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Electroencephalographic monitoring during hypothermia after pediatric cardiac arrest

From the Division of Neurology (N.S.A., R.I., M.D., D.J.D., R.R.C.) and Division of Anesthesia and Critical Care Medicine (A.T., M.H., V.N.), The Children's Hospital of Philadelphia, PA; Department of Neurology (N.S.A., R.I., D.J.D., R.R.C.), The University of Pennsylvania School of Medicine, Philadelphia; and Department of Neurology (S.T.H.), Beth Israel Deaconess Medical Center, Boston, MA.

Address correspondence and reprint requests to Dr. Nicholas S. Abend, Division of Neurology, The Children's Hospital of Philadelphia, 34th Street and Civic Center Boulevard, Philadelphia, PA 19104 abend{at}email.chop.edu

Background: Hypoxic ischemic brain injury secondary to pediatric cardiac arrest (CA) may result in acute symptomatic seizures. A high proportion of seizures may be nonconvulsive, so accurate diagnosis requires continuous EEG monitoring. We aimed to determine the safety and feasibility of long-term EEG monitoring, to describe electroencephalographic background and seizure characteristics, and to identify background features predictive of seizures in children undergoing therapeutic hypothermia (TH) after CA.

Methods: Nineteen children underwent TH after CA. Continuous EEG monitoring was performed during hypothermia (24 hours), rewarming (12–24 hours), and then an additional 24 hours of normothermia. The tolerability of these prolonged studies and the EEG background classification and seizure characteristics were described in a standardized manner.

Results: No complications of EEG monitoring were reported or observed. Electrographic seizures occurred in 47% (9/19), and 32% (6/19) developed status epilepticus. Seizures were nonconvulsive in 67% (6/9) and electrographically generalized in 78% (7/9). Seizures commenced during the late hypothermic or rewarming periods (8/9). Factors predictive of electrographic seizures were burst suppression or excessively discontinuous EEG background patterns, interictal epileptiform discharges, or an absence of the expected pharmacologically induced beta activity. Background features evolved over time. Patients with slowing and attenuation tended to improve, whereas those with burst suppression tended to worsen.

Conclusions: EEG monitoring in children undergoing therapeutic hypothermia after cardiac arrest is safe and feasible. Electrographic seizures and status epilepticus are common in this setting but are often not detectable by clinical observation alone. The EEG background often evolves over time, with milder abnormalities improving and more severe abnormalities worsening.

BS = burst suppression; CA = cardiac arrest; CPR = cardiopulmonary resuscitation; DD = developmental delay; FEN = fentanyl; FOS = fosphenytoin; HIE = hypoxic ischemic encephalopathy; LEV = levetiracetam; LZP = lorazepam; MDZ = midazolam; NCS = nonconvulsive seizures; NCSE = nonconvulsive status epilepticus; NPV = negative predictive value; PB = phenobarbital; PED = periodic epileptiform discharge; PICU = pediatric intensive care unit; PPV = positive predictive value; SE = status epilepticus; SIDS = sudden infant death syndrome; sz = seizures; TH = therapeutic hypothermia; VEC = vecuronium; VPA = valproic acid; VT = ventricular tachycardia.

Received December 10, 2008. Accepted in final form February 27, 2009.

Supported by grants from the Penn Alliance for Therapeutic Hypothermia (University of Pennsylvania Neuroscience Center), the National EpiFellows Foundation (N.S.A.), the University of Pennsylvania Clinical Trials Research Center Grant (UL1-RR-024134; A.T. and V.N.), and the Pediatric Pharmacologic Research Unit (R.R.C.).

Disclosures: Author disclosures are provided at the end of the article.

Medications and Devices: Fosphenytoin (Cerebyx; Eisai Inc., Woodcliff Lake, NJ); ketamine (Ketalor; JHP Pharmaceuticals, Parsippany, NJ); levetiracetam (Keppra; UCB Pharma, Brussels, Belguim); lorazepam (Ativan; Border Healthcare Corp., Deerfield, IL); midazolam (Versed; Roche Laboratories, Basel, Switzerland); valproic acid (Depacon; Abbott Laboratories, Abbott Park, IL); video-EEG system (Grass-Telefactor, West Warwick, RI).

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