INSPIRED ANESTHETIC GAS HUMIDIFICATION IMPROVES THERMAL UNIFORMITY DURING CANINE WHOLE-BODY HYPERTHERMIA

Supplying warmed saturated water vapour in anaesthetic gases during wh ole body hyperthermia (WBH) could potentially improve thermal uniformi ty in the trachea and esophagus. Four normal dogs were anaesthetized f or WBH at 42 degrees C. A Puritan Bennett Cascade humidifier was used to supply anaesthetic gases saturated with water vapour at an average airway temperature of either 42 degrees C or 38 degrees C. Esophageal temperature was monitored at tile thoracic inlet and 5 cm cephalad. Th ermal dose was estimated by calculating equivalent minutes for an isoe ffect at 43 degrees C (GEM 43 degrees T-x, where T-x is the site of te mperature measurement). Endotracheal mucociliary transport velocity (M CTV) was determined before and 48 h following WBH by Tc-99m-MAA scinti graphy. Compared to the 38 degrees C humidified gas group, dogs receiv ing 42 degrees C humidified gas reached 42 degrees C faster (p = 0.02) and had CEM 43 degrees T-esophageal values equivalent to the target C EM 43 degrees T-rectal. Endotracheal MCTV with 42 degrees C humidified gas, however, was reduced 53% from baseline 48 h following WBH (p = 0 .02). With 38 degrees C humidified gas, endotracheal mucociliary trans port velocity was unchanged from baseline 48 h post WBH. Tracheal hist ology was examined using light and electron microscopy in four additio nal dogs euthanatized following 90 min of 42 degrees C humidified gas combined with WBH. There was no histological evidence of tracheal or l ung thermal damage with 42 degrees C humidified gas in these four dogs . However, a moderate increase in tracheal goblet cell secretory granu le staining was observed. This change could imply temporary heat-induc ed ciliary microtubule dysfunction, rather than decreased mucus produc tion, as the likely mechanism of reduced mucociliary transport velocit y 48 h following WBH. Administration of 42 degrees C humidified anaest hetic gases with WBH improves heating rate and esophageal thermal unif ormity but temporarily depresses tracheal. mucociliary transport veloc ity.