[Preoperative prewarming as a routine measure. First experiences]

Effects of Pre-warming and Co-warming in Preventing Intraoperative Hypothermia

BACKGROUND

 Hypothermia is a condition characterized by a decreased body temperature. It takes place when the body is exposed to cold weather or water for a longer period of time. Different types of hypothermia include acute hypothermia, exhaustion hypothermia, and chronic hypothermia. Excessive shivering, breathing difficulty, slurred speech, confusion, drowsiness, a weak pulse, and a loss of consciousness are the symptoms related to hypothermia.

AIMS

The aim of this study was to see how effective co-warming and pre-warming are at reducing the risk of intraoperative hypothermia.

MATERIALS AND METHODS

A randomized, prospective, comparative clinical study was conducted in a population of 60 participants. Participants were divided into two groups. Participants in group A received pre-warming for 30 minutes at 40°C before transport to the operation theater and also received co-warming before induction of anesthesia. Group B includes those who received co-warming at 40°C from the point of induction of anesthesia.

RESULTS

The mean age (years) of participants in groups A and B was identified as 43.3 ± 11.84 and 45.93 ± 15.87, respectively. The majority of the participants in the study population were males in groups A and B, with 66.67% and 73.33%, respectively. The medians of core temperature and peripheral temperature at the baseline were identified as 36.80 (36.20 to 37.12) and 32.55 (32.38 to 32.72) in group A. Similarly, it was observed as 36 (35.70 to 36.20) and 32 (31.60 to 32.02) in group B. The medians of core temperature and peripheral temperature after the surgery were identified as 34.50 (34.20 to 35) and 32.65 (31.95 to 33) in group A. Similarly, it was identified as 34 (33.80 to 34.25) and 32 (32.10 to 32.25) in group B.

CONCLUSION

 Our study concluded that it is important to prevent hypothermia in patients undergoing surgery under general anesthesia. Pre-operative and intraoperative warming showed a decrease in the rate of fall in core temperature. Hence, both techniques are effective in reducing hypothermia.

Effect of active forced air warming during the first hour after anesthesia induction and intraoperation avoids hypothermia in elderly patients

Background

The study aimed at exploring an optimal temperature model of forced air warming during the first hour after induction and intraoperation to prevent hyperthermia for elderly patients undergoing laparoscopic abdominal surgery.

Methods

There were 218 patients that were randomly divided into 3 groups warmed with a forced-air warmer during surgery: Group L (intraoperative warming set to 38 °C, n = 63), Group H (intraoperative warming set to 42 °C, n = 65) and Group LH (intraoperative warming set to 42 °C for the first hour then set to 38 °C, n = 65). Core temperature in the preoperative room and PACU was measured by a tympanic membrane thermometer and in the operation room, a nasopharyngeal temperature probe was recorded. The rate of perioperative hypothermia, defined as a reduction in body temperature to < 36 °C was recorded as the primary outcome. Intraoperative anesthetic dosage, recovery time, adverse events, thermal comfort and satisfaction score were measured as secondary outcome.

Results

The incidence of intraoperative and postoperative hypothermia was significantly lower in Group LH and Group H than Group L (18.75 and 15.62% vs 44.44%, P<0.001; 4.69 and 4.69% vs 20.63%, P<.05). Anesthetic dosage of rocuronium was lower in Group L than other two groups, with the opposite result of recovery time. The number of patients with shivering was higher in Group L but sweating was higher in Group H. Both of the thermal comfort and satisfaction score was highest in Group LH.

Conclusion

A temperature pattern of forced air warming set at 42 °C during the first hour after anesthesia induction and maintained with 38 °C was a suitable choice for elderly patients undergoing laparoscopic abdominal surgery lasting for more than 120 min.

Trial registration

Chictr.org.cn ChiCTR-2,100,053,211.

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.

Perioperative Hypothermia-A Narrative Review

Unintentional hypothermia (core temperature < 36 °C) is a common side effect in patients undergoing surgery. Several patient-centred and external factors, e.g., drugs, comorbidities, trauma, environmental temperature, type of anaesthesia, as well as extent and duration of surgery, influence core temperature. Perioperative hypothermia has negative effects on coagulation, blood loss and transfusion requirements, metabolization of drugs, surgical site infections, and discharge from the post-anaesthesia care unit. Therefore, active temperature management is required in the pre-, intra-, and postoperative period to diminish the risks of perioperative hypothermia. Temperature measurement should be done with accurate and continuous probes. Perioperative temperature management includes a bundle of warming tools adapted to individual needs and local circumstances. Warming blankets and mattresses as well as the administration of properly warmed infusions via dedicated devices are important for this purpose. Temperature management should follow checklists and be individualized to the patient's requirements and the local possibilities.

Perioperative temperature management: a survey of 6 Asia-Pacific countries

BACKGROUND

Anesthesia leads to impairments in central and peripheral thermoregulatory responses. Inadvertent perioperative hypothermia is hence a common perioperative complication, and is associated with coagulopathy, increased surgical site infection, delayed drug metabolism, prolonged recovery, and shivering. However, surveys across the world have shown poor compliance to perioperative temperature management guidelines. Therefore, we evaluated the prevalent practices and attitudes to perioperative temperature management in the Asia-Pacific region, and determined the individual and institutional factors that lead to noncompliance.

METHODS

A 40-question anonymous online questionnaire was distributed to anesthesiologists and anesthesia trainees in six countries in the Asia-Pacific (Singapore, Malaysia, Philippines, Thailand, India and South Korea). Participants were polled about their current practices in patient warming and temperature measurement across the preoperative, intraoperative and postoperative periods. Questions were also asked regarding various individual and environmental barriers to compliance.

RESULTS

In total, 1154 valid survey responses were obtained and analyzed. 279 (24.2%) of respondents prewarm, 508 (44.0%) perform intraoperative active warming, and 486 (42.1%) perform postoperative active warming in the majority of patients. Additionally, 531 (46.0%) measure temperature preoperatively, 767 (67.5%) measure temperature intraoperatively during general anesthesia, and 953 (82.6%) measure temperature postoperatively in the majority of patients. The availability of active warming devices in the operating room (p < 0.001, OR 10.040), absence of financial restriction (p < 0.001, OR 2.817), presence of hospital training courses (p = 0.011, OR 1.428), and presence of a hospital SOP (p < 0.001, OR 1.926) were significantly associated with compliance to intraoperative active warming.

CONCLUSIONS

Compliance to international perioperative temperature management guidelines in Asia-Pacific remains poor, especially in small hospitals. Barriers to compliance were limited temperature management equipment, lack of locally-relevant standard operating procedures and training. This may inform international guideline committees on the needs of developing countries, or spur local anesthesiology societies to publish their own national guidelines.

Effects of 10-min of pre-warming on inadvertent perioperative hypothermia in intraoperative warming patients: a randomized controlled trial

Background

This study aimed to evaluate the efficacy of 10-min pre-warming in preventing inadvertent perioperative hypothermia, which is defined as a reduction in body temperature to less than 36.0℃ during the perioperative period in intraoperative warming patients.

Methods

In this prospective randomized study, 60 patients scheduled for elective surgery under general anesthesia lasting less than 120 min were divided into two groups: the 10-min pre-warming group (n = 30) and the control group (n = 30). Patients in the 10-min pre-warming group were pre-warmed for 10 min in the pre-anesthetic area using a forced-air warmer set at 47ºC. Intraoperatively, we warmed all patients with a forced-air warmer. Body temperature was measured using a tympanic membrane thermometer pre- or postoperatively and a nasopharyngeal temperature probe intraoperatively. Patients were evaluated on the shivering and thermal comfort scale in the pre-anesthetic area and post-anesthesia care unit.

Results

The incidences of intraoperative hypothermia and postoperative hypothermia were similar in both groups (10.7% vs. 28.6%, P = 0.177; 10.7% vs. 10.7%, P = 1.000 respectively). Body temperature was higher in the 10-min pre-warming group (P = 0.003). Thermal comfort during the pre-warming period was higher in the 10-min pre-warming group (P < 0.001). However, postoperative thermal comfort and shivering grades of both groups were similar.

Conclusions

Ten minutes of pre-warming has no additional effect on the prevention of inadvertent perioperative hypothermia in intraoperative warming patients.

Preventing inadvertent perioperative hypothermia

BACKGROUND

25-90% of all patients undergoing elective surgery suffer from inadvertent postoperative hypothermia, i.e., a core body temperature below 36°C. Compared to normothermic patients, these patients have more frequent wound infections (relative risk [RR] 3.25, 95% confidence interval [CI] 1.35-7.84), cardiac complications (RR 4.49, 95% CI 1.00-20.16), and blood transfusions (RR 1.33, 95% CI 1.06-1.66). Hypothermic patients feel uncomfortable, and shivering raises oxygen consumption by about 40%.

METHODS

This guideline is based on a systematic review of the literature up to and including October 2012 and a further one from November 2012 to August 2014. The recommendations were developed and agreed upon by representatives of five medical specialty societies in a structured consensus process.

RESULTS

The patient's core temperature should be measured 1-2 hours before the start of anesthesia, and either continuously or every 15 minutes during surgery. Depending on the nature of the operation, the site of temperature measurement should be oral, naso-/oropharyngeal, esophageal, vesical, or tympanic (direct). The patient should be actively prewarmed 20-30 minutes before surgery to counteract the decline in temperature. Prewarmed patients must be actively warmed intraoperatively as well if the planned duration of anesthesia is longer than 60 minutes (without prewarming, 30 minutes). The ambient temperature in the operating room should be at least 21°C for adult patients and at least 24°C for children. Infusions and blood transfusions that are given at rates of >500 mL/h should be warmed first. Perioperatively, the largest possible area of the body surface should be thermally insulated. Emergence from general anesthesia should take place at normal body temperature. Postoperative hypothermia, if present, should be treated by the administration of convective or conductive heat until normothermia is achieved. Shivering can be treated with medications.

CONCLUSION

Inadvertent perioperative hypothermia can adversely affect the outcome of surgery and the patient's postoperative course. It should be actively prevented.

[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.

[Efficacy of a novel warming blanket: prospective randomized trial]

BACKGROUND

Perioperative hypothermia is a common complication of general anesthesia and occurs in up to 50 % of patients during ear, nose and throat (ENT) surgery. In this prospective, randomized controlled study the hypothesis that a new conductive warming blanket (Barrier® EasyWarm®, Mölnlycke Health Care Erkrath, Germany) is better in reducing the incidence of perioperative hypothermia in ENT surgery than insulation with a conventional hospital duvet alone was tested.

MATERIALS AND METHODS

After approval of the local ethics committee and written informed consent 80 patients with a planned procedure time between 1 and 3 h were recruited. Anesthesia was induced and maintained using propofol, remifentanil and rocuronium and the core temperature was measured using an esophageal temperature probe. Patients in the study group were warmed at least 30 min prior to induction of anesthesia using the novel warming blanket (Barrier® EasyWarm®) and patients in the control group were insulated with a standard hospital duvet. Data were tested using Fisher's exact test, Student's t-test or the Mann-Whitney U-test as appropriate. Time-dependent changes in core temperature were evaluated using repeated measures analysis of variance (ANOVA) and post hoc Scheffé's test. Results are expressed as mean ± SD or as median and interquartile range (IQR) as appropriate. A p < 0.05 was considered to be statistically significant.

RESULTS

The ANOVA did not identify a significantly higher core temperature in the study group at any time point. Furthermore, Fisher's exact test showed no differences in the incidence of intraoperative (12 out of 29 versus 10 out of 32 patients, p = 0.44) or postoperative hypothermia (12 out of 29 versus 9 out of 32 patients, p = 0.30) between the groups. No adverse effects were observed.

CONCLUSIONS

In the studied patient group the new conductive warming blanket (Barrier® EasyWarm®) showed no superiority compared to conventional thermal insulation alone.

Standard perioperative management in gastrointestinal surgery

INTRODUCTION

The outcome of patients who are scheduled for gastrointestinal surgery is influenced by various factors, the most important being the age and comorbidities of the patient, the complexity of the surgical procedure and the management of postoperative recovery. To improve patient outcome, close cooperation between surgeons and anaesthesiologists (joint risk assessment) is critical. This cooperation has become increasingly important because more and more patients are being referred to surgery at an advanced age and with multiple comorbidities and because surgical procedures and multimodal treatment modalities are becoming more and more complex.

OBJECTIVE

The aim of this review is to provide clinicians with practical recommendations for day-to-day decision-making from a joint surgical and anaesthesiological point of view. The discussion centres on gastrointestinal surgery specifically.