Core temperatures after anesthetic induction
Core temperatures at 4 time points after anesthetic induction Demographic data included ABSTRACT 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 minutes after induction for one hour. 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 minutes after induction (p<0.006 for all comparisons), averaging between 0.39oC and 0.54oC higher. In group PROP, 60% of patients had at least one temperature below 36.0oC 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.