Presentation and Pathophysiology of seizures in the critical care environment: An overview

Seizures represent stereotypic electroencephalographic (EEG) and behavioral paroxysms as a consequence of electrical neurological derangement. Although seizures are often associated with stereotypic convulsive phenomena, in the ICU they are as likely to be subclinical as they are to express muscle contractions or behavioral symptoms. Hence, vigilance is required in the critical care setting. Due to the admission diagnoses and physiological derangements common to critically ill patients, the intensive care unit (ICU) hosts conditions appropriate for the manifestation of the entire spectrum of seizure disorders. Common etiologies of seizures in the ICU are due to primary neurological pathology or secondary to critical illness and clinical management. Alterations in neurotransmitter sensitivity via up- or down regulation of receptors, a decrease in inhibition, alterations in membrane pump functions, all may contribute to the high incidence of seizures in an ICU. Particularly prevalent as precipitants of seizures are hypoxia/ischemia, mass lesions, drug toxicity, and metabolic abnormalities. For optimal treatment, early diagnosis of the seizure type and its cause is important to ensure appropriate therapy. Most seizures and their recurrence are easily treated, and attention is focused on ascertaining the cause and correcting any medical abnormality. Convulsive status epilepticus represents the most feared seizure state, and requires emergent treatment before irreversible brain injury and severe metabolic disturbances occur. Treatment of seizures with anticonvulsants in an ICU is not without risks, and appropriate judgment and selection of therapeutic drugs are important.