The Effects of Ambient Temperature and Forced-air Warming on Intraoperative Core Temperature
Condition: Major Surgery Under General Anesthesia
Study type: Interventional

Summary: 
      The purpose of this study is to determine:

        1. the effect of ambient temperature on the rate of core temperature change from 1 to 3
           hours after induction of anesthesia (linear phase of the hypothermia curve) in major
           operations lasting at least a couple of hours and

        2. whether the relationship between ambient temperature and rate of core temperature change
           is different for patients who are or are not warmed with forced-air.
    

Detailed description: 
      Each patient will be randomly assigned to ambient temperature of 19°C, 21°C, or 23°C. Using a
      factorial approach, patients will also be randomly assigned to passive insulation or
      forced-air warming, stratified by the three types of surgery listed below. Group allocation
      will be based on computer generated codes (randomly permuted block sizes) prepared by
      Department of OUTCOMES RESEARCH statisticians using SAS statistical software. Allocation of
      consented patients to designated ambient temperature and forced-air vs. passive insulation
      will be via a web site that will be accessed by investigators in Bejing about 90 minutes
      before surgery.

      Patients assigned to passive insulation will be covered as usual with a cotton gown and
      single layer of cloth surgical draping. Patients assigned to forced-air warming will also be
      covered with a gown and surgical drapes, but a forced-air cover (Bair hugger 63500, 3M) will
      be inserted between the gown and the skin surface. A lower-body cover (about 91 by 221 cm)
      will be positioned so the lower end of the forced-air segments extend from the ankles upward
      for the entire length of the cover in thoracic and abdominal cases. The cover's foot drape
      will extend over the feet, and in turn be covered by the surgical drape. An upper-body
      forced-air cover will similarly be applied for patients having hip arthroplasties. The
      forced-air cover will be connected to a Bair Hugger blower and #635 covers set to "high"
      (≈43°C).

      Ambient temperature will be adjusted to the designated temperature about an hour before a
      patient enters the operating room and adjusted as necessary to maintain the designated
      temperature throughout surgery. General anesthesia will be induced as per usual clinical
      routine. Neuraxial (epidural or spinal) and other regional blocks are permitted.

      Any patients whose core temperature decreases to less than 34.5°C will be actively warmed
      with forced air and the ambient temperature increases to the extent practical.
    

Intervention name(s): Ambient Temperature 19°C; Ambient Temperature 21°C; Ambient Temperature 23°C; Forced-air cover (Bair hugger 63500, 3M); Passive insulation
Intervention type(s): Other; Other; Other; Device; Other
Intervention description(s): Ambient Temperature 19°C; Ambient Temperature 21°C; Ambient Temperature 23°C; Patients assigned to forced-air warming will also be covered with a gown and surgical drapes, but a forced-air cover (Bair hugger 63500, 3M) will be inserted between the gown and the skin surface.; Patients assigned to passive insulation will be covered as usual with a cotton gown and single layer of cloth surgical draping.
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: None (Open Label)
Primary purpose: Supportive Care
Keywords: Thoracic Surgery; Thoracic surgery, Video assisted; Open Abdominal Surgery; Anesthesia, General