Recommendations for research

The guideline committee has made the following recommendations for research.

As part of the 2016 update, the standing committee made 2 additional research recommendations, on combined methods of intraoperative active warming compared with a single method, and forced-air warming compared with conductive fabric warming in laminar flow theatre. Three research recommendations, on preoperative insulation and warming, comparison of intraoperative warming devices, and use of both preoperative and intraoperative warming, were removed. Details can be found in the addendum.

1 Combined methods of intraoperative active warming compared with a single method

What is the clinical and cost effectiveness of combined methods of intraoperative active warming compared with a single method in preventing inadvertent perioperative hypothermia?

Why this is important

A combination of active warming devices, such as forced-air warming together with a resistive heating mattress, is usually used to warm patients during surgery. However, there is not enough evidence to show whether this is more clinically effective than a single active warming device, such forced-air warming on its own. Randomised controlled trials (RCTs) should be carried out to compare combined methods of intraoperative active warming (such as forced-air warming together with a resistive heating mattress, or a resistive heating mattress together with a resistive heating blanket) with a single method of active warming (such as forced-air warming). All intravenous fluids should be warmed to 37°C. The RCTs should be sufficiently powered to show clinically significant differences. Primary outcomes should be core temperature at the end of surgery and incidence of hypothermia. Patients may be stratified by anaesthesia duration and type of surgery. Adverse effects and numbers of patients with complications of hypothermia (for example, cardiac events or wound infections) should be recorded. [new 2016]

2 Forced-air warming compared with conductive fabric warming in laminar flow theatre

What is the clinical and cost effectiveness of intraoperative forced-air warming compared with conductive fabric warming in laminar flow theatre?

Why this is important

It has been suggested that forced-air warming may increase the risk of surgical site infection during implantation surgery (such as joint replacement) because the air flowing through the forced-air warming device disrupts the air flow around the surgical site. Research suggests that conductive warming devices are less likely to cause surgical site infection because the disruption to air flow is less than that caused by forced-air warming. More evidence is needed on the incidence of surgical site infection in implantation surgery using different warming devices. RCTs should be carried out to compare forced-air warming with conductive warming in laminar flow theatre. The RCTs should be sufficiently powered to show clinically significant differences. Primary outcomes should be surgical site infection and core temperature at the end of surgery. Adverse effects and numbers of patients with complications of hypothermia (for example, cardiac events or increased length of hospital stay) should be recorded. [new 2016].

3 Temperature thresholds for preoperative warming

What is the optimum temperature target when warming patients preoperatively?

Why this is important

Preoperative warming is intended to minimise the impact of redistribution hypothermia by reducing the temperature difference between the patient's core temperature and peripheral temperature. There is a lack of evidence for the optimum preoperative temperature for preventing intraoperative hypothermia. Large RCTs (with at least 100 patients in each arm) should be conducted in adults undergoing surgery to compare warming patients to 36.5°C and 37.0°C in the preoperative phase. Warming should be continued intraoperatively in all patients. All intravenous fluids given should be warmed to 37°C. Primary outcomes should be the incidence of hypothermia, and patient temperature intraoperatively (at 15, 30, 60 and 120 minutes) and in recovery. The duration of warming required to achieve the target preoperative temperature should be recorded. Adverse effects (including patient discomfort) and numbers of patients with complications of hypothermia (for example, morbid cardiac events, wound infection) should be recorded. [2008]

4 Effects of nutritional solutions

Does the infusion of nutritional solutions such as amino acids and fructose further reduce the incidence of inadvertent perioperative hypothermia in patients receiving intraoperative warming?

Why this is important

Limited evidence suggests that infusion of amino acids or fructose in the preoperative and intraoperative phases may prevent hypothermia. Such infusions may also have additional benefits in fasted patients. A large RCT (with at least 100 patients in each arm) comparing infusions of amino acids, fructose and saline should be conducted in adults undergoing surgery. These infusions should be started before the induction of anaesthesia and continued throughout the intraoperative phase. All patients should receive forced-air warming intraoperatively and all intravenous fluids given should be warmed to 37°C. Primary outcomes should be the incidence of hypothermia, and patient temperature intraoperatively (at 15, 30, 60 and 120 minutes) and in recovery. Adverse effects and numbers of patients with complications of hypothermia (for example, morbid cardiac events, wound infections) should be recorded. [2008]

  • National Institute for Health and Care Excellence (NICE)