The effects of preinduction warming on temperature and blood pressure during propofol/nitrous oxide anesthesia

Strategies for perioperative hypothermia management: advances in warming techniques and clinical implications: a narrative review

Perioperative hypothermia is a frequent clinical complication resulting from the cold environment of the operating room and prolonged skin exposure, leading to adverse outcomes and increased healthcare burdens. To address this issue, this narrative review discusses in detail the currently common warming strategies for perioperative hypothermia .Forced air warming (FAW) systems are widely recognized as the most effective intervention for maintaining core body temperature. Additionally, alternative technologies, such as circulating-water mattresses, carbon-fiber resistive heating systems, self-regulated heated air garments, self-heating blankets, and chemical heat packs, offer diverse advantages and disadvantages. Passive warming methods, including thermal reflective blankets and cotton blankets, provide a cost-effective solution, albeit with reduced efficacy compared to active warming measures. Recent advancements have focused on improving both active and passive warming approaches to balance effectiveness and cost-efficiency. While FAW remains the gold standard, other systems offer specific benefits, such as improved portability and reduced costs, making them suitable for use in diverse clinical scenarios. Effective perioperative temperature management reduces hypothermia-related complications, decreases healthcare expenditures, and provides substantial social and organizational benefits. Thus, selecting the most appropriate warming intervention in clinical practice requires a tailored approach, considering both patient-specific needs and resource availability.

The Correlation Between Preoperative Perfusion Index and Intraoperative Hypothermia During Laparoscopic Radical Surgery for Urological Malignancies

This study aimed to explore the relationship between preoperative baseline perfusion index (PI) and intraoperative hypothermia during general anesthesia. PI reflects the peripheral perfusion status, which may be associated with the decrease of core temperature during general anesthesia, as the redistribution of temperature from the core compartment to the peripheral compartment depends on the peripheral perfusion status. A total of 68 patients underwent radical surgery for urological malignancies in this study. The baseline PI value was measured upon entering the operating room. Core temperature was continuously monitored using a nasal pharyngeal probe from anesthesia induction to the end of surgery, with temperature data recorded every 15 minutes. Univariate and multivariate logistic regression analyses were used to identify risk factors for intraoperative hypothermia. Intraoperative hypothermia occurred in 26 patients, whose baseline PI (2.70 ± 0.73) was significantly lower than that of the normothermic group (3.65 ± 1.05), with P<0.05. The baseline PI was independently associated with intraoperative hypothermia (PI: [OR] 0.375, 95% confidence interval [CI]: 1.584-6.876, p = 0.001). This study suggests that low baseline PI is an independent factor associated with intraoperative hypothermia. In future studies, PI value could be considered as a predictor for the treatment of intraoperative hypothermia.

Core temperature following pre-hospital induction of anaesthesia in trauma patients

INTRODUCTION

Hypothermia is a well-recognised finding in trauma patients, which can occur even in warmer climates. It is an independent predictor of increased morbidity and mortality. It is associated with pre-hospital intubation, although the reasons for this are likely to be multifactorial. Core temperature drop after induction of anaesthesia is a well-known phenomenon in the context of elective surgery, and the mechanisms of this are well established.

METHODS

We conducted a prospective observational study to examine the behaviour of core temperature in patients undergoing pre-hospital anaesthesia for traumatic injuries.

RESULTS

Between 2017 and 2021 data were collected on 48 patients. The data from 40 of these were included in the final analysis.

DISCUSSION

Our data do not show a decrease in the core temperatures of patients who receive pre-hospital anaesthesia, unlike patients who are anaesthetised without pre-warming, in operating theatres. The lack of a change could relate to patient, anaesthetic or environmental factors.

Clinical Efficacy of 10 Min of Active Prewarming for Preserving Patient Body Temperature during Percutaneous Nephrolithotomy: A Prospective Randomized Controlled Trial

Background: Percutaneous nephrolithotomy (PNL) poses a risk of hypothermia. Additionally, general anesthesia lowers the thresholds for shivering and vasoconstriction, which leads to dysfunction of central thermoregulation. Perioperative hypothermia is associated with adverse outcomes after surgery. In this study, we aimed to demonstrate that prewarming for 10 min can effectively prevent early hypothermia during PNL. Methods: A total of 68 patients scheduled for elective PNL were recruited to this study from January to June 2022, but two patients were excluded because of a change in the surgical plan. After randomization, patients in the prewarming group (n = 32) received warming using a forced-air warming device for 10 min in the preoperative area before being transferred to the operating room, while the controls (n = 34) did not. The incidence of hypothermia within the first hour after inducing general anesthesia was the primary outcome. Perioperative body temperatures and postoperative recovery findings were also evaluated. Results: Early intraoperative hypothermia decreased significantly more in the prewarming group than in the control group (9.4% vs. 41.2%, p = 0.003). Moreover, the net decrease in core body temperature during surgery was smaller in the prewarming group than in the control group (0.2 °C, vs. 0.5 °C, p = 0.003). In addition, the prewarmed patients had a lower incidence of postoperative shivering and a shorter post-anesthesia-care unit (PACU) stay (12.5% vs. 35.3%, p = 0.031; and 46 vs. 50 min, p = 0.038, respectively). Conclusions: Prewarming for 10 min decreased early hypothermia, preserved intraoperative body temperature, and improved postoperative recovery in the PACU.

Outpatient-Based High-Volume Liposuction: A Retrospective Review of 310 Consecutive Patients

BACKGROUND

Currently, the definition of large-volume liposuction is the removal of 5 L or more of total aspirate. Higher volumes of lipoaspirate come into consideration with higher BMIs, because more than 5 L is often required to achieve a satisfactory aesthetic result. The boundaries of what lipoaspirate volume is considered safe are based on historical opinion and are constantly in question.

OBJECTIVES

Because to date there have been no scientific data available to support a specific safe maximum volume of lipoaspirate, the authors discuss necessary conditions for safe high-volume lipoaspirate extraction.

METHODS

This retrospective study included 310 patients who had liposuction of ≥5 L over a 30-month period. All patients had 360° liposuction alone or in combination with other procedures.

RESULTS

Patient ages ranged from 20 to 66 with a mean age of 38.5 (SD = 9.3). Average operative time was 202 minutes (SD = 83.1). Mean total aspirate was 7.5 L (SD = 1.9). An average of 1.84 L (SD = 0.69) of intravenous fluids and 8.99 L (SD = 1.47) of tumescent fluid were administered. Urine output was maintained above 0.5 mL/kg/hr. There were no major cardiopulmonary complications or cases requiring blood transfusion.

CONCLUSIONS

High-volume liposuction is safe if proper preoperative, intraoperative, and postoperative protocols and techniques are employed. The authors believe that this bias should be modified and that sharing their experience with high-volume liposuction may help guide other surgeons to incorporate this practice with confidence and safety for better patient outcomes.

LEVEL OF EVIDENCE: 3

Verification of an intravenous fluid warmer: A prospective, two-center observational trial

Objectives

Avoiding inadvertent hypothermia during surgery is important. Intravenous fluid warmers used intraoperatively are critical for maintaining euthermia. We sought to prospectively evaluate the performance of the parylene-coated enFlow™ intravenous fluid warmer in patients undergoing surgery.

Methods

This was a prospective two-center observational clinical trial performed in inpatient surgical services of two large academic hospital systems. After written informed consent, patients were enrolled in the trial. All patients were adults scheduled for a surgery that was expected to last for at least 1 h with the administration of at least 1 L of fluid warmed prior to infusion. Patient temperature was recorded in the preoperative unit, at the induction of anesthesia, and then every 15 or 30 min until the end of surgery. Temperature monitoring continued in the recovery unit. The parylene-coated enFlow™ intravenous fluid warmer was used in addition to the usual patient warming techniques. The primary outcome was the average core temperature, and secondary analyses assessed individual temperature measurements, temperature measurements during specific time periods, and rate of hypothermic events.

Results

In all, 50 patients (29 males) with a mean age of 64 years were included in the analysis. The mean surgical time was 195 min and patients received an average of 1142 mL of fluids. Core temperature dropped by only 0.3°C approximately 60 min after induction and recovered back to the baseline level approximately 60 min later. There was no correlation between flow rate and measured core body temperature.

Conclusions

The parylene-coated enFlow intravenous fluid warmer was able to warm fluids at all flow rates during prolonged surgery. The results showed that enFlow performed as expected.

Relationship between perfusion index and central temperature before and after induction of anesthesia in laparoscopic gastrointestinal surgery: A prospective cohort study

The perfusion index (PI) cutoff value before anesthesia induction and the ratio of PI variation after anesthesia induction remain unclear. This study aimed to clarify the relationship between PI and central temperature during anesthesia induction, and the potential of PI in individualized and effective control of redistribution hypothermia. This prospective observational single center study analyzed 100 gastrointestinal surgeries performed under general anesthesia from August 2021 to February 2022. The PI was measured as peripheral perfusion, and the relationship between central and peripheral temperature values was investigated. Receiver operating characteristic curve analysis was performed to identify baseline PI before anesthesia, which predicts a decrease in central temperature 30 minutes after anesthesia induction, and the rate of change in PI that predicts the decrease in central temperature 60 minutes after anesthesia induction. In cases with a central temperature decrease of ≥ 0.6°C after 30 minutes, the area under the curve was 0.744, Youden index was 0.456, and the cutoff value of baseline PI was 2.30. In cases with a central temperature decrease of ≥ 0.6°C after 60 minutes, the area under curve was 0.857, Youden index was 0.693, and the cutoff value of the PI ratio of variation after 30 minutes of anesthesia induction was 1.58. If the baseline PI is ≤ 2.30 and the PI 30 minutes after anesthesia induction is at least 1.58-fold the PI ratio of variation, there is a high probability of a central temperature decrease of at least 0.6°C within 30 minutes after 2 time points.

Prewarming for Prevention of Hypothermia in Older Patients Undergoing Hand Surgery Under Brachial Plexus Block

Background

Older patients are more vulnerable to inadvertent perioperative hypothermia. Prewarming contributes to the prevention of inadvertent perioperative hypothermia in patients under general or neuraxial anesthesia. However, the effects of brachial plexus block (BPB) on thermoregulation and the efficacy of prewarming in the prevention of hypothermia in older patients undergoing surgery with BPB remain unclear. This study evaluated the effects of BPB on thermoregulation and the efficacy of prewarming during BPB in older patients.

Methods

Patients aged ≥65 years were randomly allocated to receive either standard preoperative insulation (control group, n=20) or preanesthetic forced-air warming for 20 minutes before BPB (prewarming group, n=20). During the perioperative period, tympanic temperatures were measured. Thermal comfort scores and shivering grades were also obtained.

Results

The tympanic temperatures at the end of surgery did not differ between the groups (36.9°C±0.5°C and 37.0°C±0.4°C in the control and prewarming groups, respectively; p=0.252). The maximum temperature change was significantly lower in the prewarming group compared to the control group (0.36°C±0.4°C and 0.65°C±0.3°C, respectively; p=0.013). The hypothermia incidence and severity, thermal comfort scores, and shivering grades did not differ between the groups.

Conclusion

Regardless of the application of prewarming, BPB did not cause a clinically significant impairment of thermoregulation. Moreover, the efficacy of prewarming appeared to be low; thus, it may not be routinely required in patients undergoing orthopedic hand surgery under BPB.

Underbody blankets have a higher heating effect than overbody blankets in lithotomy position endoscopic surgery under general anesthesia: a randomized trial

BACKGROUND

Surgery under general anesthesia results in temperature decrease due to the effect of anesthetics and peripheral vasodilation on thermoregulatory centers. Perioperative temperature control is therefore an issue of high importance. In this study, we aimed to compare the warming effect of underbody and overbody blankets in patients undergoing surgery in the lithotomy position under general anesthesia.

METHODS

From September 2018 to October 2019, 99 patients undergoing surgery for colorectal cancer in the lithotomy position were included in this randomized controlled trial and assigned to the intervention group (underbody blanket) or control group (overbody blanket).

RESULTS

The central temperature was significantly higher in the underbody blanket group than in the overbody blanket group at 90 min after the beginning of the surgery (p = 0.02); also in this group, the peripheral temperature was significantly higher 60 min after the beginning of the surgery (p = 0.02). Regarding postoperative factors, the underbody blanket group had a significantly lower frequency of postoperative shivering (p < 0.01) and a significantly shorter postoperative hospital stay (p = 0.04) than the overbody blanket group.

CONCLUSIONS

We recommend the use of underbody blankets for intraoperative temperature control in patients undergoing surgery in the lithotomy position under general anesthesia. Underbody blankets showed improved rise and maintenance of central and peripheral temperature, decreased the incidence of postoperative shivering, and shortened the postoperative length of hospital stay.

Association between preoperative toe perfusion index and maternal core temperature decrease during cesarean delivery under spinal anesthesia: a prospective cohort study

Background

The main mechanism of body temperature decrease during cesarean delivery under spinal anesthesia is core-to-peripheral redistribution of body heat, attributable to vasodilation. Perfusion index (PI) obtained with a pulse oximeter helps to assess peripheral perfusion dynamics by detecting the change in peripheral vascular tone. This study aimed to examine whether preoperative toe PI could predict the decrease in core temperature induced by spinal anesthesia during cesarean delivery.

Methods

Parturients undergoing scheduled cesarean delivery under combined spinal-epidural anesthesia from September 2019 to March 2020 were enrolled in this single-center prospective cohort study. All parturients received 0.5% hyperbaric bupivacaine (10 mg) with fentanyl (15 μg) intrathecally. A pulse oximeter probe was placed on the left second toe for continuous PI measurement. The 3 M™ Bair Hugger™ Temperature Monitoring System placed over the right temporal region was used to record core temperature over time. We evaluated the association between the maximum core temperature decrease, which is the primary outcome, and the preoperative toe PI at operating room (OR) admission using a segmented regression model (SRM) and a generalized additive model (GAM). The maximum core temperature decrease was defined as the difference between core temperature at OR admission and minimum intraoperative core temperature.

Results

Forty-eight patients were evaluated. In the SRM, the slope for the association between the maximum core temperature decrease and the preoperative toe PI changed from 0.031 to 0.124 after PI = 2.4%. Likewise, with the GAM, there was a small core temperature decrease when preoperative toe PI was greater than 2.0 to 3.0%.

Conclusions

Low preoperative toe PI was associated with maternal core temperature decrease during cesarean delivery under spinal anesthesia. Preoperative toe PI is a simple, non-invasive, and effective tool for the early prediction of perioperative core temperature decrease during cesarean delivery.

Trial registration

UMIN Clinical Trials Registry (registry number: UMIN000037965).

Blood Pressure Management by Anesthesia Professionals: Evaluating Clinician Skill From Electronic Medical Records

BACKGROUND

Avoiding intraoperative hypotension might serve as a measure of clinician skill. We, therefore, estimated the range of hypotension in patients of nurse anesthetists, and whether observed differences were associated with a composite of serious complications.

METHODS

First, we developed a multivariable model to predict the amount of hypotension, defined as minutes of mean arterial pressure (MAP) <65 mm Hg, for noncardiac surgical cases from baseline characteristics excluding nurse anesthetist. Second, we compared observed and predicted amounts of hypotension for each case and summarized "excess" amounts across providers. Third, we estimated the extent to which hypotension on an individual case level was independently associated with a composite of serious complications. Finally, we assessed the range of actual and excess minutes of MAP <65 mm Hg on a provider level, and the extent to which these pressure exposures were associated with complications.

RESULTS

We considered 110,391 hours of anesthesia by 99 nurse anesthetists. A total of 69% of 25,702 included cases had at least 1 minute of MAP <65 mm Hg, with a median (quartiles) of 4 (0-15) minutes on the case level. We were unable to explain much variance of intraoperative hypotension from baseline patient characteristics. However, cases in the highest 2 quartiles (>10 and >24 min/case more than predicted) were an estimated 27% (95% confidence interval [CI], 1.1-1.4) and 31% (95% CI, 1.2-1.5) more likely to experience complications compared to those with 0 excess minutes (both P < .001). There was little variation of the average excess minutes <65 mm Hg across the nurse anesthetists, with median (quartiles) of 1.6 (1.2-1.9) min/h. There was no association in confounder-adjusted models on the nurse anesthetist level between average excess hypotension and complications, either for continuous exposure (P = .09) or as quintiles (P = .30).

CONCLUSIONS

Hypotension is associated with complications on a case basis. But the average amount of hypotension for nurse anesthetists over hundreds of cases differed only slightly and was insufficient to explain meaningful differences in complications. Avoiding hypotension is a worthy clinical goal, but does not appear to be a useful metric of performance because the range of average amounts per clinician is not meaningfully associated with patient outcomes, at least among nurse anesthetists in 1 tertiary center.

Efficacy of prewarming prophylaxis method for intraoperative hypothermia during thoracoscopic esophagectomy

BACKGROUND

This study was performed to elucidate the clinical efficacy of the prewarming prophylaxis method for intraoperative hypothermia during thoracoscopic esophagectomy for esophageal cancer.

METHODS

We enrolled 100 consecutive patients with esophageal cancer. Two patients in the prewarming group could not undergo thoracoscopic esophagectomy because of conversion to thoracotomy. The intraoperative core temperature was measured in 50 and 48 patients classified into the control and prewarming groups, respectively. Patients in the prewarming group wore a Bair Hugger warming gown (3 M, Maplewood, MN, USA) in the ward for 30 min before entering the operation room. The primary outcome measure was the difference in the intraoperative body core temperature between the control and prewarming groups, and the secondary outcome measure was the difference in postoperative infectious complications between the control and prewarming groups.

RESULTS

The intraoperative core temperature was significantly different between the two groups at each 30-min time point from the starting of operation to the ending of the thoracic procedure (P < 0.001). The incidence of infectious surgical complications was not significantly different between the control and prewarming groups (30.0% vs. 14.6%, respectively; P = 0.11).

CONCLUSION

The prewarming prophylaxis method was effective for maintaining normothermia during thoracoscopic esophagectomy.

The effect of combination of warm intravenous fluid infusion and forced air warming versus forced air warming alone on maternal temperature and shivering during cesarian delivery under spinal anesthesia

Objective

Administration of warm intravenous (IV) fluid infusion and use of forced air warmers is the most easy and physiologically viable method for maintaining normothermia during surgery and postsurgical periods This study was conducted to assess the effect of combination of active warming (AW) methods namely warm IV fluid infusion and forced air warming versus forced air warming only (WA) on maternal temperature during elective C-delivery under spinal anesthesia.

Materials and Methods

A total of 100 patients scheduled for elective c-section were grouped into those who received both warmed IV fluid infusion and forced air warmer (Combination of active warming WI= 50) and those who received only forced air warmer (WA = 50). Core body temperature and shivering incidence were recorded using a tympanic thermometer from prespinal till the end of surgery every 10 min and in postanesthesia care unit (PACU) at 0, 15, and 30 min.

Results

Core temperature showed statistically significant difference in 15, 35, 45, and 55 min between air warmer and warm infusion groups and in PACU at 0, 15, and 30 min, it was statistically significant (P = 0.000) among WI group (mean temperature = 36.79°C) when compared to WA group (mean temperature = 35.96°C). There was a lower incidence of shivering in WI compared to WA group, which is statistically significant.

Conclusion

Combination of warm Intravenous fluid infusion and Forced air warming is better than forced air warming alone. In maintaining near normal maternal core body temperature during elective cesarean section following spinal anesthesia. Combined warming method also reduces shivering incidence.

Prewarming Followed by Active Warming is Superior to Passive Warming in Preventing Hypothermia for Short Procedures in Adult Rats (Rattus norvegicus) Under Isoflurane Anesthesia

General anesthesia is a common procedure in laboratory rats; however, it impairs thermoregulation, rapidly leading to hypothermia as warm core blood is distributed to the cooler periphery. The protective strategy of prewarming before the onset of anesthesia delays hypothermia, but only for a short period. This prospective, randomized, cross-over, experimental study in adult male and female SD rats (n = 8) was designed to compare passive (fleece blanket) and active (temperature controlled heating pad) warming. Initial treatment order was randomized, with a cross-over after a minimum 5 d washout period. Both groups underwent a period of prewarming in a warming box to increase core temperature by 1% (median 0.4 °C). At completion of prewarming, general anesthesia was induced and maintained for 30 min with isoflurane carried in oxygen. Core temperature was monitored for a further 30 min after anesthesia. Active warming resulted in higher core temperatures during anesthesia. During passive warming, hypothermia occurred after approximately 30 min of anesthesia and continued into recovery. In contrast, active warming prevented hypothermia. Prewarming followed by passive warming delayed hypothermia for approximately 30 min, but active warming was more effective at maintaining normothermia both during and after general anesthesia.

Short interruptions between pre-warming and intraoperative warming are associated with low intraoperative hypothermia rates

BACKGROUND

Prevention of inadvertent hypothermia is recommended for procedures >30 minutes because hypothermia increases the risk of myocardial ischemia, intraoperative blood loss, transfusion and wound complications. Therefore, short warming interruptions between pre-warming and intraoperative warming might result in lower hypothermia rates. The aim of this retrospective investigation was to determine whether the incidence of inadvertent intraoperative hypothermia was affected by the warming interruption.

METHODS

The lowest intraoperative body core temperature value and the warming interruption time were taken from anaesthesia records. Body core temperature was recorded continuously, and a patient was classified to be hypothermic if the lowest recorded temperature value was <36°C. Hypothermia rates and the correlation between warming interruption times and intraoperative hypothermia rates were calculated.

RESULTS

Five thousand eighty-four patients were analysed. The intraoperative hypothermia rate was 15.3%. Nineteen patients (0.4%) had a recorded temperature of <35.0°C. An increase in forced-air warming interruption time was significantly associated with an increase in intraoperative hypothermia rates (P < .0001). Patients with interruptions in forced-air warming >20 minutes showed significantly higher hypothermia rates than those with interruptions of ≤20 minutes (P < .0001).

CONCLUSION

Intraoperative hypothermia rates increased significantly with longer forced-air warming interruptions between pre-warming and intraoperative warming. Short warming interruptions can preserve the effect of pre-warming and are associated with low intraoperative hypothermia rates.

Pre-warming before general anesthesia with isoflurane delays the onset of hypothermia in rats

General anesthesia causes hypothermia by impairing normal thermoregulatory mechanisms. When using inhalational anesthetic agents, Redistribution of warm blood from the core to the periphery is the primary mechanism in the development of hypothermia and begins following induction of anesthesia. Raising skin temperature before anesthesia reduces the temperature gradient between core and periphery, decreasing the transfer of heat. This prospective, crossover study (n = 17 adult male and female SD rats) compared three treatment groups: PW1% (pre-warming to increase core temperature 1% over baseline), PW40 (pre-warming to increase core temperature to 40°C) and NW (no warming). The PW1% group was completed first to ensure tolerance of pre-warming. Treatment order was then randomized and alternated after a washout period. Once target temperature was achieved, anesthesia was induced and maintained with isoflurane in oxygen without further external temperature support. Pre-warming was effective at delaying the onset of hypothermia, with a significant difference between PW1% (12.4 minutes) and PW40 (19.3 minutes, p = 0.0044 (95%CI -12 to -2.2), PW40 and NW (7.1 minutes, p < 0.0001 (95%CI 8.1 to 16.0) and PW1% and NW (p = 0.003, 95%CI 1.8 to 8.7). The rate of heat loss in the pre-warmed groups exceed that of the NW group: PW1% versus NW (p = 0.005, 95%CI 0.004 to 0.027), PW40 versus NW (p < 0.0001, 95%CI 0.014 to 0.036) and PW1% versus PW40 (p = 0.07, 95%CI -0.021 to 0.00066). Pre-warming alone confers a protective effect against hypothermia during volatile anesthesia; however, longer duration procedures would require additional heating support.

Effects of combined warmed preoperative forced-air and warmed perioperative intravenous fluids on maternal temperature during cesarean section: a prospective, randomized, controlled clinical trial

Background

Preventing the frequent perioperative hypothermia incidents that occur during elective caesarean deliveries would be beneficial. This trial aimed at evaluating the effect of preoperative forced-air warming alongside perioperative intravenous fluid warming in women undergoing cesarean sections under spinal anesthesia.

Methods

We randomly allocated 135 women undergoing elective cesarean deliveries to either the intervention group (preoperative forced-air and intravenous fluid warming, n = 69) or the control group (no active warming, n = 66). The primary outcome measure was the core temperature change between groups from baseline to the end of the surgical procedure. Secondary outcomes included thermal comfort scores, the incidences of shivering and hypothermia (< 36 °C), the core temperature on arrival at the post-anesthesia care unit, neonatal axillary temperature at birth, and Apgar scores.

Results

Two-way repeated measures ANOVA revealed significantly different core temperature changes (from the pre-spinal temperature to that at the end of the procedure) between groups (F = 13.022, P < 0.001). The thermal comfort scores were also higher in the intervention group than in the control group (F = 9.847, P = 0.002). The overall incidence of perioperative hypothermia was significantly lower in the intervention group than in the control group (20.6% vs. 51.6%, P < 0.0001).

Conclusions

Warming preoperative forced-air and perioperative intravenous fluids may prevent maternal hypothermia, reduce maternal shivering, and improve maternal thermal comfort for patients undergoing cesarean sections under spinal anesthesia.

Trial registration

The study was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR1800019117) on October26, 2018.

Induction techniques that reduce redistribution hypothermia: a prospective, randomized, controlled, single blind effectiveness study

Background

While much effort has been devoted to correcting intraoperative hypothermia, less attention has been directed to preventing redistribution hypothermia. In this study, we compared three different anesthetic induction techniques to standard IV propofol inductions (control) in their effect on reducing redistribution hypothermia.

Methods

Elective, afebrile patients, age 18 to 55 years, were randomly assigned to one of four groups (n = 50 each). Group “INH/100” was induced with 8% sevoflurane in 100% oxygen, Group “INH/50” with 8% sevoflurane in 50% oxygen and 50% nitrous oxide, Group “PROP” with 2.2 mg/kg propofol, and Group “Phnl/PROP” with 2.2 mg/kg propofol immediately preceded by 160 mcg phenylephrine. Patients were maintained with sevoflurane in 50% nitrous oxide and 50% oxygen in addition to opioid narcotic. Forced air warming was used. Core temperatures were recorded every 15 min after induction for 1 h.

Results

Compared to control group PROP, the mean temperatures in groups INH/100, INH/50, and Phnl/PROP were higher 15, 30, 45 and 60 min after induction (p < 0.001 for all comparisons), averaging between 0.39 °C and 0.54 °C higher. In group PROP, 60% of patients had at least one temperature below 36.0 °C in the first hour whereas only 16% did in each of groups INH/100, INH/50, and Phnl/PROP (p < 0.0001 in each group compared to PROP).

Conclusions

In this effectiveness trial, inhalation inductions with sevoflurane or with prophylactic phenylephrine bolus prior to propofol induction reduced the magnitude of redistribution hypothermia by an average of 0.4 to 0.5 °C in patients aged 18 to 55 years.

Trial registration

Retrospectively registered on clinical-trials.gov as NCT02331108, November 20, 2014.

Preventing hypothermia in outpatient plastic surgery by self-warming or forced-air-warming blanket: A randomised controlled trial

BACKGROUND

In our outpatient post anaesthesia unit patients reported that they were feeling cold with or without shivering. Anaesthetic agents cause reduced thermoregulation, initially by redistribution of blood flow from core to periphery, later by negative balance between thermogenesis and heat loss. Even mild peri-operative hypothermia increases the risk of surgical wound infections, bleeding, impaired cardiac function, shivering, and decreases comfort.

OBJECTIVE(S)

We aimed to evaluate which of our current active warming measures, self-warming blanket or forced-air-warming blanket, were most effective in preventing inadvertent intraoperative heat loss. Secondarily, we assessed whether they prevented inadvertent peri-operative hypothermia when defined as core body temperature below 36 °C.

DESIGN

Randomised controlled trial, parallel group design.

SETTING

Aleris Solsiden hospital for outpatient surgery, Trondheim, Norway, from March to June 2016.

PATIENTS

A total of 112 consecutive patients planned for outpatient plastic surgery. Reasons for noninclusion: failing to meet the criteria for outpatient surgery according to the standard of the national society of anaesthesiology.

INTERVENTION(S)

Patients were randomised to active warming by a self-warming blanket or a forced-air-warming blanket. All patients received routine measures to prevent hypothermia with a high temperature in the operation theatres, prewarmed fluids, cotton blankets and surgical draping outside the surgical field.

MAIN OUTCOMES

Temperature, measured pre-operatively, every 10 min during general anaesthesia and postoperatively with a zero-heat-flux temperature sensor.

RESULTS

Core temperature was significantly lower in the self-warming blanket compared with the forced-air-warming blanket group during anaesthesia, P less than 0.0001. Hypothermia (<36 °C) was recorded in 47%, n = 22, patients in the self-warming blanket group and 25%, n = 16, in the forced-air-warming blanket group during the registration period, P = 0.02.

CONCLUSION

An underbody forced-air-warming blanket reduced heat loss to a greater extent than a self-warming blanket. But none of the interventions were sufficient to prevent inadvertent peri-operative hypothermia.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03163563.

Effects of indoor environmental parameters related to building heating, ventilation, and air conditioning systems on patients' medical outcomes: A review of scientific research on hospital buildings

The indoor environment of a mechanically ventilated hospital building controls infection rates as well as influences patients' healing processes and overall medical outcomes. This review covers the scientific research that has assessed patients' medical outcomes concerning at least one indoor environmental parameter related to building heating, ventilation, and air conditioning (HVAC) systems, such as indoor air temperature, relative humidity, and indoor air ventilation parameters. Research related to the naturally ventilated hospital buildings was outside the scope of this review article. After 1998, a total of 899 papers were identified that fit the inclusion criteria of this study. Of these, 176 papers have been included in this review to understand the relationship between the health outcomes of a patient and the indoor environment of a mechanically ventilated hospital building. The purpose of this literature review was to summarize how indoor environmental parameters related to mechanical ventilation systems of a hospital building are impacting patients. This review suggests that there is a need for future interdisciplinary collaborative research to quantify the optimum range for HVAC parameters considering airborne exposures and patients' positive medical outcomes.

A prospective comparative study between prewarming and cowarming to prevent intraoperative hypothermia

Background and Aims:

Inadvertent perioperative hypothermia defined as the perioperative core temperature of <36°C is a common problem in day-to-day anesthesia practice. It is not clear from the literature whether prewarming, that is, initiation of convective warming of the patient at a time point prior to induction of anesthesia is superior or comparable to cowarming, that is, initiation of convective warming simultaneously with induction of anesthesia. We conducted this study to find whether cowarming is as good as prewarming in preventing the occurrence of intraoperative hypothermia.

Material and Methods:

Sixty-two adult patients undergoing major abdominal surgery under general anesthesia were randomized to receive either prewarming for 60 min at 40° C or cowarming using the Level 1® Equator ® body warmer. All patients who were prewarmed also received cowarming during induction of anesthesia. In both the groups, convective warming was continued during intraoperative period. Incidence of intraoperative hypothermia, core, and peripheral body temperatures were compared between the two groups.

Results:

Among 27 patients in each group who completed the study core temperature decreased to <35° C toward the end of surgery in 17 patients in group prewarming [mean (SD) 34.59 (1.17° C)] and 18 patients in group cowarming [mean (SD) 34.31 (1.34° C)]. The incidence of intraoperative hypothermia and the core temperature at the end of surgery were comparable (P = 0.42).

Conclusion:

Cowarming is as effective as prewarming to prevent intraoperative hypothermia.

Quantifying and Trending the Thermal Signal as an Index of Perfusion in Patients Sedated with Propofol

We examined the feasibility of a thermal imager smart phone attachment as a potential proxy of skin perfusion by assessing shifts in skin temperature following administration of the vasodilatory anesthetic propofol. Four limb distal extremity thermal images were taken before propofol administration and at 5-min intervals thereafter during monitored anesthesia. The study enrolled 60 patients with ages ranging from 1.3 to 18 years (mean 10.7 years old) from April 2016 to January 2017. Five minutes following propofol administration, the median temperature differential (delta temperature) between the core and extremity skin significantly decreased in both upper and lower extremities, 7.9 to 3.6 °C (p < 0.0001) and 12.1 to 6.9 °C (p < 0.0001), respectively. By 10 min, the median delta temperatures further decreased significantly in the upper (p = 0.0068) and lower extremities (p = 0.0018). There was a concordant decrease in mean blood pressure (MBP). These trends reverted back when the subject awoke. There was no significant difference between the four operators who used the camera (p = 0.0831). Blood pressure and time temperature change was the only value of significance. Mobil thermal imaging represents a non-invasive modality to assess perfusion in real time. Further studies are required to validate the clinical utility.

Prevention of laparoscopic surgery induced hypothermia with warmed humidified insufflation: Is the experimental combination of a warming blanket synergistic?

INTRODUCTION

Maintaining normothermia during anesthesia is imperative to provide quality patient care and to prevent adverse outcomes. Prolonged laparoscopic procedures have been identified as a potential risk factor for hypothermia, due to continuous insufflation of cold and dry carbon dioxide. Perioperative hypothermia is associated with increased hospital cost and many complications including; impaired drug metabolism, impaired immune function, cardiac morbidity, shivering, coagulopathy.

METHODS

In this experimental study, four pigs underwent four interventions each, resulting in 16 total trials. Using standardized general anesthesia in a randomized Latin-square sequence the four interventions include: 1. Control group without an administered pneumoperitoneum, 2. Administered standard pneumoperitoneum using 21°C insufflated gas and under-body forced-air warming, 3. Administered pneumoperitoneum with insufflation of warmed/humidified carbon dioxide, 4. Administered pneumoperitoneum with insufflation of warmed/humidified carbon dioxide and under-body forced-air warming. The primary outcome was distal esophageal temperature change 4 hours after trocar insertion.

RESULTS

Four hours after trocar insertion, pigs in the control group lost 2.1 ± 0.4°C; pigs with warmed and humidified insufflation lost 1.8 ± 0.4°C; pigs with forced-air warming group lost 1.3 ± 0.9°C; and pigs exposed to a combination of warmed and humidified insufflation with forced-air warming increased by 0.3 ± 0.2°C.

CONCLUSION

This experimental animal study provides evidence that a combination of warmed and humidified insufflation of carbon dioxide (CO2) in conjunction with forced-air warming is an effective strategy in the prevention of perioperative hypothermia. Further clinical trials investigating humans are therefore indicated.

Effects of Ambient Temperature and Forced-air Warming on Intraoperative Core Temperature

Background

The effect of ambient temperature, with and without active warming, on intraoperative core temperature remains poorly characterized. The authors determined the effect of ambient temperature on core temperature changes with and without forced-air warming.

Methods

In this unblinded three-by-two factorial trial, 292 adults were randomized to ambient temperatures 19°, 21°, or 23°C, and to passive insulation or forced-air warming. The primary outcome was core temperature change between 1 and 3 h after induction. Linear mixed-effects models assessed the effects of ambient temperature, warming method, and their interaction.

Results

A 1°C increase in ambient temperature attenuated the negative slope of core temperature change 1 to 3 h after anesthesia induction by 0.03 (98.3% CI, 0.01 to 0.06) °Ccore/(h.°Cambient) (P &lt; 0.001), for patients who received passive insulation, but not for those warmed with forced-air (–0.01 [98.3% CI, –0.03 to 0.01] °Ccore/[h.°Cambient]; P = 0.40). Final core temperature at the end of surgery increased 0.13°C (98.3% CI, 0.07 to 0.20; P &lt; 0.01) per degree increase in ambient temperature with passive insulation, but was unaffected by ambient temperature during forced-air warming (0.02 [98.3% CI, –0.04 to 0.09] °Ccore/°Cambient; P = 0.40). After an average of 3.4 h of surgery, core temperature was 36.3° ± 0.5°C in each of the forced-air groups, and ranged from 35.6° to 36.1°C in passively insulated patients.

Conclusions

Ambient intraoperative temperature has a negligible effect on core temperature when patients are warmed with forced air. The effect is larger when patients are passively insulated, but the magnitude remains small. Ambient temperature can thus be set to comfortable levels for staff in patients who are actively warmed.

Effects of Thermal Protection in Patients Undergoing Body Contouring Procedures: A Controlled Clinical Trial

BACKGROUND

Hypothermia is common in many plastic surgery procedures, but few measures to prevent its occurrence are taken.

OBJECTIVES

This study evaluated the effect of hypothermia in patients undergoing plastic surgery procedures and the effect of utilizing simple and inexpensive measures to prevent patient hypothermia during surgery.

METHODS

A randomized controlled clinical trial was performed among 3 groups of patients who underwent body contouring surgery for longer than 3.5 hours. In group 1, no protective measures were taken to prevent hypothermia; in group 2, maneuvers were applied intraoperatively for the duration of the entire surgical procedure; and in group 3, measures were taken preoperatively and intraoperatively. The results were quantified and analyzed through a bivariate analysis, including degree of hypothermia, anesthesia recovery time, time spent in the recovery area, intensity of pain, cold perception, response to opioids, and nausea.

RESULTS

There were 122 patients included in the study: 43 in group 1, 39 in group 2, and 40 in group 3. All patients in group 1 had a higher degree of hypothermia, longer recovery time from anesthesia, longer overall recovery time, increased pain, increased feeling of cold, and more nausea. These patients also required a greater amount of opioids compared with the patients in groups 2 and 3. Many of the results were statistically significant.

CONCLUSIONS

The adoption of simple and inexpensive measures before and during plastic surgery can prevent patient hypothermia during the procedures, leading to a shorter anesthesia recovery time and avoiding the undesirable effects associated with hypothermia. In addition, these measures may have significant economic savings.

LEVEL OF EVIDENCE 2

Prewarming: Preventing Intraoperative Hypothermia

Perioperative hypothermia can be followed by severe complications. The greatest proportion of temperature decrease is attributed to heat redistribution, which mainly occurs during the first hour of anaesthesia and is difficult to treat intraoperatively. Prewarming, based on active warming techniques, has been proposed. Even a short period of prewarming may significantly increase peripheral tissue temperature, minimise normal core-to-peripheral temperature gradient, and keep core temperature within normal limits.

The impact of operative time and hypothermia in acute burn surgery

BACKGROUND

Prolonged operative time and intraoperative hypothermia are known to have deleterious effects on surgical outcomes. Although millions of burn injuries undergo operative treatment globally every year, there remains a paucity of evidence to guide perioperative practice in burn surgery. This study evaluated associations between hypothermia and operative time on post-operative complications in acute burn surgery.

METHOD

A historical cohort study from January 1, 2006 to October 31, 2015 was completed at an American Burn Association verified burn centre. 1111 consecutive patients undergoing acute burn surgery were included, and 2171 surgeries were analyzed. Primary outcomes included post-operative complications, defined a priori as either infectious or noninfectious. Statistical analysis was undertaken using a modified Poisson model for relative risk, adjusted for total body surface area, inhalation injury, co-morbidities, substance abuse, and age.

RESULTS

The mean operative time was 4.4h (SD 3.7-4.7h; range 0.58-11h), and 18.6% of patients became hypothermic intra-operatively. Operative time was independently associated with the incidence of hypothermia (p<0.05), and both infectious (RR1.5; 1.2-1.9, p<0.0004) and non-infectious complications (RR2.3; 1.3-4.1, p<0.0066). In patients with major burns (TBSA≥20%), hypothermia predisposed to infectious (RR1.3; 1.1-1.5, p<0.0017) and non-infectious complications (RR1.7; 1.2-2.5; p<0.0049). Risk stratification revealed that hypothermic patients with major burns undergoing prolonged surgery had an increased risk of both infectious (RR1.4; 1.1-1.7, p<0.0068) and non-infectious complications (RR1.8; 1.1-3.0, p<0.0132) when compared with those without these risk factors.

CONCLUSIONS

Patients who undergo prolonged surgeries and become hypothermic are more likely to develop complications. We therefore advocate for diligent adherence to strategies to prevent hypothermia and recommend limiting operative time in clinical circumstances where intraoperative measures are unlikely to adequately prevent hypothermia.

A novel thermal compression device for perioperative warming: a randomized trial for feasibility and efficacy

Background

Inadvertent perioperative hypothermia (IPH) leads to surgical complications and increases length of stay. IPH rates are high with the current standard of care, forced air warming (FAW). Our hypothesis is that a prototype thermal compression device that heats the popliteal fossa and soles of the feet, with lower leg compression, increases perioperative temperatures and reduces IPH compared to the current standard of care.

Methods

Thirty six female breast surgery patients, at a tertiary academic hospital, were randomized to the device or intraoperative FAW (stage I) with a further 18 patients randomized to the device with a single heating area only (stage II, popliteal fossa or sole of the feet). Stage I: 37 patients recruited (final 36). Stage II: 18 patients recruited (final 18). Inclusion criteria: general anesthesia with esophageal monitoring for over 30 min, legs available and able to fit the device and no contraindications to leg heating or compression. The intervention was: Stage I: Investigational prototype thermal compression device (full device group) or intraoperative FAW. Stage II: Device with only a single heating location. Primary outcomes were perioperative temperatures and incidence of IPH. Secondary outcomes were local skin temperature, general and thermal comfort scores and presence of perioperative complications, including blood loss.

Results

Mean temperatures in the full device group were significantly higher than the FAW group in the pre-operative (36.7 vs 36.4 °C, p < 0.001), early intraoperative (36.3 vs 35.9 °C, p < 0.001), intraoperative (36.6 vs 36.2 °C, p < 0.001) and postoperative periods (36.8 vs 36.5 °C, p < 0.001). The incidence of IPH in the device group was also significantly lower (16.7% vs 72.0%, p = 0.001). Thermal comfort scores were significantly higher in the full device group and hypothermia associated wound complications were higher in the FAW group.

Conclusions

The thermal compression device is feasible and has efficacy over the FAW. Further studies are recommended to investigate clinically significant outcomes.

Trial registration

clinicaltrials.gov (NCT02155400)

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-017-0395-2) contains supplementary material, which is available to authorized users.

Warming infusion improves perioperative outcomes of elderly patients who underwent bilateral hip replacement

BACKGROUND

This prospective, randomized, and controlled study was performed to determine the benefits of prewarmed infusion in elderly patients who underwent bilateral hip replacement.

METHODS

Between September 2015 and April 2016, elderly patients who underwent bilateral hips replacement that met the inclusion and exclusion criteria were included in this study. After inclusion, patients were randomized into one of the study groups: in the control group, patients received an infusion of fluid kept at room temperature (22-23°C); in the warming infusion group, patients received an infusion of fluid warmed using an infusion fluid heating apparatus (35°C). Postoperative outcomes, including recovery time, length of hospital stay, visual analogue scale (VAS) score, and postoperative complications rate of patients from both groups, were compared.

RESULTS

A total of 64 patients were included in our study (71.2 ± 7.6 years, 53.1% males), with 32 patients in the control group and 32 patients in warming infusion group. No significant difference was found in terms of demographic data and intraoperative blood transfusion rate between 2 groups (P > 0.05). Patients receiving a prewarmed infusion had a significantly shorter time to spontaneous breath, eye opening, consciousness recovery, and extubation than the control group (P < 0.05). In addition, significant differences were found in Steward score and VAS score between 2 groups (P < 0.05). Moreover, warming infusion group also showed an obviously decreased incidence of shivering and postoperative cognitive dysfunction (P < 0.05).

CONCLUSION

A prewarmed infusion could reduce the incidence of perioperative hypothermia and improve outcomes in the elderly during bilateral hip replacement.

The Optimal Time and Method for Surgical Prewarming: A Comprehensive Review of the Literature

PURPOSE

Inadvertent hypothermia is a common problem in the operating room. This can contribute to many unfavorable outcomes --rising costs, increased complications, and higher morbidity rates.

DESIGN

This review determined the optimal method and time to prewarm a surgical patient to prevent perioperative hypothermia.

METHODS

CINAHL and PubMed were searched. Fourteen articles were ultimately included in this review.

FINDINGS

Based on the literature reviewed, it was suggested that forced-air warming was most effective in preventing perioperative hypothermia. Eighty-one percent of the experimental studies reviewed found that there was a significantly higher temperature throughout surgery and in the postanesthesia care unit for patients who received forced-air prewarming.

CONCLUSIONS

Thirty minutes was found to be the average suggested amount of time for prewarming among the literature; however, a minimum of 10 minutes of prewarming was suggested to significantly reduce rates of hypothermia in perioperative patients and decrease the adverse effects of hypothermia.

The effect of 30 to 60 minutes of forced-air pre-warming on maintaining intraoperative core temperatures during the first hour post-anesthesia induction in adult patients undergoing general anesthesia: a systematic review protocol

REVIEW QUESTION/OBJECTIVE

The objective of this review is to identify the effectiveness of 30 to 60 minutes of forced-air pre-warming on maintaining intraoperative core temperatures in adult patients undergoing general anesthesia. The review question will focus on the effects of forced-air pre-warming on preventing redistribution hypothermia in the first hour post induction of anesthesia, which is considered the most critical due to an internal core-to-peripheral redistribution of body heat and subsequent loss of heat to the operative room surroundings.

Effect of Prewarming during Induction of Anesthesia on Microvascular Reactivity in Patients Undergoing Off-Pump Coronary Artery Bypass Surgery: A Randomized Clinical Trial

BACKGROUND

General anesthesia may induce inadvertent hypothermia and this may be related to perioperative cardiovascular complications. Microvascular reactivity, measured by the recovery slope during a vascular occlusion test, is decreased during surgery and is also related to postoperative clinical outcomes. We hypothesized that microvascular changes during surgery may be related to intraoperative hypothermia. To evaluate this, we conducted a randomized study in patients undergoing off-pump coronary artery bypass surgery, in which the effect of prewarming on microvascular reactivity was evaluated.

METHODS

Patients scheduled for off-pump coronary artery bypass surgery were screened. Enrolled patients were randomized to the prewarming group to receive forced-air warming during induction of anesthesia or to the control group. Measurement of core and skin temperatures and vascular occlusion test were conducted before anesthesia induction, 1, 2, and 3 h after induction, and at the end of surgery.

RESULTS

In total, 40 patients were enrolled and finished the study (n = 20 in the prewarming group and n = 20 in the control group). During the first 3 h of anesthesia, core temperature was higher in the prewarming group than the control group (p < 0.001). The number of patients developing hypothermia was lower in the prewarming group than the control group (4/20 vs. 13/20, p = 0.004). However, tissue oxygen saturation and changes in recovery slope following a vascular occlusion test at 3 h after anesthesia induction did not differ between the groups. There was no difference in clinical outcome, including perioperative transfusion, wound infection, or hospital stay, between the groups.

CONCLUSIONS

Prewarming during induction of anesthesia decreased intraoperative hypothermia, but did not reduce the deterioration in microvascular reactivity in patients undergoing off-pump coronary artery bypass surgery.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02186210.

Prewarming neurosurgical patients to minimize hypotension on induction of anesthesia: a randomized trial

PURPOSE

Prewarming prior to surgery is effective in preventing perioperative hypothermia. There is a paucity of evidence, however, regarding the hemodynamic effects of prewarming. We hypothesized that the nadir mean arterial pressure during anesthesia induction would be higher after prewarming than after no prewarming.

METHODS

We randomized 32 patients prior to elective neurosurgery to receive either one hour of forced-air convective warming at 46°C or routine care (full body blanket with convective warmer attached but not turned on). All patients had invasive blood pressure, heart rate, and core temperature monitoring before and during warming and underwent a protocolized intravenous anesthetic induction with propofol and remifentanil target-controlled infusions. The primary endpoint was the nadir mean arterial blood pressure (MAP) during induction. Hypotension was defined as systolic blood pressure (SBP) < 90 mmHg, MAP < 60 mmHg, or a reduction in either SBP or MAP > 20% from baseline values.

RESULTS

No difference was found in the mean (SD) nadir MAP between the prewarmed group and the control group [64 (11) mmHg vs 68 (16) mmHg, respectively; mean difference, 5 mmHg; 95% confidence interval (CI), -6 to 15; P = 0.36]. Similarly, there was no difference between groups in the incidence of hypotension (100% of prewarmed vs 93% of control patients; relative risk, 1.07; 95% CI, 0.94 to 1.23; P = 0.32) or in the requirement for vasopressors during induction (four patients in each group required metaraminol; P = 1.00).

CONCLUSION

Prewarming with convective forced air for one hour prior to intravenous anesthetic induction did not prevent hypotension during the induction period (Australian New Zealand Clinical Trials Registry [ANZCTR] ACTRN12615000431527).

Anesthesia and sedation outside of the operating room

Due to rapid evolution and technological advancements, medical personnel now require special training outside of their safe zones. Anesthesiologists face challenges in practicing in locations beyond the operating room. New locations, inadequate monitoring devices, poor assisting staff, unfamiliarity of procedures, insufficient knowledge of basic standards, and lack of experience compromise the quality of patient care. Therefore, anesthesiologists must recognize possible risk factors during anesthesia in nonoperating rooms and familiarize themselves with standards to improve safe practice. This review article emphasizes the need for standardizing hospitals and facilities requiring nonoperating room anesthesia, and encourages anesthesiologists to take the lead in applying these practice guidelines to improve patient outcomes and reduce adverse events.

Intraoperative Mean Arterial Pressure Variability and 30-day Mortality in Patients Having Noncardiac Surgery

Background:

Little is known about the relationship between intraoperative blood pressure variability and mortality after noncardiac surgery. Therefore, the authors tested the hypothesis that blood pressure variability, independent from absolute blood pressure, is associated with increased 30-day mortality.

Methods:

Baseline and intraoperative variables plus 30-day mortality were obtained for 104,401 adults having noncardiac surgery lasting 60 min or longer. In confounder-adjusted models, the authors evaluated the associations between 30-day mortality and both time-weighted average intraoperative mean arterial pressure (TWA-MAP) and measures of intraoperative MAP variability—including generalized average real variability of MAP (ARV-MAP) and SD of MAP (SD-MAP).

Results:

Mean ± SD TWA-MAP was 84 ± 10 mmHg, and ARV-MAP was 2.5 ± 1.3 mmHg/min. TWA-MAP was strongly related to 30-day mortality, which more than tripled as TWA-MAP decreased from 80 to 50 mmHg. ARV-MAP was only marginally related to 30-day mortality (P = 0.033) after adjusting for TWA-MAP. Compared with median ARV-MAP, odds ratio (95% CI) for 30-day mortality was 1.14 (1.03 to 1.25) for low ARV-MAP (first quartile) and 0.94 (0.88 to 0.99) for high ARV-MAP (third quartile). Odds of 30-day mortality decreased as five-level categorized ARV-MAP increased (0.92; 0.87 to 0.99 for one category increase; P = 0.015). Secondarily, cumulative duration of MAP less than 50, 55, 60, 70, and 80 mmHg was associated with increased odds of 30-day mortality (all P &lt; 0.001).

Conclusion:

Although lower mean arterial pressure is strongly associated with mortality, lower intraoperative blood pressure variability per se is only mildly associated with postoperative mortality after noncardiac surgery.

Intraoperative core temperature patterns, transfusion requirement, and hospital duration in patients warmed with forced air

BACKGROUND

Core temperature patterns in patients warmed with forced air remain poorly characterized. Also unknown is the extent to which transient and mild intraoperative hypothermia contributes to adverse outcomes in broad populations.

METHODS

We evaluated esophageal (core) temperatures in 58,814 adults having surgery lasting >60 min who were warmed with forced air. Independent associations between hypothermic exposure and transfusion requirement and duration of hospitalization were evaluated.

RESULTS

In every percentile subgroup, core temperature decreased during the first hour and subsequently increased. The mean lowest core temperature during the first hour was 35.7 ± 0.6°C. Sixty-four percent of the patients reached a core temperature threshold of <36°C 45 min after induction; 29% reached a core temperature threshold of <35.5°C. Nearly half the patients had continuous core temperatures <36°C for more than an hour, and 20% of the patients were <35.5°C for more than an hour. Twenty percent of patients had continuous core temperatures <36°C for more than 2 h, and 8% of the patients were below 35.5°C for more than 2 h. Hypothermia was independently associated with both transfusions and duration of hospitalization, although the prolongation of hospitalization was small.

CONCLUSIONS

Even in actively warmed patients, hypothermia is routine during the first hour of anesthesia. Thereafter, average core temperatures progressively increase. Nonetheless, intraoperative hypothermia was common, and often prolonged. Hypothermia was associated with increased transfusion requirement, which is consistent with numerous randomized trials.

Thermoregulation and Risk of Surgical Site Infection

Surgical site infections (SSIs) occur in approximately 2%–5% of patients undergoing surgery in the acute care setting in the United States. These infections result in increased length of stay, higher risk of death, and increased cost of care compared with that in uninfected surgical patients. Given the inclusion of maintenance of perioperative normothermia for all major surgeries as a means of lowering the risk of infection in the Surgical Care Improvement Project 2009, we prepared a summary of the literature to determine the strength and quantity of the evidence underlying the performance measure. Although the data are generally supportive of perioperative normothermia as a means of reducing the risk of SSIs, a more rigorous approach using standard SSI definitions as well as standardized temperature measurements (and timing thereof) will further delineate the role played by temperature regulation in SSI development.

[Prewarming. Yesterday's luxury, today's minimum requirement]

Prewarming is a useful and effective measure to reduce perioperative hypothermia. Due to §23(3) of the German Infektionsschutzgesetz (Gesetz zur Verhütung und Bekämpfung von Infektionskrankheiten beim Menschen, Infection Act, act on protection and prevention of infectious diseases in man) and the recommendations of the Hospital Hygiene and Infection Prevention Committee of the Robert Koch Institute, implementation of prewarming is clearly recommended. There are several technically satisfactory and practicable devices available allowing prewarming on the normal hospital ward, in the preoperative holding area or in the induction room of the operating theater (OR) The implementation of prewarming requires additional equipment and training of staff. Using a locally adapted concept for the implementation of prewarming does not lead to inefficiency in the perioperative process. In contrast, the implementation can help to achieve stable arrival times for patients in the OR.

Preventing hypothermia in elective arthroscopic shoulder surgery patients: a protocol for a randomised controlled trial

Background

Patients having arthroscopic shoulder surgery frequently experience periods of inadvertent hypothermia. This common perioperative problem has been linked to adverse patient outcomes such as myocardial ischaemia, surgical site infection and coagulopathy. International perioperative guidelines recommend patient warming, using a forced air warming device, and the use of warmed intraoperative irrigation solutions for the prevention of hypothermia in at-risk patient groups. This trial will investigate the effect of these interventions on patients’ temperature, thermal comfort, and total recovery time.

Method/Design

The trial will employ a randomised 2 x 2 factorial design. Eligible patients will be stratified by anaesthetist and block randomised into one of four groups: Group one will receive preoperative warming with a forced air warming device; group two will receive warmed intraoperative irrigation solutions; group three will receive both preoperative warming and warmed intraoperative irrigation solutions; and group four will receive neither intervention. Participants in all four groups will receive active intraoperative warming with a forced air warming device. The primary outcome measures are postoperative temperature, thermal comfort, and total recovery time. Primary outcomes will undergo a two-way analysis of variance controlling for covariants such as operating room ambient temperature and volume of intraoperative irrigation solution.

Discussion

This trial is designed to confirm the effectiveness of these interventions at maintaining perioperative normothermia and to evaluate if this translates into improved patient outcomes.

Australian New Zealand Clinical Trials Registry number

ACTRN12610000591055