Match each patient's clinical presentation to the primary pathophysiological mechanism responsible for their psychiatric emergency or drug-induced toxicity.
- A 32-year-old man on the inpatient psychiatric unit develops a temperature of 40.0°C (104.0°F), profound 'lead-pipe' muscle rigidity, and diaphoresis three days after his haloperidol dosage was increased. Labs show a creatine kinase of 5,000 U/L.Central dopamine D2 receptor blockade causing hypothalamic thermoregulatory failure and extrapyramidal dysfunction
- A 24-year-old woman in the emergency department exhibits severe agitation, a temperature of 38.5°C (101.3°F), bilateral lower extremity hyperreflexia, and spontaneous ankle clonus after initiating phenelzine while still taking fluoxetine.Overactivation of central and peripheral 5-HT1A and 5-HT2A receptors leading to neuromuscular hyperactivity
- A 19-year-old man presents to the emergency department with acute, painful, and sustained upward deviation of his eyes and contraction of his neck muscles 48 hours after receiving an intramuscular injection of fluphenazine for acute psychosis.Disruption of nigrostriatal dopamine-acetylcholine balance resulting in a localized state of cholinergic excess
- A 45-year-old woman is brought to the emergency department obtunded with a heart rate of 120/min, dry flushed skin, mydriasis, and an ECG demonstrating sinus tachycardia with a QRS duration of 140 msec following an intentional drug overdose.Competitive blockade of fast cardiac sodium channels combined with systemic muscarinic receptor antagonism
- A 50-year-old man with bipolar disorder presents to the clinic with a new-onset coarse hand tremor, severe ataxia, confusion, and vomiting two weeks after his primary care physician started him on hydrochlorothiazide for hypertension.Enhanced proximal renal tubule reabsorption of a specific cation secondary to diuretic-induced volume depletion
Answer
The clinical presentations match their pathophysiological mechanisms as follows: NMS is caused by D2 blockade; Serotonin Syndrome by 5-HT overactivation; Acute Dystonia by nigrostriatal cholinergic excess; TCA toxicity by sodium channel blockade and muscarinic antagonism; and Lithium toxicity by enhanced proximal tubule reabsorption.
Each psychiatric emergency requires matching the distinct clinical toxidrome to its underlying receptor or pharmacokinetic etiology. Neuroleptic Malignant Syndrome (characterized by lead-pipe rigidity and extreme hyperthermia) is driven by profound dopamine D2 receptor blockade. Serotonin Syndrome (presenting with hyperreflexia and ankle clonus) is caused by excess 5-HT receptor activation. Acute dystonia (manifesting as sustained muscle contractions like torticollis) results from a relative cholinergic excess in the nigrostriatal tract following D2 blockade. TCA toxicity (presenting with a widened QRS and severe anticholinergic signs) is characterized by fast sodium channel blockade in the myocardium. Finally, Lithium toxicity (presenting with coarse tremor and ataxia) is frequently precipitated by thiazide diuretics, which induce volume depletion and trigger a compensatory proximal tubule reabsorption of both sodium and lithium.
Step-by-Step Solution
Key Concept
Psychiatric Emergencies and Toxidromes: Pathophysiology and Presentation