Somatosensory potentials, CSF creatine kinase BB activity, and awakening after cardiac arrest

Objective: To examine the utility of somatosensory evoked potential (SEP) p eaks and CSF creatine kinase BE isoenzyme activity (CKBB) in predicting non awakening from coma due to cardiac arrest. Background: Accurate predictors of neurologic outcome in patients comatose after cardiac arrest are needed to improve medical decision making. Methods: A total of 72 comatose patient s had bilateral median SEPs, and of these, 52 had CSF and CKBB. Awakening w as defined as following commands or having comprehensible speech. Both shor t (N1) and long (N3) latency SEP peaks were analyzed. Nonparametric analyse s were used. Results: For patients who had both tests, CKBB greater than or equal to 205 U/L predicted nonawakening with a sensitivity of 49% and a sp ecificity of 100%. Bilateral absence of the N1 peak predicted nonawakening with a sensitivity of 53% and a specificity of 100%. Using CKBB greater tha n or equal to 205 Un, bilaterally absent SEP N1 peaks, or both predicted no nawakening with a sensitivity of 69% and a specificity of 100%. Using CKBB greater than or equal to 205 U/L, bilaterally absent N1 peaks, bilateral N3 greater than or equal to 176 msec or absent, or some combination predicted nonawakening with a sensitivity of 78% and a specificity of 100%. Conclusi on: The combination of an absent N1 peak and elevated CKBB performs better than either alone in predicting nonawakening after cardiac arrest. Prolonge d or absent N3 latency may increase sensitivity. These results should be in terpreted with caution given the small number of patients and the possibili ty of a self-fulfilling prophecy.