Retrospective study of the prevalence of postanaesthetic hypothermia in dogs.

The anaesthetic records of 1525 dogs were examined to determine the prevalence of postanaesthetic hypothermia, its clinical predictors and consequences. Temperature was recorded throughout the anaesthesia. At the end of the procedure, details coded in were: hyperthermia (>39.50°C), normothermia (38.50°C-39.50°C), slight (38.49°C-36.50°C), moderate (36.49°C-34.00°C) and severe hypothermia (<34.00°C). Statistical analysis consisted of multiple regression to identify the factors that are associated with the temperature at the end of the procedure. Before premedication, the temperature was 38.7 ± 0.6°C (mean ± sd). At 60, 120 and 180 minutes from induction, the temperature was 36.7 ± 1.3°C, 36.1 ± 1.4°C and 35.8 ± 1.5°C, respectively. The prevalence of hypothermia was: slight, 51.5 per cent (95 per cent CI 49.0 to 54.0 per cent); moderate, 29.3 per cent (27.1-31.7 per cent) and severe: 2.8% (2.0-3.7%). The variables that associated with a decrease in the temperature recorded at the end of the anaesthesia were: duration of the preanesthetic time, duration of the anaesthesia, physical condition (ASA III and ASA IV dogs showed lower temperatures than ASA I dogs), the reason for anaesthesia (anaesthesia for diagnostic procedures or thoracic surgery reduce the temperature when compared with minor procedures), and the recumbency during the procedure (sternal and dorsal recumbencies showed lower temperatures than lateral recumbency). The temperature before premedication and the body surface (BS) were associated with a higher temperature at the end of the anaesthesia, and would be considered as protective factors.