Forced‐air warming blanket and surgical access

It is well documented that accidental peri-operative hypothermia can be associated with adverse consequences to the surgical patient. These include impaired clotting with resultant increased blood loss [1], increased risk of myocardial ischaemia [2] and increased incidence of wound infection [3, 4]. If the patient is at risk of peri-operative hypothermia, the anaesthetist should attempt to minimise heat loss: the operating theatre should be at an appropriate temperature, any period of total patient exposure should be kept to an absolute minimum, the inspired gases should be warmed and moisturised by the use of a heat and moisture exchanger, an under warming blanket should be employed where practicable, intravenous fluids should be warmed and a forced-air warming device may be used. Of the above mentioned interventions, use of the forced-air warming device has been shown to be the most effective method of preserving or increasing body temperature [5]. The usual blanket used in conjunction with the forced-air warmer is of similar shape and dimensions to a single duvet cover. Fenestrated blankets in a variety of shapes and dimensions are available but are more expensive than the rectangular design and unless a series of different designs are kept in stock, they are less universally applicable; generally, only the rectangular blankets are regularly available. For the patient who is to undergo a laparotomy, thoracotomy or spinal surgery, it is only possible to cover a limited part of the patient's body with the rectangular forced-air blanket, in order that the surgical field is not obscured. As a result, a significant part of the patient's surface area is not benefiting from the warming effect of the device. A simple solution to the problem is to position the blanket so as to completely cover the patient's body. A ‘window’ may then be cut to allow access to the surgical field (Figure 1). The ‘raw’ edges are sealed by sticking the blanket to the patient leaving an aperture for surgical access. If the seal is less than airtight, warmed air escapes under the blanket so that a warm ‘microcosm’ exists around the patient. By this means, the patient benefits maximally from the device which is in contact with the majority of the upper body surface. In conjunction with a fluid warmer it is generally possible to maintain normothermia despite prolonged surgery even in the elderly with exposed body cavities. Another advantage of the system is that blood from the surgical field generally runs over the surface of the blanket and hence to the floor rather than down onto the stretcher canvas, with the result that it is less likely that the patient is lying on wet (and hence cooling) undersheets.