Seizures

Overview

Seizures are caused by excessive, synchronous cerebrocortical neuronal discharge and when lasting more than 5 minutes can be considered as 'status epilepticus', requiring emergency treatment. Status epilepticus is a life-threatening condition due to the very high metabolic demand placed on the brain, which has the potential to result in brain injury and death. Cluster seizures are defined as two or more seizures within a 24 hour period and are often treated to prevent the progression to status epilepticus.

Causes

• Metabolic or toxic insult to the brain
• Infection or inflammation
• Progressive intracranial disease such as neoplasia
• Idiopathic epilepsy (seizures with no identifiable cause)

Goals of treatment

• Stop seizure activity
• Minimise complications of status epilepticus and side-effects of treatment
• Treat the underlying disease

Treatment phase 1

Emergency treatment

Diazepam: 0.5 - 1mg/kg IV or rectal - repeat after 3 minutes up to 3 doses.

OR

Midazolam: 0.3mg/kg IV or rectal - repeat after 3 minutes up to 3 doses.

The duration of effect is short (15-30 minutes), so once seizures are controlled, continue on a constant-rate-infusion of midazolam at 0.3mg/kg/hour.

If the above does not control seizures:

Propofol: 1 - 4 mg/kg IV to induce, followed by a CRI of 0.1 - 0.4 mg/kg/min

In the emergency setting, check blood biochemistry for underlying metabolic causes. Where this is not available in-house, evaluation of blood glucose on a simple glucometer can rule-out hypoglycaemia.

Treatment phase 2

In animals suffering cluster seizures or ongoing status epilepticus, maintenance anti-convulsant therapy is indicated. Phenobarbital is the initial maintenance anti-convulsant of choice in dogs.

Phenobarbital: 20mg/kg loading dose over a 24 hour period. This dose should be divided into 2-4mg/kg IV boluses and given every 20 minutes until the full loading dose is given. No more than 20mg/kg total should be given in any 24 hour period. After the loading dose, a daily maintenance dose of 3-5mg/kg every 12 hours (BID), either IV or orally (PO) can be given as ongoing anti-convulsant therapy.