Postoperative ventilatory and circulatory effects of heating after aortocoronary bypass surgery. Postoperative external heat supply.

The effects of postoperative external heat supply on shivering, oxygen uptake, carbon dioxide production, ventilatory requirements and haemodynamic variables were studied postoperatively after aortocoronary bypass surgery in 24 men with stable angina pectoris. After hypothermic cardiopulmonary bypass (CPB) at 25 degrees C, the patients were rewarmed to a nasopharyngeal temperature of at least 38 degrees C, resulting in a rectal temperature of about 34 degrees C before termination of CPB. Twelve patients, forming the control group, were given no other external heat supply. In another group (n = 12), the "radiant heat supply group", additional external heat was provided postoperatively, the main source of which was a thermal ceiling supplemented with heated, humidified respiratory gases. In this latter group the postoperative rewarming was accomplished earlier and was converted into a mainly passive process. Shivering, oxygen uptake, CO2 production and ventilation volumes were significantly reduced compared with the control group. Cardiac index and stroke index were higher and systemic oxygen extraction was lower in the radiant heat supply group. Postoperative hypertension and vasoconstriction were greatly decreased, suggesting that residual hypothermia is an important cause of the postoperative vasoconstriction.