Recognition of a generalized seizure is straightforward in previously alert patients not receiving neuromuscular junction blocking agents; however, such patients are less common in intensive care practice than in other areas. Partial (focal) seizures that do not secondarily generalize are also difficult to detect in these patients. The intensive care unit (ICU) staff must maintain a high index of suspicion for the development of seizures in such patients, and maintain a correspondingly low threshold for neurological consultation and electroencephalographic studies. Table 1 presents some guidelines for the recognition of seizures in the ICU. One should strive to make a definitive diagnosis of the etiology of altered alertness, even if that diagnosis is metabolic encephalopathy, to avoid missing the possibility of such remediable disorders as seizures or status epilepticus.
Table 1 Recognizing seizures in critically ill patients
When one suspects a seizure, an EEG should be obtained without delay. This is of particular importance when a patient does not return to baseline mental status, which suggests progression to non-convulsive status epilepticus. Most patients will need a brain imaging study in this setting, since a majority of critical care patients with new onset seizures have intracranial structural lesions. Although magnetic resonance imaging (MRI) is the method of choice in patients with new onset seizures, critically ill patients may not be able to undergo this procedure if they depend on infusion pumps for vasoactive drugs. MRI can be performed on mechanically ventilated patients using non-ferromagnetic ventilators. CT scanning remains a useful alternative; a scan is obtained before and after contrast enhancement, unless the patient has a serious contraindication to contrast material, because many causes of seizures in these patients are not apparent without enhancement. The need for other studies, such as lumbar puncture for cerebrospinal fluid analysis, depends on the likely diagnostic possibilities. If bacterial meningitis is suspected at any stage, appropriate antibiotic therapy should be instituted without waiting to obtain a lumbar puncture.
Classifying the seizure according to the International Classification of Epileptic Seizures aids in the etiological diagnosis and often has therapeutic implications ( Table 2).
table 2 Classification of epileptic seizures
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