Anoxic Damage to the Human Brain
abstracts & commentary
Sources: Zandbergen EGJ, et al. Systematic review of early prediction of poor outcome in anoxic-ischaemic coma. Lancet 1998;352:1808-1812; Krieger DW. Evoked potentials not just to confirm hopelessness in anoxic brain injury. Commentary. Lancet 1998;352:1796-1797.
Zandbergen and colleagues provide the results of a literature search concerning reliable indicators of death or a vegetative state in patients comatose following severe acute anoxia or anoxemia. To fulfill their goals, they selected 33 previous reports on the subject. Within these reports, they identified 14 individual clinical or neurophysiological tests used to determine factors that reliably predicted poor outcome by the end of the first week. As readers might expect, they found that by the third day after anoxic coma, absence of either the pupillary light reflex or any muscular response to noxious stimuli predicted that the patient’s one-month outcome would consist of either brain death or the vegetative state. Zandbergen et al also claim that during the latter part of the week, either the absence of N-20 somatosensory evoked potentials (SSEP) or the appearance of burst-suppression or iso-electric patterns in the EEG also provided an almost certain (100%) prediction of brain death. Depending on the absence of SSEPs earlier in the first week, however, appears to be unwise of rare reports of an early, transient loss of N-20 potentials in persons who nevertheless recovered consciousness.
Krieger, in his Lancet commentary of Zandbergen et al’s report, emphasizes the low sensitivity of SSPP in that its pattern may reappear in fairly normal form even though the patient remains severely neurologically injured. Krieger makes the sensible statement in his commentary that given the reliability of pupillary reflexes and lost motor responses makes "the futility of continuing with life support obvious without (any) measurement of the evoked potential." Neurology Alert agrees.
Commentary
This paper, to quote Yogi Berra, provides us with "deja vu all over again." Many studies published in the medical literature indicate that skilled neurologists or cardiologists can predict brain death or poor outcome in most anoxic patients within as few as six hours following cardiac arrest or severe anoxemia. Unless such patients are restless and moving bodily members (signs that death is not an immediate outcome), therapeutic paralysis or anesthesia rarely complicate the problem by obliterating neurological responses. Levy and associates described the ultimate outcomes of 210 patients who failed to recover consciousness within six hours following a bout of severe anoxia.1 Edgren and associates reported findings similar to Levy et al’s in 262 patients following cardiac arrest.2 Both studies noted that at the initial post-arrest evaluation, performed during the first few hours of post-anoxic coma, patients with absent pupillary and/or absent motor responses to pain had about an 80% risk of death or permanent unconsciousness. At three days, 100% of patients showing either of those findings faced only death or vegetative outcomes. It stands that in the setting of critical care medicine these sturdy clinical indicants provide imperative information that must be promptly shared with families and friends. Only rarely in your editor’s experience, except when seizures occur, has electrophysiologic testing been needed for either the patient’s management or the family’s understanding.
References
1. Levy DE, et al. Predicting outcome from hypoxic-ischemic coma. JAMA 1985;253:1420-1426.
2. Edgren E, et al. Assessment of neurological prognosis in comatose survivors of cardiac arrest. BRCT I Study Group. Lancet 1994;343:1055-1059.
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