A 42-year-old man with schizophrenia on haloperidol 15 mg daily for 8 years presents to the emergency department with a 2-day history of fever, severe muscle rigidity, and altered mental status. His wife reports he has been increasingly withdrawn and confused over the past 48 hours. On examination, temperature is 40.1°C, blood pressure 162/98 mmHg, heart rate 126/min. He is profoundly rigid (lead-pipe type), with decreased level of consciousness. Laboratory investigations show: CK 3200 IU/L, creatinine 1.8 mg/dL, potassium 5.8 mEq/L. Urine is dark brown. What is the most appropriate immediate management?

Explanation

## Diagnosis and Management of Neuroleptic Malignant Syndrome (NMS) ### Clinical Diagnosis: NMS This patient presents with the **classic tetrad of NMS**: 1. **Fever** (40.1°C) — hyperthermia 2. **Rigidity** — lead-pipe type (characteristic of NMS) 3. **Altered mental status** — confusion, decreased consciousness 4. **Autonomic instability** — hypertension, tachycardia ### Risk Factors Present - **Antipsychotic exposure:** Haloperidol (typical/first-generation antipsychotic) — high-risk agent - **Chronicity:** 8 years on same agent increases vulnerability - **Acute decompensation:** Withdrawal, reduced medication compliance, or environmental stress may precipitate ### Laboratory Findings: Evidence of Rhabdomyolysis **Key Point:** The elevated CK (3200 IU/L), acute kidney injury (creatinine 1.8), hyperkalemia (5.8), and dark urine (myoglobinuria) indicate **rhabdomyolysis with acute renal failure** — a life-threatening complication of NMS. ### Pathophysiology **Clinical Pearl:** NMS results from dopamine D~2~ receptor blockade in the hypothalamus and basal ganglia, leading to: - Loss of thermoregulation → hyperthermia - Increased muscle tone → rigidity and rhabdomyolysis - Sympathetic hyperactivity → autonomic instability ### Immediate Management Algorithm ```mermaid flowchart TD A[Suspected NMS]:::outcome --> B[Stop antipsychotic immediately]:::action B --> C[Supportive care]:::action C --> D[IV fluids for rhabdomyolysis]:::action D --> E[Dantrolene sodium 1 mg/kg IV]:::action E --> F{CK declining?<br/>Renal function stable?}:::decision F -->|Yes| G[Continue dantrolene 1 mg/kg Q4-6H]:::action F -->|No| H[Escalate fluids, monitor urine output]:::action I[Avoid re-exposure to antipsychotics] --> J[Consider atypical antipsychotic<br/>after full recovery]:::action ``` ### Why Dantrolene Sodium? **High-Yield:** Dantrolene works by: - Inhibiting calcium release from sarcoplasmic reticulum in skeletal muscle - Reducing muscle contractility and heat generation - **Dose:** 1 mg/kg IV bolus, then 1 mg/kg every 4–6 hours (max 10 mg/kg/day) - **Monitoring:** Continue until signs of NMS resolve or max dose reached ### Supportive Care Priorities 1. **Aggressive IV hydration** — maintain urine output >200 mL/hr to prevent myoglobin precipitation in renal tubules 2. **Urinary alkalinization** — sodium bicarbonate to raise urine pH >6.5 (myoglobin is more soluble in alkaline urine) 3. **Electrolyte monitoring** — hyperkalemia (5.8 here) requires urgent management; consider calcium gluconate, insulin + glucose, or dialysis if severe 4. **Cooling measures** — ice packs, cooling blankets 5. **Monitoring:** Serial CK, creatinine, potassium, urine myoglobin ### Comparison: NMS vs. Serotonin Syndrome | Feature | NMS | Serotonin Syndrome | |---------|-----|--------------------| | **Trigger** | Antipsychotic (D~2~ blockade) | Serotonergic drugs (SSRI + MAOI, etc.) | | **Onset** | 24–72 hours | Hours to 24 hours | | **Rigidity type** | Lead-pipe | Hyperreflexia, clonus prominent | | **GI symptoms** | Rare | Common (diarrhea) | | **CK elevation** | Marked (often >1000) | Mild to moderate | | **Treatment** | Dantrolene, bromocriptine | Cyproheptadine, benzodiazepines | ### Why NOT the Other Options? **Option A (Continue haloperidol + dantrolene):** Continuing the offending agent is contraindicated; it perpetuates dopamine blockade and prevents recovery. **Option C (Switch to second-generation antipsychotic):** Switching antipsychotics during acute NMS is dangerous — cross-sensitivity can occur, and the patient is already in rhabdomyolysis. Wait for full recovery (days to weeks) before reintroduction. **Option D (Bromocriptine + continue haloperidol):** While bromocriptine (dopamine agonist) is an alternative agent for NMS, it is **secondary** to dantrolene in acute management. Continuing haloperidol is contraindicated. ### Prognosis and Recovery - Mortality: 5–20% (higher with rhabdomyolysis and AKI) - Recovery: 24–72 hours after stopping antipsychotic; full neurological recovery may take weeks - **Re-exposure:** Avoid the same antipsychotic; if antipsychotic is necessary, use a low-potency typical or atypical agent after full recovery [cite:Harrison 21e Ch 470; Kaplan & Sadock's Synopsis of Psychiatry 12e Ch 28]