We wanted to find out the effects of extra insulation on preventing hypothermia and its complications for adults having an operation.
People can get cold during operations, particularly because of the drugs used as anaesthetics. This can sometimes cause potentially dangerous heart problems. The cold can also make people shiver and feel uncomfortable after an operation. Ways have therefore been developed to try to keep people warm during an operation. One way is to use reflective blankets or clothing as extra insulation.
We looked at the evidence up to February 2014 and found 22 studies involving several hundred patients. The studies involved people aged over 18 years having routine or emergency surgery. We disregarded studies where people were deliberately kept cold during the operation, where they were having head surgery or skin grafts, or where the person was having a procedure under local anaesthetic.
We looked at studies comparing what happened when using reflective blankets or clothing against what happened when someone had normal care, using non-reflective blankets or clothing.
We also looked at studies comparing what happened when using a machine to force warm air through the person’s blankets (forced air warming) against what happened when using reflective blankets or clothing.
There is no clear evidence that using reflective blankets or clothing increases a person’s temperature compared with what happens when someone has usual care.
There is some evidence that using forced air warming increases a person’s temperature compared with what happens when using reflective blankets or clothing. The temperature increase was between 0.5 ºC and 1 ºC. It is unclear how this temperature difference would reduce the consequences of coldness, with uncertain effects on blood loss, shivering and time spent in recovery. We were unable to find sufficient information to look at adverse effects of insulation or warming, or major events affecting the heart or circulatory system.
Quality of the evidence
Most of the evidence was low quality. We were particularly concerned about the potential for skewed results from operating theatre staff changing their behaviour when they knew ways of keeping the patient warm had changed.