Status Epilepticus

By: Roger E. Kelley, M.D.

Page by: E.J. Mayeaux, Jr., M.D.

Louisiana State University Medical Center Shreveport, Louisiana

Definition: According to the International Classification of Seizures, it is ''a condition characterized by an epileptic seizure that is so frequent or so prolonged as to create a fixed and lasting condition". From a practical standpoint, continuous, generalized, tonic­clonic seizure activity lasting 30 minutes or longer, i.e., grand mal status epilepticus, is most worrisome and represents a life­threatening emergency.

Diagnostic evaluation:

• Immediately send off a CBC, a serum chemistry profile, and drug screen.
• Assess for possible drug intoxication or drug withdrawal as effectively as possible. Keep in mind that anticonvulsant drug withdrawal is a common cause of status epilepticus.
• Obtain an arterial blood gas if there is evidence of respiratory compromise.
• Obtain a brain scan (CT or MRI), with and without contrast as quickly as feasible to assess for a possible mass lesion.
• Evaluate for lumbar puncture, especially if there is clinical evidence of an infectious process and there is no contraindication by brain scan and bleeding studies.
• An EEG, on an emergency basis, may be indicated if there is an atypical presentation or a suboptimal response to medical intervention.
  

Management: It is important to establish that there is no respiratory compromise and no evidence of cardiovascular collapse. Preparation for possible intubation and respiratory support should be made. Correction for metabolic disturbance, if present, is clearly indicated. Low serum Na+, glucose, Ca++, or Mg++ can result in recurrent seizure activity. Drug or alcohol withdrawal, or certain drug intoxication, can be precipitating factors. It is important to recognize that withdrawal from phenobarbital generally requires resumption of phenobarbital with a loading dose which will necessitate intubation with respiratory support.

An intravenous line is mandatory. Initial, i.e., short­term, control of generalized seizure activity can often be obtained with either intravenous lorazepam, at a dose of 0.1 mg/kg, or diazepam at 0.2 mg/kg. Either agent is infused over two minutes. It is important to recognize that these agents can promote respiratory depression at relatively small doses in certain individuals. If either of these agents is used, it is with the understanding that longer term, i.e., maintenance, therapy must also be initiated unless there is a recognized metabolic derangement that can be rapidly corrected.

Fosphenytoin is now available as the replacement for parenteral phenytoin. Each fosphenytoin vial contains 75 mg/ml which is equivalent to 50 mg/ml of phenytoin ( 1.5 equivalents). Its primary advantages over phenytoin include: significantly reduced risk risk of cardiovascular depression, markedly improved local infusion tolerance, and the ability to give it intramuscularly. Its dosing is expressed as phenytoin equivalents (PE). The loading dose in status epilepticus is 15 to 20 mg PE/kg at a maximum intravenous infusion rate of 150 PE/min. (For example the order for a 67 kg man would be: "Fosphenytoin 1000mg PE to be infused IV over 10 minutes". In such a circumstance, intravenous administration is preferred to intramuscular because the intravenous route allows less time to achieve a therapeutic plasma concentration. Fosphenytoin is converted to phenytoin after parenteral administration. It is recommended that phenytoin blood levels not be measured until the conversion of fosphenytoin to phenytoin is complete. This occurs approximately two hours after completion of the intravenous infusion.

If the patient continues to have seizure activity despite adequate intravenous loading with fosphenytoin, then phenobarbital loading is indicated. Phenobarbital is given at an intravenous dose of approximately 20 mg/kg at an infusion rate of no more than 1.5 mg/kg/min. This translates into approximately 100 mg/min in adults. If this is unsuccessful, then intravenous pentothal is given at a loading dose of 3 to 4 mg/kg over two minutes followed by a continuous infusion at a rate of 0.2 mg/kg/min. The dose is then adjusted upward, every 3 to 5 minutes by 0.1 mg/kg/min, until the EEG becomes isoelectric.

Roger E. Kelley, M.D. - LSUHSC Department of Neurology

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