Kristi Downey’s research while affiliated with University of Toronto and other places

The purpose of our study was to determine the minimum effective dose of oxytocin maintenance infusion required to maintain adequate uterine tone in 90% of patients (ED90) after administration of the initial bolus at elective Cesarean delivery (CD) under spinal anesthesia. We conducted a prospective, double-blind dose-finding study with biased coin up-down design. Immediately after delivery, a 1-IU oxytocin bolus was administered, followed by a maintenance infusion. The obstetrician assessed the uterine tone by palpation as satisfactory or unsatisfactory. In case of unsatisfactory response, the dose for the next patient was increased by 2 IU·hr−1. For satisfactory response, the dose for the next patient was either decreased by 2 IU·hr−1 with a probability of 1/9, or remained unchanged. The primary outcome was a satisfactory uterine tone from five minutes after delivery until discharge from postanesthesia care unit. The secondary outcomes were blood loss, need for additional uterotonics, and side effects. We analyzed data for 40 patients. The ED90 of oxytocin maintenance infusion was 4.5 IU·hr−1 (95% confidence interval, 3.3 to 5.5) based on the isotonic regression estimator. The median [interquartile range] blood loss was 861 [553–1,181] mL; 18% received additional uterotonics, and 38% developed hypotension post delivery. Based on the results of this dose-finding study, we recommend a maintenance infusion rate of 4.5 IU·hr−1 following an oxytocin bolus of 1 IU for adequate uterine tone in pregnant patients undergoing elective CDs. This infusion rate is four-fold lower than that required without an initial bolus. ClinicalTrials.gov (NCT04946006); first submitted 25 June 2021.

BACKGROUND There is a paucity of literature examining the differences between patient-reported outcome measures after planned and unplanned cesarean delivery using a validated quality of recovery tool. The Obstetric Quality of Recovery-10 (ObsQoR-10) scoring tool has been validated to quantify functional recovery after cesarean delivery. We aimed to use the ObsQoR-10 to compare the postoperative recovery characteristics of patients undergoing planned and unplanned cesarean deliveries. METHODS We conducted a prospective single-center observational study. Patients undergoing planned and unplanned cesarean deliveries under neuraxial anesthesia were asked to complete the ObsQoR-10 questionnaire 24 hours, 48 hours, and 1 week postpartum. We collected information on total in-hospital postoperative opioid consumption and patients´ perception of readiness for discharge at 24 and 48 hours postpartum. Additionally, patient characteristics were collected to assess their correlation with our findings. RESULTS We included 112 patients (56 in each group). No statistical differences in ObsQoR-10 scores at 24 hours, 48 hours, and 1 week postpartum were observed between the planned and unplanned cesarean deliveries. Additionally, there was no difference between the groups in patients’ perception of readiness for hospital discharge at 24 and 48 hours and opioid consumption in the first 2 days after surgery. Most patients in both groups did not think they would be ready for discharge at 24 hours postpartum. Analysis of the individual components of ObsQoR-10 at 24 hours showed a difference in the responses assessing the severity of shivering (higher in unplanned cesarean deliveries) and the ability to look after personal hygiene (lower in unplanned cesarean deliveries). CONCLUSIONS As assessed by the ObsQoR-10, no significant difference in the quality of recovery was observed between patients undergoing planned and unplanned cesarean delivery.

A zone of differential block to cold has been recently documented during labour epidural analgesia, with an upper sensory block level (USBL) and a lower sensory block level (LSBL). We aimed to determine the correlation between USBL and LSBL to cold and pinprick and sensory block level to light touch during labour epidural analgesia. We conducted a prospective observational study in patients requesting labour epidural analgesia. We placed an epidural catheter at L2/L3 or L3/L4, followed by a programmed intermittent epidural bolus plus patient-controlled epidural analgesia regimen. We assessed the sensory block levels 140 min after administering the loading dose. The primary outcomes were the USBL and LSBL to cold and pinprick and the sensory block level to light touch. We studied 30 patients. The median [interquartile range (IQR)] USBL and LSBL to ice were T7 [T7–T6] and T9 [T10–T8], respectively. The median [IQR] USBL and LSBL to pinprick were T8 [T10–T6] and T10 [T12–T10], respectively. There was a strong correlation between USBL to ice and pinprick (Spearman correlation coefficient, 0.57) and between LSBL to ice and pinprick (Spearman correlation coefficient, 0.52). There was no significant correlation between sensory block level to light touch and either USBL or LSBL to ice or pinprick. We observed two sensory block levels to ice and pinprick. Further studies are required to understand if one modality—cold or pinprick—is superior to the other in assessing sensory block levels in this context. Light touch is unreliable as a modality of sensory block assessment during labour epidural analgesia. ClinicalTrials.gov (NCT05187962); registered 12 January 2022.

Background and Aims Pregnant people with obesity class 3 are thought to be at higher risk of adverse respiratory-events. There is little information in the literature on the incidence and severity of obesity-related postpartum respiratory depression. Our institution’s current standard of practice is to consider maintaining patients with BMI>50 who have received long-acting neuraxial opioids following cesarean delivery(CD) in the Labour and Delivery Unit for respiratory monitoring. This represents a significant workload for the system. This study aimed to determine the incidence of respiratory complications in this subset of patients. Methods We reviewed medical records of patients with BMI>40 who underwent CD and received long-acting neuraxial opioids between January 2015- December 2022. Patients were divided into three groups according to their BMI: 40-49, 50-59, and >60. Clinically significant respiratory-events (see the definition in table 1) within the first 24 hours post-CD were compared. Results Demographics, patient characteristics, comorbidities, and respiratory events are presented in table 1. No severe respiratory events were observed in any of the groups from 497 patients (figure 1). Three moderate respiratory-events were observed, one in each group. Thirteen, 9 and 5 mild respiratory-events were observed in BMI 40-49, 50-59, and >60groups, respectively.View this table: • View inline • View popup • Download powerpoint Abstract EP197 Table 1 Patient characteristics and incidence of postoperative respiratory events • Download figure • Open in new tab • Download powerpoint Abstract EP197 Figure 1 Comparison of the respiratory events (%) per study groups Conclusions Our results suggest that there is no association between BMI and severe respiratory-events after CD under neuraxial anesthesia and the use of long- acting neuraxial opioids. Extended admission to a high-acuity setting may not be necessary for the majority of these patients. In addition to BMI, the presence of patient comorbidities and physician assessment may prove valuable in determining the necessity for admission.Initial Ethics Commity Approval Letter 22-0202-C

Background: Multiple pregnancy is associated with higher risk of uterine atony, postpartum hemorrhage (PPH), blood transfusion, hysterectomy, and death. The optimal dose of oxytocin at cesarean delivery in people with twin pregnancy is unknown. We sought to determine the effective bolus dose of oxytocin required to initiate adequate uterine tone in 90% of people (ED90) with twin pregnancy undergoing elective cesarean delivery. Our hypothesis was that the dose of oxytocin would be higher than 0.5 international units (IU) but lower than 5 IU. Methods: A double-blind dose-finding study using the biased coin up-down method was undertaken in people with twin pregnancy ≥36 weeks gestational age undergoing elective cesarean delivery under neuraxial anesthesia. Those with additional risk factors for PPH, apart from twin pregnancy, were excluded. Oxytocin was administered as an intravenous bolus over 1 minute on delivery of the second fetus. The first patient received 0.5 IU, and subsequent oxytocin doses were administered according to a sequential allocation scheme. The actual doses administered were 0.5, 1, 2, 3, 4, and 5 IU of oxytocin. The primary outcome was the response defined as the satisfactory uterine tone at 2 minutes after completion of administration of the oxytocin bolus, as assessed by the operating obstetrician. Secondary outcomes included need for rescue uterotonic drugs, adverse effects, and estimated blood loss. The ED90 was estimated using the Dixon-Mood and the isotonic regression methods. Results: Thirty patients were included in study. The estimated ED90 of oxytocin was 4.38 IU (95% confidence interval [CI], 3.68-4.86 IU) and 3.41 IU (95% CI, 2.83-3.98 IU) by the isotonic regression and Dixon-Mood methods, respectively. Seven patients had inadequate tone at the 2-minute evaluation point and required rescue uterotonic drugs. The median (interquartile range [IQR]) estimated blood loss was 1031 mL (732-1462 mL) calculated by the change in 24-hour hematocrit. Incidence of hypotension after oxytocin administration was 27%, nausea 30%, and vomiting 17%. Conclusions: Our results demonstrated that people with twin pregnancy require a much higher dose of oxytocin than those with singleton pregnancies. We recommended people with twin pregnancies should receive an initial 5 IU bolus over at least 1 minute when undergoing elective cesarean delivery under neuraxial anesthesia.

Purpose: The preferred neuraxial anesthetic technique for patients with class 3 obesity undergoing elective Cesarean delivery is still under debate. We aimed to describe the anesthetic technique used in our tertiary institution across body mass index (BMI) groups and different surgical incisions. Method: In this historical cohort study, we reviewed medical records of patients with a BMI ≥ 40 kg·m-2 undergoing elective Cesarean delivery between July 2014 and December 2020. We collected data on patient characteristics, anesthetic and surgical technique, and procedural times. For data analysis, we stratified patients by BMI into three different groups: 40.0-49.9 kg·m-2, 50.0-59.9 kg·m-2, and ≥ 60.0 kg·m-2. Results: We included 396 deliveries, distributed as follows: 258 with a BMI 40.0-49.9 kg·m-2, 112 with a BMI 50.0-59.9 kg·m-2, and 26 with a BMI ≥ 60.0 kg·m-2. For patients with a BMI 40.0-49.9 kg·m-2, the anesthetic technique of first choice was predominantly spinal anesthesia (71%), whereas for those with a BMI ≥ 60.0 kg·m-2, spinal anesthesia was never used as the anesthetic of first choice. With regard to the surgical incision, spinal anesthesia was almost exclusively used for patients undergoing Pfannenstiel incision and was rarely used for a higher supra- or infraumbilical transverse or midline incision. The overall incidence of general anesthesia was low (7/396, 1.8%). Anesthetic time, surgical time, and operating room time increased almost twofold in patients with a BMI ≥ 60.0 kg·m-2 compared with those with a BMI of 40.0-49.9 kg·m-2. Conclusion: Neuraxial anesthesia was successfully used in approximately 98% of patients with class 3 obesity undergoing elective Cesarean delivery. The choice of regional anesthesia technique varied with increasing BMI and with the planned surgical incision. Procedural times increased with increasing BMI. This information should prove useful for comparing anesthetic choices and outcomes in this challenging population.

PurposeIn the context of a programmed intermittent epidural bolus (PIEB) regimen for labour analgesia, one can identify an upper sensory block level (USBL), defined as the highest dermatome with any altered sensation to cold, and a lower sensory block level (LSBL), defined as the highest dermatome with complete sensory block to cold. This study investigated whether and how these sensory block levels vary within PIEB cycles.Methods We enrolled patients requesting epidural analgesia. An epidural catheter was placed at L2/L3 or L3/L4. A test dose of 3 mL of bupivacaine 0.125% with fentanyl 3.3 µg·mL−1 was administered, followed by 12 mL of the same solution as the loading dose. A PIEB plus patient-controlled epidural analgesia (PCEA) regimen was initiated 40 min after the loading dose, with bupivacaine 0.0625% with fentanyl 2 µg·mL−1: PIEB 10 mL, PIEB interval 40 min, PCEA 5 mL, lockout interval 10 min, maximum hourly 30 mL. As per institutional protocol, sensory block levels to ice were assessed 20 min after the loading dose and then hourly. Patients included in the study underwent eight extra assessments: immediately before the second and fourth PIEB and 10, 20, and 30 min after the second and third PIEB.ResultsWe studied 30 patients. The USBL and LSBL achieved their peak value 100 min after the loading dose. The median [interquartile range] USBL was T8 [T9–T7] and T6 [T7–T4] 20 and 100 min after the loading dose, respectively; LSBL was T10 [T11–T6] and T8 [T9–T6], respectively. There was no significant variation in USBL or LSBL within the PIEB cycle between the second and the third or the third and the fourth PIEB.Conclusion Once peak sensory block levels are established, there is no significant variation in the USBL and LSBL within the PIEB cycles.Study registrationwww.clinicaltrials.gov (NCT04716660); registered 21 January 2021.

Background Ultrasound is commonly used to facilitate epidural catheter placement. However, data are lacking regarding its potential to confirm its position in the epidural space. Our aim was to visualize flow in the epidural space of patients receiving epidural analgesia for labor using color flow Doppler ultrasound. Methods We conducted a prospective observational cohort study that included patients who had delivered vaginally under epidural analgesia. We used a 5–2 mHz curvilinear probe in a left and right paramedian longitudinal oblique view to visualize the anterior and posterior complex at the interspace of epidural catheter insertion, one and two interspaces above and below. At each window, the color flow Doppler function was used to visualize flow within the epidural space on injection of normal saline (1 mL). If no flow was visualized at any interspace, one assessment at the level of insertion was repeated with a 1 mL air/saline mixture. We studied a convenience sample size of 40 patients. Results We visualized flow in the epidural space in all 40 patients. Flow was visualized on injection of 1 mL of saline in 37/40 patients (93%). In the remaining 3/40 patients (7%), flow was visualized with an air/saline mixture. Flow on injection of saline was visualized only at the interspace of insertion in 26/37 patients (70%), at the interspace of insertion and one interspace above in 10/37 (27%), or only at one interspace above in 1/37 (3%). Flow was visualized only on the left or on the right paramedian view in 19/37 patients (51%), despite a symmetrical sensory block in all patients. Conclusion Color flow Doppler ultrasound is a feasible and fast way to determine flow in the epidural space in the obstetric population. Its potential clinical uses are confirmation of the epidural catheter position after placement, as well as troubleshooting of unsatisfactory epidural analgesia. Interestingly, our results suggest that epidural catheters predominantly remain at the interspace of insertion. Trial registration number NCT05126745 .