Heat conservationvsconvective warming in adults undergoing elective surgery

Purpose: To determine the relative efficacy of heat conservation and convective warming in maintaining penoperative normothermia. (central temperature ≥36°C). Methods: Thirty-seven patients undergoing elective gynaecological, orthopaedic, or general surgery scheduled to last two hours were prospectjvely studied. Patients were randomized to one of two groups. Group I patients received heat conservation with reflective blankets (Thermadrape™, Vital Signs, Inc., Totowa, NJ) applied preoperatively and warmed iv fluids (Hotline™ SIMS Level I Technologies, Inc, Rockland, MA). Group 2 patients received convective warming (BairHugger, Augustine Medical, Inc., Eden Prairie, MN) after induction of anaesthesia andivfluids at room temperature. All patients received general anaesthesia with isoflurane. Tympanic membrane and forearm-fingertip skin temperature gradients were measured penoperatively at 15 min intervals. Results: Central temperature decreased after induction to a minimum level of 35.9 ± 0.1°C in group I and 36.0 ± 0.1°C in group 2 and then increased towards pre-induction values in group 2, and were higher (P < 0.05) than in group 1: 95% group 2 patients had central temperature ≥ 36.0°C at the end of surgery (vs 69% of group l.P< 0.05). During the first 30 mm in PACU, central temperatures were higher in group 1 than in group 2 (36.8 ± 0.1°C vs 36.2 ± 0.2°C. P<0.05). After 60 mm, central temperatures were similar (36.8°C). The incidence of shivering and degree of penpheral cutaneous vasoconstnction were also similar. Conclusion: Patients receiving convective warming were more likely to leave the operating room normothermic. and had higher central temperatures dunng the first 30 mm in the recovery room. The intergroup temperature differences were small, and by 60 min, had disappeared.