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Preventing hypothermia in outpatient plastic surgery by self-warming or forced-air-warming blanket

A randomised controlled trial

Tyvold, Stig S.

European Journal of Anaesthesiology (EJA): November 2019 - Volume 36 - Issue 11 - p 843–850
doi: 10.1097/EJA.0000000000001087
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BACKGROUND In our outpatient post anaesthesia unit patients reported that they were feeling cold with or without shivering. Anaesthetic agents cause reduced thermoregulation, initially by redistribution of blood flow from core to periphery, later by negative balance between thermogenesis and heat loss. Even mild peri-operative hypothermia increases the risk of surgical wound infections, bleeding, impaired cardiac function, shivering, and decreases comfort.

OBJECTIVE(S) We aimed to evaluate which of our current active warming measures, self-warming blanket or forced-air-warming blanket, were most effective in preventing inadvertent intraoperative heat loss. Secondarily, we assessed whether they prevented inadvertent peri-operative hypothermia when defined as core body temperature below 36 °C.

DESIGN Randomised controlled trial, parallel group design.

SETTING Aleris Solsiden hospital for outpatient surgery, Trondheim, Norway, from March to June 2016.

PATIENTS A total of 112 consecutive patients planned for outpatient plastic surgery. Reasons for noninclusion: failing to meet the criteria for outpatient surgery according to the standard of the national society of anaesthesiology.

INTERVENTION(S) Patients were randomised to active warming by a self-warming blanket or a forced-air-warming blanket. All patients received routine measures to prevent hypothermia with a high temperature in the operation theatres, prewarmed fluids, cotton blankets and surgical draping outside the surgical field.

MAIN OUTCOMES Temperature, measured pre-operatively, every 10 min during general anaesthesia and postoperatively with a zero-heat-flux temperature sensor.

RESULTS Core temperature was significantly lower in the self-warming blanket compared with the forced-air-warming blanket group during anaesthesia, P less than 0.0001. Hypothermia (<36 °C) was recorded in 47%, n = 22, patients in the self-warming blanket group and 25%, n = 16, in the forced-air-warming blanket group during the registration period, P = 0.02.

CONCLUSION An underbody forced-air-warming blanket reduced heat loss to a greater extent than a self-warming blanket. But none of the interventions were sufficient to prevent inadvertent peri-operative hypothermia.

TRIAL REGISTRATION identifier: NCT03163563.

From Aleris Hospital and Radiology Solsiden Trondheim, Norway

Correspondence to Stig S. Tyvold, Aleris Solsiden, Innherredsveien 74, N-7014 Trondheim, Norway Tel: +47 73 87 20 00; e-mail:

Published online 16 September 2019

© 2019 European Society of Anaesthesiology