Comparison of a New Patient Warming System Using Polymer Conductive Warming With Forced Air Warming During Surgery
Condition: Hypothermia
MeSH terms: Hypothermia
Study type: Interventional
Phase: Phase 3

Summary: 
      Two patient warming systems will be compared with 40 patients each in a convective warming
      group (BairHugger, Arizant) and in a conductive warming group (HotDog, Augustine Biomedical).

      The patients will undergo small to medium trauma surgery and will be warmed with the
      randomized device - the hypothesis is, that the area under the standardized core temperature
      / time curve is significantly greater in the conductive warming group. Secondary outcome is
      the mean skin temperature / time area under the curve.
    

Detailed description: 
      General study design We will study 200 patients (18-90 years) undergoing elective orthopedic
      surgery at the trauma surgery unit. The patients must have normal weight (20-30 BMI), the
      duration of surgery should last between 3 - 4 hours. There will be no other exclusion
      criteria (except severe peripheral arterial disease in the warmed extremity), as forced air
      patient warming is routinely used for all patients during this procedure.

      The patients will be randomly assigned via a computer generated randomization list to
      treatment with either polymer or forced air warming. Anaesthesia and fluid management will be
      administered as desired by the anaesthesiologist.

      Before warming four skin temperature probes will be attached to the upper arm, chest, abdomen
      and back of the patients to calculate mean body temperature. A probe (Mallinckrodt
      Anesthesiology Products, Inc., St. Louis, MO) will be introduced in the ear to measure core
      temperature. Afterwards, treatment with BairHugger or HotDog will be started.

      The measurements will be recorded every five minutes until the end of surgery when
      intraoperative warming is stopped.

      Differences between core temperatures will be analyzed both by using the summary measure of
      AUC (area under the curve) and by comparing the core-temperature at the end of surgery in the
      polymer and the forced air group with two-tailed, unpaired t tests if normally distributed
      and with a Wilcoxon test, if not normally distributed (distribution tested by K-S-test).

      Results are expressed as means ± standard deviations if normally distributed, as median
      (IQ-Range) when not normally distributed.

      Differences will be considered statistically significant when P < 0.05. We consider a
      difference in core temperature at the end of surgery of 0.5°C as clinically important.
      Considering this difference as well as a known standard deviation of approximately 1.5°C we
      will have to study 40 patients in each arm of the study to achieve statistical significance
      using a power of 90% and a p-value of 0.05.
    

Intervention name(s): Patient Warming with conductive / convective warming
Intervention type(s): Device
Intervention description(s): Warming device set to maximum (43 °C)
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: patient warming; convective warming; conductive warming; intraoperative normothermia; accidental hypothermia; intraoperative hypothermia