Heat loss during induction of anaesthesia for elective aortic surgery

Abstract

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.

The effect of heat and moisture exchanger on humidity and body temperature in a low‐flow anaesthesia system

“…These studies also demonstrate that the core temperatures prevailing after the induction did not change significantly during the first hour of anaesthesia. This is congruent with our findings that the core temperature initially rapidly decreased (14,15). In accordance with the findings of Stoneham et al the temperature decrease in our study correlated with the time interval between the induction of the general anaesthesia and the surgical incision, while the subsequent decrease in temperature during anaesthesia was insignificant (14).…”

“…This is congruent with our findings that the core temperature initially rapidly decreased (14,15). In accordance with the findings of Stoneham et al the temperature decrease in our study correlated with the time interval between the induction of the general anaesthesia and the surgical incision, while the subsequent decrease in temperature during anaesthesia was insignificant (14). Therefore, our findings favour the view that an early redistribution of body heat is the major reason for the intraoperative core temperature drop.…”

“…It has been shown that core hypothermia after induction of general anaesthesia results from an internal coreto-peripheral redistribution of heat, resulting in a loss of heat to the environment via conduction and convection (13,14). These studies also demonstrate that the core temperatures prevailing after the induction did not change significantly during the first hour of anaesthesia.…”

The effect of preoperative warming on patients' postoperative temperatures

“…Temperatures lower than 36° C (96.8° F) are associated with multiple adverse postoperative outcomes. Even mild hypothermia can cause a negative nitrogen balance (ie, vasoconstriction results in less perfusion to the kidney, which causes less filtering of metabolic waste products from the blood, causing a rise in blood urea nitrogen levels), 3 cause cardiac arrhythmias (eg, bradycardia, premature ventricular contractions, a trial fibrillation, ventricular fibrillation); 3 cause respiratory distress; 3 decrease medication metabolism; 3 delay recovery from anesthesia; 6 impair platelet and clotting cascade function; 2 impair wound healing; 3 increase blood loss and postoperative fluid requirements; 7 increase patient discomfort from shivering and the feeling of being cold; 8 prolong medication action; 2 and reduce resistance to sureical wound infections 2 …”

The Safe and Efficient Use of Forced‐Air Warming Systems

“…Prewarming, however, has not yet become a routine part of preoperative preparation 16 . Stoneham et al 17 found that a period of active preinduction warming is needed to avoid the common decreases in core temperature seen during general anesthesia induction.…”