Cooling responses in shivering and non-shivering dogs during induced hypothermia.

1. Hypothermia to a temperature of 30 degrees C was induced in both shivering and non-shivering groups of dogs. 2. There was a sustained increase in oxygen consumption in the dogs allowed to shiver and this was up to 300% greater than the oxygen consumption in the relaxed dogs. 3. The increased tissue requirement for oxygen was met both by increased cardiac output and increased oxygen extraction from haemoglobin. 4. Oxygen utilization remained adequate in hypothermia, as shown by the absence of hypoxic acidosis. 5. Heart rate fell during cooling and stroke volume increased to meet the increased oxygen demands associated with shivering during the induction of hypothermia.