Prospective observational study of the effectiveness of prewarming on perioperative hypothermia in surgical patients submitted to spinal anesthesia

The Effect of Prewarming on Perioperative Hypothermia: A Systematic Review and Meta-analysis of Randomized Controlled Studies

PURPOSE

One of the methods for maintaining perioperative normothermia is prewarming. This study was conducted to investigate the effect of a preoperative prewarming intervention on perioperative body temperature.

DESIGN

Systematic review and meta-analysis.

METHODS

A literature review was conducted using PubMed, CINAHL, Cochrane Central, Science Direct, Springer Link, Scopus, Web of Science, and Ovid databases. Randomized controlled trials that investigate the effect of prewarming on body temperature in the prevention of perioperative hypothermia were included. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement guidelines. Methodological quality was assessed using the Cochrane Collaboration "risk of bias" tool. Meta-analysis was performed with Comprehensive Meta-Analysis, version 2. Moderator analysis and publication bias assessment were performed. Funnel plots were analyzed using Orwin's fail-safe N, Trim, and Fill test method to investigate the source of heterogeneity.

FINDINGS

A total of 907 studies were found. The systematic review included 27 studies. Of these, 23 were included in the intraoperative meta-analysis, and 16 were included in the postoperative meta-analysis. According to the meta-analysis results, the prewarming intervention was effective in maintaining normothermia in the intraoperative (Hedge's g = 0.972, 95% confidence intervaI = 0.674 to 1.270) and postoperative (Hedge's g = 0.818, 95% confidence intervaI = 0.520 to 1.114) periods.

CONCLUSIONS

The findings of this systematic review and meta-analysis showed that preoperative prewarming played a significant role in providing and maintaining perioperative normothermia.

Perioperative hypothermia in robotic-assisted thoracic surgery: Incidence, risk factors, and associations with postoperative outcomes

OBJECTIVE

Inadvertent perioperative hypothermia has been associated with poor surgical outcomes. The purpose of this study was to evaluate the incidence and associated postoperative complications of inadvertent perioperative hypothermia in patients undergoing robotic-assisted thoracic surgery lung resections.

METHODS

This was a single-center, retrospective cohort study evaluating all consecutive patients who underwent robotic-assisted thoracic surgery lung resection between January 1, 2021, and November 30, 2022. Temperatures were measured at 5 time points: preprocedure unit, anesthesia induction, 30 minutes postinduction, extubation, and recovery room arrival. Temperature changes were calculated at each interval. Adjusted and unadjusted comparison was performed between those who experienced varying levels of inadvertent perioperative hypothermia (Hypothermia I: <36 °C, Hypothermia II: <35.5 °C, and Hypothermia III: <35 °C) and those who did not.

RESULTS

A total of 313 patients were included, and 201 (64.2%) lobectomies, 50 (16.0%) segmentectomies, and 62 (19.8%) wedge resections were performed. Across all patients, 291 (93.0%) had a temperature less than 36 °C, 195 (62.3%) had a temperature less than 35.5 °C, and 100 (31.9%) had a temperature less than 35.0 °C. Patients experienced significant temperature change at all intervals (P < .001), with the greatest loss occurring during the preprocedure interval (between leaving preprocedure unit and anesthesia induction). On adjusted analysis, patients who experienced inadvertent perioperative hypothermia less than 35.5 °C were older (odds ratio, 1.03; 95% CI, 1.01-1.05), had lower body mass index (odds ratio, 0.95; 95% CI, 0.87-0.98), and had increasing operative time (odds ratio, 1.00; 95% CI, 1.00-1.01). Patients who experienced inadvertent perioperative hypothermia had higher risk-adjusted rates of overall morbidity and infectious postoperative complications.

CONCLUSIONS

The majority of patients undergoing robotic-assisted thoracic surgery lung resections experience some degree of inadvertent perioperative hypothermia and have associated increased rates of 30-day morbidity. Structured and interval-specific interventions should be implemented to decrease rates of inadvertent perioperative hypothermia and subsequent complications.

Inadvertent Perioperative Hypothermia in Ambulatory Surgery Patients: Incidence, Risk Factors, and Prevention Initiatives

PURPOSE

Although the number and complexity of ambulatory surgical interventions has grown considerably over the years, it has not been fully established whether hypothermia still poses a risk for these interventions. In this study, we aimed to determine the incidence, risk factors, and methods applied to prevent perioperative hypothermia in ambulatory surgery patients.

DESIGN

A descriptive research design was used.

METHODS

The study was conducted with 175 patients between May 2021 and March 2022 in the outpatient units of a training and research hospital in Mersin, Turkey. Data were collected using the Patient Information and Follow-up Form.

FINDINGS

The incidence of perioperative hypothermia was 20% in ambulatory surgery patients. Hypothermia developed in 13.7% of the patients at the 0th minute at the PACU, and 96.6% of the patients were not warmed intraoperatively. We noted a statistically significant relationship between perioperative hypothermia and advanced age (≥60 years), high American Society of Anesthesiologists' (ASA) class, and low hematocrit values. In addition, we determined that the female gender, presence of chronic diseases, general anesthesia, and a long operation time were other risk factors for hypothermia in the perioperative period.

CONCLUSIONS

The incidence of hypothermia during ambulatory surgeries is lower than that in inpatient surgeries. The warming rate of ambulatory surgery patients, which is quite low, can be improved by increasing the awareness of the perioperative team and following the guidelines.

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.

Comparison of the Effect of Forced-air Warming and Warmed Intravenous Fluid on the Comfort and Prevention of Shivering After Spinal Anesthesia in Patients Undergoing Orthopedic Surgery

PURPOSE

This study aimed to compare the effect of forced-air warming and warmed intravenous fluid on the comfort and prevention of shivering after spinal anesthesia in patients undergoing orthopaedic surgery.

DESIGN

Randomized controlled clinical trial.

METHODS

A total of 120 patients were randomly divided into three groups: forced-air warming (38°C), warmed intravenous fluid (37°C), and the control group. Patients' comfort and severity of shivering were measured and recorded five times (immediately and 15 minutes after spinal anesthesia, end of the surgery, time of entrance to the recovery room, and 15 minutes after entering the recovery room), and compared with each other.

FINDINGS

There was a significant difference between the three groups in terms of comfort at all points of evaluation times (P < .001). The comfort score in the control group was significantly higher than the two intervention groups (P < .001). Moreover, the comfort score in the warmed intravenous fluid group was significantly higher than the forced-air warming group (P < .001). In addition, there was a significant difference in shivering severity between the three groups at the end of the surgery, entrance to the recovery room, and 15 minutes after surgery (P < .001). The majority of patients in the forced-air warming group (90%) had no shivering at all three times, while the warmed IV fluid and control groups was 65% and 30% respectively.

CONCLUSIONS

Non-pharmacological methods such as forced-air warming and warmed intravenous fluid can provide comfort and prevent shivering in orthopaedic patients undergoing spinal anesthesia. However, the use of forced-air warming is more effective than warmed intravenous fluid in providing comfort and preventing shivering in these patients. It is recommended that these methods be used in the operating room to provide comfort and prevent shivering in these patients.

Development and internal validation of an algorithm to predict intraoperative risk of inadvertent hypothermia based on preoperative data

Intraoperative hypothermia increases perioperative morbidity and identifying patients at risk preoperatively is challenging. The aim of this study was to develop and internally validate prediction models for intraoperative hypothermia occurring despite active warming and to implement the algorithm in an online risk estimation tool. The final dataset included 36,371 surgery cases between September 2013 and May 2019 at the Vienna General Hospital. The primary outcome was minimum temperature measured during surgery. Preoperative data, initial vital signs measured before induction of anesthesia, and known comorbidities recorded in the preanesthetic clinic (PAC) were available, and the final predictors were selected by forward selection and backward elimination. Three models with different levels of information were developed and their predictive performance for minimum temperature below 36 °C and 35.5 °C was assessed using discrimination and calibration. Moderate hypothermia (below 35.5 °C) was observed in 18.2% of cases. The algorithm to predict inadvertent intraoperative hypothermia performed well with concordance statistics of 0.71 (36 °C) and 0.70 (35.5 °C) for the model including data from the preanesthetic clinic. All models were well-calibrated for 36 °C and 35.5 °C. Finally, a web-based implementation of the algorithm was programmed to facilitate the calculation of the probabilistic prediction of a patient's core temperature to fall below 35.5 °C during surgery. The results indicate that inadvertent intraoperative hypothermia still occurs frequently despite active warming. Additional thermoregulatory measures may be needed to increase the rate of perioperative normothermia. The developed prediction models can support clinical decision-makers in identifying the patients at risk for intraoperative hypothermia and help optimize allocation of additional thermoregulatory interventions.

Effect of prewarming on body temperature in short-term bladder or prostatic transurethral resection under general anesthesia: A randomized, double-blind, controlled trial

Perioperative hypothermia causes postoperative complications. Prewarming reduces body temperature decrease in long-term surgeries. We aimed to assess the effect of different time-periods of prewarming on perioperative temperature in short-term transurethral resection under general anesthesia. Randomized, double-blind, controlled trial in patients scheduled for bladder or prostatic transurethral resection under general anesthesia. Eligible patients were randomly assigned to receive no-prewarming or prewarming during 15, 30, or 45 min using a forced-air blanket in the pre-anesthesia period. Tympanic temperature was used prior to induction of anesthesia and esophageal temperature intraoperatively. Primary outcome was the difference in core temperature among groups from the induction of general anesthesia until the end of surgery. Repeated measures multivariate analysis of covariance modeled the temperature response at each observation time according to prewarming. We examined modeled contrasts between temperature variables in subjects according to prophylaxis. We enrolled 297 patients and randomly assigned 76 patients to control group, 74 patients to 15-min group, 73 patients to 30-min group, and 74 patients to the 45-min group. Temperature in the control group before induction was 36.5 ± 0.5 °C. After prewarming, core temperature was significantly higher in 15- and 30-min groups (36.8 ± 0.5 °C, p = 0.004; 36.7 ± 0.5 °C, p = 0.041, respectively). Body temperature at the end of surgery was significantly lower in the control group (35.8 ± 0.6 °C) than in the three prewarmed groups (36.3 ± 0.6 °C in 15-min, 36.3 ± 0.5 °C in 30-min, and 36.3 ± 0.6 °C in 45-min group) (p < 0.001). Prewarming prior to short-term transurethral resection under general anesthesia reduced the body temperature drop during the perioperative period. These time-periods of prewarming also reduced the rate of postoperative complications.Study Registration Registered at ClinicalTrials.gov (Identifier: NCT03630887).

Incidence of Severe Hypothermia and Its Impact on Postoperative Surgical Complications and Time Delay to Adjunct Treatments in Breast Surgery Cancer Patients: A Case-Controlled Study

Introduction: Unintended postoperative hypothermia frequently occurs upon arrival in the post anesthesia care unit (PACU). As part of our quality assurance program in anesthesia, we regularly monitor the incidence of this complication through our anesthesia information management system (AIMS). In this case-controlled retrospective study, our goal was to detect the incidence of unintended severe hypothermia in our breast surgery cancer patients, and subsequently to analyze the consequence of this complication in terms postoperative cutaneous infection, as well as its impact on further complementary treatment, such as radiotherapy and chemotherapy. Methods: This study was a retrospective analysis conducted through our AIMS system from 2015 through 2019, with extraction criteria based on year, type of surgery (breast), and temperature upon arrival in PACU. A tympanic temperature of less than 36 °C was considered to indicate hypothermia. Severe hypothermia was considered for patients having a temperature lower than 35.2 °C (hypothermic) (n = 80), who were paired using a propensity score analysis with a control group (normothermic) (n = 80) of other breast cancer surgery patients. Extracted data included time of surgery, sex, age, ASA status, and type and duration of the intervention. Results: The mean incidence of hypothermia was 21% from 2015 through 2019. The body mass index (BMI) was significantly lower in the hypothermia group before matching, 23.5 ± 4.1 vs. 26.4 ± 6.1 kg/m² in normothermic patients (p < 0.05). The hypothermia group also had significantly fewer monitoring and active warming devices. No difference was noted for wound complications. Time to complementary chemotherapy and or radiotherapy did not differ between groups (52 ± 21 days in group hypothermia vs 49 ± 22 days in the control group). Conclusion: Severe intraoperative hypothermia remains an important quality assurance issue in our breast surgery cancer patients, but we could not detect any long-term effect of hypothermia.

Short-Periods of Pre-Warming in Laparoscopic Surgery. A Non-Randomized Clinical Trial Evaluating Current Clinical Practice

Background: Pre-warming prevents perioperative hypothermia. We evaluated the current clinical practice of pre-warming and its effects on temperature drop and postoperative complications; Methods: This prospective, observational pilot study examines clinical practice in a tertiary hospital on 99 patients undergoing laparoscopic urological surgery. Pre-warming was performed in the pre-anesthesia room. Patients were classified into three groups: P 0 (non-prewarmed), P 5–15 (pre-warming 5–15 min) and P > 15 (pre-warming 15–30 min). Tympanic temperature was recorded in the pre-anesthesia room, prior to anesthesia induction, and in the PACU. Esophageal temperature was recorded intraoperatively. The occurrence of shivering, pain intensity, length of stay in PACU, and postoperative complications during hospital stay were also recorded; Results: After pre-warming, between-group difference in body temperature was higher in P > 15 than in P 0 (0.4 °C, 95% CI 0.14–0.69, p = 0.004). Between P 5–15 and P 0 difference was 0.2 °C (95% CI 0.04–0.55, p = 0.093). Temperature at the end of surgery was higher in pre-warmed groups [mean between-group difference 0.5 °C (95% CI 0.13–0.81, p = 0.007) for P 5–15; 0.9 °C (95% CI 0.55–1.19, p < 0.001) for P > 15]. Pain and shivering was less common in pre-warmed groups. Postoperative transfusions and surgical site infections were lower in P > 15; Conclusion: Short-term pre-warming prior to laparoscopic urological surgery decreased temperature perioperative drop and postoperative complications.

Effects of a preoperative forced-air warming system for patients undergoing video-assisted thoracic surgery: A randomized controlled trial

BACKGROUND

The incidence of intraoperative hypothermia is still high despite the proposal of different preventive measures during thoracoscopic surgery. This randomized control study evaluated the effects of 30-minute prewarming combined with a forced-air warming system during surgery to prevent intraoperative hypothermia in patients undergoing video-assisted thoracic surgery under general anesthesia combined with erector spinae nerve block.

METHODS

Ninety-eight patients were randomly and equally allocated to prewarming or warming groups (n = 49 each). The primary outcome was the incidence of intraoperative hypothermia. Secondary outcomes were core temperature, irrigation and infused fluid, estimated blood loss, urine output, type of surgery, intraoperative anesthetic dosage, hemodynamics, recovery time, the incidence of postoperative shivering, thermal comfort, postoperative sufentanil consumption and pain intensity, patient satisfaction, and adverse events.

RESULTS

The incidence of intraoperative hypothermia was significantly lower in the prewarming group than the warming group (12.24% vs 32.65%, P = .015). Core temperature showed the highest decrease 30 minutes after surgery start in both groups; however, the rate was lower in the prewarming than in the warming group (0.31 ± 0.04°C vs 0.42 ± 0.06°C, P < .05). Compared with the warming group, higher core temperatures were recorded for patients in the prewarming group from T1 to T6 (P < .05). Significantly fewer patients with mild hypothermia were in the prewarming group (5 vs 13, P = .037) and recovery time was significantly reduced in the prewarming group (P < .05). Although the incidence of postoperative shivering was lower in the prewarming group, it was not statistically significant (6.12% vs 18.37%, P = .064). Likewise, the shivering severity was similar for both groups. Thermal comfort was significantly increased in the prewarming group, although patient satisfaction was comparable between the 2 groups (P > .05). No adverse events occurred associated with the forced-air warming system. Both groups shared similar baseline demographics, type of surgery, total irrigation fluid, total infused fluid, estimated blood loss, urine output, intraoperative anesthetic dosage, hemodynamics, duration of anesthesia and operation time, postoperative sufentanil consumption, and pain intensity.

CONCLUSION

In patients undergoing video-assisted thoracic surgery, prewarming for 30 minutes before the induction of anesthesia combined with a forced-air warming system may improve perioperative core temperature and the thermal comfort, although the incidence of postoperative shivering and severity did not improve.

Incidence of Unintentional Intraoperative Hypothermia in Pediatric Scoliosis Surgery and Associated Preoperative Risk Factors

Introduction

Intraoperative hypothermia is associated with perioperative complications such as blood loss and wound infection. Thus, perioperative heat retention methods to prevent perioperative hypothermia such as providing a warmed blanket and active patients' warming are important. Although major surgery and pediatric patient age are noted as risk factors, only a few studies focus on hypothermia as an intraoperative complication in pediatric scoliosis surgery. The aim of this study is to investigate the incidence of intraoperative hypothermia in pediatric scoliosis surgery and the associated preoperative risk factors.

Methods

We retrospectively reviewed the records of pediatric patients who underwent posterior spinal fusion at a single institution between 2015 and 2019. We recorded the background data, perioperative data, lowest recorded core temperature, and perioperative complications. Patients were divided into those whose temperature decreased below 36°C (Group H) and those who maintained a temperature of 36°C or greater (Group N) during surgery. We compared the two groups and performed multivariate analysis to identify preoperative risk factors for intraoperative hypothermia.

Results

A total of 103 patients underwent posterior spinal fusion; 56 for adolescent idiopathic scoliosis and 47 for neuromuscular scoliosis. Hypothermia was observed in 40 patients (38.8%). Group H had more non-adolescent idiopathic scoliosis (AIS) patients, lower mean body mass index, greater mean blood loss, greater number of fused vertebrae, larger preoperative Cobb angle, and lower initial core body temperature (immediately after induction of anesthesia). On multivariate analysis, a diagnosis of neuromuscular scoliosis, a lower body mass index, and a lower initial core body temperature were identified as independent risk factors for intraoperative hypothermia.

Conclusions

The incidence of hypothermia in pediatric posterior scoliosis surgery is 38.8%. Diagnosis of non-AIS, lower body mass index, and lower core body temperature at the time of anesthesia induction are preoperative risk factors for intraoperative hypothermia.

Effects of Low Intraperitoneal Pressure on Quality of Postoperative Recovery after Laparoscopic Surgery for Genital Prolapse in Elderly Patients Aged 75 Years or Older

STUDY OBJECTIVE

Previous clinical trials for laparoscopic surgery have included few elderly patients aged ≥75 years. We aimed to evaluate the quality of postoperative recovery after laparoscopic surgery using low intraperitoneal pressure (IPP) (6 mm Hg) and warmed, humidified carbon dioxide gas for genital prolapse in elderly patients aged ≥75 years.

DESIGN

Prospective consecutive case series.

SETTING

University hospital.

PATIENTS

Consecutive patients (n = 30) aged ≥75 years planning to undergo laparoscopic surgery for genital prolapse by the same surgeon were recruited from October 2016 through December 2019.

INTERVENTIONS

Laparoscopic promontofixation for the treatment of genital prolapse was performed using low IPP and warmed, humidified carbon dioxide gas. When a promontory could not be easily identified, laparoscopic pectopexy was alternatively performed.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the Quality of Recovery-40 (QoR-40) score at 24 hours postoperatively. The secondary outcomes were postoperative pain using a 100-mm visual analog scale and the length of hospital stay after surgery (LHSS). For the global QoR-40 score and for 4 dimensions of the QoR-40, "emotional state," "physical comfort," "psychologic support," and "pain," no differences were observed between the baseline score and the score at 24 hours. The score for the "physical independence" dimension at 24 hours was significantly lower than the baseline score (p <.001). No patient had visual analog scale pain scores >30 out of 100 at 12 hours or later. LHSS was <48 hours in 22 patients (73.3%) and <72 hours in 8 patients (26.7%). Multivariable analysis showed that the odds of an LHSS >48 hours were more than 8 times higher in patients who were discharged from the operating room in the afternoon compared with those with a morning discharge.

CONCLUSION

The use of a low IPP is feasible, safe, and has clinical benefits for elderly patients aged ≥75 years who undergo laparoscopic surgery for genital prolapse.