Eveline G. J. Zandbergen

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 not led to precise, generally accepted, prognostic rules. We did a systematic review of the relevant literature to assess whether such rules could be derived from the combined results of these studies. METHODS From Medline and Embase databases we selected studies concerning patients older than 10 years with anoxic-ischaemic coma in which findings from early neurological examination, electroencephalogram (EEG), or somatosensory evoked potentials (SSEP) were related to poor outcome--defined as death or survival in a vegetative state. We selected variables with a specificity of 100% for poor outcome in all studies, and expressed the overall prognostic accuracy of these variables as pooled positive-likelihood ratios and as 95% CIs of the pooled false-positive test rates. FINDINGS In 33 studies, 14 prognostic variables were studied, three of which 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 false-positive test rate 0-11.9%); absent motor response to pain on day 3 (16.8 [3.4-84.1]; 0-6.7%); and bilateral absence of early cortical SSEP within the 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 relevant studies (pooled positive-likelihood ratio 9.0 [2.5-33.1]; 95%CI pooled false-positive test rate 0.2-5.9%). These characteristics were present in 19%, 31%, 33%, and 33% of pooled patient populations, respectively. For the 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 ratio and its pooled false-positive test rate. Because evoked potentials are also the least susceptible to metabolic changes and drugs, recording of SSEP is the most useful method to predict poor outcome.

Prediction of poor outcome within the first 3 days of postanoxic coma

Objective: To determine the optimal timing of somatosensory evoked potential (SSEP) recordings and the additional value of clinical and biochemical variables for the prediction of poor outcome in patients who remain comatose after cardiopulmonary resuscitation (CPR). Methods: A prospective cohort study was conducted in 32 intensive care units including adult patients still unconscious 24 hours after CPR. Clinical, neurophysiologic, and biochemical variables were recorded 24, 48, and 72 hours after CPR and related to death or persisting unconsciousness after 1 month. Results: Of 407 included patients, 356 (87%) had a poor outcome. In 301 of 305 patients unconscious at 72 hours, at least one SSEP was recorded, and in 136 (45%), at least one recording showed bilateral absence of N20. All these patients had a poor outcome (95% CI of false positive rate 0 to 3%), irrespective of the timing of SSEP. In the same 305 patients, neuron-specific enolase (NSE) was determined at least once in 231, and all 138 (60%) with a value >33 μg/L at any time had a poor outcome (95% CI of false positive rate 0 to 3%). The test results of SSEP and NSE overlapped only partially. The performance of all clinical tests was inferior to SSEP and NSE testing, with lower prevalences of abnormal test results and wider 95% CI of false positive rates. Conclusion: Poor outcome in postanoxic coma can be reliably predicted with somatosensory evoked potentials and neuron-specific enolase as early as 24 hours after cardiopulmonary resuscitation in a substantial number of patients.

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. Conclusion: 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.

Acute posthypoxic myoclonus after cardiopulmonary resuscitation

BackgroundAcute posthypoxic myoclonus (PHM) can occur in patients admitted after cardiopulmonary resuscitation (CPR) and is considered to have a poor prognosis. The origin can be cortical and/or subcortical and this might be an important determinant for treatment options and prognosis. The aim of the study was to investigate whether acute PHM originates from cortical or subcortical structures, using somatosensory evoked potential (SEP) and electroencephalogram (EEG).MethodsPatients with acute PHM (focal myoclonus or status myoclonus) within 72 hours after CPR were retrospectively selected from a multicenter cohort study. All patients were treated with hypothermia. Criteria for cortical origin of the myoclonus were: giant SEP potentials; or epileptic activity, status epilepticus, or generalized periodic discharges on the EEG (no back-averaging was used). Good outcome was defined as good recovery or moderate disability after 6 months.ResultsAcute PHM was reported in 79/391 patients (20%). SEPs were available in 51/79 patients and in 27 of them (53%) N20 potentials were present. Giant potentials were seen in 3 patients. EEGs were available in 36/79 patients with 23/36 (64%) patients fulfilling criteria for a cortical origin. Nine patients (12%) had a good outcome. A broad variety of drugs was used for treatment.ConclusionsThe results of this study show that acute PHM originates from subcortical, as well as cortical structures. Outcome of patients admitted after CPR who develop acute PHM in this cohort was better than previously reported in literature. The broad variety of drugs used for treatment shows the existing uncertainty about optimal treatment.

Interobserver variation in the interpretation of SSEPs in anoxic–ischaemic coma

OBJECTIVE To study interobserver variation in the interpretation of median nerve SSEPs in patients with anoxic-ischaemic coma. METHODS SSEPs of 56 consecutive patients with anoxic-ischaemic coma were interpreted independently by 5 experienced clinical neurophysiologists using guidelines derived from a pilot study. Interobserver agreement was expressed as kappa coefficients. RESULTS Kappa ranged from 0.20 to 0.65 (mean 0.52, SD 0.14). Disagreement was related with noise level and failure to adhere strictly to the guidelines in 15 cases. The presence or absence of N13 and cortical peaks caused disagreement in 5 cases each. For recordings with a noise level of 0.25 microV or more, mean kappa was 0.34; for recordings with a noise level below 0.25 microV mean kappa was 0.74. CONCLUSIONS Interobserver agreement for SSEPs in anoxic-ischaemic coma was only moderate. Since the noise level strongly influenced interobserver variation, utmost attention should be given to its reduction. If an artefact level over 0.25 microV remains, absence of N20 cannot be judged with sufficient certainty and the SSEP should be repeated at a later stage. SIGNIFICANCE Because of its moderate interobserver agreement, great care has to be given to accurate recording and interpretation of SSEPs before using the recordings for non-treatment decisions.

Prediction of poor outcome in anoxic-ischemic coma.

Summary Most patients who are comatose a few hours after a period of global cerebral ischemia have a poor prognosis. In a series of studies selected with strict criteria for study design, the median prevalence of death or survival in a vegetative state was 78% (range, 56–90%) (Zandbergen et al., 1998). Most nonsurvivors die within the first weeks, not from brain damage, but from cardiac or pulmonary complications. Uncertainty about treatment and nontreatment decisions is therefore most critical during this period. To reduce this uncertainty among caregivers, and the related anxiety among family members, early identification of patients with such a poor prognosis is desirable.

P30.37 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. CONCLUSION 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.