Efficacy of intraoperative heat administration by ventilation with warm humidified gases and an oesophageal warming system

Abstract

We measured changes in body temperature in 12 hypothermic (mean aural temperature 34.4 (SD 1.0) degrees C) pigs during general anaesthesia with an open abdominal cavity and the effect of two warming systems: heating of inspired gases to 39 degrees C (intratracheal temperature) and oesophageal warming to 39 degrees C by a water perfused oesophageal heat exchanger. Each animal underwent both treatments and the control period in random sequence. Each condition was studied over 1 h. No additional protection against heat loss (drapes, blankets, i.v. fluids warming, etc.) was used. Anaesthesia, room temperature and relative humidity, amount and temperature of infusions and extension of exposed visceral surfaces were standardized. Mean decrease in body temperature was 1.0 (0.7) degree C (P < 0.005) without warming and 0.6 (0.2) degree C (P < 0.005) with heated inspired gases: this difference was not statistically significant. Oesophageal warming was very efficient as mean body temperature did not change significantly (-0.1 (0.2) degree C; ns).

Fluid heating system (SAF®): effects on clinical and biochemistry parameters in dogs submitted to inhalatory anesthesia

“…Thus, even in face of positive correlation between RT and CT, the latter may not precisely reflect the animal's temperature, for they refer to different compartments, central and peripheral, respectively. The same observation was reported by Beck et al 6 in a study employing swine, in which CT and RT were different in pre and postoperative periods.…”

“…The modification of the protocol used by Beck et al 6 was based on the impossibility of access to some sites used by the author, mainly on mammary, crural and gastrocnemius regions, due to surgical act disturbance. This author states that CT values aid on the inferences of body heat loss.…”

“…Rectal temperature (RT) was assessed using a digital thermometer. Using na infrared thermometer, cutaneous temperature was assessed on thoracic and pelvic limbs, modifying the protocol employed by Beck et al 6 in swine. The modification consisted of calculating the mean cutaneous temperature (CT) of the limbs, by the arithmetical mean of the temperature in each limb, on carps and tarsal regions.…”

Effect of heated humidified ventilation on bronchial mucus transport velocity in general anaesthesia: A randomized trial

“…3 Heated humidifier studies have been generally performed in intensive care unit settings; few studies have investigated patients under general anaesthesia in surgical situations. [4][5][6][7][8] Bronchial mucus transport velocity (BTV) is simply and directly assessed via fibreoptic bronchoscope (FOB), and offers a visual assessment of mucociliary clearance in the lower respiratory tract. 9,10 The aim of this prospective randomized study was to evaluate the effects of heated humidified ventilation on BTV, in patients undergoing general anaesthesia.…”

“…3 Heated humidifier studies have been generally performed in intensive care unit settings; few studies have investigated patients under general anaesthesia in surgical situations. 4–8…”