• The critical endpoints to be evaluated in making this determination are 1) % of subjects with an average intraoperative esophageal temperature of ≥ 36º C [ Time Frame: During surgical procedure ] [ Designated as safety issue: Yes ]
• % of subjects with an initial PACU sublingual temperature of ≥ 36º C. [ Time Frame: Temp taken just prior to surgery ] [ Designated as safety issue: Yes ]

• comparison of the core body temperatures @ 60 minutes post anesthesia induction, [ Time Frame: 60 minutes post anesthesia induction ] [ Designated as safety issue: Yes ]
• comparison of temperature trends during surgery [ Time Frame: during surgery ] [ Designated as safety issue: Yes ]
• comparison of the subjects' PACU temperature trends and hypothermic symptoms such as shivering [ Time Frame: Within an hour after surgery ] [ Designated as safety issue: Yes ]

Hypothermia is a common and serious complication during anesthesia and surgery. Anesthetic-induced hypothermia results from the inhibition of thermoregulatory control and exposure to cold operating room environment.

Various warming methods, such as warm blankets, forced-air warmers and circulating water mattresses, are currently used to prevent and treat mild perioperative hypothermia. All are cutaneous approaches that rely on heating the peripheral tissues in order to increase the thermal core temperature. 5, 6 Application of cutaneous warming system blankets/pads are limited by location/extent of operative site; for example, in certain procedures such as laparatomies, reconstructive plastic surgery or orthopedic surgery, only a limited amount of skin surface is available for warming application. 7, 8, 9 The Dynatherm vitalHEAT technology takes advantage of the body's natural thermoregulatory system to channel thermal energy to the body's core non-invasively at a rapid rate. The vH2 system is designed to treat hypothermia during the peri-operative period through a combination of localized heat and vacuum application to one hand & forearm; this application 1) opens the arteriovenous anastamoses located in the palm of the hand and 2) conductively warms the extremity thus effectively warming the blood flow to the body's core. The vH2 system is a portable and compact warming device which provides a non-invasive approach to warming patients during surgery.

The primary objective of this study is to determine if the Dynatherm Medical vitalHEAT (vH2) Temperature Management System is as effective as the forced-air warming Bair Hugger™ (Arizant Healthcare, Eden Prairie, MN) for maintenance of intraoperative body temperature in patients undergoing abdominal surgery under general anesthesia. The critical endpoints to be evaluated in making this determination are 1) % of subjects with an average intraoperative esophageal temperature of ≥ 36º C and 2) % of subjects with an initial PACU sublingual temperature of ≥ 36º C. Secondary objectives include 1) comparison of the core body temperatures @ 60 minutes post anesthesia induction, 2) comparison of temperature trends during surgery and 3) comparison of the subjects' PACU temperature trends and hypothermic symptoms such as shivering.

• Device: Dynatherm Medical vitalHEAT Temperature Management System vH2
• Device: Bair Hugger™ (Arizant Healthcare, Eden Prairie, MN)

• Experimental: The vH2 system consists of a Control Unit containing the heating system and the vacuum generation pump which connects via an umbilical containing the fluid and vacuum tubing to the Warming Sleeve. The Control Unit also contains the user interface and alarm management systems. The disposable Warming Sleeve consists of a manifold attached to the warming pads and a polyurethane pouch (Vacuum Sleeve) that are placed over the patient's hand and forearm and secured with tape. The Warming Sleeve manifold contains connectors for the fluid and vacuum tubing contained in the umbilical. The vH2 System will be used for patient warming during these surgical procedures. Monitoring of core temperature via esophageal probe will be done for the purpose of data collection.
• Active Comparator: The Bair Hugger system is the current standard of care at TGH. It consists of a Temperature Management Unit that contains the heating element, the air circulating motor and the temperature control mechanisms. This unit connects via a hose to the operating room blankets. The Bair Hugger technology relies on heated air convection. Warm air is circulated evenly through the air space in the specially designed blanket, warming the skin surface as well as any insulating blankets placed over the Bair Hugger blanket. The Bair Hugger System is the site's current approach to patient warming during these surgical procedures. Monitoring of core temperature via esophageal probe will be done for the purpose of data collection.

• Insler SR, Sessler DI. Perioperative thermoregulation and temperature monitoring. Anesthesiol Clin. 2006 Dec;24(4):823-37. Review.
• Sessler DI. Perioperative heat balance. Anesthesiology. 2000 Feb;92(2):578-96. Review.
• Taguchi A, Ratnaraj J, Kabon B, Sharma N, Lenhardt R, Sessler DI, Kurz A. Effects of a circulating-water garment and forced-air warming on body heat content and core temperature. Anesthesiology. 2004 May;100(5):1058-64.
• Giesbrecht GG, Ducharme MB, McGuire JP. Comparison of forced-air patient warming systems for perioperative use. Anesthesiology. 1994 Mar;80(3):671-9.

Inclusion Criteria:

• Patients undergoing elective open abdominal surgical procedures with an expected duration of 2 to 4 hours and requiring general anesthesia
• American Society of Anesthesiologists(ASA) physical status I-III
• Patient age: > 18 years and <80 years

Exclusion Criteria:

• Patient age: < 18 years and >80 years
• Patients with break in skin integrity on the extremity selected as the application site
• Patients with history of upper extremity peripheral vascular disease
• Patients with history of allergic skin conditions of the upper extremities
• Patients with history of bleeding disorders/coagulopathy
• Patient with history of malignant hyperthermia
• Patients who are pregnant
• Patient unwilling or unable to give informed consent