Pre-emptive use of the space blanket reduces shivering after general anaesthesia

Abstract

We have investigated the role of aluminized metal foil (space blanket, UN 320), used pre-emptively, in post-anaesthetic shivering and patients' subjective perception of cold after general anaesthesia of short duration. Sixty-eight ASA I and II patients undergoing orthopaedic and plastic surgery on the peripheries were allocated randomly to two groups: those in group 1 were wrapped (not less than 60% of body surface area) in the space blanket before induction of anaesthesia. In group 2 patients had standard surgical draping. In all subjects, anaesthesia was induced with fentanyl and propofol, and maintained with nitrous oxide and enflurane in oxygen, after a laryngeal mask airway was positioned. Patients were asked to grade their perception of cold on a visual analogue scale, before induction and on recovery. Skin (dorsum of hand) and core (nasopharyngeal) temperatures were recorded at 15-min intervals. Occurrence of shivering and cold scores were recorded by blinded observers. Groups were similar in age and gender; duration of anaesthesia was also similar (mean 41.6 (SEM 4.8) vs 47.5 (3.3) min, respectively). Theincidences of shivering were 15% and 63% in groups 1 and 2, respectively (P < 0.001). Cold scores were 2.4 (0.4) and 5.7 (0.5), respectively (P < 0.001). Skin temperatures increased with increasing duration of anaesthesia in both groups but were greater at 15, 30 and 45 min in group 1 (33.38 (0.25) vs 31.56 (0.31), 34.46 (0.25) vs 32.45 (0.31) and 35.22 (0.36) vs 33.13 (0.34), respectively; P < 0.001 each comparison). Core temperature increased slightly in group 1 and decreased in group 2 (P=0.11). We conclude that in spontaneously breathing patients, the use of a space blanket decreased the incidence of postanaesthetic shivering and patients' perception of cold, and resulted in higher skin temperatures, even after relatively short general anaesthetics. (Br. J. Anaesth. 1994; 72: 393-396) © 1994 British Journal of Anaesthesia.