Intraoperative hypothermia is seen in almost all surgical patients who are not warmed and occurs due to thermoregulatory impairment happening because of GA, lower OT temperatures and exposure of deep tissues to cool surroundings. GA leads to impairment of thermoregulatory center in the brain which leads to decrease in core body temperature as there is redistribution of heat from core to periphery due to vasodilatation. Most cellular functions of human body require a narrow temperature range hence even 1 or 2°C fall in core temperature may have adverse effects. Therefore, it is vitally important to maintain normothermia during intraoperative period. As there is no study where forced air warmer (FAW) system has been compared to Fluid warming system in spine surgeries under GA, hence this study is planned.

The study will be conducted in the Department of Anaesthesia and Intensive Care, Government Medical College and Hospital, Chandigarh-32. After approval by the institutional Ethics Committee and registration with clinical trial registry of India (CTRI). A total of 63 patients of either sex, aged 18-80 years, undergoing elective/scheduled spine surgeries under general anaesthesia will be enrolled after obtaining written informed consent.

The patients will be randomly assigned into three groups.

Group Forced Air Warming System (Group F) - patient will receive over body temperature regulated forced air warming system, along with passive insulation.

Group Hotline fluid warming Device (Group H) - patient will receive fluid warmed at 42 ℃ along with passive insulation to cover the body.

Group C in which we will use combination of FAW blanket and Hotline fluid warmer along with passive insulation.

Standard ASA monitoring will be done.

Temperature of nasopharynx, tympanic membrane and skin will be recorded firstly in preoperative room and then after every 15 minutes from induction of anaesthesia till the extubation and finally at post anaesthesia care unit (PACU).

MAP, HR, SpO2, EtCO2 will be recorded every 30 min till the patient is extubated.

Extubation will be carried out as per our hospital protocol or according to the direction of the on-table anesthesiologist.

Intervention will be done if temperature of the patient during intraoperative period goes out of range i.e. 35 to 38℃.

If temperature falls below 35℃, then intervention will be done by switching on forced air warmer in Hotline group and hotline fluid warmer will be started in group forced air warmer group. If the temperature exceeds beyond 38℃, then intervention will be done by switching off the forced air warmer and/or hotline fluid warmer in the respective groups

Study design: Randomized single blind study.

Duration of surgery: 18 months

Sample Size Calculation

Since 3 groups will be taken for the study, the sample size was calculated based on the expected difference between 2 groups, while adjusting the alpha error for multiple comparisons (3 comparisons in case of 3 groups).

The sample size for the study was based on Yasar et al (2022), who reported the mean temperature in two of the three groups as follows:

The sample size required in each arm of the study was calculated according to the formula given by Snedecor & Cochran (1989):

Based on the formula given above, using the mentioned values, assuming 80% Power and 95% Confidence interval, the minimum sample size required is 21 in each group (total 63).

Randomisation: A computer-generated simple randomization will be used to allocate patients in one of the 3 groups. The allocation of patients will be concealed with sequentially numbered and sealed opaque envelopes that will be opened by the attending anesthesiologist after the patient arrived in the preoperative waiting area. Patients will be blinded to the group allocation. The anesthesiologists who will anaesthetize and supervise the warming will not be blinded to the group allocation.

All the obsevations will be noted in the prescribed proforma and will be subjected to appropriate statistical tests to draw comparison between forced air warming system and hotline fluid warmer in prevention of intraoperative hypothermia.