Evaluating Adult Patient Temperatures During Lower Spinal Surgery

Comparing Patient Temperatures in Adults During Lower Spinal Surgery Using Either a Heated Ventilator Circuit or a Standard Ventilator Circuit With a Heat-Moisture Exchanger

The purpose of this study is to evaluate patients' temperatures after using one of two ventilator circuits (breathing systems): the ANAPOD™ Heat and Humidification System (ANAPOD™ system) or the standard ventilator circuit with a heat-moisture exchanger (standard ventilator). The ANAPOD™ system will provide additional heat and humidity to patients through their breathing tube while the standard ventilator will not. The investigators are doing this research study to find out if the ventilator circuit providing additional heat and humidity will keep patients warmer during surgery and after surgery.

Patients were randomly assigned to either the treatment group or the control group prior to surgery. Prior to induction, patients in the control group were given inspiratory gas at ambient air temperature (20-22 degrees Celsius) and patients in the treatment group were given inspiratory gas at warmed temperatures (40-41 degrees Celsius). All patients were induced with general anesthesia in the supine position and repositioned prone following endotracheal intubation and placement of an esophageal stethoscope with a temperature sensor, as per usual hospital practice. Esophageal temperatures were recorded within 30 minutes of the baseline esophageal temperature and every 10 minutes thereafter for the first hour post-induction. All patients had a blanket and forced air warming applied to their lower extremities and upper back at 43 degrees Celsius after draping. All patients had esophageal temperature measurements recorded every 30 minutes until the patient was repositioned supine. Core temperatures were recorded four hours post-induction for those patients reaching that timeframe.

Patients were randomly assigned to either the treatment group or the control group prior to surgery. Group randomization was performed using a randomization schedule prepared by the Division of Clinical Statistics with patients randomized in blocks of four. For consented and enrolled patients on the day of surgery in the admit areas, a participant was assigned the next sequential participant ID number and the appropriate sealed envelope was opened to reveal the participant's randomized intervention. This occurred before the patient was transferred to the operating suite. Individuals who performed data analysis were blinded to treatment group.

Heated and humidified inspired gases using the ANAPOD™ Heat and Humidification System (Westmed; Tucson, Arizona, USA) circuit prior to induction of general anesthesia in addition to standard ventilation and temperature management.

active heat and humidification during anesthesia by warming inspire gases without a heat-moisture exchanger

Core body temperature will be taken in the esophagus. The last recorded esophageal temperature will be used for surgeries not reaching 3 hours duration.

Shivering in the post-anesthesia care unit will be assessed using the Bedside Shivering Assessment Scale. This is a 4 point scale and rate shivering as the following: absent, mild, moderate, or severe. Only the highest degree of patient shivering was used in the analysis.

The estimated blood loss per case was determined by the anesthesia provider by measuring the volume of blood in the suction canister while taking into account the amount of irrigation solution used.

Inclusion Criteria: Elective spine surgery anticipated greater than three hours in duration Posterior approach An operative site between lumbar one and sacral one Involving two or more levels with fusion and/or instrumentation and/or revisions American Society of Anesthesiologists (ASA) Status of I-III Exclusion Criteria: Patients with a tracheostomy Preoperative temperature >38°C or <36°C on the day of surgery Active infection or erythema to the back White blood cell count greater than 10,500/microliter (mcL)