Changes in somatosensory evoked potentials in dogs following cardiac arrest and resuscitation

The effect of cardiac arrest induced global cerebral ischemia on the peripheral, spinal cord, and cortical somatosensory evoked potentials (SSEP) was studied in 7 mongrel dogs. Following the recording of control responses in each animal, ventricular fibrillation was induced and the dogs were allowed to fibrillate for a random time varying between 30 s and 15 min. The animals were then resuscitated using a standardized resuscitation protocol, and evoked potentials were recorded at intervals up to 1 h post resuscitation. A grading scale was devised to categorize the evoked potentials according to degree of abnormality. We found that peripheral SSEPs were well preserved up to 22 min ischemia time. Spinal cord potentials became abnormal with ischemia times greater than 9.5 min. Cortical traces were essentially normal with less than 4 min ischemia time, variable with 4-9.5 min and markedly abnormal with greater than 9.5 min ischemia. Somatosensory evoked potentials may be a useful adjunct in the monitoring of cerebral function following cardiac arrest.