The effects of combining intraoperative warming methods on core temperature in obese and non-obese patients during intravenous anesthesia

BACKGROUND AND OBJECTIVE: Obese individuals show less intraoperative (IOP) hypothermia than non-obese ones due to higher vasoconstriction threshold. A combination of warming methods may be better than an isolated one in preventing IOP hypothermia. Our aim was to evaluate whether the combination of a heat and moisture exchanger (HME) on inhaled gas with IOP forced air warming blanket (WB) or warming intravenous (IV) fluids (HF) prevents IOP hypothermia in obese (OB) and non-obese (NOB) women under intravenous anesthesia. METHODS: Forty patients scheduled for gynecological abdominal surgery were anesthetized with propofol and remifentanil in a target controlled infusion. All patients had a HME on the inhaled gas. Patients were randomly distributed into 4 groups according to body mass index (BMI) and IOP thermal management. Ten OB grade I (BMI between 30 and 34.9 kg.m-2) and 10 NOB (BMI between 18.5 and 24.9 kg.m-2) had WB on the lower limbs. Ten OB and 10 NOB patients received IV HF. Core temperatures were recorded at baseline, after 15, 30, 60, 90, and 120 minutes of ventilatory system installation, and at the end of surgery. Core temperature was also followed for 60 minutes in the Post Anesthetic Care Unit (PACU). Core temperature and BMI were correlated in the groups with the same hypothermia treatment method. RESULTS: OB/WB group presented a higher IOP core temperature higher than the other groups (P<0.001). The proportion of normothermic patients at end of surgery and in PACU admission was higher in OB/WB than the other groups (P<0.05). There was a positive correlation between BMI and core temperature in the skin-surface warming groups (P<0.001). CONCLUSIONS: The combination of IOP skin-surface warming with HME on the inhaled gas in female obese patients, but not in non-obese ones, minimizes hypothermia. The combination of warming IV fluids and HME does not avoid IOP hypothermia in female obese or non-obese patients.