Patient warming: optimising surgical care

Inadvertent hypothermia for patients undergoing surgery has severe but preventable consequences for the recovery of the patient. Without active methods to retain or provide heat approximately half of all patients undergoing surgery develop a core temperature of less than 36°C and in one third of all patients the temperature drops below 35°C.1 It therefore behoves all of us involved in surgical care, wherever it takes place, to be reviewing our practice to ensure that it meets the current evidence base and recommendations for best practice. The National Institute for Health and Clinical Excellence (NICE) has provided us with just such evidence with many recommendations, not only for further research but for a considerable challenge and potential change to current practice.2 “Perioperative”, as defined in the clinical guideline, encompasses the hour immediately before surgery when patients are being prepared for surgery in the ward and the post-operative phase is extended to the first 24 hours after surgery. The implication is that surgical teams both within the wards and in the operating theatres will need to collaborate, to define more closely their policies and procedures, as well as ensuring that handovers of care include specific data on patient warmth. Equipment sourced for all areas will need to be compatible. Departments in acute hospitals will also need to be involved – such as A&E, HDU and intensive care units, as well as day care surgery units.

Hypothermia and its potential consequences

Prevention of hypothermia has long been the domain of the anaesthetist, and is well researched as a known consequence of the induction of anaesthesia. This is due to the loss of normal behavioural response to cold, and impairment of the thermoregulatory heat preserving mechanisms which occur under general and regional anaesthesia. In addition, anaesthesia causes peripheral vasodilation, causing redistribution of the blood volume with associated heat loss leading to significant drops in patients’ core temperatures. However, the broader effects of hypothermia, which are brought to the fore within the clinical guideline, are less well known and involve many other professionals. Hypothermia is defined within the guideline as a patient core temperature of 36°C. The phrase “comfortably warm” which specifically relates to the preoperative and post-operative episodes of surgical care, is defined as a normal temperature range of 36.5°C and 37.5°C. The guideline specifies that the recommendations they make relate to adult surgical care and not to children or neonates. The clinical guideline has an entire section (section 8) which reviews the consequences of inadvertent perioperative hypothermia (IPH). The evidence demonstrates the risk of morbid cardiac events, and surgical wound infections as well as an increased risk of requiring post-operative mechanical ventilation. There was weak evidence to suggest that the risk of blood transfusion postoperatively is increased.