Hypertensive Encephalopathy

Acute cerebral dysfunction from severe hypertension with loss of cerebral autoregulation, capillary leak and vasogenic oedema, mainly in the posterior circulation (posterior reversible encephalopathy syndrome).

• Triggers: severe uncontrolled hypertension, eclampsia, renal failure, immunosuppressants (ciclosporin, tacrolimus), cytotoxic chemotherapy, autoimmune disease, stimulants.
• Reversible if treated early; delay causes haemorrhage, infarction and permanent deficits.

• Severe headache, confusion progressing to drowsiness or coma, visual disturbance (blurring, cortical blindness), nausea and vomiting, generalised or focal seizures.
• Blood pressure is typically greater than 180/120 mmHg, though lower levels can cause it in children, pregnancy and acute renal disease.
• Fundoscopy: retinal haemorrhages, exudates, papilloedema. Focal deficits are uncommon and suggest stroke.
• Differential diagnosis: ischaemic or haemorrhagic stroke, subarachnoid haemorrhage, meningitis or encephalitis, hypoglycaemia, intracerebral mass, eclampsia, cerebral venous thrombosis, intoxication.
• Complications: intracerebral haemorrhage, infarction, status epilepticus, permanent visual loss, chronic epilepsy.

• Clinical, confirmed by imaging. MRI with FLAIR shows symmetrical posterior white matter oedema; diffusion weighted imaging helps to separate infarction. CT may be normal early and excludes haemorrhage.
• Glucose, electrolytes (sodium, calcium, magnesium), renal function, urinalysis, full blood count, pregnancy test, drug levels (ciclosporin, tacrolimus), toxicology screen.
• Lumbar puncture only if meningitis is suspected and after imaging.

• High dependency care. Reduce mean arterial pressure by 20 to 25% in the first hour, then to about 160/100 mmHg over 2 to 6 hours, then gradually to normal over 24 to 48 hours.
• Labetalol 20 mg IV then 20 to 80 mg every 10 minutes (maximum 300 mg), or infusion 0.5 to 2 mg/min. Avoid in bradycardia, heart block, asthma.
• Nicardipine 5 mg/h increased by 2.5 mg/h every 5 to 15 minutes to a maximum of 15 mg/h.
• Avoid nitroprusside and nitrates where possible (cerebral vasodilatation raises intracranial pressure), and avoid hydralazine except in pregnancy.
• Seizures: lorazepam 4 mg IV (0.1 mg/kg) repeated once after 10 minutes; then levetiracetam 20 to 60 mg/kg IV (maximum 4500 mg), or phenytoin 20 mg/kg IV at 50 mg/min or less with ECG monitoring.
• Eclampsia: magnesium sulfate 4 to 6 g IV over 15 to 20 minutes then 1 to 2 g/h; check reflexes, respiratory rate (keep at 12 per minute or more) and urine output (keep at 25 mL/h or more). Calcium gluconate 1 g IV reverses toxicity. Delivery is the definitive treatment.
• Raised intracranial pressure: head up 30 degrees, mannitol 0.5 to 1 g/kg IV over 20 minutes, airway protection and ventilation if Glasgow Coma Scale is 8 or less.
• Remove offending drugs (reduce or switch ciclosporin or tacrolimus; stop stimulants).
• Special groups: pregnancy (labetalol, nifedipine, magnesium); children (smaller BP reduction targets, specialist input); renal failure (dialysis for volume control).
• Follow up: repeat MRI in 1 to 2 weeks to document resolution; neurological and visual review; withdraw anticonvulsants within 3 to 6 months if seizure free; complete workup for the cause of hypertension.