posted: 20/Apr/2017

Seizures are a common presenting problem in the emergency setting, and can often seem quite daunting at first. However, with a basic understanding of aetiology, diagnostics and treatment, they can often be managed successfully.

Definitions

Seizures are caused by synchronous and excessive neuronal discharge within the cerebrum.

  • Generalized tonic-clonic seizures (previously known as grand mal seizures) are characterized by:
    • Loss of consciousness
    • Tonic phase = extensor rigidity
    • Clonic phase = paddling/alternating flexion and extension of limbs; exaggerated chewing movements
    • Often urinate, defecate and salivate
  • Seizures can also be partial, and in these cases, consciousness may or may not be altered

Cluster seizures are 2 or more seizures within a 24 hour period

The definition of status epilepticus is not universally accepted, but is often understood to consist of a continuous seizure or two or more seizures between which there is incomplete recovery of consciousness, lasting at least 10 minutes.

Physical and neurological examination

  • Establish IV access immediately
  • Assess ABCs (airway, breathing and circulation) and correct these as necessary
  • Neurological examination
    • Level of consciousness, mentation
    • Response to menace, PLR, facial sensation, proprioception
    • A more thorough neurological examination can be performed once seizures are controlled

Minimum database

  • CBC, serum chemistry panel, urinalysis, blood glucose, blood pressure
  • If normal, extra-cranial is less likely
  • Further diagnostics to consider:
    • Bile acid stimulation test
    • Serum insulin if hypoglycaemic
    • Infectious disease titres (Toxoplasma, Neospora, Cryptococcus)
    • Thyroid function tests
  • If intra-cranial disease is suspected and extra-cranial disease is ruled out, advanced imaging (CT or MRI) is recommended

Causes:

Structural brain disease

Neoplasia

Infectious

Inflammatory

Congenital abnormalities

Trauma

Cerebrovascular accident

Nutritional deficiencies

 

Metabolic causes

Hypoglycaemia

Hepatic encephalopathy

Uraemic encephalopathy

Hypocalcaemia

Polycythaemia

 

Idiopathic causes

Epilepsy

Heat stroke

Toxins

Organophosphates

Carbamates

Pyrethrins

Strychnine

Metaldehyde

Ivermectin

Marijuana

Cocaine

Amphetamines and similar

Lead

Mercury

Iron

Caffeine

Methylxanthines

Fungal toxins

Ethylene glycol

Snake envenomation

 

Importance of signalment

  • Any animal presenting with seizures and progressive neurological abnormalities is likely to have a progressive intracranial disease
  • Patients less 5 years old:
    • Epilepsy is the most common cause
    • Diagnosis of exclusion
  • Patients <1 year old
    • Also consider structural brain disease and congenital metabolic conditions
  • Dogs that are >7 years old when first seizure is seen, with a normal neurological examination and no metabolic abnormalities have ≥50% probability of an underlying tumour
  • In cats of any age with no neurological abnormalities, still consider infectious causes (FIP, Cryptococcus, Toxoplasma)
  • In cats >5 years old also consider an intra-cranial tumour or cerebrovascular disease secondary to hypertension (renal disease, hyperthyroidism)

Specific treatment

  • Diazepam
    • 0.5-1.0mg/kg IV
    • May also be given at 1-2mg/kg per rectum
    • Usually limited to 3 doses, but if seizures are poorly controlled after first dose, consider second line anticonvulsants in combination with second dose of diazepam
  • Midazolam
    • Can be used as an alternative to diazepam
    • 0.2-0.5mg/kg IM, IV
    • Should not be given rectally due to low bioavailability
  • Phenobarbitone
    • Bolus 2-10mg/kg, up to 20mg/kg over 24 hours
    • Can cause profound sedation if excessive doses are used
  • Levetiracetam
    • Doses up to 60mg/kg IV have been reported for use in dogs with refractory seizures
    • May be a useful adjunct to diazepam and phenobarbitone when waiting for phenobarbitone to take effect
    • Not as useful for long-term therapy as other anticonvulsants
  • Propofol CRI
    • If seizures are refractory to the above treatments, intubation and general anaesthesia is indicated
    • Dose = 2-8mg/kg IV as a bolus; may be continued as a CRI at 0.1-0.6mg/kg/min
  • Ketamine
    • A recent case study has suggested a benefit of using ketamine in patients with refractory status epilepticus
    • Dose = 5mg/kg IV as a bolus;  may be continued as a CRI at 5mg/kg/h

Supportive treatment

  • Control hyperthermia
    • Active cooling
      • Commence if rectal temperature is >40.5C
      • Wet towels (using room temperature water) over body; fanning;
      • Do not use alcohol, ice packs or cold water
      • Stop once temperature is <39.5C
    • IV fluid therapy
  • Prevent/control cerebral oedema if suspected
    • Patients that are hyperthermic and have been seizuring may develop cerebral oedema
    • Pinpoint pupils are a potential indicator of cerebral oedema and increased intracranial pressure
    • Treat with mannitol 0.5g/kg IV over 20 minutes – ensure patient is well hydrated prior to administration
    • Alternatively, treat with hypertonic saline (HTS) given IV over 5-10mins
      • 4-5ml/kg of 7% HTS
      • 1.5ml/kg of 20% HTS diluted 1:2 with LRS or 0.9% NaCl
  • Treat hypoglycaemia if present
    • Administer 50% glucose at 0.5-1.0 ml/kg IV (dilute 1:2-1:4 with LRS or 0.9% NaCl)
    • Continue as a CRI if required
  • Treat hypocalcaemia if present
    • Using 10% calcium gluconate, administer 0.5-1.5 ml/kg IV slowly over 10 minutes; monitor HR and rhythm during administration; stop if bradycardia or arrhythmias occur
  • Provide oxygen supplementation as required
  • Turn patient every 4 hours if laterally recumbent



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