Haemodynamic study of prolonged deep accidental hypothermia.

Right heart catheterisation was undertaken in six patients with accidental deep hypothermia. Studies were carried out before and after rapid blood volume expansion, with and without Isoproterenol infusion, and were repeated at normal body temperatures. The initial haemodynamic pattern indicated a marked hypovolemia with a simultaneous decrease of both cardiac output and ventricular filling pressures, and a decreased measured total blood volume. Rapid correction of the hypovolemia revealed cardiac insufficiency, in part due to the persisting bradycardia. Left ventricular function was depressed in patients with prolonged cold exposure and normal in patients with short exposure. These abnormalities disappeared after Isoproterenol infusion during hypothermia, and spontaneously after return to normothermia. No imbalance existed between the decreased cardiac output and oxygen uptake in hypothermia, arterio-venous oxygen difference being within normal limits.