Porphyric Crisis (Acute Neurovisceral Crisis)
Background:
-The porphyrias are caused by enzyme deficiencies in the heme production pathway. Such deficiencies may be due to inborn errors of metabolism or exposure to environmental toxins or infectious agents.
-The disease was named porphyria due to the red
discoloration of urine in affected patients, (Figure 1).
-Crises are four to five times more common in women and usually occur in their early 30s.
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| Figure 1: Porphyria Red Urine |
Triggering factors:
Enzyme-inducing drugs:
-Barbiturates (Thiopental, Methohexital), Etomidate, Enflurane, Alcuronium, Mepivacaine, Pentazocine, Nifedipine, Verapamil, Diltiazem, Phenytoin, Hydralazine, Phenoxybenzamine, Aminophylline
Physiological:
-Menstruation, Fasting, Dehydration, Stress, Infection, Anemia, Endogenous hormones
Habits:
-Smoking, Alcohol
Clinical Picture:
CNS:
-Autonomic neuropathy (Fever, Pain, Constipation, Gastroparesis, Postural hypotension)
-Peripheral neuropathy (Skeletal muscle weakness, Quadriparesis, Bulbar palsy, Respiratory failure)
-Cranial nerve palsy
-Seizures
-Psychiatric features (Mood disturbance, Confusion, Psychosis)
CVS:
-Tachycardia, Hypertension
GIT:
Acute abdominal pain, Vomiting, Diarrhea, Dehydration, Electrolyte disturbance (↓ [Na⁺, K⁺, Mg⁺²])
Management:
Remove triggering factors (above)
Specific R:
-Hematin, Heme arginate / Heme albumin, Somatostatin, Plasmapheresis
Symptomatic R:
-Pain: Substantial doses of Opioids
-Nausea and Vomiting: Prochlorperazine, Ondansetron
-Anxiety: Lorazepam, Midazolam in low doses
-Insomnia: Zopiclone
-Delirium: Haloperidol
-Tachycardia & Hypertension: β-adrenergic blocking agents, Glyceryl trinitrate
-Seizures: Benzodiazepines, Levetiracetam, Clonazepam, Gabapentin, Vigabatrin, Magnesium sulphate
-Sedation: Propofol, Alfentanil infusions. The clinical safety of prolonged midazolam infusion is unknown.
-Thromboembolic prophylaxis: LMW heparins
-Stress ulcer prevention: IV Omeprazole, Ranitidine
-Correction of electrolytes
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