Haemodynamic and metabolic effects of surface rewarming after coronary revascularization

Cardiac surgery is often associated with a postoperative increase in the patient's metabolic rate; surface rewarming has been suggested to decrease the energy expenditure by preventing hypothermia. Thirty patients, undergoing coronary revascularization, were randomly divided into two groups; after surgery group A was rewarmed by a new device that acts by both conduction and convection, while group B was just covered with cotton blankets. Blood, oesophagus and skin (thigh and foot) temperatures were recorded on admission to the intensive care unit (ICU) and 30, 60, 90, 180, 270, and 450 min later. Haemodynamic parameters, oxygen delivery, calculated oxygen consumption, and plasma lactate concentration were assessed as well. Group A warmed up quicker than group B as far as the skin was concerned while the core temperature was unaffected. Group A was also characterized by lower cardiac indices and oxygen consumption. As the occurrence of a dependence of oxygen consumption on delivery could be reasonably ruled out in warmed patients because blood lactate levels were lower than in the controls, we conclude that surface rewarming might have some positive effect in decreasing metabolic demand after cardiac surgery even if the patient's core temperature is little affected. The inhibition of skin temperature receptors could possibly explain this finding.