No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
An Old Cold Killer...Overview of Perioperative Hypothermia
ResearchGate has not been able to resolve any citations for this publication.
Administration of general anesthesia requires continuous monitoring of vital parameters of the body including body temperature. However, temperature continues to be one of the least seriously monitored parameters perioperatively. Inadvertent perioperative hypothermia is a relatively common occurrence with both general and regional anesthesia and can have significant adverse impact on patients' outcome. While guidelines for perioperative temperature management have been proposed, there are no specific guidelines regarding the best site or best modality of temperature monitoring and management intraoperatively. Various warming and cooling devices are available which help maintain perioperative normothermia. This article discusses the physiology of thermoregulation, effects of anesthesia on thermoregulation, various temperature monitoring sites and methods, perioperative warming devices, guidelines for perioperative temperature management and inadvertent temperature complications (hypothermia/hyperthermia) and measures to control it in the operating room.
Introduction
Therapeutic hypothermia (TH) is now recommended for the treatment neonates with hypoxic-ischemic encephalopathy (HIE). This treatment protocol is applied in our department since June 2012. The aim of this study is to report the first experience with head cooling in asphyxiated neonates in Morocco.
Patients and Methods
Prospective study of newborns admitted for HIE from July 18, 2012, to May 15, 2014, in Neonatal Intensive Care Unit (NICU) of Mohamed VI University Hospital. The results were studied by comparing a newborn group who received hypothermia to a control group.
Results
Seventy-two cases of neonates with perinatal asphyxia were admitted in the unit. According to inclusion criteria thirty-eight cases were eligible for the study. Only 19 cases have received the hypothermia protocol for different reason; the arrival beyond six hours of life was the main cause accounting for 41%. Complications of asphyxia were comparable in both groups with greater pulmonary hypertension recorded in the control group. The long-term follow-up of protocol group was normal in almost half of cases.
Conclusion
Our first experience with the controlled TH supports its beneficial effect in newborns with HIE. This treatment must be available in all the centers involved in the neonatal care in Morocco.
In the past few decades, surgery has advanced greatly because of an improved understanding of perioperative pathophysiology, development of minimally invasive operative techniques and advanced anaesthetic techniques. Fewer operations are requiring extended periods of hospital stay and a growing number of procedures are performed on an ambulatory basis. The pressure on medical systems is continuously growing as a result of economic constraints, increasing numbers of patients undergoing surgical procedures and greater patient autonomy. Patient awareness is steadily increasing along with their participation in their own care, leading to expectations of a higher standard of care. This has led to the development of a new concept of fast-track surgery.
Background:
During head and neck surgery including orthognathic surgery, mild intraoperative hypothermia occurs frequently. Hypothermia is associated with postanesthetic shivering, which may increase the risk of other postoperative complications. To improve intraoperative thermoregulation, devices such as forced-air warming blankets can be applied. This study aimed to evaluate the effect of supplemental forced-air warming blankets in preventing postanesthetic shivering.
Methods:
This retrospective study included 113 patients who underwent orthognathic surgery between March and September 2015. According to the active warming method utilized during surgery, patients were divided into two groups: Group W (n = 55), circulating-water mattress; and Group F (n = 58), circulating-water mattress and forced-air warming blanket. Surgical notes and anesthesia and recovery room records were evaluated.
Results:
Initial axillary temperatures did not significantly differ between groups (Group W = 35.9 ± 0.7℃, Group F = 35.8 ± 0.6℃). However, at the end of surgery, the temperatures in Group W were significantly lower than those in Group F (35.2 ± 0.5℃ and 36.2 ± 0.5℃, respectively, P = 0.04). The average body temperatures in Groups W and F were, respectively, 35.9 ± 0.5℃ and 36.2 ± 0.5℃ (P = 0.0001). In Group W, 24 patients (43.6%) experienced postanesthetic shivering, while in Group F, only 12 (20.7%) patients required treatment for postanesthetic shivering (P = 0.009, odds ratio = 0.333, 95% confidence interval: 0.147-0.772).
Conclusions:
Additional use of forced-air warming blankets in orthognathic surgery was superior in maintaining normothermia and reduced the incidence of postanesthetic shivering.
Background:
Thermal care is an important element of Baby Friendly Hospital.
Aim:
The objective of this study was to determine the prevalence of neonatal hypothermia and associated risk factors in healthy full term newborns at a Baby Friendly Hospital.
Subjects and methods:
A cross-sectional, descriptive study was conducted on consecutively healthy full term neonates recruited during a 1 year. Temperatures were recorded immediately after birth and at the age of 1, 2 and 4 h after birth in order to estimate the prevalence of neonatal hypothermia, defined as axillary temperature less than 36.0°C. The data were collected using an especially questionnaire; data of history of abortion, parity, mode of vaginal delivery, gestational age, birth weight, newborn temperatures, time of the first skin-to-skin contact, time of first breast feeding, first wrapping and first visiting by the pediatrician. Association between neonatal hypothermia and risk factors was determined using logistic regression.
Results:
Axillary temperature showed 41.2%, 47.5%, 46.4% and 37.2% of the a consecutive number of 522 healthy full term neonates were moderately hypothermia immediately after birth, at 1 h, 2 h and 4 h respectively. Spontaneous labor and warming room were associated with decreased risk of hypothermia. A persistently high prevalence of neonatal hypothermia was shown within the first 4 h of vaginal birth. All analyses were carried out using the SPSS version 17.0 (Chicago IL, USA). Test of the associations were done, stepwise multiple logistic regressions. Odds ratios (ORs) were assessed using maximum likelihood and associated 95% confidence intervals were computed. A P ≤ 0.05 was considered to be statistically significant.
Conclusion:
The findings of this study indicated that a high prevalence of neonatal hypothermia was identified among healthy full term newborn in a Baby Friendly Hospital Initiative. Therefore, it is necessary to emphasize on the development "warm chain" in preventing neonatal hypothermia in Baby Friendly Hospital.
Brain injury after stroke and other cerebral ischemic events is a leading cause of death and disability worldwide. Our purpose here is to argue in favor of combined mild hypothermia (35 degrees C) and magnesium as an acute neuroprotective treatment to minimize ischemic brain injury.
Drawing on our own experimental findings with mild hypothermia and magnesium, and in light of the moderate hypothermia trials in cardiac arrest/resuscitation and magnesium trials in ischemic stroke (IMAGES, FAST-Mag), we bring attention to the advantages of mild hypothermia compared with deeper levels of hypothermia, and highlight the existing evidence for its combination with magnesium to provide an effective, safe, economical, and widely applicable neuroprotective treatment after brain ischemia. With respect to effectiveness, our own laboratory has shown that combined mild hypothermia and magnesium treatment has synergistic neuroprotective effects and reduces brain injury when administered several hours after global and focal cerebral ischemia.
Even when delayed, combined treatment with mild hypothermia and magnesium has broad therapeutic potential as a practical neuroprotective strategy. It warrants further experimental investigation and presents a good case for assessment in clinical trials in treating human patients after brain ischemia.
General anesthesia markedly impairs normal control of body temperature, reducing the threshold (triggering core temperature) for thermoregulatory vasoconstriction from approximately 37 to approximately 34.5 degrees C. Sweating and active vasodilation thresholds similarly are increased, widening the range of temperatures not triggering regulatory compensations from approximately 0.2 to approximately 4 degrees C. However, once initiated, the gains (slopes of response intensity vs. core temperature curves) and maximum intensities of thermoregulatory responses are nearly normal. Intraoperative core temperature initially decreases rapidly because anesthetic-induced inhibition of tonic thermoregulatory vasoconstriction causes a core-to-peripheral redistribution of body heat. The subsequent slower, linear decrease in body temperature results from heat loss exceeding metabolic heat production. And finally, after 3-4 h of anesthesia, core temperature stabilizes at an abnormally low value. In patients experiencing minimal heat loss, and therefore not becoming sufficiently hypothermic to trigger vasoconstriction, this plateau can be passive steady state in which heat loss equals production. Conversely, patients becoming sufficiently hypothermic will trigger thermoregulatory vasoconstriction that both decreases cutaneous heat loss and sequesters some metabolic heat in the core. Epidural and spinal anesthesia also cause core hypothermia by inhibiting tonic thermoregulatory vasoconstriction, producing an internal redistribution of heat from the warm core to cooler peripheral tissues. Core hypothermia provokes thermoregulatory responses including vasoconstriction (above the block level) and shivering. Nonetheless, many patients feel warmer after induction of regional anesthesia, apparently because perceived skin temperature is elevated. The following review will focus on anesthetic-induced impairment of normal thermoregulatory control and the resulting alterations in heat balance.
Cardiac arrest outside the hospital is common and has a poor outcome. Studies in laboratory animals suggest that hypothermia induced shortly after the restoration of spontaneous circulation may improve neurologic outcome, but there have been no conclusive studies in humans. In a randomized, controlled trial, we compared the effects of moderate hypothermia and normothermia in patients who remained unconscious after resuscitation from out-of-hospital cardiac arrest.
The study subjects were 77 patients who were randomly assigned to treatment with hypothermia (with the core body temperature reduced to 33 degrees C within 2 hours after the return of spontaneous circulation and maintained at that temperature for 12 hours) or normothermia. The primary outcome measure was survival to hospital discharge with sufficiently good neurologic function to be discharged to home or to a rehabilitation facility.
The demographic characteristics of the patients were similar in the hypothermia and normothermia groups. Twenty-one of the 43 patients treated with hypothermia (49 percent) survived and had a good outcome--that is, they were discharged home or to a rehabilitation facility--as compared with 9 of the 34 treated with normothermia (26 percent, P=0.046). After adjustment for base-line differences in age and time from collapse to the return of spontaneous circulation, the odds ratio for a good outcome with hypothermia as compared with normothermia was 5.25 (95 percent confidence interval, 1.47 to 18.76; P=0.011). Hypothermia was associated with a lower cardiac index, higher systemic vascular resistance, and hyperglycemia. There was no difference in the frequency of adverse events.
Our preliminary observations suggest that treatment with moderate hypothermia appears to improve outcomes in patients with coma after resuscitation from out-of-hospital cardiac arrest.
This review focuses on the initial presentation and in-hospital management of acute myocardial infarction, including selection of a management strategy and options for antithrombotic therapy.
Background: Humans maintain constant body temperature within a wide range of changes in external environment. Core body temperature is maintained within narrow range; Enzyme systems in the body have narrow temperature ranges in which they function optimally for caring out different activities in the body as metabolism, conduction of nervous function and skeletal muscle contraction. Perioperative hypothermia is one of the major problems during surgery that can affect operated patients. It has been shown by different researchers that Perioperative hypothermia will result in to various adverse events such as myocardial ischemia, coagulopathy, delayed awakening and wound infections.
Objective: The objective of this study was to determine incidence of perioperative hypothermia and determinant factors among patients operated in Gondar university hospital from March to April, 2015.
Methods: A prospective observational study was conducted to determine incidence of perioperative hypothermia and associated risk factors among patients that underwent surgery in Gondar university hospital. All consecutive patients from both elective and emergency surgery were included in this study.
Result: A total of 312 patients were participated in this study. The incidence of Pre, Intra and post-operative hypothermia were 23.4%, 49.7% and 50.6% respectively. Use of general anesthesia (AOR=2.3), co-morbidity (AOR=2.1), low body temperature before the start of anesthesia (AOR=4.7) and elective procedures (AOR=2.1) were found to be independent predictors of intra-operative hypothermia.
Conclusion and Recommendation: The incidence of perioperative hypothermia is high in Gondar University Hospital. Passive and active warming techniques should be implemented in the hospital.
An abstract is unavailable. This article is available as HTML full text and PDF.
Hypothermia among newborns is considered an important contributor to neonatal morbidity and mortality in low-resource settings. However, in these settings only limited progress has been made towards understanding the risk of mortality after hypothermia, describing how this relationship is dependent on both the degree or severity of exposure and the gestational age and weight status of the baby, and implementing interventions to mitigate both exposure and the associated risk of poor outcomes. Given the centrality of averting neonatal mortality to achieving global milestones towards reductions in child mortality by 2015, recent years have seen substantial resources and efforts implemented to improve understanding of global epidemiology of neonatal health. In this article, a summary of the burden, consequences, and risk factors of neonatal hypothermia in low-resources settings is presented, with a particular focus on community-based data. Context-appropriate interventions for reducing hypothermia exposure and the role of these interventions in reducing global neonatal mortality burden are explored.
Perioperative hypothermia is a common and serious complication of anesthesia and surgery and is associated with many adverse perioperative outcomes. It prolongs the duration of action of inhaled and intravenous anesthetics as well as the duration of action of neuromuscular drugs. Mild core hypothermia increases thermal discomfort, and is associated with delayed post anaesthetic recovery. Mild hypothermia significantly increases perioperative blood loss and augments allogeneic transfusion requirement. Only 1.9 degrees C core hypothermia triples the incidence of surgical wound infection following colon resection and increases the duration of hospitalization by 20%. Hypothermia adversely affects antibody- and cell-mediated immune defences, as well as the oxygen availability in the peripheral wound tissues. Furthermore mild hypothermia triples the incidence of postoperative adverse myocardial events. Thus, even mild hypothermia contributes significantly to patient care costs and needs to be avoided.
Heat transfer between the core and its environment in normothermic and slightly hypothermic situations is determined largely by the influence of vasomotion on convection. Tonic vasoconstriction, the normal barrier to heat loss from the core, is impaired upon induction of anesthesia. The resulting dilation of the arteriovenous shunts leads to redistribution of heat from the core to the periphery, diminishing the temperature gradient between the two compartments. With reemergence of thermoregulatory vasoconstriction at core temperatures near 34 degrees C, the core and the periphery are again separated, with metabolic heat being largely constrained to the core. Under normal conditions of mild thermal stress, thermoregulatory vasoconstriction is thus able to protect core temperature by reducing cutaneous heat transfer and functionally isolating the peripheral and core thermal compartments. Consequently, anesthetic-induced alterations in vasomotor tone is one of the major factors influencing core temperature in patients who are not actively cooled or warmed. In contrast, thermoregulatory tone is insufficient to prevent core temperature perturbations in patients undergoing vigorous cutaneous cooling or warming.
In summary, both regional and general anesthesia markedly impair the normal precise regulation of core body temperature. Consequently, inadvertent perioperative hypothermia is common. Hypothermia develops because the typical operating room environment is cold; however, it is anesthetic-induced impairment of thermoregulatory responses that contributes most. Internal redistribution of body heat is a surprisingly important factor, contributing more to core hypothermia than net heat loss in most patients. There is now convincing evidence that a typical amount of intraoperative hypothermia, say 2 degrees C, predisposes numerous complications and alters patient outcome. Fortunately, effective methods are available for preventing hypothermia.
The use of infrared thermometry to measure temperatures in hospitalized patients is increasing. Although infrared thermometers have been proven to be accurate when they are used by well-trained personnel, no previous studies have examined their accuracy during routine hospital use.
To determine the accuracy and observer variability of temperatures measured with an infrared tympanic thermometer (TT).
Prospective, observational study.
ICUs of a 300-bed teaching community hospital.
Fifty-one critically ill patients.
The mean of three tympanic temperatures measured with the infrared TT (tempTTs) was compared to temperatures simultaneously measured with the thermistor of right heart catheters and rectal mercury thermometers for the following three groups of observers who had been certified in the use of the infrared TT: a single critical care nurse (CCN)/educator (Ed); CCNs, and floor nurses (FNs)/clinical care practitioners (CCPs).
Two rounds of measurements were given to 51 patients by 153 observers. Temperatures of the pulmonary artery (PA) measured with the thermistor of right heart catheters (tempPAs) ranged from 96.5 to 102.6 degrees F, with a mean (-/+ SD) of 99.3+/-1.1 degrees F. The intraobserver variabilities (correlation coefficients) of the tempTTs ranged from 0.90 for those measured by FNs/CCPs, to 0.92 for those measured by CCNs, to 0.98 for those measured by the CCN/Ed. Accuracy, arbitrarily defined as within a deviation of -/+0.5 degrees F of the tempPA, was 100% for the rectal mercury thermometer and 98.0% for the infrared TT when used by the CCN/Ed. The accuracy of the infrared TT was 80% when measured by CCNs and 61% when measured by FNs/CCPs. Differences between tempPAs and tempTTs measured by the CCN/Ed ranged from 0 to 0.7 degrees F, with a mean of 0.2 degrees F. Similarly, differences between tempPAs and tempTTs measured by CCNs ranged from 0 to 2.4 degrees F, with a mean difference of 0.3 degrees F. However, differences between tempPAs and tempTTs measured by FNs/CCPs ranged from 0 to 3.0 degrees F, with a mean of 0.6 degrees F (greater differences than those obtained by the CCNs; p < 0.01). The accuracy of rectal mercury thermometry was 100%. If a temperature > or = 101.0 degrees F had been considered as the threshold at which a fever is present, and if the mean of three measurements had been used to designate temperature, workups that were either inappropriately performed or omitted would have resulted from 2% of tempTTs measured by the CCN/Ed, 1% of those measured by CCNs, and 4% of those measured by FNs/CCPs.
When used properly, both tympanic and rectal thermometry are very accurate. However, the infrared TT produced measurements that were both less accurate and less reproducible when used by nurses who routinely used it in clinical practice.
A new system has been developed that circulates warm water through a whole body garment worn by the patient during surgery. In this study the authors compared two different strategies for the maintenance of intraoperative normothermia. One strategy used a new water garment warming system that permitted active warming of both the upper and lower extremities and the back. The other strategy used a single (upper body) forced-air warming system.
In this prospective, randomized study, 53 adult patients were enrolled in one of two intraoperative temperature management groups during open abdominal surgery with general anesthesia. The water-garment group (n = 25) received warming with a body temperature (rectal) set point of 36.8 degrees C. The forced-air-warmer group (n = 28) received routine warming therapy using upper body forced-air warming system (set on high). The ambient temperature in the operating room was maintained constant at approximately 20 degrees C. Rectal, distal esophageal, tympanic, forearm, and fingertip temperatures were recorded perioperatively and during 2 h after surgery. Extubated patients in both groups were assessed postoperatively for shivering, use of additional warming devices, and subjective thermal comfort.
The mean rectal and esophageal temperatures at incision, 1 h after incision, at skin closure, and immediately postoperatively were significantly higher (0.4-0.6 degrees C) in the group that received water-garment warming when compared with the group that received upper body forced-air warming. The calculated 95% confidence intervals for the above differences in core temperatures were 0.7-0.1, 0.8-0.2, 0.8-0.2, and 0.9-0.1, retrospectively. In addition, 14 and 7% of patients in the control upper body forced-air group remained hypothermic (< 35.5 degrees C) 1 and 2 h after surgery, respectively. No core temperature less than 35.5 degrees C was observed perioperatively in any of the patients from the water-garment group. A similar frequency of the thermal stress events (shivering, use of additional warming devices, subjective thermal discomfort) was observed after extubation in both groups during the 2 h after surgery.
The investigated water warming system, by virtue of its ability to deliver heat to a greater percentage of the body, results in better maintenance of intraoperative normothermia that does forced-air warming applied only to the upper extremities, as is common practice.
Perioperative hypothermia is common in high-risk surgical patients. Anaesthesia impairs central thermoregulation, allowing re-distribution of body heat. Cool ambient temperatures and high-volume fluid administration accelerate loss of heat to the environment. Randomized, controlled trials have proven that mild hypothermia increases the incidence of wound infection and prolongs hospitalization, increases the incidence of morbid cardiac events and ventricular tachycardia, and impairs coagulation. Other complications include enhanced anaesthetic drugs effects, prolonged recovery room stays, shivering, and impaired immune function. There is compelling animal evidence for cerebral protection by mild hypothermia. However, evidence for protection in surgical patients is not yet available. The most effective means of preventing perioperative hypothermia is active pre-warming. High ambient temperatures, warmed intravenous fluids and active cutaneous warming are useful intra-operatively, while active cutaneous warming and intravenous pethidine abolish post-operative shivering. Proper thermal management may reduce complications and improve the outcome in high-risk surgical patients.
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.