Heat loss during induction of anaesthesia for elective aortic surgery

We have studied core temperature changes occurring during induction of general anaesthesia and surgery in 18 patients undergoing elective aortic aneurysm repair. In the operating theatre, all patients were warmed with a forced-air warmer and a warming mattress, and received warmed (37 degrees C) intravenous fluids. Despite this, mean (SD) [range] core temperatures in the anaesthetic room decreased by 1.5 (0.3)[1.1-2.2] degrees C, while intravascular lines, epidural and urinary catheters were inserted before the introduction of warming methods in theatre. In one-third of patients, the core temperature was still below 36 degrees C at the end of surgery. The overall temperature decrease correlated significantly with the duration of time between induction of general anaesthesia and surgical incision (R2 = 0.6912), when the patients were not being warmed. Hypothermia may thus be prevented by minimising the period that the patient is anaesthetised without being warmed. Vascular lines, urinary and epidural catheters should be inserted before the induction of general anaesthesia or, alternatively, warming methods should be introduced in the anaesthetic room.