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.
Members of my Hospital Pharmacy Academy have access to in-depth practical trainings on the use of ketamine in critical care and the treatment of status epilepticus from a pharmacist’s point of view. This is in addition to over 140 other trainings, weekly literature digests, and resources to help precept residents and students. To join now to get immediate access, go to pharmacyjoe.com/academy.
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