CHANGES IN BRAIN-STEM AUDITORY-EVOKED RESPONSE LATENCY PREDICT SURVIVAL AFTER CPR IN A RAT MODEL OF CARDIAC-ARREST AND RESUSCITATION

Brainstem auditory evoked responses (BAER) are routinely used to monit or brainstem function in hospitalized comatose patients. We used a rat model of cardiac arrest and resuscitation to explore the possibility that the BAER, monitored during and immediately after cardiopulmonary resuscitation (CPR), could be used to determine whether the CPR was ef fective in restoring brainstem blood flow. Long-Evans rats were subjec ted to 7 min of cardiac arrest, induced by chest compression under Ket amine anesthesia sufficient to mechanically prevent the heart from pum ping blood and were then resuscitated using a standard CPR protocol. D uring CPR, click stimuli were applied to one ear at 11/s and BAER aver ages recorded every 15 s. In three rats the BAER did not return after CPR; none of these rats respired spontaneously and all died. In 33 rat s the BAER did return; within 15 min after the start of CPR BAER peak latencies decreased rapidly, increased again and then decreased. If th e increase in the latency of the N2 peak was less than 0.3 ms, then th e rat survived. If it was greater than 0.35 ms the rat died. This sign al was used as a cue for intervention in three rats; two survived. Thu s, in this preparation, the BAER provided a useful measure of CPR effe ctiveness, in time to permit successful intervention. (C) 1998 Elsevie r Science Ireland Ltd.