Neuroleptic Malignant Syndrome (NMS)

Neuroleptic malignant syndrome (NMS) is a rare, life-threatening reaction to dopamine receptor-blocking agents (typical antipsychotics such as haloperidol, atypical antipsychotics, antiemetics such as metoclopramide) or rapid withdrawal of dopaminergic medications (levodopa). The pathogenesis involves acute central dopamine D2 receptor blockade in the hypothalamus (disrupting thermoregulation) and basal ganglia (causing rigidity), combined with sympathetic nervous system hyperactivity and peripheral muscle contraction. The tetrad of clinical features includes hyperthermia (often greater than 40 degrees C from skeletal muscle heat production and impaired hypothalamic thermoregulation), severe lead-pipe muscular rigidity, altered mental status (confusion, agitation, catatonia, progressing to coma), and autonomic instability (tachycardia, labile blood pressure, diaphoresis, tachypnea). Laboratory findings include markedly elevated creatine kinase (from rhabdomyolysis), leukocytosis, metabolic acidosis, elevated liver enzymes, and myoglobinuria. The nurse immediately discontinues the offending agent, administers dantrolene sodium (muscle relaxant blocking calcium release from sarcoplasmic reticulum) and bromocriptine (dopamine agonist), implements aggressive cooling measures, monitors for acute kidney injury from myoglobinuria (aggressive IV hydration to maintain urine output greater than 200 mL/hour), monitors CK and renal function serially, and provides continuous hemodynamic monitoring.