Efficacy of a Convective Prewarming System in Prevention of Perioperative Hypothermia

Although several measures for prevention of perioperative hypothermia have been introduced the last decades, perioperative hypothermia is still a frequent complication and associated with a negative outcome. For not long lasting surgery without specific risk for hypothermia the standard procedure for prevention of perioperative hypothermia is insulation. However, the insulation is often not effective enough to prevent intra- and postoperative hypothermia. The implementation of a prewarming is difficult because of variable OR schedules and therefore not often applied. In the planed prospective, multicenter, randomised-controlled trial will the efficacy of a convective prewarming system on prevention of intra- and perioperative hypothermia (Thermoflect™, TSCI, Amersfoort, NL) be compared to an intraoperative application of forced air warming with or without passive insulation before induction of anesthesia. The studied prewarming device is easy to use and will be applied on the nursery ward 30-60 minutes before transfer of the patient to the OR. Perioperative hypothermia is a common complication in general aesthesia. Perioperative hypothermia is associated with medical risks as intraoperative impaired coagulation due to reversible platelet dysfunction, a prolonged bleeding time and increased intraoperative blood loss. In the postoperative course the perioperative hypothermia is especially for patients with cardiopulmonary diseases a relevant problem. Not at least sensual cold and shivering is uncomfortable for the patient. The study is conducted as a multicenter, prospective, randomised controlled trial. All patients will receive intraoperatively a forced air warming device (Termoflect™/Mistral Air ™). For one intervention group will additionally the insulation with the Thermoflect™ will be applied on nursery ward, the second intervention group will receive additionally a convective air warmer/ reflective blanket (Thermoflect™/Mistral Air™, TSCI, Amersfoort, NL) preoperatively on study day on nursery ward. The aim of the study is to prove the hypothesis that a preoperative insulation with a commercial insulation material (Thermoflect™, TSCI, Amersfoort, NL) leads to a lower incidence of perioperative hypothermia in general anesthesia. The second hypothesis is, that an active prewarming (Thermoflect™ with Mistral Air™, TSCI, Amersfoort, NL) is associated with a more less incidence of periopative hypothermia.

No prewarming Intraoperative forced air warming (Thermoflect™/Mistral Air™) (after induction of anaesthesia, before surgery starting) Passive insulation with Thermoflect™ material. All fluids administrated intraoperative will be warmed.

Passive prewarming / insulation on nursery ward before transport to the OR (Thermoflect TSCI, Amersfoort, NL) Intraoperative forced air warming (Thermoflect™ / Mistral Air ™) The forced air warming will be applied after induction of anaesthesia. All fluids administrated intraoperative will be warmed.

Active prewarming on nursery ward before transport to the OR (Thermoflect™/Mistral Air™, TSCI, Amersfoort, NL) Intraoperative forced air warming (Thermoflect™ / Mistral Air ™) The forced air warming will be applied after induction of anaesthesia. All fluids administrated intraoperative will be warmed.

Inclusion Criteria: Age from 18 to 75 years BMI from 20 to 30 kg/m2 Risk class ASA I to III Scheduled time for surgery 30 to 120 minutes Scheduled anaesthesia with remifentanil, propofol, rocuronium and sevofluran Ability of informed consent Exclusion Criteria: Adipositas permagna Risk class ASA IV to V Hypo- and Hyperthyroidism Febrile infection Pregnancy Scheduled time for surgery < 30 or > 120 minutes Known incompatibility for midazolam, remifentanil, propofol oder rocuronium