This topic almost certainly lies outside the purview of the FRCA exams, though is included here for personal reference after being asked by a junior colleague how to manage such seizures in a post-resuscitation patient during the middle of the night.
There is often substantial overlap, with both clinical and EEG seizures present
Clinical seizures, however, may only become apparent during sedation holds owing to the seizure-suppressive effects of propofol/benzodiazepines
Although EEG is beneficial, continuous EEG monitoring probably adds little except cost and tangled wires
Myoclonic seizures
The most common seizure type in post-arrest patients (approx. 2/3rds)
May be focal, multi-focal or generalised
Origin is predominantly cortical, but may arise subcortically
Develops in the first 48hrs post-arrest
May be transient i.e. cease by 1 week post-arrest
Often associated with a poor prognosis
Post-hypoxic myoclonic status epilepticus is associated with a >95% mortality or PVS rate (<2% survive with good neurological outcome)
Conversely, single seizure events or sporadic focal myoclonus do not predict poor outcome
Lance-Adams syndrome
A type of myoclonic seizure in the post-resuscitation patient who regains consciousness
More common after hypoxic cardiac arrest
Develops days or weeks post-arrest
Predominantly affects the limbs
Myoclonus is induced by purposeful motor movement or sensory stimulation
May be chronic and disabling
Cannot be distinguished from 'standard' myoclonus on EEG
Other
Focal seizures
Generalised tonic-clonic seizures
Prophylaxis
Both Resus Council (2021) and ERC/ESICM (2021) guidelines do not advise seizure prophylaxis, acknowledging that the evidence base is very low certainty
Treatment of seizures
Conversely, both the aforementioned guidelines suggest treating seizures if they arise, again acknowledging that the evidence base is very low certainty
The increased CMRO2 caused by seizure activity may exacerbate cerebral injury and therefore treatment is reasonable
Treatment of post-hypoxic myoclonic status epilepticus is difficult
Does treating seizures affect outcome?
The recent TELSTAR trial (NEJM, 2022)
randomised post-resuscitation patients to a protocolised 48hr anti-seizure regimen vs. standard care alone
There was no difference in 90-day neurological outcome or 90-day mortality between the arms
Those in the intervention arm had slightly longer durations of mechanical ventilation and ICU stay
A case series demonstrated up to 44% of patients with post-anoxic status epilepticus had a good outcome following treatment with multiple anti-epileptic drugs; of note those treated had delayed awakening too
Choice of drug(s)
There is limited evidence that conventional anti-epileptic drugs suppress EEG epileptiform activity in the post-resuscitation patient, despite suppressing myoclonus of other origin
If conventional anti-epileptics are to be used, choices include:
(Fos)phenytoin
Phenytoin can cause hypotension via negative inotropic and vasodilating effects, especially if rapidly administered, so is less suitable
Fosphenytoin equally caused more hypotension compared to other agents when used to treat status epilepticus
Levetiracetam
Valproate
Each is equally effective in terminating 'traditional' convulsive status epilepticus (NEJM, 2019)
Be mindful that treatment can delay awakening, prolong duration of mechanical ventilation and ICU stay
Another option is use of general anaesthetic agents, which the patient is probably already receiving via infusion, e.g. propofol, a benzodiazepine or thiopentone
One perhaps has to be mindful that excessive drug administration may cloud brainstem death testing from 72hrs
Treatment regimen
The TELSTAR protocol was three tiered:
Tier
Sedative Agent
Anti-epileptic Agent
1
Midazolam or lorazepam infusion
Phenytoin 15 - 20mg/kg loading then 150mg BD
2
Propofol up to 8mg/kg/hr
Keppra (1.5g loading then 1g BD) or valproate
3
Thiopentone
As one's patient on a UK ICU is likely to already be receiving a propofol infusion, it seems sensible to:
Up-titrate the propofol infusion, until either clinician discomfort or haemodynamics preclude further increases (say 30 - 35ml/hr of 1% propofol)
Add in further agent(s) if seizures persist and are causing harm e.g. difficulty ventilating appropriately, lines being displaced etc.
E.g. addition of a midazolam infusion ± keppra loading
Strongly consider whether further pharmacotherapy will add patient benefit if seizures continue despite the above