Author: Cliff D.; Tierney J.; McGrath C.
Abstract: The detrimental effects of even mild perioperative core hypothermia are well known and wide-ranging, including increased wound infection, cardiac morbidity, blood transfusion requirement and longer hospital stay [1]. Pneumatic tourniquets are commonly used during limb surgery to reduce blood loss and improve the quality of the surgical field. A significant fall in core temperature following limb tourniquet release has been demonstrated in patients undergoing general or epidural anaesthesia, presumably due to redistribution of body heat and efflux of hypothermic blood from the tourniqueted limb[2, 3]. Sub-arachnoid anaesthesia is a commonly used method for lower limb orthopaedic procedures including knee arthroplasty, with beneficial effects including lower incidence of deep vein thrombosis and a potential increased cost effectiveness when compared to general anaesthesia[4]. Methods Having gained approval from the regional ethics committee, and participants' written informed consent, a prospective observational study was conducted. Twenty patients undergoing elective primary unilateral knee arthroplasty with use of a lower limb pneumatic tourniquet under sub-arachnoid anaesthesia and with conscious sedation via a propofol target controlled infusion were recruited. During surgery, core temperature was attempted to be maintained between 36.5 - 37.5 degreeC using warmed intravenous fluid and a forced air warming blanket. At the end of surgery, warming methods were continued and core body temperature was observed at the time of
tourniquet release and then for the following ten minutes. Data was analysed using a multiple dependent samples t-test. Results Mean core temperature at tourniquet deflation was 36.25oC (SD 0.44). Mean maximal core temperature drop was 0.13oC (SD 0.12). Any change in core temperature after tourniquet release was not significant (p= 6.62). Discussion Our study would suggest a potential benefit from use of subarachnoid anaesthesia in avoidance of core hypothermia associated with tourniquet release when compared to epidural or general anaesthesia. A further study with a larger number of patients would be indicated to investigate this.
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