25°C).
Conclusions:
The closest portion of the nasopharyngeal mucosa to the ICA is within the upper or mid-nasopharynx. The depth from the nares to the upper one-third of the nasopharynx is approximately 10 cm. Less than half of nasopharyngeal temperature probes placed blindly by practitioners were optimally positioned.
Inadvertent perioperative hypothermia causes serious morbidity in surgical patients. However, recent reports suggest that patients might still be hypothermic after elective surgery. We thus surveyed intraoperative temperature monitoring and management practices in Europe.
Postal survey of 801 representative hospitals from 17 European countries on the same day. The questions addressed the number of surgical procedures and type of anaesthesia performed, mode and site of temperature monitoring and method of patient warming. Mean and standard error of the mean or count and percentage were calculated. The t-test or contingency table analysis with the Fisher's exact test were used.
Eight thousand and eighty-three surgical procedures were assessed from 316 responding hospitals (39.4%). Overall, patient temperature monitored in 19.4% and 38.5% of the patients were actively warmed. Under general anaesthesia, body temperature was monitored in 25% and during regional anaesthesia in 6%, P = 0.0005. Nasopharyngeal temperature was most often taken under general anaesthesia, while tympanic temperature was preferred during regional anaesthesia. Under general anaesthesia, 43% of patients were actively warmed as compared to 28% with regional anaesthesia, P = 0.0005. Forced-air warming was the method of choice for both general and regional anaesthesia.
Intraoperative temperature monitoring is still uncommon and hence active patient warming is not a standard of care in Europe. Awareness of perioperative hypothermia is critical to its prevention, and thus temperature monitoring is a pre-requisite. The objective is to maintain normothermia in patients throughout surgery. A European practice guideline for perioperative patient temperature management is warranted.
All current methods of core temperature monitoring have limitations. There is at least one skin temperature probe that can be modified to a nasal temperature probe (NP). This study was conducted to validate this modified skin temperature probe as an accurate surrogate measure of core temperature by comparing the temperature measurements obtained from NP to those from the esophageal stethoscope (ES).
In 45 adult patients undergoing general anesthesia, one pair of simultaneous temperature measurements were obtained from the ES (E (temp)) and the NP (N (temp)).
The NP was easily inserted in all patients. No patient developed epistaxis. The magnitudes of the differences between N (temp) and E (temp) measurements were 0.2 degrees C or less in 43 out of 45 patients (95.6%); 0.1 degrees C or less in 33 patients (73.3%). On average, the E (temp) was 0.05 degrees C higher than the N (temp). The 95% prediction interval for the E (temp)-N (temp) difference was -0.2 degrees C to +0.3 degrees C. Thus we expect the magnitude of the temperature difference to be less than 1/3 degrees C in the next future individual patient.
In adults, the NP readings closely match the core temperature readings obtained by ES and thus can be used as a reliable surrogate measure of core temperature. This technique may be useful and advantageous in various situations, particularly when other methods of core temperature monitoring are not available or reliable.
Using tympanic membrane (TM) temperature as a standard for core temperature, we quantitated the accuracy and precision of seven other temperature monitoring sites during anesthesia, namely, the nasopharynx, esophagus, rectum, bladder, axilla, forehead, and great toe. Accuracy was quantitated as the difference between TM temperature and the temperature at each of the other sites; precision was quantitated as the correlation between TM temperature and the temperature at each of the other sites. Results indicate that the accuracy of measurements made using the great toe, forehead, and axilla is less than the accuracy of measurements made using the nasopharynx, esophagus, bladder, and rectum. Precision of measurements made using the nasopharynx, esophagus, and bladder is greater than the precision at the axilla, forehead, and rectum, and much higher than the precision at the great toe. Measurements of body temperature using the nasopharynx, esophagus, and bladder are recommended for intraoperative use as providing the best combination of accuracy and precision.
Mild intraoperative hypothermia is common. We therefore studied the effects of mild hypothermia on propofol pharmacokinetics, hepatic blood flow, and atracurium duration of action in healthy volunteers. Six young volunteers were studied on two randomly assigned days, at either 34 degrees C or 37 degrees C. Anesthesia was induced with thiopental, 3 mg/kg, and maintained with 70% N2O and 0.6% isoflurane. Core hypothermia was induced by conductive and convective cooling. On the other study day, normothermia was maintained by a Bair Hugger (Augustine Medical, Inc., Eden Prairie, MN) forced-air warmer. Propofol, 1 mg/kg lean body mass (LBM), then was given, followed by a 4-h infusion at 5 mg.kg-1.h-1. After 2 h, atracurium 0.5 mg/kg was administered as an intravenous bolus. Indocyanine green was administered for estimation of hepatic blood flow. Arterial blood was assayed for propofol and indocyanine green concentration. Pharmacokinetic analysis was performed using NONMEM. Results are reported as means +/- SEM. Propofol blood concentrations averaged approximately 28% more at 34 degrees C than at 37 degrees C (P < 0.05). Hepatic blood flow decreased 23% +/- 11% in normothermic volunteers during the propofol infusion, and 33% +/- 11% in hypothermic volunteers (P = not significant). A three-compartment mamillary model fitted the data best. Inclusion of hepatic blood flow change from the prepropofol baseline as a covariate for total body clearance significantly improved the fit. The intercompartmental clearances were decreased in the presence of hypothermia.(ABSTRACT TRUNCATED AT 250 WORDS)
Mild perioperative hypothermia, which is common during major surgery, may promote surgical-wound infection by triggering thermoregulatory vasoconstriction, which decreases subcutaneous oxygen tension. Reduced levels of oxygen in tissue impair oxidative killing by neutrophils and decrease the strength of the healing wound by reducing the deposition of collagen. Hypothermia also directly impairs immune function. We tested the hypothesis that hypothermia both increases susceptibility to surgical-wound infection and lengthens hospitalization.
Two hundred patients undergoing colorectal surgery were randomly assigned to routine intraoperative thermal care (the hypothermia group) or additional warming (the normothermia group). The patient's anesthetic care was standardized, and they were all given cefamandole and metronidazole. In a double-blind protocol, their wounds were evaluated daily until discharge from the hospital and in the clinic after two weeks; wounds containing culture-positive pus were considered infected. The patients' surgeons remained unaware of the patients' group assignments.
The mean (+/- SD) final intraoperative core temperature was 34.7 +/- 0.6 degrees C in the hypothermia group and 36.6 +/- 0.5 degrees C in the normothermia group (P < 0.001) Surgical-wound infections were found in 18 of 96 patients assigned to hypothermia (19 percent) but in only 6 of 104 patients assigned to normothermia (6 percent, P = 0.009). The sutures were removed one day later in the patients assigned to hypothermia than in those assigned to normothermia (P = 0.002), and the duration of hospitalization was prolonged by 2.6 days (approximately 20 percent) in hypothermia group (P = 0.01).
Hypothermia itself may delay healing and predispose patients to wound infections. Maintaining normothermia intraoperatively is likely to decrease the incidence of infectious complications in patients undergoing colorectal resection and to shorten their hospitalizations.
Limited information is available about the correlation between cerebral temperature and routine temperature measurements during cardiopulmonary bypass in infants. Nasopharyngeal, tympanic membrane and rectal temperatures were compared with jugular bulb temperature in ten infants operated on with moderate or deep hypothermia. The cerebral arteriovenous saturation differences were correlated with the temperatures at the four measurement sites. The jugular bulb and nasopharyngeal temperatures showed the most rapid response during cooling and rewarming. The tympanic temperature response varied in an unpredictable way. Rectal temperature, which was the target for rewarming, lagged behind during both cooling and rewarming. Overwarming at the end of cardiopulmonary bypass, seen as jugular bulb and nasopharyngeal temperatures exceeding 38 degrees C, was common after deep hypothermia. A high correlation was found between the cerebral arteriovenous oxygen saturation differences and the jugular bulb temperature (r = 0.81) and the nasopharyngeal and the tympanic temperature (r = 0.79), whereas the correlation with rectal temperature was weaker (0.66).
Hypothermia during general anesthesia develops with a characteristic three-phase pattern. The initial rapid reduction in core temperature after induction of anesthesia results from an internal redistribution of body heat. Redistribution results because anesthetics inhibit the tonic vasoconstriction that normally maintains a large core-to-peripheral temperature gradient. Core temperature then decreases linearly at a rate determined by the difference between heat loss and production. However, when surgical patients become sufficiently hypothermic, they again trigger thermoregulatory vasoconstriction, which restricts core-to-peripheral flow of heat. Constraint of metabolic heat, in turn, maintains a core temperature plateau (despite continued systemic heat loss) and eventually reestablishes the normal core-to-peripheral temperature gradient. Together, these mechanisms indicate that alterations in the distribution of body heat contribute more to changes in core temperature than to systemic heat imbalance in most patients. Just as with general anesthesia, redistribution of body heat is the major initial cause of hypothermia in patients administered spinal or epidural anesthesia. However, redistribution during neuraxial anesthesia is typically restricted to the legs. Consequently, redistribution decreases core temperature about half as much during major conduction anesthesia. As during general anesthesia, core temperature subsequently decreases linearly at a rate determined by the inequality between heat loss and production. The major difference, however, is that the linear hypothermia phase is not discontinued by reemergence of thermoregulatory vasoconstriction because constriction in the legs is blocked peripherally. As a result, in patients undergoing large operations with neuraxial anesthesia, there is the potential of development of serious hypothermia. Hypothermic cardiopulmonary bypass is associated with enormous changes in body heat content. Furthermore, rapid cooling and rewarming produces large core-to-peripheral, longitudinal, and radial tissue temperature gradients. Inadequate rewarming of peripheral tissues typically produces a considerable core-to-peripheral gradient at the end of bypass. Subsequently, redistribution of heat from the core to the cooler arms and legs produces an afterdrop. Afterdrop magnitude can be reduced by prolonging rewarming, pharmacologic vasodilation, or peripheral warming. Postoperative return to normothermia occurs when brain anesthetic concentration decreases sufficiently to again trigger normal thermoregulatory defenses. However, residual anesthesia and opioids given for treatment of postoperative pain decreases the effectiveness of these responses. Consequently, return to normothermia often needs 2-5 h, depending on the degree of hypothermia and the age of the patient.
(a) To investigate in a newborn animal model whether nasopharyngeal temperature is more closely related to epidural brain temperature than rectal temperature and (b) to investigate in human neonates whether measurement of nasopharyngeal temperature is dependent on the measurement site and other conditions.
(a) Animal experiment in newborn piglets, at an institute for surgical research. (b) Prospective study in human neonates, at a neonatal intensive care unit of a tertiary care university hospital. ANIMALS AND PATIENTS: (a) Nineteen tracheostomized ventilated newborn piglets. (b) Twenty-two spontaneously breathing human newborns nursed either in an incubator or a cot.
(a) In the piglets nasopharyngeal temperature (Tnasoph) measured at the nose-ear distance, defined as distance from the inner brim of the nostril to the tragus and inner rim of the meatus accusticus, most closely reflected epidural temperature (Tepidur) at the epidural surface (r2 = 0.89), followed by skin temperature at the temple, rectal temperature (Trectum) at 2 cm depth, and esophageal temperature (Tesoph) in the middle esophagus. Tnasoph did not significantly differ before and after tracheostomy. (b) In the newborns Tnasoph was significantly lower than Trectum. Measurements of Tnasoph at nose-ear distance within a feeding tube had a high precision and were unaffected by breathing or head turning. A nasopharyngeal probe was imaged by magnetic resonance imaging in four newborns of various body weight; its tip when inserted to a depth equal to nose-ear distance was anatomically closest to the brain base but separated from it by tissue layer 2.2 cm thick.
Tnasoph measured at a position anatomically closest to the brain reflects epidural brain temperature more closely than Trectum. When measured at nose-ear distance it is unaffected by breathing or head turning. Measuring Tnasoph within a feeding tube and standardizing the measuring position is crucial for its use as brain temperature analogue.
A potential morbidity of incomplete re-warming following hypothermic cardiopulmonary bypass (CPB) is cardiac arrest. In contrast, attempts to fully re-warm the patient can lead to cerebral hyperthermia. Similarly, rigid adherence to 37.0 degrees C during normothermic CPB may also cause cerebral overheating. The literature demonstrates scant information concerning the actual temperatures measured, the sites of temperature measurement and the detailed thermal strategies employed during CPB. A prospective, randomized, controlled study was undertaken to investigate the ability to manage perfusion temperature control in a group of hypothermic patients (28 degrees C) and a group of normothermic patients (37 degrees C). Eighty patients presenting for first-time, elective coronary artery bypass graft surgery (CABG) were randomly allocated to the hypothermic and normothermic groups. All surgery was performed by one surgeon and the anaesthesia managed by one anaesthetist. Temperature measurements were made at the nasopharyngeal (NP) site, as well as in the arterial line of the CPB circuit. The hypothermic group had the arterial blood temperature lowered to 25.0 degrees C to maintain the NP temperature at 28.0-28.5 degrees C. During re-warming, the arterial blood was raised to 38.0 degrees C. Meanwhile, in the normothermic group, the arterial blood temperature was raised to a maximum of 37.0 degrees C to maintain NP temperature at 36.5-37.0 degrees C. Despite strict guidelines, some patients transgressed the temperature control limits. Two patients in the hypothermic group failed to reach an NP temperature of 28.5 degrees C. Twenty-six patients were managed entirely within the control limits. During rewarming in both groups, control of both arterial and NP temperature was well managed with only 25% patients breaching the respective upper control limits. During the re-warming phases of CPB, we were unable to make any correlation between NP temperature and arterial blood temperature, using body weight or body mass index as predictors. Based on the results obtained, we recommend that strict criteria should be implemented for the management of temperature during CPB, in conjunction with more emphasis being placed on monitoring arterial blood temperature as a marker of potential cerebral hyperthermia. We should, therefore, not rely on NP temperature measurement alone during CPB.
Most clinically available thermometers accurately report the temperature of whatever tissue is being measured. The difficulty is that no reliably core-temperature-measuring sites are completely noninvasive and easy to use-especially in patients not undergoing general anesthesia. Nonetheless, temperature can be reliably measured in most patients. Body temperature should be measured in patients undergoing general anesthesia exceeding 30 min in duration and in patients undergoing major operations during neuraxial anesthesia. Core body temperature is normally tightly regulated. All general anesthetics produce a profound dose-dependent reduction in the core temperature, triggering cold defenses, including arteriovenous shunt vasoconstriction and shivering. Anesthetic-induced impairment of normal thermoregulatory control, with the resulting core-to-peripheral redistribution of body heat, is the primary cause of hypothermia in most patients. Neuraxial anesthesia also impairs thermoregulatory control, although to a lesser extent than does general anesthesia. Prolonged epidural analgesia is associated with hyperthermia whose cause remains unknown.
Anesthetic-induced hypothermia is known to reduce platelet function and impair enzymes of the coagulation cascade. The objective of this meta-analysis and systematic review was to evaluate the hypothesis that mild perioperative hypothermia increases surgical blood loss and transfusion requirement.
The authors conducted a systematic search of published randomized trials that compared blood loss and/or transfusion requirements in normothermic and mildly hypothermic (34-36 degrees C) surgical patients. Results are expressed as a ratio of the means or relative risks and 95% confidence intervals (CI); P < 0.05 was considered statistically significant.
Fourteen studies were included in analysis of blood loss, and 10 in the transfusion analysis. The median (quartiles) temperature difference between the normothermic and hypothermic patients among studies was 0.85 degrees C (0.60 degrees C versus 1.1 degrees C). The ratio of geometric means of total blood loss in the normothermic and hypothermic patients was 0.84 (0.74 versus 0.96), P = 0.009. Normothermia also reduced transfusion requirement, with an overall estimated relative risk of 0.78 (95% CI 0.63, 0.97), P = 0.027.
Even mild hypothermia (<1 degree C) significantly increases blood loss by approximately 16% (4-26%) and increases the relative risk for transfusion by approximately 22% (3-37%). Maintaining perioperative normothermia reduces blood loss and transfusion requirement by clinically important amounts.
Nasopharyngeal temperatures do not follow tympanic core temperatures during cardiopulmonary bypass surgery
- H Sato
- M Yamakage
- K Okuyama
- Y Imai
- H Iwashita
- T Ishiyama
- T Matsukawa
Sato H, Yamakage M, Okuyama K, Imai Y, Iwashita H, Ishiyama
T, Matsukawa T. Nasopharyngeal temperatures do not follow
tympanic core temperatures during cardiopulmonary bypass
surgery. Med Equip Insight 2008;1:9-13
- Cork
Nasopharyngeal temperatures do not follow tympanic core temperatures during cardiopulmonary bypass surgery.
- Sato