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Information should be taken from multiple different tests, all based on clinical context, for the estimation of neurologic prognosis after cardiac arrest. Decisions should not be made on one test alone.
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Poor neurologic outcomes are expected in comatose patients after cardiac arrest if there are absent pupillary light responses or corneal reflexes, extensor or absent motor response, or myoclonus status epilepticus.
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Sedative and analgesic medications can eliminate the corneal reflexes and motor
Anoxic-Ischemic Brain Injury
Section snippets
Key points
Pathophysiology
In contrast to most acute brain pathologies, anoxia induces a global brain injury. The extent of neuronal and glial damage is largely related to the duration of interrupted CBF. Brain cells become ischemic as CBF drops below levels needed to sustain brain metabolism. During a cardiac arrest, the decrease in CBF is uniform throughout the brain, but the damage to individual cells is not, because neuronal vulnerability is variable among different areas of the brain.4 The regions most susceptible
Clinical management
The most immediate threat following resuscitation from cardiac arrest is cardiovascular collapse. Interventions to optimize blood pressure and maintain systemic perfusion (eg, boluses of intravenous fluid, vasopressors, and inotropes) are often required. In parallel with resuscitation efforts, the cause of cardiac arrest should be determined. A brief baseline neurologic examination should be performed. Asymmetric motor responses are not expected following cardiac arrest and should prompt urgent
Prognosis
Estimating neurologic prognosis in comatose patients after cardiac arrest is a challenge. Decisions to withdraw life-sustaining therapies in these situations often rely heavily on the neurologic prognosis. Thus it is crucial that if a poor prognosis is stated, that it is without uncertainty and that tests that predict a prognosis have false-positive rates that are close to zero. The importance of estimating prognosis with a multifaceted approach, integrating information from several different
Neurologic examination
The neurologic examination is fundamental to the assessment; all additional tests are ancillary and must be interpreted in the clinical context. One of the most important parts of the clinical assessment is determining whether the patient's examination is reliable, or whether it is confounded by the administration of medications. Even medications that are no longer being given, but were administered within the previous few days could still be confounding the examination. Any estimation of
Electrophysiology
SSEPs and EEG are commonly used ancillary tests in the estimation of neurologic prognosis after cardiac arrest. SSEPs consist of stimulation of both median nerves near the wrist with monitoring and averaging of electrical responses at different points throughout the neuraxis. The cortical response (N20) has been well studied in prognosticating outcomes after cardiac arrest. Within Days 1 to 3 after cardiac arrest, the outcome is invariably poor if the N20 response is absent bilaterally (Fig. 1).
Biomarkers
There has been great interest in studying serum biomarkers as a measure of the severity of anoxic-ischemic brain injury. The most studied biomarkers are serum NSE and S100. NSE is a gamma isomer of enolase that is located in neurons, whereas S100 is a calcium-binding protein found in astrocytes. The usefulness of these biomarkers in prognostication may be limited because of heterogeneity between centers in the collection and processing of fluids, the detection of markers, and because of long
Neuroimaging
The use of neuroimaging continues to grow as an adjunct to estimating neurologic prognosis in comatose survivors of cardiac arrest, despite a lack of high-quality evidence. Most studies are retrospective and assess imaging as a single factor in prognosis. Furthermore, in some studies, clinicians may have used results of imaging to make decisions on prognosis that could have resulted in a self-fulfilling prophecy. Yet it is not uncommon that a patient after cardiac arrest remains comatose but
Summary
The estimation of prognosis in comatose survivors of CPR is important in clinical practice. It allows discussion about the level of care, whether the patient would have wanted another resuscitative effort, or whether medical care should be escalated. In many cases, the family decides to withdraw support. However, with all of these prognosticating studies, there continues to be a concern about prognostication error. Prognostication is difficult in patients who have received sedative drugs,
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Disclosure Statement: Dr J.E. Fugate has nothing to disclose.