Harrison's Practice : Status Epilepticus

Harrison's Practice

Status Epilepticus

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Definition

A state of continuous seizures or repetitive, discrete seizures with impaired consciousness in the interictal period
- Duration
  - Traditional criterion: 15–30 minutes
  - Practical criterion: duration prompting acute use of anticonvulsant therapy; typically > 5 minutes
- May occur with all type of seizures: grand mal (tonic-clonic) status, myoclonic status, petit mal status, and temporal lobe (complex partial) status
- Associated with major cerebral and systemic physiologic changes
  - Initial stage (first 30–60 minutes)
    - Cerebral metabolism is greatly increased because of seizure activity, but physiologic mechanisms are sufficient to meet the metabolic demands.
    - Cerebral: increased blood flow, increased metabolism
    - Autonomic and cardiovascular: hypertension, increased cardiac output, massive catecholamine release, tachycardia, arrhythmias, hyperpyrexia
    - Metabolic: lactic acidosis, hyperglycemia
  - Decompensated phase
    - Cerebral metabolic demands cannot be fully met, resulting in hypoxia and altered cerebral and systemic metabolic patterns.
    - Cerebral: hypoxia, hypoglycemia, increased intracranial pressure
    - Autonomic and cardiovascular: hypoxia, hypotension, hyperpyrexia
    - Metabolic: hypoglycemia, hyponatremia, hyperkalemia, metabolic acidosis
- Generalized status is life threatening when accompanied by hyperpyrexia, acidosis (from prolonged muscle activity), and respiratory or cardiovascular compromise.

Epidemiology

Incidence in the U.S.
- 18–50 cases per 100,000 annually
  - Half are secondary to acute central nervous system (CNS) insult.
  - One-third are unprovoked first seizure.
  - One-sixth are in patients with known epilepsy.
    - Noncompliance with medications is primary risk factor in patients with known epilepsy.
Prevalence
- Occurs in ~10% of children who have diagnosis of epilepsy
Age
- More common in children, especially in first year of life
- More common in patients older than age 60
Sex
- Occurs equally in males and females

Risk Factors

Anticonvulsant withdrawal or noncompliance
Previous incident of status epilepticus (SE)
Refractory epilepsy
Head trauma
Metabolic disturbances
Drug toxicity
CNS infection
CNS tumors
Cerebrovascular disease
Fever (especially in children)

Etiology

Seizures are caused by a shift in the normal balance of excitation and inhibition within the CNS.
SE occurs in 3 general clinical scenarios.
- SE precipitated by focal or global CNS injury
  - Head trauma
  - Metabolic disturbance (e.g., hyponatremia, hypoglycemia)
  - Infection (encephalitis, abscess)
  - Drugs (both prescription and illicit)
  - Brain tumor
  - Stroke (acute or remote), hypoxia
- SE as initial presentation of a seizure disorder
- SE as exacerbation of known epilepsy
  - Primary risk factor is noncompliance with medications.
  - More common in patients with prior history of SE

Symptoms & Signs

Generalized SE
- Overt convulsions
- After 30–45 minutes of uninterrupted seizures, signs may become increasingly subtle.
  - Mild clonic movements of only the fingers
  - Fine, rapid movements of the eyes
  - Paroxysmal episodes of tachycardia, hypertension, and pupillary dilation
- Patients who remain unresponsive following termination of overt convulsions may remain in nonconvulsive SE, a condition often detectable only by electroencephalogram (EEG).

Differential Diagnosis

Coma
- After overt seizures, if patient remains comatose, EEG should be obtained to evaluate for ongoing nonconvulsive SE.
Nonepileptic SE
- May occur in patient with psychogenic nonepileptic seizures

Diagnostic Approach

SE is a medical emergency.
Patients must be evaluated promptly and appropriate therapy instituted without delay.
Treatment of ongoing seizures must occur in parallel with an investigation of the cause of the seizures in order to prevent recurrence and treat any underlying abnormalities.
The patient who remains comatose following termination of overt seizures should have an EEG to evaluate for ongoing nonconvulsive SE.

Laboratory Tests

Laboratory studies to consider:
- Anticonvulsant levels
- Complete blood count with differential
- Serum electrolytes including calcium, magnesium, and phosphate
- Creatinine and blood urea nitrogen
- Glucose
- Creatine phosphokinase
- Serum osmolality
- Liver and renal function tests
- Toxicology tests: blood and urine
- Arterial blood gas
- Carboxyhemoglobin

Imaging

CT or MRI of brain
- If indicated to determine cause of SE
- Obtained as soon as possible once seizures have been controlled and patient is medically stable

Diagnostic Procedures

EEG
- Evaluate with EEG as soon as possible.
- If overt seizures stop, but patient remains comatose, perform EEG to exclude ongoing SE.

Treatment Approach

Patients must be evaluated promptly and appropriate therapy instituted without delay.
- General critical care supportive measures (e.g., airway, breathing, circulation)
- Anticonvulsant therapy (see below)
Consultation with a neurologist and critical care physician is advised.

Specific Treatments

Treatment protocol: General measures

Assess carefully for evidence of respiratory or cardiovascular insufficiency.
- With careful monitoring and standard airway protection, patients usually do not require intubation (if intubation is necessary, use short-acting paralytics).
Establish intravenous access and administer:
- 50% dextrose in water 50 mL
- Thiamine 100 mg
- Naloxone 0.4 mg
Perform a brief medical and neurologic examination.
Treat hyperthermia.
Send samples for laboratory studies aimed at identifying metabolic abnormalities.

Treatment protocol: Anticonvulsant therapy

Lorazepam (0.1 mg/kg IV at 2 mg/min)
- Additional emergency drug therapy may not be required if seizures stop and the cause of SE is rapidly corrected.
If seizures continue
- Phenytoin (20 mg/kg IV at 50 mg/min) or fosphenytoin (20 mg/kg phenytoin sodium equivalents [PE] IV at 150 mg/min)
- Monitor blood pressure; electrocardiogram; and, if possible, EEG during infusion.
- Side effects: Phenytoin can cause precipitous fall in blood pressure if given too quickly, especially in elderly patients.
- Precautions: Do not administer phenytoin with 5% dextrose in water as phenytoin precipitates at low pH. This is not a problem with fosphenytoin.
- If seizures are not controlled, a repeat bolus of phenytoin (5–10 mg/kg) or fosphenytoin (5–10 mg/kg) may be given.
If seizures continue
- May add phenobarbital (20 mg/kg IV at 50–75 mg/min)
- If lorazepam and phenytoin are ineffective in terminating SE, many physicians now bypass use of phenobarbital and proceed to anesthesia with midazolam or propofol, especially if patient displays severe systemic disturbances or has had seizures for longer than 60 minutes.
If seizures continue
- Anesthesia with midazolam, propofol, or pentobarbital

Monitoring

Perform EEG monitoring for:
- Continued seizure activity
- Termination of seizure activity
- Recurrent seizure activity
- Unexplained coma despite termination of overt seizures
Monitor for complications of SE and complications of therapy.
- Rhabdomyolysis, renal failure, liver failure, aspiration pneumonia
Monitor anticonvulsant drug levels.

Complications

Cardiorespiratory dysfunction
- Hypoxia
- Aspiration pneumonia
- Arrhythmia
- High-output cardiac failure
Hyperthermia
Metabolic derangements
- Lactic acidosis
- Hyponatremia
- Hyperkalemia
- Hypoglycemia
- Hypercapnia
Acute renal failure due to rhabdomyolysis
Profound CNS injury can occur when the patient is paralyzed with neuromuscular blockade but continues to have electrographic seizures.
Irreversible neuronal injury
Death

Prognosis

Prognosis is dependent on underlying disorder.
Mortality rate is 20% in tonic-clonic status.
Incidence of permanent neurologic sequelae is 10–30%.

Prevention

Secondary prevention
- Adequate therapeutic control of underlying seizure disorder
- Compliance with anticonvulsant regimen
- Parents of children diagnosed with epilepsy should be educated regarding the steps to take if a seizure does not rapidly terminate.
  - For children at high risk for SE (e.g. previous history of SE, younger age at onset), parents can be given abortive therapy to be used prior to arrival of emergency medical services.

ICD-9-CM

345.3 Grand mal status (includes status epilepticus, not otherwise specified)