Systematic review of early prediction of poor outcome in anoxic-ischaemic coma

Background Studies to assess the prognostic value of early neurological and neurophysiological findings in patients with anoxic-ischaemic coma have no t led to precise, generally accepted, prognostic rules. We did a systematic review of the relevant literature to assess whether such rules could be de rived from the combined results of these studies. Methods From Medline and Embase databases we selected studies concerning pa tients older than 10 years with anoxic-ischaemic coma in which findings fro m early neurological examination, electroencephalogram (EEG), or somatosens ory evoked potentials (SSEP) were related to poor outcome-defined as death dr survival in a vegetative state. We selected variables with a specificity of 100% for poor outcome in ail studies, and expressed the overall prognos tic accuracy of these variables as pooled positive-likelihood ratios and as 95% Cls of the pooled false-positive test rates. Findings In 33 studies, 14 prognostic variables were studied, three of whic h had a specificity of 100%: absence of pupillary light reflexes on day 3 ( pooled positive-likelihood ratio 10.5 [95% CI 2.1-52.4]; 95% CI pooled fals e-positive test rate 0-11.9%): absent motor response to pain on day 3 (16.8 [3.4-8.41]; 0-6.7%); and bilateral absence of early cortical SSEP within t he first week (12.0 [5.3-27.6]; 0-2.0%). EEG recordings with an isoelectric or burst-suppression pattern had a specificity of 100% in five of six rele vant studies (pooled positive-likelihood ratio 9.0 [2.5-33.1]; 95% CI poole d false-positive test rate 0.2-5.9%). These characteristics were present in 19%, 31%, 33%, and 33% of pooled patient populations, respectively. For th e 11 SSEP studies, results did not significantly differ between studies in which the treating physicians were or were not masked from the test result, prospective and retrospective studies, studies with short and long follow- up periods, and studies with high or low overall poor outcome. Interpretation SSEP has the smallest CI of its pooled positive-likelihood r atio and its pooled false-positive test rate. Because evoked potentials are also the least susceptible to metabolic changes and drugs, recording of SS EP is the most useful method to predict poor outcome.