## Neuroleptic Malignant Syndrome: Diagnosis & Management ### Clinical Recognition **Key Point:** This patient presents the **classic tetrad of NMS**: 1. **Fever** (38.8°C) 2. **Muscle rigidity** (lead-pipe, not cogwheel) 3. **Altered mental status** (mutism, confusion) 4. **Elevated CK** (3200 U/L with myoglobinuria) ### Pathophysiology NMS is a **life-threatening idiosyncratic reaction** to antipsychotics (dopamine antagonists). The mechanism involves: - Dopamine blockade in the hypothalamus → loss of thermoregulation - Dopamine blockade in the basal ganglia → severe extrapyramidal rigidity - Muscle hypermetabolism → rhabdomyolysis, acute kidney injury (AKI) **High-Yield:** NMS is a **medical emergency** with mortality 5–20% if untreated. The presence of **myoglobinuria + elevated creatinine** indicates acute rhabdomyolysis and imminent renal failure. ### Diagnostic Criteria (DSM-5) | Feature | Present in This Case | |---------|----------------------| | Exposure to antipsychotic | Yes (haloperidol + chlorpromazine) | | Hyperthermia (>38.5°C) | Yes (38.8°C) | | Muscle rigidity | Yes (lead-pipe) | | Altered mental status | Yes (mutism) | | Elevated CK (>1000 U/L) | Yes (3200 U/L) | | Evidence of rhabdomyolysis | Yes (myoglobinuria, ↑ creatinine) | ### Immediate Management Algorithm ```mermaid flowchart TD A[Suspected NMS with Rhabdomyolysis]:::urgent --> B[STOP all antipsychotics immediately]:::action B --> C[Aggressive IV hydration]:::action C --> D[Urine alkalinization with NaHCO3]:::action D --> E{CK > 5000 or Cr rising?}:::decision E -->|Yes| F[Dantrolene 2.5 mg/kg IV Q5-10 min]:::action E -->|No| G[Supportive care, monitor Q2-4H]:::action F --> H[ICU monitoring, dialysis standby]:::action G --> H H --> I[Reassess antipsychotic in 1-2 weeks]:::action I --> J[Consider atypical agent or different class]:::outcome ``` ### Dantrolene Sodium: Mechanism & Dosing **Mechanism:** Blocks calcium release from sarcoplasmic reticulum → reduces muscle contraction and heat production. **Dosing:** - **Loading:** 2.5 mg/kg IV push, repeated every 5–10 minutes until rigidity resolves or max 10 mg/kg - **Maintenance:** 1 mg/kg IV Q4–6H for 24–48 hours - **Oral:** 1 mg/kg/day in divided doses (post-acute phase) **High-Yield:** Dantrolene is the **only specific pharmacologic treatment** for NMS; it directly reduces muscle rigidity and heat production. ### Supportive Care Essentials 1. **Fluid resuscitation:** Target urine output 200–300 mL/hour 2. **Urine alkalinization:** NaHCO~3~ to maintain urine pH > 6.5 (prevents myoglobin precipitation in renal tubules) 3. **Cooling measures:** Ice packs, cooling blankets, cold IV saline 4. **Electrolyte monitoring:** K^+^, Ca^2+^, phosphate (rhabdomyolysis causes hyperkalemia and hypocalcemia) 5. **Renal function:** Monitor creatinine, BUN, urinalysis for myoglobin 6. **ICU admission:** Continuous cardiac monitoring (hyperkalemia → arrhythmias) **Clinical Pearl:** The presence of myoglobinuria with rising creatinine indicates **acute kidney injury is imminent**. Aggressive hydration and urine alkalinization must begin immediately to prevent irreversible renal damage and dialysis dependence. ### Why Antipsychotics Must Be Stopped **Mnemonic: STOP NMS = Stop Antipsychotics, Then Observe, Plan Alternatives** - Continuing haloperidol or switching to another typical antipsychotic will perpetuate the crisis - Chlorpromazine (also typical) added to haloperidol increased dopamine blockade - Do NOT rechallenge with antipsychotics for **at least 1–2 weeks** after NMS resolves - When restarting, consider **atypical antipsychotics** (lower NMS risk) or **non-antipsychotic alternatives** (mood stabilizers, benzodiazepines) **Warning:** Benztropine (anticholinergic) does NOT treat NMS and may worsen hyperthermia by impairing sweating. 
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