Risk Factors For Intraoperative Hypothermia During Gastrointestinal Tumor Resection And Association Of Hypothermia And Postoperative Complications

Part 1:The incidence and risk factors of intraoperative hypothermia with different definitionsObjective: To explore risk factors of intraoperative hypothermia with different definitions.Methods: A total of 6156 patients undergoing gastrointestinal tumor surgery under general anesthesia from May 2017 to May 2020 were selected.General characteristics and perioperative information were collected.The nasopharyngeal temperature or bladder temperature recorded every 5 minutes during surgical procedures was the core temperature of the patient,and the temperature < 36 °C is defined as intraoperative hypothermia.The four different definitions of hypothermia explored in this study were: 1.time-weighted average temperature,calculated as the area under the curve for all temperature measurements taken in a patient using a trapezoidal rule,divided by the total measurement time of the patient;2.final intraoperative temperature,calculated as the temperature measured at the end of surgery;3.temperature nadir,calculated as the patient’s lowest body temperature during surgery;4.mean intraoperative temperature,calculated as the sum of all patient temperature measurements divided by the number of measurements.The patientswere divided into normal temperature group and hypothermic group,and risk factors of intraoperative hypothermia were analyzed in terms of different definitions.Results: 1.The incidence of intraoperative hypothermia: Based on the time-weighted average temperature,there is an incidence of 17.7%(1087/6156)for intraoperative hypothermia.As for the final intraoperative temperature,the incidence of intraoperative hypothermia is 20.7%(1274/6156).The incidence of it is 35.9%(2212/6156)for the temperature nadir.For the mean intraoperative temperature,the incidence of intraoperative hypothermia is17.4%(1074/6156).The results showed that the mean intraoperative temperature and time-weighted average temperature were almost exactly consistent(kappa=0.990,P<0.001),while the time-weighted average temperature was moderate consistent with the final intraoperative temperature(kappa=0.601,P<0.001)or the temperature nadir(kappa=0.555,P<0.001).The final intraoperative temperature has moderate consistency with the temperature nadir(kappa=0.633,P<0.001).2.The risk factors of intraoperative hypothermia: Analyzed by the time-weighted average temperature,age ≥ 65 years,BMI <25 kg/m2,summer(June-August),laparoscopic surgery,intraoperative infusion ≥ 2000 m L and lower gastrointestinal tumor were considered as risk factors for intraoperative hypothermia in patients with gastrointestinal tumors,while intraoperative blood transfusion and winter(December-February)reduced the risk of it(P<0.05).Based on the final intraoperative temperature during surgery,age ≥65 years,BMI <25 kg/m2,summer,laparoscopic surgery,intraoperative infusion ≥2000 m L and Charlson score ≥5 were categorized as risk factors for intraoperative hypothermia in patients with gastrointestinal tumors,while the risk of intraoperative hypothermia was negatively correlated with men and winter(P<0.05).Based on temperature nadir,age ≥65 years,BMI <25 kg/m2,summer(June-August),laparoscopic surgery,operation duration ≥3 h,intraoperative infusion ≥2000 m L and lower gastrointestinal tumors were risk factors for intraoperative hypothermia in patients with gastrointestinal tumors,while performing surgical procedures in winter has the lower risk of intraoperative hypothermia(P<0.05).Conclusion: With various definitions,the pattern of intraoperative temperature is different.Risk factors are also changing for different definitions,and clinical measures should betaken to keep body temperature normal.Part 2: The correlation between different definitions of intraoperative hypothermia and postoperative complicationsObjective: To explore the relationship between intraoperative hypothermia under different definitions and different postoperative complications.Methods: Based on the study cohort in part 1,in order to minimize possible confounding factors and establish a well-matched cohort,the 1:1 propensity score matching(PSM)method was used to match hypothermic and normothermic patients.A multivariate logistic regression model was used to analyze the relationship between intraoperative hypothermia under three different definitions and postoperative complications.The different temperature patterns,discussed in this part,include time-weighted average temperature,the final intraoperative temperature and temperature nadir.Postoperative complications and associated recovery indicators include postoperative severe complications,postoperative coagulopathy,anesthesia recovery time,and postoperative length of hospital stay.Restricted cubic spline(RCS)was used to fit the relationship between the duration of intraoperative hypothermia and postoperative coagulation function.Results: 1.The relationship between intraoperative hypothermia and postoperative severe complications: The study cohort after PSM matching was below: a.Time-weighted average temperature(N=2170): normal temperature group vs.hypothermia group = 1085:1085;b.The final intraoperative temperature(N=2544): normal temperature group vs.hypothermia group=1272:1272;c.temperature nadir(N=3630): normal temperature group vs.hypothermia group=1815:1815.There was no significant difference in confounding factors between the two groups(P>0.05).Intraoperative hypothermia based on time-weighted average temperature(P>0.05),the final intraoperative temperature(P>0.05)and Temperature nadir(P>0.05)were not significantly related to the postoperative severe complications in patients with gastrointestinal tumors.Other factors that affect postoperative severe complications include high ASA grade,intraoperative blood transfusion,and intraoperative infusion.2.The relationship between intraoperative hypothermia and postoperative coagulationfunction: The study cohort after PSM matching was below: a.Time-weighted average temperature(N=1046): normal temperature group vs.hypothermia group = 523:523;b.The final intraoperative temperature(N=1200): normal temperature group vs.hypothermia group=600:600;c.temperature nadir(N=1736): normal temperature group vs.hypothermia group=868:868.There was no significant difference in confounding factors between the two groups(P>0.05).Intraoperative hypothermia based on time-weighted average temperature was closely related to postoperative coagulation dysfunction(OR=1.555,95% CI: 1.193-2.026,P=0.001),while intraoperative hypothermia and coagulation function based on the final intraoperative temperature and temperature nadir were not significant(P>0.05).The RCS curve showed that the total duration of intraoperative body temperature below 36 °C was greater than 52 minutes,and the risk of developing coagulopathy after surgery may increase.The results of the multivariate logistic regression model showed that patients with intraoperative temperature below 36 °C for a duration of 1 to 2 hours had a 1.5-fold risk of developing coagulopathy compared with patients with a duration of less than 1 hour(OR=1.520,95% CI: 1.110-2.082,P=0.009).Other factors that affect postoperative coagulation include age,intraoperative bleeding,and type of disease.3.The relationship between intraoperative hypothermia and anesthesia recovery time: The study cohort after PSM matching was below.a.Time-weighted average temperature(N=2174): normal temperature group vs.hypothermia group = 1087:1087;b.The final intraoperative temperature(N=2544): normal temperature group vs.hypothermia group=1272:1272;c.temperature nadir(N=3826): normal temperature group vs.hypothermia group=1913:1913.There was no significant difference in confounding factors between the two groups(P>0.05).Intraoperative hypothermia based on time-weighted average temperature(OR=1.215,95% CI: 1.017-1.453,P=0.032)and the final intraoperative temperature(OR=1.359,95% CI: 1.151-1.604,P<0.001)were closely related to the anesthesia recovery time,while the temperature nadir(OR=1.118,95% CI: 0.979-1.278,P=0.100)was not significant.Other factors that affect the anesthesia recovery time include sex,the use of muscle relaxant antagonists and type of disease.4.The relationship between intraoperative hypothermia and the postoperative length ofhospital stay: The study cohort after PSM matching was below.a.Time-weighted average temperature(N=2170): normal temperature group vs.hypothermia group = 1085:1085;b.The final intraoperative temperature(N=2544): normal temperature group vs.hypothermia group=1272:1272;c.temperature nadir(N=3630): normal temperature group vs.hypothermia group=1815:1815.There was no significant difference in confounding factors between the two groups(P>0.05).Intraoperative hypothermia based on these three definitions(P>0.05)had no significant relationship with the length of hospital stay of patients with gastrointestinal tumors.Other factors that affect the length of hospital stay after surgery include high ASA grade,intraoperative blood transfusion and type of disease.Conclusion: Intraoperative hypothermia was not significantly associated with postoperative severe complications.Intraoperative hypothermia based on time-weighted average temperature is closely related to postoperative coagulation dysfunction,and the duration of intraoperative hypothermia greater than 1 h increases the risk of coagulopathy.There are different influences on postoperative coagulopathy for intraoperative hypothermia defined by different ways.Intraoperative hypothermia based on time-weighted average temperature and the final intraoperative temperature significantly prolonged resuscitation time for anesthesia,while the temperature nadir was not significant.Intraoperative hypothermia had no significant effect on the postoperative length of hospital stay.