Effects of different forced-air warming systems on the core temperature of patients: a manikin and multi-center clinical study.

BACKGROUND: The use of forced-air warming (FAW) blankets is widely recognized for preventing shivering and hypothermia in patients under general anesthesia. Various types of products are currently available for hospitals, and we have conducted a preliminary evaluation of insulation equipment based on expert opinions and initial parameters. However, we lack real-world experiments and accurate clinical data to validate these parameters and the accuracy of our decision-making results. This study aims to confirm the effectiveness of different FAW systems by assessing the thermal protection and operational characteristics of the equipment in both experimental and clinical settings, thereby enhancing our evaluation database. METHODS: In the manikin test, we conducted six tests including heat distribution and heating rate, heater outlet temperature stability, etc. In the clinical study, patients were randomly assigned to four groups [Group A (Bair Hugger Therapy, 3 M, St. Paul, MN, USA; 63500); Group B (EQUATOR® level I, Smith Medical ASD, MN, USA; Snuggle Warm, SW-2013); Group C (Jiang Men Da Cheng Medical Devices Co., Ltd, China; IOB-006); and Group D (Shang Hai Nest Tech Medical Materials Co., Ltd, China; BH-017)], with each group comprising 30 individuals. At the start of anesthesia induction, the FAW blanket was activated and set to 43 °C until the completion of surgery. The primary endpoint was the average core body temperature during surgery. Secondary endpoints included hemodynamic and surgical variables, adverse events, and recovery metrics. RESULTS: In the manikin test, the observed results of the experimental parameters (heat distribution, air pressure difference, and hole observation test) for Group A are superior to those of the other groups. In the clinical study, although the mean perioperative core body temperature remained above 36 °C across all groups [Group A: 36.31 ± 0.04; Group B: 36.26 ± 0.06; Group C: 36.17 ± 0.03; Group D: 36.25 ± 0.05], patients in Group A maintained higher temperatures compared to the other groups (p < 0.001). CONCLUSIONS: Among patients undergoing laparoscopic radical resection of colorectal cancer with general anesthesia, all four FAW systems effectively prevented perioperative hypothermia. However, the system in Group A minimized heat loss more effectively than the others, providing superior thermal protection. TRIAL REGISTRATION: ChiCTR2200065394, 03/11/2022.

Effect of Perioperative Active Warming on Postoperative Pain and Shivering in Preschool Pediatric Patients: A Randomized Controlled Trial.

OBJECTIVE: To evaluate the effects of perioperative active warming on the core body temperature, postoperative pain, shivering and agitation in pediatric patients. METHOD: Children aged 2-6 years undergoing elective surgery, including orthopedic soft tissue surgeries, ear nose throat surgical procedures and general surgical interventions, all performed under general anesthesia, were randomized to receive either active warming (using the forced-air warming gowns, Bair Hugger, in the pre- and postoperative period, and a carbon fiber blanket in intraoperative period; Group A), or conventional warming using green blankets pre-and post-operatively and a carbon fiber blanket intraoperatively (Group B). Children undergoing emergency surgery, surgeries involving major body cavities (abdominal, thoracic, cranial surgery), or those with endocrinological pathologies, or baseline fever, were excluded. Core body temperature (t-core), postoperative pain, shivering and agitation scores were compared between the two groups. RESULTS: Seventy children were included, with 35 in each group. No significant difference was observed between the groups in t-core values at 0 and 15 minutes preoperatively (P > 0.05). However, the value at 30 minutes preoperatively and all subsequent t-core values were higher in Group A (P < 0.001). Postoperative pain and shivering scores at 0 minutes, 30 minutes and 6 hours were significantly lower in Group A compared to Group B. No significant difference was observed in agitation scores in the immediate postoperative period, although, Group A showed reduced agitation at 30 minutes (P = 0.03). CONCLUSION: Active warming in the pre- and post-operative period significantly maintained higher core temperatures and reduced postoperative pain and shivering in children undergoing surgery compared to those receiving conventional passive warming measures in the pre- and post-operative period.

Adaptive Induction of Nonshivering Thermogenesis in Muscle Rather Than Brown Fat Could Counteract Obesity.

Warm-blooded animals such as birds and mammals are able to protect stable body temperature due to various thermogenic mechanisms. These processes can be facultative (occurring only under specific conditions, such as acute cold) and adaptive (adjusting their capacity according to long-term needs). They can represent a substantial part of overall energy expenditure and, therefore, affect energy balance. Classical mechanisms of facultative thermogenesis include shivering of skeletal muscles and (in mammals) non-shivering thermogenesis (NST) in brown adipose tissue (BAT), which depends on uncoupling protein 1 (UCP1). Existence of several alternative thermogenic mechanisms has been suggested. However, their relative contribution to overall heat production and the extent to which they are adaptive and facultative still needs to be better defined. Here we focus on comparison of NST in BAT with thermogenesis in skeletal muscles, including shivering and NST. We present indications that muscle NST may be adaptive but not facultative, unlike UCP1-dependent NST. Due to its slow regulation and low energy efficiency, reflecting in part the anatomical location, induction of muscle NST may counteract development of obesity more effectively than UCP1-dependent thermogenesis in BAT.

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.

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.

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.

Metabolic Manipulation and Therapeutic Hypothermia.

Hypothermia has multiple physiological effects, including decreasing metabolic rate and oxygen consumption (VO2). There are few human data about the magnitude of change in VO2 with decreases in core temperature. We aimed to quantify to magnitude of reduction in resting VO2 as we reduced core temperature in lightly sedated healthy individuals. After informed consent and physical screening, we cooled participants by rapidly infusing 20 mL/kg of cold (4°C) saline intravenously and placing surface cooling pads on the torso. We attempted to suppress shivering using a 1 mcg/kg intravenous bolus of dexmedetomidine followed by titrated infusion at 1.0 to 1.5 µg/(kg·h). We measured resting metabolic rate VO2 through indirect calorimetry at baseline (37°C) and at 36°C, 35°C, 34°C, and 33°C. Nine participants had mean age 30 (standard deviation 10) years and 7 (78%) were male. Baseline VO2 was 3.36 mL/(kg·min) (interquartile range 2.98-3.76) mL/(kg·min). VO2 was associated with core temperature and declined with each degree decrease in core temperature, unless shivering occurred. Over the entire range from 37°C to 33°C, median VO2 declined 0.7 mL/(kg·min) (20.8%) in the absence of shivering. The largest average decrease in VO2 per degree Celsius was by 0.46 mL/(kg·min) (13.7%) and occurred between 37°C and 36°C in the absence of shivering. After a participant developed shivering, core body temperature did not decrease further, and VO2 increased. In lightly sedated humans, metabolic rate decreases around 5.2% for each 1°C decrease in core temperature from 37°C to 33°C. Because the largest decrease in metabolic rate occurs between 37°C and 36°C, subclinical shivering or other homeostatic reflexes may be present at lower temperatures.

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.

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.

Modulation of cold-induced shivering activity by intermittent and continuous voluntary suppression.

This investigation assessed the physiological effects of voluntary suppression of shivering thermogenesis in response to whole body cooling. Eleven healthy volunteers underwent passive air cooling (10°C), across three visits: NO_SUP, where participants allowed their body to freely regulate against the cold; FULL_SUP, where participants constantly suppressed shivering; INT_SUP, where participants intermittently suppressed shivering (5 min phases), interspersed with 5 min free regulation. Shivering was assessed via electromyography (EMG), mechanomyography (MMG), and whole body oxygen uptake (V̇o2), whereas body temperature and heat exchange were assessed via skin temperature, rectal temperature, and heat flux sensors. A 29% increase was observed in shivering onset time in the FULL_SUP trial compared with NO_SUP (P = 0.032). Assessing shivering intensity, EMG activity decreased by 29% (P = 0.034), MMG activity decreased by 35% (P = 0.031), whereas no difference was observed in V̇o2 (P = 0.091) in the FULL_SUP trial compared with NO_SUP. Partitioning the no-suppression and suppression phases of the INT_SUP trial, acute voluntary suppression significantly decreased V̇o2 (P = 0.001), EMG (P < 0.001), and MMG (P = 0.012) activity compared with the no-suppression phases. Shivering activity was restored in the no-suppression phases, equivalent to that in the NO_SUP trial (P > 0.3). No difference was observed in thermal metrics between conditions up to 60 min (P > 0.4). Humans can both constantly and periodically suppress shivering activity, leading to a delay in shivering onset and a reduction in shivering intensity. Following suppression, regular shivering is resumed.

Hypothermia evoked by stimulation of medial preoptic nucleus protects the brain in a mouse model of ischaemia.

Therapeutic hypothermia at 32-34 °C during or after cerebral ischaemia is neuroprotective. However, peripheral cold sensor-triggered hypothermia is ineffective and evokes vigorous counteractive shivering thermogenesis and complications that are difficult to tolerate in awake patients. Here, we show in mice that deep brain stimulation (DBS) of warm-sensitive neurones (WSNs) in the medial preoptic nucleus (MPN) produces tolerable hypothermia. In contrast to surface cooling-evoked hypothermia, DBS mice exhibit a torpor-like state without counteractive shivering. Like hypothermia evoked by chemogenetic activation of WSNs, DBS in free-moving mice elicits a rapid lowering of the core body temperature to 32-34 °C, which confers significant brain protection and motor function reservation. Mechanistically, activation of WSNs contributes to DBS-evoked hypothermia. Inhibition of WSNs prevents DBS-evoked hypothermia. Maintaining the core body temperature at normothermia during DBS abolishes DBS-mediated brain protection. Thus, the MPN is a DBS target to evoke tolerable therapeutic hypothermia for stroke treatment.

Clinical efficacy of short-term prewarming in elderly and adult patients: A prospective observational study.

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.

Thermogenic responses to different clamped skin temperatures in cold-exposed men and women.

Despite many decades of research examining thermoregulatory responses under varying cold stresses in humans, very little is known about the variability in metabolic heat production and shivering activity. Here, we used a novel closed-loop mean skin temperature clamping technique with a liquid-conditioned suit to isolate the effects of mean skin temperature on the subjective evaluation of thermal sensation, heat production, shivering responses, and oxidative fuel selection in young, lean, and healthy men (n = 12) and women (n = 12). Our results showed a skin temperature-dependent increase in metabolic heat production (5.2 ± 1.2 kJ/min, 5.9 ± 1.5 kJ/min, and 7.0 ± 1.8 kJ/min with skin temperature maintained at 31 ± 0.1°C, 29 ± 0.2°C, and 27 ± 0.1°C, respectively; P < 0.0001) and shivering intensity in both men and women [0.6 ± 0.1% maximal voluntary contraction (MVC), 1.1 ± 0.4% MVC, and 2.5 ± 0.7% MVC, respectively; P < 0.0001], including sex-dependent differences in heat production at all three temperatures (P < 0.005). Even when controlling for lean body mass and fat mass, sex differences persisted (P = 0.048 and P = 0.004, respectively), whereas controlling for differences in body surface area eliminated these differences. Interestingly, there were no sex differences in the cold-induced change in thermogenesis. Despite clamping skin temperature, there was tremendous variability in the rate of heat production and shivering intensity. Collectively this data suggests that many of the interindividual differences in thermogenesis and shivering may be explained by differences in morphology and body composition.

Effects of a short-term cold exposure on circulating microRNAs and metabolic parameters in healthy adult subjects.

This discovery study investigated in healthy subjects whether a short-term cold exposure may alter circulating microRNAs and metabolic parameters and if co-expression networks between these factors could be identified. This open randomized crossover (cold vs no cold exposure) study with blind end- point evaluation was conducted at 1 center with 10 healthy adult male volunteers. Wearing a cooling vest perfused at 14°C for 2 h reduced the local skin temperature without triggering shivering, increased norepinephrine and blood pressure while decreasing copeptin, C-peptide and heart rate. Circulating microRNAs measured before and after wearing the cooling vest twice (4 time points) identified 196 mature microRNAs with excellent reproducibility over 72 h. Significant correlations of microRNA expression with copeptin, norepinephrine and C-peptide were found. A co-expression-based microRNA-microRNA network, as well as microRNA pairs displaying differential correlation as a function of temperature were also detected. This study demonstrates that circulating miRNAs are differentially expressed and coregulated upon cold exposure in humans, supporting their use as predictive and dynamic biomarkers of cardio-metabolic disorders.

Independent and combined impact of hypoxia and acute inorganic nitrate ingestion on thermoregulatory responses to the cold.

PURPOSE: This study assessed the impact of normobaric hypoxia and acute nitrate ingestion on shivering thermogenesis, cutaneous vascular control, and thermometrics in response to cold stress. METHOD: Eleven male volunteers underwent passive cooling at 10 °C air temperature across four conditions: (1) normoxia with placebo ingestion, (2) hypoxia (0.130 FiO2) with placebo ingestion, (3) normoxia with 13 mmol nitrate ingestion, and (4) hypoxia with nitrate ingestion. Physiological metrics were assessed as a rate of change over 45 min to determine heat loss, and at the point of shivering onset to determine the thermogenic thermoeffector threshold. RESULT: Independently, hypoxia expedited shivering onset time (p = 0.05) due to a faster cooling rate as opposed to a change in central thermoeffector thresholds. Specifically, compared to normoxia, hypoxia increased skin blood flow (p = 0.02), leading to an increased core-cooling rate (p = 0.04) and delta change in rectal temperature (p = 0.03) over 45 min, yet the same rectal temperature at shivering onset (p = 0.9). Independently, nitrate ingestion delayed shivering onset time (p = 0.01), mediated by a change in central thermoeffector thresholds, independent of changes in peripheral heat exchange. Specifically, compared to placebo ingestion, no difference was observed in skin blood flow (p = 0.5), core-cooling rate (p = 0.5), or delta change in rectal temperature (p = 0.7) over 45 min, while nitrate reduced rectal temperature at shivering onset (p = 0.04). No interaction was observed between hypoxia and nitrate ingestion. CONCLUSION: These data improve our understanding of how hypoxia and nitric oxide modulate cold thermoregulation.

Thermoregulation and shivering responses in elite alpine skiers.

This study aimed to characterise the thermoregulatory responses of elite alpine skiers. Core (gastro-intestinal) and skin temperatures were recorded continuously from 4 national team skiers representing 18 training-sessions for a total of 83 ski runs (average ambient temperature 1.9°C). Shivering responses were estimated from quadriceps and hamstrings EMG recordings during 77 chairlifts. Temperature responses were also obtained from 6 accompanying staffs representing 16 training-sessions (passive in 10 cases, following the skiers in 6 cases). Core temperature of the skiers (P < .001) but not the staff (P = .103) increased during training and was higher in skiers than staff after one-third of the training session (P < .006). Conversely, average skin temperature of the skiers decreased during training (P < .001) and was lower in skiers than staff for the second half of the training. Muscle activity during chairlifts remained below 1% and there was no meaningful shivering. Muscle activity decreased whilst mean and median power frequency increased during the chairlift (P < .020). Muscle activity was also lower during the last lift than the first one whilst mean and median power frequency were higher (P < .020). In conclusion, skin temperature decreased during Slalom and Giant Slalom in elite alpine skiers, likely due to the limited insulative capacity of the racing suit and the high velocity increasing convective heat loss. Conversely, core temperature increased during the training session suggesting that the metabolic heat production was larger than the convective heat loss, and was also sufficient to maintain homeostasis without shivering.

Acute basilar artery occlusion with recurrent shivering: A case report.

RATIONALE: Shivering is an important physiological response of the body that causes muscle tremors to maintain temperature homeostasis. Traumatic brain injuries that affect the hypothalamus cause hypothermia, and physical removal of suprasellar tumors causes thermoregulation imbalance. However, no study has reported shivering due to ischemic stroke. PATIENT CONCERNS: A 58-year-old male patient was admitted to our emergency department to evaluate severe stenosis of the basilar artery. While waiting for further examination, he exhibited coarse shivering and severe dysarthria. DIAGNOSIS: Brain computed tomography angiography revealed occlusion of the entire basilar artery, and cerebral hypoperfusion was diagnosed in that area. INTERVENTIONS: Transfemoral cerebral angiography (TFCA) was immediately performed, followed by thrombectomy of the basilar artery. OUTCOMES: Neurological deficits, including shivering, were rapidly reversed. The same symptom reoccurred 5 hours later, and TFCA was performed for thrombectomy and stenting, and neurological symptoms immediately reversed. The patient's neurological symptoms did not worsen during hospitalization. LESSONS: Patients with acute basilar artery occlusion need prompt management because they have a higher mortality rate than those with other intracranial artery occlusions. When a patient exhibits neurological deficits accompanied by abrupt shivering for no specific reason, basilar artery occlusion must be considered.

Multiorgan contribution to non-shivering and shivering thermogenesis and vascular responses during gradual cold exposure in humans.

PURPOSE: Human brown adipose tissue (BAT) is known to be a significant thermoeffector in non-shivering thermogenesis (NST), albeit with individual variations in the BAT activity. We hypothesized that humans with less BAT would have more contribution from the skeletal muscle (SM) to NST or earlier shivering onset and greater vasoconstriction to compensate for less BAT-mediated thermogenesis. METHODS: Eighteen males participated in this study. Their BAT activity and detectable volume were investigated. A gradual cold exposure was conducted for inducing NST at 18.6 °C and initiating shivering at 11.6 °C. The energy expenditure, electromyograph of the pectoralis major, skin blood flow, and rectal (Tre) and skin temperatures were evaluated. RESULTS: BAT volume significantly correlated with the change in metabolic heat production during mild cold phase relative to baseline (NST; r = 0.562, P < 0.05), but not with shivering initiation phase (NST+ ST). SM mass correlated with baseline metabolic heat production (Mbase; r = 0.839, P < 0.01) but not with NST or NST + ST. A positive correlation was noted between BAT volume and Tre at the end of the 18.6 °C exposure period (r = 0.586, P < 0.05), which positively correlated with shivering onset time (r = 0.553, P < 0.05). The skin blood flow, mean skin temperature, and forearm and finger skin temperature difference at the end of the 18.6 °C exposure period did not correlate with NST or BAT volume. CONCLUSION: BAT volume positively correlated with NST. Notably, lower Tre in individuals with less BAT volume induced earlier shivering onset for offsetting the less NST. Whereas, no correlation between metabolic and vasomotor responses was observed.

Effect of intrathecal lipophilic opioids on the incidence of shivering in women undergoing cesarean delivery after spinal anesthesia: a systematic review and bayesian network meta- analysis of randomized controlled trials.

BACKGROUND: Shivering is a common side effect in women having cesarean delivery (CD) under spinal anesthesia, which can be bothersome to the patient, and it can also interfere with perioperative monitoring. In several studies, the intrathecal (IT) addition of a lipophilic opioid to local anesthetics has been shown to decrease the incidence of shivering. OBJECTIVE: We performed this network meta-analysis to evaluate the effects of intrathecal lipophilic opioids in preventing the incidence of shivering in patients undergoing CD. METHODS: This review was planned according to the PRISMA for Network Meta-Analysis (PRISMA-NMA) guidelines. An English literature search of multiple electronic databases was conducted. We included randomized controlled trials (RCTs) that reported on the incidence of shivering, with study groups receiving either IT fentanyl, sufentanil, or meperidine in women undergoing CD under spinal anesthesia. Quality of the studies was assessed using the modified Oxford scoring system. Using random-effects modeling, dichotomous data were extracted and summarized using odds ratio (OR) with a 95% credible interval (CrI). Statistical analysis was conducted using R studio version 1.0.153 - Inc. RESULTS: Twenty-one studies consisting of 1433 patients (Control group: 590 patients in twenty-one studies; Fentanyl group:199 patients in seven studies; Sufentanil group: 156 patients in five studies; Meperidine group: 488 patients in ten studies) met the inclusion criteria for this systematic review investigating the effect of intrathecal lipophilic opioids in preventing the incidence of shivering in women undergoing cesarean delivery under spinal anesthesia. Methodological validity scores ranged from 3 to 7. The Bayesian mixed network estimate showed the incidence of shivering was significantly lower with IT fentanyl (pooled odds ratio (OR): 0.13; 95% credible interval (CrI): 0.04 to 0.35; P = 0.0004) and IT meperidine (OR: 0.12; 95% CrI: 0.05 to 0.29; P < 0.00001), but not with IT sufentanil (OR: 0.37; 95% CrI: 0.11 to 1.22; P = 0.23). The IT fentanyl group had a significantly lower incidence of intraoperative discomfort [Risk Ratio (RR): 0.19; 95% CI: 0.10-0.35; P < 0.00001], the IT sufentanil group had a significantly higher incidence of pruritus (RR: 6.18; 95% CI: 1.18-32.46; P = 0.03) The IT meperidine group had a significantly lower incidence of intraoperative discomfort (2.7% vs. 13.6%; RR: 0.22; 95% CI: 0.09-0.55; P = 0.001), but there was a significant increase in nausea and vomiting (IT meperidine group vs. Control group: 42.7% vs. 19.4%; RR: 2.56; 95% CI: 1.14-5.75; P = 0.02). Meta-regression analysis based on the opioid dose and quality of the study did not impact the final inference of our result. CONCLUSION: IT fentanyl significantly decreased the incidence of shivering in women undergoing CD under spinal anesthesia without increasing maternal adverse events, confirming that routine use in this patient population is a good choice. IT sufentanil did not decrease the incidence of shivering. IT meperidine decreased the incidence and severity of shivering, but its use was also associated with significant nausea and vomiting.

Safety of intraoperative hypothermia for patients: meta-analyses of randomized controlled trials and observational studies.

BACKGROUND: Previous studies have shown that intraoperative hypothermia was associated with higher risks of clinical adverse events, but we found otherwise from recent evidences. This study aims to synthesize the existing evidence evaluating safety of intraoperative hypothermia. METHODS: Articles, reviews, ongoing trials and grey literatures were retrieved from PubMed, The Cochrane Library, Clinical Trails and CNKI (a Chinese national database) till February 2nd, 2019. Both randomized controlled trials and observational studies compared incidences of all sorts of intra- and post-operative consequences between hypothermia and normothermia were included. Researches comparing different warming systems were excluded. We also examined risks of hypothermia using lowered standards (35.5 °C and 35 °C) from a Chinese trial (ChiCTR-IPR-17011099). RESULTS: A total of 9 RCT studies and 11 observational studies were included. RCT-synthesized results showed that intraoperative hypothermia was associated with higher risks of bleeding (MD = 131.90, 95%CI: 117.42, 146.38), surgical site infection (RD = 0.14, 95%CI: 0.06, 0.21) and shivering (RD = 0.32, 95%CI: 0.06, 0.58) but with no significant differences in duration of surgery, hospital stay or mortality. Observational study-synthesized evidences showed that intraoperative hypothermia did not result in higher risks in any of these adverse events. Results didn't change even if the standard of hypothermia was lowered by 0.5-1.0 °C. CONCLUSIONS: The study indicates that the synthesized risks resulted by intra-operative hypothermia might be overestimated and the eligibility of 36 °C to define hypothermia is not sensitive enough. Given body-temperature protection has not been popularized in China, it is still critical to normalize the hypothermia prevention at this stage.