In this episode, I’ll discuss the role for ketamine in status epilepticus.
The initial therapy for status epilepticus is to use one of the following benzodiazepines:
Lorazepam 0.1 mg/kg capped at 4 mg IV
Midazolam 0.2 mg/kg capped at 10 mg IM
Diazepam 0.15 mg/kg capped at 10 mg IV
But what happens if the patient does not respond to this initial therapy?
An anti-epileptic such as levetiracetam, fosphenytoin, or valproate should be given. If this does not terminate the seizures then therapy should progress to general-anesthetic levels of midazolam, propofol, or pentobarbital.
With any of these options, respiratory failure is a real possibility and the patient will likely need to be intubated for protection of their airway.
If using midazolam, I give 0.2 mg/kg IV bolus followed by an infusion of 0.1 mg/kg/hr. Beware of tachyphylaxis.
If using propofol, I give a 1 or 2 mg/kg IV bolus followed by an infusion titrated as high as necessary to stop the seizures. Beware of hypotension, propofol infusion syndrome & don’t use very high doses any longer than absolutely necessary.
If using pentobarbital (which is rare), I give 5mg/kg IV over 10 minutes, followed by 1mg/kg/hr. Beware of severe hypotension.
Unfortunately running through this sequence of medications from initial benzo, to antiepileptic, to general anesthesia can take a long time. The longer a seizure goes on, the less likely it is that GABA agonists will be effective.
However NMDA antagonists such as ketamine may maintain the chance of efficacy despite seizure duration. A retrospective study described the role of ketamine in the treatment of refractory status epilepticus.
Common features of successful use of ketamine included use of a loading dose (median: 1.5mg/kg; maximum: 5mg/kg) followed by a continuous infusion (median: 2.75 mg/kg/h; maximum: 10 mg/kg/h).
Ketamine was always part of a multi-drug regimen that ranged from two to 12 concurrent medications
The mortality rate was 43% (26/60), but was lower when SE was controlled within 24h of ketamine initiation (16% vs. 56%, p=0.0047).
No likely responses were observed when infusion rates were lower than 0.9mg/kg/h.
Based on this data, in the rare event I am using ketamine for refractory status epilepticus, I use a 2 or 3 mg/kg IV bolus followed by an infusion of at least 1 mg/kg/hr.
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