RAPID ACTIVE INTERNAL CORE COOLING FOR INDUCTION OF MODERATE HYPOTHERMIA IN HEAD-INJURY BY USE OF AN EXTRACORPOREAL HEAT-EXCHANGER

OBJECTIVE: Moderate hypothermia (32 degrees C) may limit postischemic neuronal damage and is increasingly used clinically in head injury and stroke. For the use of hypothermia as a neuroprotective agent in the prevention of ischemic damage, it is necessary to induce it as soon as possible after the insult and to keep it at the lowest safe level. Ac tive core cooling using an extracorporeal heat exchanger may circumven t the rather slow induction speed and temperature drifts experienced w ith surface cooling techniques. METHODS: In eight patients with severe head injuries (Glasgow Coma Scale score, 4-5), a venovenous extracorp oreal circulation was established via a percutaneously introduced doub le-lumen cannula in the femoral vein. A heat exchanger was connected v ia a pressure-controlled roller pump. In addition to standard paramete rs, brain white matter temperature was continuously recorded as the ta rget temperature. Cooling was initiated as early as possible with an e xtracorporeal temperature of 30 degrees C and maintained at a 32 degre es C brain temperature for 48 hours, and then gradual rewarming for 24 hours. RESULTS: Cooling was able to be initiated within 6 hours and 4 8 minutes +/- 3 hours and 47 minutes (mean +/- standard deviation) aft er trauma. A brain temperature of 32 degrees C was reached within 1 ho ur and 53 minutes +/- 1 hour and 21 minutes after induction of cooling with a cooling speed of 3.5 degrees C per hour. Brain temperature was able to be controlled within 0.1 degrees C intervals, which was espec ially helpful in gradual rewarming. No cardiac abnormalities or statis tically significant changes in coagulation parameters occurred. Mean p latelet count decreased to 89,614 +/- 42,090 on Day 3 after treatment. No clinical bleeding complications or problems resulting from extraco rporeal circulation occurred. Moderate hypothermia was a helpful tool for managing increased intracranial pressure; however, five patients o f this series died either of their intracranial abnormalities (n = 4) or of a delayed septic shock after pneumonia (n = 1) at various points in time during therapy. The three survivors experienced either an exc ellent or a good recovery. CONCLUSION: The results of this investigati on suggest that the use of an extracorporeal heat exchanger to achieve active core cooling is suitable for fast and accurately controllable induction, maintenance, and reversal of moderate hypothermia in emerge ncy situations;with reliable control of temperature. In this small ser ies of highly selected patients with severe head injuries, we did not note a beneficial effect of hypothermic therapy on outcome.