Limiting heat loss during surgery in small animals

Abstract

OPERATING room (or ambient) temperatures (T°amb) seldom exceed the core body temperature (T°core) of domestic species, so during anaesthesia, when thermoregulatory mechanisms are impaired, dogs (Redondo and others 2012b) and cats (Redondo and others 2012a) lose heat down thermal gradients at rates proportional to the environment-animal temperature difference. Hypothermia produces effects aggravating other problems arising from anaesthesia including: alveolar hypoventilation, reduced cardiac output, renal and splanchnic blood flow, glomerular filtration rate and liver metabolism with delayed drug detoxification, increased blood viscosity, a 'left-shifted' oxyhaemoglobindissociation curve, dysrhythmias, metabolic acidosis, prolonged coagulation time, and hyperglycaemia (Stine 1977). Paradoxically, these derangements may be exacerbated by thermoregulatory reflexes responding to subnormal T°core values during recovery from anaesthesia. For example, the effects of reduced oxygen delivery arising from blood hyperviscosity and left-shifted oxyhaemoglobin may worsen because shivering increases whole body oxygen consumption (Hemingway 1963).