Clinical markers predict outcome of hypoxic coma

Using sensory evoked potentials (SEPs) to investigate patients in hypoxic coma adds very modestly to conventional clinical markers in predicting poor outcomes, a meta-analysis by Melbourne neurologists has concluded. Associate Professor Thanh Phan from Monash Medical Centre and colleagues identified 25 eligible studies on the topic. The absence of SEPs – an EEG marker of severe cortical damage – was statistically superior to the M1, M2, M3 system of grading motor signs using criteria from the Glasgow Coma Scale. In addition, SEP was only marginally better than the pupillary response. The superiority of SEP over conventional measures was slight and not necessarily clinically significant, and occurred only in the first day of coma, the doctors said. Facilities for performing an SEP were not available in many rural areas of Australia, and were rare in underdeveloped countries. “In those contexts, a careful clinical examination provides a reasonable compromise,” the analysis concluded. It reviewed studies that had investigated adults with hypoxia secondary to cardiac arrest, respiratory failure, drowning, or hypotensive shock (excluding sepsis and trauma). ‘Poor outcomes’ were defined as severe neurological deficit, a persistent vegetative state or death. Only about 30% of patients with hypoxic coma ever regained awareness, the researchers noted in Neurology. Previous research had produced conflicting results on the prognostic value of clinical and electrophysiological markers. Neurology 2010; 74: 572-580....