## Neuroleptic Malignant Syndrome (NMS): Recognition and Management ### Clinical Diagnosis This patient has the classic tetrad of NMS: 1. **Hyperthermia** (>38.5°C) — 39.8°C 2. **Muscle rigidity** — "lead pipe" or "waxy flexibility" 3. **Altered mental status** — confusion, delirium 4. **Autonomic instability** — hypertension, tachycardia, diaphoresis **High-Yield:** NMS is a medical emergency with mortality 5–20% if untreated. It can occur at any time during antipsychotic therapy, even with stable dosing. ### Pathophysiology Antipsychotics block dopamine D2 receptors in the basal ganglia and hypothalamus, leading to: - Loss of thermoregulation - Increased muscle tone and metabolic heat production - Sympathetic hyperactivity **Key Point:** Unlike serotonin syndrome (hours to days), NMS develops insidiously over 24–72 hours and is triggered by dopamine antagonists (antipsychotics, metoclopramide, prochlorperazine). ### Complications This patient has evidence of rhabdomyolysis: - CK 3200 U/L (normal <200) - Myoglobinuria - Acute kidney injury (Cr 1.8, up from 0.9) Rhabdomyolysis → myoglobin precipitation in renal tubules → acute tubular necrosis → oliguric renal failure, hyperkalemia, and death if untreated. ### Immediate Management Algorithm ```mermaid flowchart TD A[Suspected NMS]:::outcome --> B[STOP antipsychotic immediately]:::urgent B --> C[Supportive care]:::action C --> D[IV hydration aggressive]:::action C --> E[Active cooling measures]:::action C --> F[Monitor: CK, Cr, K+, urine myoglobin]:::action D --> G{CK >1000 or renal dysfunction?}:::decision G -->|Yes| H[Consider dantrolene or bromocriptine]:::action G -->|No| I[Supportive care alone may suffice]:::action H --> J[Dantrolene 1 mg/kg IV q4-6h up to 10 mg/kg/day]:::action H --> K[OR Bromocriptine 2.5-5 mg PO/NG q6-8h]:::action J --> L[Monitor for recurrence after drug discontinuation]:::action K --> L ``` ### Step-by-Step Management 1. **Discontinue antipsychotic immediately** — this is non-negotiable 2. **Aggressive IV hydration** — target urine output 200–300 mL/hour to flush myoglobin from renal tubules 3. **Active cooling** — ice packs, cooling blanket, cold IV saline 4. **Benzodiazepines** — lorazepam for agitation (NOT to replace antipsychotic) 5. **Pharmacotherapy** (if CK markedly elevated or renal dysfunction): - **Dantrolene** 1 mg/kg IV every 4–6 hours (max 10 mg/kg/day) — reduces muscle rigidity by inhibiting Ca²⁺ release from sarcoplasmic reticulum - **Bromocriptine** 2.5–5 mg PO/NG every 6–8 hours — dopamine agonist to restore dopaminergic tone 6. **Monitor:** CK, creatinine, potassium, urine myoglobin, fluid balance 7. **Prevent recurrence:** Avoid all antipsychotics for ≥5 half-lives; if reinitiation is necessary, use lowest effective dose of an atypical antipsychotic (e.g., quetiapine) after full recovery and informed consent. **Clinical Pearl:** Aggressive hydration is the cornerstone of management; it prevents acute kidney injury and reduces mortality more than any pharmacological agent. ### Comparison: Serotonin Syndrome vs. NMS | Feature | Serotonin Syndrome | NMS | |---------|-------------------|-----| | **Trigger** | Serotonergic drugs (SSRI, MAOI, tramadol) | Antipsychotics, metoclopramide | | **Onset** | Hours to 24 hours | 24–72 hours | | **Clonus** | Present (spontaneous/inducible) | Absent | | **Tremor** | Fine, prominent | Coarse, less prominent | | **Diarrhea** | Common | Rare | | **CK** | Mild elevation | Marked (often >1000) | | **Recovery** | Hours to days | Days to weeks | | **First-line treatment** | Stop drug, cyproheptadine | Stop drug, supportive care, dantrolene/bromocriptine | **Mnemonic — NMS (Neuroleptic Malignant Syndrome):** - **N**euroleptic exposure - **M**uscle rigidity - **S**evere hyperthermia **Warning:** Continuing the antipsychotic (option A) is dangerous and will worsen rhabdomyolysis. Switching to clozapine (option C) without a washout period risks recurrence. Bromocriptine alone without stopping the antipsychotic (option D) is inadequate. 
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