The thermal benefit of prewarming in children

Abstract

Background: It has been suggested that warming patients before induction of anaesthesia (prewarming) reduces the drop in core temperature (Tcore) normally associated with the induction of anaesthesia [1]. It may also reduce the incidence of surgical wound infection [2, 3]. Neither the ideal ambient temperature (Tambient), nor the duration necessary to achieve these aims, is established for adults or children. Since drops in Tcore can take some time to reverse with intra‐operative heating [4], there may be benefit in starting off at a higher Tcore. We therefore conducted a prospective randomized clinical study to assess the impact of prewarming on Tcore behaviour after induction of anaesthesia in children.Aims: We aimed to quantify the impact of prewarming vs standard ambient temperature on core temperature behaviour after induction of anaesthesia in children.Methods: Prospective clinical study with randomization to either 26°C or 21°C ambient temperature. Well children scheduled for elective surgery where presurgical anaesthetic duration exceeded 20 mins. Continuous oesophageal temperature monitoring until operative procedure commenced.Results: There were 30 children in each group. Those in the prewarmed group had significantly higher initial Tcore, a reduced drop in their Tcore and a longer time to reach the same fall in Tcore.Conclusions: The demonstrated differences are considered clinically insignificant. When the surgical procedure is short or when convective heating is available and will last for at least 45 mins, there is no clinically important ‘thermal advantage’ in prewarming. This is independent of age, weight, height and body surface area.References1 Sessler DI, McGuire J, Moayeri A, Hynson JM. Isoflurane‐induced vasodilation minimally increases cutaneous heat loss. Anesthesiology 1991; 74: 226–232.2 Melling AC, Baqar A, Scott EM, Leaper DJ. Effects of preoperative warming on the incidence of wound infection after clean surgery: a randomized controlled trial The Lancet 2001; 358(15): 876–880.3 Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical‐wound infection and shorten hospitalization. New Engl J Med 1996; 334: 1209–1215.4 Cassey J, Armstrong P, Smith GE, Farrell PT. The safety and effectiveness of a modified convection heating system for children during anesthesia. Pediatr Anesth 2006; 16: 654–662.