The purpose of this study is to see if the combination of a circulating water mattress beneath the patient combined with forced air warming over top of the patient will prevent hypothermia (low body temperature) just as well as a garment that circulates warm water around the patient, during your major abdominal surgery. Patients will be randomly assigned to one of these two groups.

Group A: This group will receive the circulating water garment Group B: This group will receive the circulating water mattress and be covered by a forced air warming device for both the upper body and lower body

Once the patient is moved to the operating room table, the surface of the back will begin to be warmed using either the circulating-water garment for those in Group A or the circulating-water mattress for those in Group B. Following the start of anesthesia, additional warming will be done by covering the large parts of the legs and the upper and side of the chest using either the circulating-water garment for those in Group A or upper- and lower-body forced-air warmers for those in Group B.

Patient involvement will last until the warming devices are removed prior to departure from the operating room. There is no follow-up to this study.

Inclusion Criteria:

• MaJor abdominal surgery
• Age between 18 and 85 years.

Exclusion Criteria:

• Fever (core temperature >38°C)
• Combined procedures (e.g.: simultaneous liver and kidney transplantation)
• Contraindication to forced-air or circulating-water warming which would be impacted by use of warming blanket
• Anticipated veno-venous bypass
• Current Pregnancy

Male or female patients between 18-85 years of age who are undergoing major abdominal surgery who do not have a contradiction to forced-air or circulating water warming. Patient's undergoing combined procedures are not eligible to participate. Patient can not have a core temperature over 38°C, be pregnant or