Impact of intraoperative hypothermia on the recovery period of anesthesia in elderly patients undergoing abdominal surgery.

BACKGROUND: This study aimed to investigate the impact of intraoperative hypothermia on the recovery period of anesthesia in elderly patients undergoing abdominal surgery. METHODS: A prospective observational study was conducted based on inclusion and exclusion criteria. A total of 384 elderly patients undergoing abdominal surgery under general anesthesia were enrolled in a grade A tertiary hospital in Chengdu, Sichuan Province from October 2021 and October 2022. After anesthesia induction, inflatable warming blankets were routinely used for active heat preservation, and nasopharyngeal temperature was monitored to observe the occurrence of intraoperative hypothermia. Patients were divided into hypothermia group and nonhypothermia group according to whether hypothermia occurred during the operation. Anesthesia recovery time and the incidence of adverse events or unwanted events during anesthesia recovery between the two groups were compared. RESULTS: The numbers (percentage) of 384 patients who underwent abdominal surgery developed intraoperative hypothermia occurred in 240 (62.5%) patients, all of whom had mild hypothermia. There were statistically significant differences between mild hypothermia after active warming and nonhypothermia in the occurrence of shivering (χ2 = 5.197, P = 0.023) and anesthesia recovery time (Z = -2.269, P = 0.02) in elderly patients undergoing abdominal surgery during anesthesia recovery, and there were no statistically significant differences in hypoxemia, nausea or vomiting, hypertension, hypokalemia, hypocalcemia, analgesic drug use,postoperative wound infection or postoperative hospitalization days. CONCLUSIONS: The incidence of intraoperative mild hypothermia after active warming was high in elderly patients who underwent abdominal surgery. Mild hypothermia increased the incidence of shivering and prolonged anesthesia recovery time in elderly patients undergoing abdominal surgery.

The Effect of Clonidine Premedication on Hemodynamic Changes Following Tracheal Intubation and Co2 Gas Insufflation and Postoperative Shivering In Patients Undergoing Laparoscopic Cholecystectomy; a Randomized Clinical Trial.

BACKGROUND: Laparoscopic cholecystectomy is a proper treatment for cholecystitis but the Carbon dioxide gas which is used in surgery stimulates the sympathetic system and causes hemodynamic changes and postoperative shivering in patients undergoing operations. This study was conducted to evaluate the effects of clonidine on reducing hemodynamic changes during tracheal intubation and Carbon dioxide gas insufflation and postoperative shivering in patients undergoing laparoscopic cholecystectomy. MATERIAL AND METHODS: This prospective, randomized, triple-blind clinical trial was conducted on 60 patients between the 18-70 years-old age group, who were candidates of laparoscopic cholecystectomy surgery. The patients randomized into two groups (30 patients received 150 µg oral clonidine) and 30 patients received 100 mg oral Vitamin C). Heart rate and mean arterial pressure of patients were recorded before anesthesia, before and after laryngoscopy, before and after Carbon dioxide gas insufflation. Data were analyzed using Chi-2, student t-test, and analysis of variance by repeated measure considering at a significant level less than 0.05. RESULTS: The findings of this study showed that both heart rate and mean arterial pressure in clonidine group after tracheal intubation and Carbon dioxide gas insufflation were lower than patients in the placebo group, but there was not any statistically significant difference between the two groups (p>0.05) and also postoperative shivering was not different in groups. There was no significant statistical difference in postoperative shivering between the two groups (p>0.05). CONCLUSION: Using 150 µg oral clonidine as a cheap and affordable premedication in patients undergoing laparoscopic cholecystectomy improves hemodynamic stability during operation.

The Effect of Granisetron, Ondansetron, and Meperidine in Preventing Postoperative Shivering: Controlled Clinical Trial.

BACKGROUND: Recently, use of HT35 receptor antagonists to prevent postoperative shivering has attracted a great deal of attention. This study was conducted with the aim of investigating the effectiveness of granisetron as an HT35 antagonist when compared with ondansetron and meperidine in preventing postoperative shivering. MATERIAL AND METHODS: In this triple blind random clinical trial study, 90 patients 18-50 years of age with ASA Class I and II undergoing general anesthesia were randomly assigned into one of the three drug groups: O (4-mg ondansetron), G (40 µg/kg of granisetron), and P (25 mg meperidine), immediately before induction of anesthesia. After anesthesia induction, at the end of the surgery, after the entrance and after leaving the recovery state, central temperature, peripheral temperature, heart rate, systolic blood pressure, diastolic blood pressure, and shivering were measured and documented. Two-tailed P < 0.05 was considered significant. RESULTS: In the meperidine, ondansetron, and granisetron groups, 4 (13.3%), 3 (10%), and 10 (33.3%) of patients experienced shivering during recovery, where the difference between the ondansetron and granisetron groups was significant (p-value=0.02). The variations in the mean arterial pressure during the investigation stages only in the ondansetron group were not significant (p>0.05). At the beginning of recovery, the reduction of peripheral temperature significantly was lower in the ondansetron group (p<0.05), while reduction of the central temperature was significantly (p<0.05) higher in the granisetron group. By the end of the recovery, the variations in the peripheral temperature across the three groups were consistent with the changes at the beginning of recovery, but variations of the central temperature across the three groups was not significantly diverse. CONCLUSION: Granisetron was not found to be much effective in preventing postoperative shivering. Ondansetron and meperidine were equally effective in preventing postoperative shivering. Ondansetron also causes less hemodynamic changes compared to other drugs, while granisetron is more effective in terms of preventing nausea and vomiting.

Non-pharmacological treatments for shivering post neuraxial anaesthesia for caesarean section: a scoping review.

BACKGROUND: Shivering occurs more frequently for women having caesarean section under neuraxial anaesthesia compared to other patient groups and causes an increase in pain and interrupts bonding with her newborn. AIM: This study aimed to report the evidence on non-pharmacological methods to treat shivering, defined as uncontrollable shaking, because of being cold, frightened, or excited, post neuraxial anaesthesia; the use of local anaesthesia inserted around the nerves of the central nervous system such as spinal anaesthesia and epidural in women having a caesarean section. METHODS: A scoping review was conducted using six electronic health databases that were searched with no restrictions placed on language, date, or study type. FINDINGS: Of the 1399 studies identified, following screenings only one study was deemed suitable for inclusion. The study, a randomised controlled trial, compared forced air warming blankets (intervention) with the usual care of warmed cotton blankets (control) and its impact on maternal and newborn outcomes. The only statistically significant difference found was the perceived thermal comfort of the mother. DISCUSSION: Non-pharmacological treatments for shivering are underrepresented in the literature; only one study identified where the impact of active warming was compared to warmed cotton blankets (usual care) for the measures of: oral temperature; degree of shivering; and thermal comfort pain scores. There was a decline in temperature in both groups at odds with some women reporting feeling too warm such that they asked for the active warmer to be turned down. CONCLUSION: Social engagement strategies are interventions that send a signal of safety to the nervous system leading to a sense of calm and wellbeing and have biological plausibility and warrant evaluation. Recommendations for further research: design a robust study to test the effectiveness of social engagement strategies on shivering for women having caesarean section under neuraxial anaesthesia.

Neural circuits of long-term thermoregulatory adaptations to cold temperatures and metabolic demands.

The mammalian brain controls heat generation and heat loss mechanisms that regulate body temperature and energy metabolism. Thermoeffectors include brown adipose tissue, cutaneous blood flow and skeletal muscle, and metabolic energy sources include white adipose tissue. Neural and metabolic pathways modulating the activity and functional plasticity of these mechanisms contribute not only to the optimization of function during acute challenges, such as ambient temperature changes, infection and stress, but also to longitudinal adaptations to environmental and internal changes. Exposure of humans to repeated and seasonal cold ambient conditions leads to adaptations in thermoeffectors such as habituation of cutaneous vasoconstriction and shivering. In animals that undergo hibernation and torpor, neurally regulated metabolic and thermoregulatory adaptations enable survival during periods of significant reduction in metabolic rate. In addition, changes in diet can activate accessory neural pathways that alter thermoeffector activity. This knowledge may be harnessed for therapeutic purposes, including treatments for obesity and improved means of therapeutic hypothermia.

Preventing hypothermia in pediatric neurosurgery in Africa-A randomized controlled non-inferiority trial of insulation versus active warming.

PURPOSE: The objective of this study was to compare the efficacy of a low-cost heat-preserving method in preventing intraoperative hypothermia with that of forced-air warming in a resource-limited setting. METHODS: In this randomized controlled non-inferiority trial, we recruited children younger than 12 years scheduled for cranial neurosurgery in a large East-African hospital. Patients were block-randomized by age to intraoperative warming measures using Hibler's method (intervention) or warm air (comparator). Hibler's group patients were circumferentially wrapped in transparent plastic sheeting (providing a vapor-trap) over a layer of cotton blankets, then laid on an insulating foam mattress. Warm air group patients were treated with forced-air convection via an underlying Snuggle Warm™ Pediatric Full Body mattress. Allocated warming measures were initiated in the operating theatre and discontinued upon anesthesia emergence. Perioperative temperatures were measured using noninvasive forehead probes (SpotOn™). The primary outcome was incidence of hypothermia (core temperature < 36.0° for longer than 5 min). Our null hypothesis was that Hibler's method is inferior in efficacy to the warm air method by a margin exceeding 20%. Among secondary outcomes were duration of hypothermia as proportion of surgical duration, incidence of postoperative shivering and rescue measure requirements. RESULTS: We analyzed data for 77 participants (Hibler's = 38; warm air = 39). There was no significant difference between the Hibler's and warm air arms of the study in the primary outcome of incidence of hypothermia (59.0% vs. 60.5% respectively; OR 1.07; 95% CI 0.43-2.65; p = .890). However, the risk difference (1.55%; 95% CI -0.20 to -0.24) exceeded the 0.2 margin and non-inferiority could not be declared. There was considerable need for rescue measures in both groups (71.1 0% vs. 69.2%; OR 1.09; 95% CI 0.41-2.90; p = .861). There was no statistically significant difference between groups for any prespecified secondary outcome. CONCLUSION: Although perioperative core temperatures were not significantly different, we could not declare an inexpensive heat-preserving method non-inferior to warm air convection in preventing intraoperative hypothermia in children undergoing anesthesia for cranial neurosurgery in a resource-limited setting. The extensive need for rescue measures may have masked important differences. TRIAL REGISTRATION: US National Institutes of Health Clinicaltrials.gov database (ID no. NCT02975817).

The Effect of Warmed Serum on Shivering and Recovery Period of Patients Under General and Spinal Anesthesia: A Randomized Clinical Trial.

PURPOSE: Postoperative hypothermia followed by shivering is a common phenomenon in patients undergoing surgery under anesthesia, and should be prevented and treated in postoperative patient care units. This study was conducted to investigate the effect of warmed serum injection on postoperative shivering and recovery period of patients operated under general and spinal anesthesia. DESIGN: In this clinical trial, patients to be operated on under general and spinal anesthesia were randomly assigned into two groups of test and control. In the test group, patients received warmed intravenous fluids and blood products. All patients were monitored to record vital signs, incidences of hypothermia and shivering, and recovery period. METHODS: The collected data were analyzed with repeated measures analysis of variance to detect significant differences between groups and significant changes within groups over time. FINDINGS: The incidence of nausea, vomiting, and shivering in the intervention and control groups was (4.7%, 42%), (2.8%, 16.8%), and (6.6%, 43%), respectively. Patients in the intervention group had higher body temperature than the control group (<0.001). Also, patients under spinal anesthesia had higher body temperature than patients under general anesthesia (<0.001). Blood pressure reduction was also significantly higher in the control group than in the intervention group. The patients who received warm intravenous serum, and especially those who had received spinal anesthesia spent less time in the recovery room (<0.001). CONCLUSIONS: The use of warmed intravenous serum increased the patients' core temperature, reduced their postoperative shivering, and shortened their recovery period. Considering the potential risks associated with hypothermia, using such methods for hypothermia prevention can be highly effective in preventing shivering and prolongation of the recovery period and other potential complications. Anesthesia specialists and technicians are therefore encouraged to use this method as a preventive measure.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 4: evolution, thermal adaptation and unsupported theories of thermoregulation.

This review is the final contribution to a four-part, historical series on human exercise physiology in thermally stressful conditions. The series opened with reminders of the principles governing heat exchange and an overview of our contemporary understanding of thermoregulation (Part 1). We then reviewed the development of physiological measurements (Part 2) used to reveal the autonomic processes at work during heat and cold stresses. Next, we re-examined thermal-stress tolerance and intolerance, and critiqued the indices of thermal stress and strain (Part 3). Herein, we describe the evolutionary steps that endowed humans with a unique potential to tolerate endurance activity in the heat, and we examine how those attributes can be enhanced during thermal adaptation. The first of our ancestors to qualify as an athlete was Homo erectus, who were hairless, sweating specialists with eccrine sweat glands covering almost their entire body surface. Homo sapiens were skilful behavioural thermoregulators, which preserved their resource-wasteful, autonomic thermoeffectors (shivering and sweating) for more stressful encounters. Following emigration, they regularly experienced heat and cold stress, to which they acclimatised and developed less powerful (habituated) effector responses when those stresses were re-encountered. We critique hypotheses that linked thermoregulatory differences to ancestry. By exploring short-term heat and cold acclimation, we reveal sweat hypersecretion and powerful shivering to be protective, transitional stages en route to more complete thermal adaptation (habituation). To conclude this historical series, we examine some of the concepts and hypotheses of thermoregulation during exercise that did not withstand the tests of time.

Effects of ketamine, granisetron and dexmedetomidine on postoperative shivering and hemodynamic changes after general anesthesia: a double-blind randomized clinical trial.

Postoperative shivering is one of the most common complications of surgeries. The current research compared the effects of ketamine, granisetron, and dexmedetomidine on reducing postoperative shivering after general anesthesia. This double-blind clinical trial enrolled 148 patients (39.08 ± 5.99 years old) who had been admitted to Vali-Asr Hospital of Arak, Iran in 2019-2021. The study drugs, including dexmedetomidine, ketamine, granisetron and normal saline, were administered in corresponding groups 30 minutes before the end of surgery. The results showed that dexmedetomidine reduced mean arterial pressure and heart rate in patients. The lowest incidence of shivering was observed in the dexmedetomidine group and it increased the duration of recovery. Overall, dexmedetomidine is recommended to reduce postoperative shivering after general anesthesia, but the increase in duration of recovery should be considered.

Effects of a forced-air warming system and warmed intravenous fluids on hemodynamic parameters, shivering, and time to awakening in elderly patients undergoing open cardiac surgery.

Background: As one of the most common postoperative complications, hypothermia is the main cause of numerous problems during treatment, especially in elderly patients with decreased cardiac reserves. Objectives: The aim of the present study was to compare the effects of forced-air warming system (FAWS), warmed intravenous fluids (WIVFs) and routine method on hemodynamic parameters, arterial blood gases (ABGs), shivering, and time to awakening in elderly patients undergoing open cardiac surgery (OCS). Methods: This clinical randomized controlled trial was conducted on 94 elderly patients who underwent OCS at Ayatollah Rouhani Hospital, Babol, Iran. They were divided into three groups, namely FAWS (n=31), WIVFs (n=31) and routine rewarming method (RRWM, with a blanket) (n=32). The data were then recorded in a checklist. Descriptive and inferential statistics were performed using SPSS 26 at a significance level of less than 0.05. Results: The findings demonstrated that the degree of hypothermia had a significant decreasing trend in the groups receiving FAWS and WIVFs (P=0.002). Additionally, increased respiratory rate (P=0.013), higher bicarbonate (HCO3-) levels on arrival up to 4 hours after surgery (P=0.045), reduced lactate level (P=0.005), normal base excess (BE) and accelerated time to awakening (P=0.004) were observed in patients receiving FAWS. There was no significant difference in the study groups regarding shivering. Conclusion: The results revealed that FAWS could mitigate the degree of hypothermia, increase body temperature and decrease the postoperative serum lactate levels. Moreover, BE as one of the most important parameters for ABGs, could remain at a normal level. Besides, the use of FAWS could lead to early awakening, and thus facilitate weaning and extubation of these patients.

Examining the efficacy of intravenous ibuprofen and meperidine for preventing post-operative shivering after laparoscopic cholecystectomy with general anesthesia.

Postoperative shivering is a common complication that can lead to increased postoperative complications. This study aimed to compare the effectiveness of intravenous ibuprofen and meperidine in preventing shivering following laparoscopic cholecystectomy. A total of 120 patients, aged 20-70 and classified as ASA I-II, were enrolled in this triple-blind clinical trial. The participants were randomly assigned to one of three groups: ibuprofen (800mg IV), meperidine (30 mg), or placebo (normal saline 2 ml), administered 30 minutes before the end of surgery. The occurrence of postoperative shivering was assessed and recorded at regular intervals (0, 5, 10, 15, 30, and 60 minutes after surgery). Additionally, postoperative pain levels were measured using a visual analog scale (VAS), sedation levels were evaluated using the Ramsay Sedation Scale (RSS), and the incidence of postoperative nausea and vomiting was documented. The prevalence and severity of postoperative shivering were not statistically significant between groups. The VAS was significantly lower in the meperidine group than the ibuprofen group throughout the study (p <0.001). The VAS was significantly lower in the ibuprofen group than the placebo group at 0 and 15 minutes after surgery. Although the incidence of nausea was slightly higher in the meperidine group, the difference was not statistically significant (p=0.75). Sedation scores were consistently lower in the ibuprofen group and higher in the meperidine group compared to the other groups (p<0.0001) The meperidine group had a significantly higher sedation score indicative of deep sleepiness (score of 4) than the other groups. Intravenous ibuprofen demonstrated comparable efficacy to meperidine in controlling shivering. Additionally, the incidence of nausea, vomiting, and sleepiness was lower in the intravenous ibuprofen group, suggesting it is a potential alternative to meperidine.

Effect of early oral carbohydrate intake after elective Cesarean delivery on maternal body temperature and satisfaction: a randomized controlled trial.

PURPOSE: Although the Enhanced Recovery After Cesarean Delivery (ERAC) consensus statement provides recommendations for early postoperative drinking and eating, evidence from high-quality clinical research directly addressing parturients is sparse. Our objective was to assess if early oral carbohydrate intake after elective Cesarean delivery improves maternal recovery. METHODS: In this randomized controlled trial, we enrolled parturients undergoing elective Cesarean delivery under spinal anesthesia with tympanic membrane temperatures ≤ 36.5 °C immediately upon arrival at the postanesthesia care unit. Parturients were randomized to either 100 mL of oral complex carbohydrate intake (group CC) or 10 mL of water (group C). The primary outcome was maternal tympanic membrane temperature. Other outcomes included maternal thermal comfort score, degree of shivering, satisfaction, degree of thirst and hunger, and gastric emptying assessed by ultrasonography. RESULTS: We included 90 participants in the final analysis. The mean (standard deviation [SD]) maternal body temperature at 120 min after ingestion was 36.7 (0.3) °C in group CC and 36.6 (0.3) °C in group C (difference in means, 0.14 °C; 95% confidence interval, 0.02 to 0.26; P = 0.02). Furthermore, using repeated measure models, the linear trends of temperature changes over time between groups CC and C were significantly different (P = 0.04). The thermal comfort scores at 120 min after ingestion were higher in group CC than in group C (P = 0.02), and the linear trends of shivering score changes over time between groups CC and C also were different (P = 0.003). The mean (SD) visual analogue scale scores for maternal satisfaction were 84 (13) mm in group CC and 47 (20) mm in group C (P < 0.001). Nevertheless, at 90 and 120 min after ingestion, there were no differences between the two groups in the number of participants with a gastric antrum cross-sectional area > 10.3 cm2. CONCLUSIONS: Early oral carbohydrate intake after Cesarean delivery helped to restore maternal body temperature postoperatively and improve maternal satisfaction. Nevertheless, the clinical importance of these finding is unclear, given that most of the differences were small. In addition, there was no delay in maternal gastric emptying after consumption of a complex carbohydrate beverage in the early post-Cesarean period. STUDY REGISTRATION: www.chictr.org.cn (ChiCTR2000031085); first submitted 13 November 2022.

RéSUMé: OBJECTIF: Bien que la déclaration de consensus sur la Récupération améliorée après un accouchement par césarienne (ERAC/RAAC) fournisse des recommandations pour l'ingestion postopératoire précoce de liquides et d'aliments, les données probantes issues de recherches cliniques de haute qualité portant directement sur les personnes parturientes sont rares. Notre objectif était d'évaluer si l'ingestion précoce de glucides par voie orale après une césarienne programmée améliorait la récupération maternelle. MéTHODE: Dans cette étude randomisée contrôlée, nous avons recruté des personnes parturientes bénéficiant d'une césarienne programmée sous rachianesthésie avec une température tympanique ≤ 36,5 °C immédiatement après leur arrivée en salle de réveil. Les personnes parturientes ont été randomisées à recevoir soit 100 mL de glucides complexes par voie orale (groupe GC) ou 10 mL d'eau (groupe C). Le critère d'évaluation principal était la température tympanique maternelle. Les autres critères d'évaluation comprenaient, chez la mère, le score de confort thermique, le degré de frissons, la satisfaction, le degré de soif et de faim, et la vidange gastrique évaluée par échographie. RéSULTATS: Nous avons inclus 90 personnes dans l'analyse finale. La température corporelle maternelle moyenne (écart type [ET]) à 120 minutes après l'ingestion était de 36,7 (0,3) °C dans le groupe GC et de 36,6 (0,3) °C dans le groupe C (différence dans les moyennes, 0,14 °C; intervalle de confiance à 95 %, 0,02 à 0,26; P = 0,02). De plus, à l'aide de modèles à mesures répétées, les tendances linéaires des changements de température au fil du temps entre les groupes GC et C étaient significativement différentes (P = 0,04). Les scores de confort thermique à 120 minutes après l'ingestion étaient plus élevés dans le groupe GC que dans le groupe C (P = 0,02), et les tendances linéaires des changements de score de frissons au fil du temps entre les groupes GC et C étaient également différentes (P = 0,003). Les scores moyens (ET) de l'échelle visuelle analogique concernant la satisfaction maternelle étaient de 84 (13) mm dans le groupe GC et de 47 (20) mm dans le groupe C (P < 0,001). Néanmoins, à 90 et 120 minutes après l'ingestion, il n'y avait aucune différence entre les deux groupes dans le nombre de personnes présentant une section transversale de l'antre gastrique > 10,3 cm2. CONCLUSION: L'ingestion précoce de glucides par voie orale après un accouchement par césarienne a aidé à rétablir la température corporelle maternelle postopératoire et à améliorer la satisfaction maternelle. Néanmoins, l'importance clinique de ces résultats n'est pas claire, étant donné que la plupart des différences étaient faibles. De plus, il n'y avait pas de retard dans la vidange gastrique maternelle après la consommation d'une boisson glucidique complexe au début de la période post-césarienne. ENREGISTREMENT DE L'éTUDE: www.chictr.org.cn (ChiCTR2000031085); soumis pour la première fois le 13 novembre 2022.

Perioperative administration of dexamethasone to prevent postoperative shivering: a systematic review and meta-analysis of randomized controlled trials.

OBJECTIVE: To evaluate the perioperative administration of dexamethasone to prevent postoperative shivering. METHODS: We searched PubMed, Embase, Google Scholar, Web of Science, and Cochrane Library for relevant studies of the administration of dexamethasone to prevent postoperative shivering published through 31 May 2023. The primary outcome was the incidence of postoperative shivering. Secondary outcomes comprised the incidence of postoperative nausea, vomiting, and postoperative nausea and vomiting (PONV). RevMan 5.3 software was used for the data analysis. RESULTS: We included 12 randomized controlled trials (1276 participants). The results revealed a benefit favoring the perioperative administration of dexamethasone to prevent postoperative shivering (relative risk [RR]: 0.39; 95% confidence interval [CI]: 0.23-0.63), as well as the grade of shivering. The administration of dexamethasone also reduced the incidence of postoperative nausea (RR: 0.54; 95% CI: 0.39-0.73), postoperative vomiting (RR: 0.37; 95% CI: 0.20-0.65), and PONV (RR: 0.50; 95% CI: 0.26-0.95) compared with the control group. CONCLUSION: This study indicated that perioperative administration of dexamethasone prevented postoperative shivering and decreased the incidence of other complications.PROSPERO registration number: CRD42020164488.

Droperidol lowers the shivering threshold in rabbits.

PURPOSE: Perioperative shivering is common and can occur as a result of hypothermia or changes in the threshold of thermoregulation. Droperidol usage for anesthesia is currently limited to its sedative and antiemetic effects. We investigated the effects of high and low doses of droperidol on the shivering threshold in rabbits. METHODS: Forty-two male Japanese white rabbits were anesthetized with isoflurane and randomly assigned to the control, high-dose, or low-dose group. Rabbits in the high-dose group received a 5 mg/kg droperidol bolus followed by continuous infusion at 5 mg/kg/h, those in the low-dose group received a 0.5 mg/kg droperidol bolus, and those in the control group received the same volume of saline as the high-dose group. Body temperature was reduced at a rate of 2-3 °C/h, and the shivering threshold was defined as the subject's core temperature (°C) at the onset of shivering. RESULTS: The shivering thresholds in the control, high-dose, and low-dose groups were 38.1 °C ± 1.1 °C, 36.7 °C ± 1.2 °C, and 36.9 °C ± 1.0 °C, respectively. The shivering thresholds were significantly lower in the high-dose and low-dose groups than in the control group (P < 0.01). The thresholds were comparable between the high-dose and low-dose groups. CONCLUSIONS: Droperidol in high and low doses effectively reduced the shivering threshold in rabbits. Droperidol has been used in low doses as an antiemetic. Low doses of droperidol can reduce the incidence of shivering perioperatively and during the induction of therapeutic hypothermia.

Pharmacologic interventions for the therapy of postanesthetic shivering in adults: a systematic review and network meta-analysis.

INTRODUCTION: Shivering is a common side effect after general anesthesia. Risk factors are hypothermia, young age and postoperative pain. Severe complications of shivering are rare but can occur due to increased oxygen consumption. Previous systematic reviews are outdated and have summarized the evidence on the topic using only pairwise comparisons. The objective of this manuscript was a quantitative synthesis of evidence on pharmacological interventions to treat postanesthetic shivering. EVIDENCE ACQUSITION: Systematic review and frequentist network meta-analysis using the R package netmeta. Endpoints were the risk ratio (RR) of persistent shivering at one, five and 10 minutes after treatment with saline/placebo as the comparator. Data were retrieved from Medline, Embase, Central and Web of Science up to January 2022. Eligibility criteria were: randomized, controlled, and blinded trials comparing pharmacological interventions to treat shivering after general anesthesia. Studies on shivering during or after any type of regional anesthesia were excluded as well as sedated patients after cardiac surgery. EVIDENCE SYNTHESIS: Thirty-two trials were eligible for data synthesis, including 28 pharmacological interventions. The largest network included 1431 patients. The network geometry was two-centered with most comparisons linked to saline/placebo or pethidine. The best interventions were after one minute: doxapram 2 mg/kg, tramadol 2 mg/kg and nefopam 10 mg, after 5 minutes: tramadol 2 mg/kg, nefopam 10 mg and clonidine 150 µg and after 10 minutes: nefopam 10 mg, methylphenidate 20 mg and tramadol 1 mg/kg, all reaching statistical significance. Pethidine 25 mg and clonidine 75 µg also performed well and with statistical significance in all networks. CONCLUSIONS: Nefopam, tramadol, pethidine and clonidine are the most effective treatments to stop postanesthetic shivering. The efficacy of doxapram is uncertain since different doses showed contradictory effects and the evidence for methylphenidate is based on a single comparison in only one network. Furthermore, both lack data on side effects. Further studies are needed to clarify the efficacy of dexmedetomidine to treat postanesthetic shivering.

Minimizing Shivering During Targeted Normothermia: Comparison Between Novel Transnasal and Surface Temperature-Modulating Devices.

BACKGROUND: Shivering is a common adverse effect of achieving and maintaining normothermia in neurocritical care patients. We compared the burden of shivering and shivering-related interventions between a novel transnasal temperature-modulating device (tnTMD) and surface cooling temperature-modulating devices (sTMDs) during the first 24 h of targeted normothermia in mechanically ventilated febrile neurocritical care patients. METHODS: This is a case-control study controlling for factors that impact shiver burden: age, sex, body surface area. All patients underwent transnasal cooling (CoolStat, KeyTech, Inc.) as part of an ongoing multicenter clinical trial (NCT03360656). Patients undergoing treatment with sTMDs were selected from consecutively treated patients during the same time period. Data collected included the following: core body temperature (every 2 h), bedside shivering assessment scale (BSAS) score (every 2 h), and administration of antishivering medication for a BSAS score > 1. Time to normothermia (≤ 37.5 °C), as well as temperature burden > 37.5 °C (°C × h), were compared between groups using Student's t-test for mean differences. The proportion of patients requiring interventions, as well as the number of interventions per patient, was compared using the χ2 test. Significance was determined based on a p value < 0.05. RESULTS: There were 10 tnTMD patients and 30 sTMD patients included in the analysis (mean age: 62 ± 4, 30% women, body surface area = 1.97 ± 0.25). There were no differences between groups in temperature at cooling initiation (tnTMD: 38.5 ± 0.2 °C vs. sTMD: 38.7 ± 0.5 °C, p = 0.3), time to ≤ 37.5 °C (tnTMD: 1.8 ± 1.5 h vs. sTMD: 2.9 ± 1.4 h, p = 0.1), or temperature burden > 37.5 (tnTMD: - 0.4 ± 1.13 °C × h vs. sTMD median [IQR]: - 0.57 ± 0.58 °C × h, p = 0.67). The number of tnTMD patients who received pharmacologic shivering interventions was lower than the number of controls (20 vs. 67%, p = 0.01). tnTMD patients also had fewer shivering interventions per patient (0 [range: 0-3] vs. 4 [range: 0-23], p < 0.001). CONCLUSIONS: A transnasal cooling approach achieved similar time to normothermia and temperature burden with less shivering than surface cooling. This approach may be a feasible option to consider for mechanically ventilated febrile neurocritical care patients.

Sedation and shivering management after cardiac arrest.

Management of sedation and shivering during targeted temperature management (TTM) after cardiac arrest is limited by a dearth of high-quality evidence to guide clinicians. Data from general intensive care unit (ICU) populations can likely be extrapolated to post-cardiac arrest patients, but clinicians should be mindful of key differences that exist between these populations. Most importantly, the goals of sedation after cardiac arrest are distinct from other ICU patients and may also involve suppression of shivering during TTM. Drug metabolism and clearance are altered considerably during TTM when a low goal temperature is used, which can delay accurate neuroprognostication. When neuromuscular blockade is used to prevent shivering, sedation should be deep enough to prevent awareness and providers should be aware that this can mask clinical manifestations of seizures. However, excessively deep or prolonged sedation is associated with complications including delirium, infections, increased duration of ventilatory support, prolonged ICU length of stay, and delays in neuroprognostication. In this manuscript, we review sedation and shivering management best practices in the post-cardiac arrest patient population.

Nitrous oxide consistently attenuates thermogenic and thermoperceptual responses to repetitive cold stress in humans.

Divers are at enhanced risk of hypothermia, due to the independent action of the inspired inert gases on thermoregulation. Thus, narcosis induced by acute (≤2 h) exposure to either hyperbaric nitrogen or normobaric nitrous oxide (N2O) impairs shivering thermogenesis and accelerates body core cooling. Animal-based studies, however, have indicated that repeated and sustained N2O administration may prevent N2O-evoked hypometabolism. We, therefore, examined the effects of prolonged intermittent exposure to 30% N2O on human thermoeffector plasticity in response to moderate cold. Fourteen men participated in two ∼12-h sessions, during which they performed sequentially three 120-min cold-water immersions (CWIs) in 20°C water, separated by 120-min rewarming. During CWIs, subjects were breathing either normal air or a normoxic gas mixture containing 30% N2O. Rectal and skin temperatures, metabolic heat production (via indirect calorimetry), finger and forearm cutaneous vascular conductance (CVC; laser-Doppler fluxmetry/mean arterial pressure), and thermal sensation and comfort were monitored. N2O aggravated the drop in rectal temperature (P = 0.01), especially during the first (by ∼0.3°C) and third (by ∼0.4°C) CWIs. N2O invariably blunted the cold-induced elevation of metabolic heat production by ∼22%-25% (P < 0.001). During the initial ∼30 min of the first and second CWIs, N2O attenuated the cold-induced drop in finger (P ≤ 0.001), but not in forearm CVC. N2O alleviated the sensation of coldness and thermal discomfort throughout (P < 0.001). Thus, the present results demonstrate that, regardless of the cumulative duration of gas exposure, a subanesthetic dose of N2O depresses human thermoregulatory functions and precipitates the development of hypothermia.NEW & NOTEWORTHY Human thermoeffector plasticity was evaluated in response to prolonged iterative exposure to 30% N2O and moderate cold stress. Regardless of the duration of gas exposure, N2O-induced narcosis impaired in a persistent manner shivering thermogenesis and thermoperception.

Comparative effects of warming systems applied to different parts of the body on hypothermia in adults undergoing abdominal surgery: A systematic review and network meta-analysis of randomized controlled trials.

STUDY OBJECTIVE: The prevention of perioperative hypothermia after anesthesia induction is a critical concern in patients undergoing abdominal surgery. The effectiveness of various warming systems for preventing hypothermia and shivering when applied to specific areas of the body remains undetermined. DESIGN: Systematic review and network meta-analysis. SETTING: Operating room. INTERVENTION: Five electronic databases were searched, including only randomized control trials (RCTs) reporting the effects of warming systems applied to specific body sites on the intraoperative core temperature and postoperative risk of shivering in adults undergoing abdominal surgery. A multivariate random-effects network meta-analysis with a frequentist framework was implemented for data analysis. MEASUREMENTS: The primary outcome was the core body temperature 60 and 120 min after anesthesia induction for abdominal surgery. The secondary outcome was the incidence of postoperative shivering. RESULTS: This review comprised a total of 24 RCTs including 1119 patients. At 60 and 120 min after anesthesia induction, a forced-air warming system applied to the upper body (0.3 °C and 95% confidence intervals = [0.3 to 0.4], 1.0 °C [0.7 to 1.3]), lower body (0.4 °C [0.3 to 0.5], 0.9 °C [0.5 to 1.2]), and underbody (0.5 °C [0.5 to 0.6], 1.2 °C [0.9 to 1.6]) was superior to passive insulation in terms of core body temperature regulation. Compared with passive insulation, the forced-air warming system applied to the lower body (odds ratio = 0.06) or underbody (0.44) and the electric heating blanket to the lower body (0.02) or the whole body (0.07) significantly reduced the risk of shivering. CONCLUSIONS: The results of this NMA revealed that forced-air warming with an underbody blanket effectively elevates core body temperatures in 60 and 120 min after induction of anesthesia and prevents shivering in patients recovering from abdominal surgery.