SSEPs and prognosis in postanoxic coma: only short or also long latency responses?
BACKGROUND
Short latency somatosensory evoked potential (SSEP) (N20) is a good predictor of poor outcome in postanoxic coma. It has been suggested that the long latency response (N70) may increase the sensitivity of SSEPs for predicting poor outcome.


METHODS
As part of a prospective cohort study in 407 adult patients unconscious 24 hours after cardiopulmonary resuscitation (CPR), N20 was recorded 24, 48, and 72 hours after CPR, and N70 was recorded at least once in 319 patients. Poor outcome was defined as death or persistent vegetative state 1 month after CPR.


RESULTS
Absent N20 had a 0% false positive test rate at all time intervals, with prevalence of poor test result varying from 37 to 48%. Addition of abnormal N70 (absent or delayed > 130 msec) with present N20 as poor test result added 21 to 28% to this prevalence, but at the cost of a false positive test rate of 4 to 15%. Good outcome could not be predicted reliably with either of the tests, as only 28% of patients with normal N20 and N70 had a good outcome.


CONCLUSIONS
Determination of presence or absence of the N70 in patients with postanoxic coma gives additional information about the likelihood of poor outcome, but it is not precise enough to base treatment decisions solely on its absence.
Zandbergen
E G J
EG
Department of Neurology and Clinical Neurophysiology, D2-112 Academic Medical Centre, University of Amsterdam, P.O. Box 22660, 1100 DD, Amsterdam, The Netherlands.
Koelman
J H T M
JH
de Haan
R J
RJ
Hijdra
A
A
D015331:Cohort Studies; D003128:Coma / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy*; D015897:Comorbidity; D003422:Critical Care / Q000379:methods / Q000706:statistics & numerical data; D004569:Electroencephalography / Q000379:methods / Q000706:statistics & numerical data*; D005073:Evoked Potentials, Somatosensory; D006323:Heart Arrest / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy*; D006801:Humans; D007036:Hypothermia, Induced; D020925:Hypoxia-Ischemia, Brain / Q000175:diagnosis / Q000453:epidemiology / Q000628:therapy; D009426:Netherlands / Q000453:epidemiology; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011379:Prognosis; D011930:Reaction Time; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016896:Treatment Outcome