Drs Ross-Anderson and Patel make an excellent point, but they admit they are using a special population to support their contentions. However, I can assure them that the same results are possible more generally, if one understands that the routes of heat loss from general surgical patients are not as diverse as they suggest. Radiant heat loss into a room at a comfortable temperature is only marginally greater than the heat gain (it is proportional to the relative differences in temperature in Kelvin, i.e. relative to absolute zero). Evaporative loss from wounds is frequently exaggerated, and if we use airway filters and low flow systems, is likely to be small from the respiratory tract. Conductive heat loss is also limited because we generally use air-filled sponge matresses. We are left with convection, and this can be prevented simply and cheaply with thin clear plastic bags. Take four 900 x 600 mm general duty hospital domestic waste bags and loosely apply one on each arm and leg. Use a 600 x 600 one for the head. Small holes can be made to allow things like tubes in and out (take care not to catch a film of plastic in a connection such as an tracheal tube!). Results: perfect insulation against heat loss by convection from much of the patient surface. In many cases it also keeps the patient clean (but a bit sweaty). Using this system, a year's audit shows that patients undergoing prolonged major gynaecological surgery in a modern air conditioned operating theatre arrive in recovery with temperatures over 36^o C. It'll never catch on though: no funding for a randomised controlled trial for NICE to assess, no product for a company to hawk around, and not exciting enough for a trainee to do a study on!