A 35-year-old woman with a family history of perioperative death is scheduled for elective cesarean section. Her mother died under anesthesia at age 40 with unexplained intraoperative fever and muscle rigidity. The patient is anxious about anesthesia. Which of the following is the most appropriate anesthetic plan to minimize the risk of malignant hyperthermia?

Explanation

## Risk Stratification and Anesthetic Planning in Suspected MH Susceptibility ### Clinical Context **Key Point:** A family history of perioperative death with intraoperative fever and muscle rigidity is a **red flag for malignant hyperthermia susceptibility (MHS)**. This patient requires a **trigger-free anesthetic plan**. **High-Yield:** MH susceptibility is inherited as an **autosomal dominant trait** with variable penetrance. Mutations in the **RYR1 gene** (ryanodine receptor) or **CACNA1S gene** (calcium channel) account for ~70% of cases. ### Anesthetic Triggers vs. Safe Agents | Category | Agents | Status | |----------|--------|--------| | **TRIGGERS** | Volatile anesthetics (sevoflurane, isoflurane, desflurane, halothane) | **AVOID** | | **TRIGGERS** | Succinylcholine | **AVOID** | | **SAFE** | Propofol, thiopental, etomidate | ✓ Use | | **SAFE** | Nitrous oxide | ✓ Use | | **SAFE** | Opioids (morphine, fentanyl, remifentanil) | ✓ Use | | **SAFE** | Non-depolarizing neuromuscular blockers (rocuronium, vecuronium, cisatracurium) | ✓ Use | | **SAFE** | Local anesthetics | ✓ Use | | **SAFE** | Benzodiazepines, anticholinergics, alpha-2 agonists | ✓ Use | **Warning:** Nitrous oxide is safe in MH but should be avoided in cesarean section due to risk of PONV and aspiration. Propofol is the preferred induction and maintenance agent. ### Optimal Anesthetic Plan for MHS Patient ```mermaid flowchart TD A[Patient with Family Hx of MH]:::outcome --> B{Regional anesthesia feasible?}:::decision B -->|Yes| C[Spinal/Epidural anesthesia]:::action C --> D[Minimal sedation or propofol-based sedation only]:::action D --> E[Avoid all volatile agents and succinylcholine]:::action B -->|No or inadequate| F[General anesthesia required]:::decision F --> G[Propofol induction]:::action G --> H[Non-depolarizing NMB: rocuronium, vecuronium]:::action H --> I[TIVA: propofol + opioid]:::action I --> J[Avoid volatile agents and succinylcholine]:::action E --> K[Prepare dantrolene at bedside]:::urgent J --> K K --> L[Monitor: core temp, ETCO₂, CK post-op]:::action ``` **Clinical Pearl:** Regional anesthesia is the **safest choice** for MHS patients because it avoids the need for general anesthesia and eliminates exposure to all triggering agents. Spinal anesthesia is ideal for cesarean section. ### If General Anesthesia is Necessary 1. **Induction:** Propofol 2 mg/kg IV (safe; no trigger potential) 2. **Maintenance:** Total intravenous anesthesia (TIVA) with propofol + remifentanil or fentanyl - **NO volatile anesthetics** - **NO succinylcholine** 3. **Neuromuscular blockade:** Rocuronium 1.2 mg/kg IV (non-depolarizing; safe) 4. **Analgesia:** Opioids (fentanyl, remifentanil) — safe and effective 5. **Sedation if needed:** Benzodiazepines, dexmedetomidine — all safe **High-Yield:** Propofol is the gold standard induction and maintenance agent for MHS patients. It has **no trigger potential** and provides excellent hemodynamic stability. ### Perioperative Precautions 1. **Pre-operative:** Counsel patient on MH risk; arrange genetic testing (RYR1, CACNA1S) if not already done 2. **Intraoperative:** - Prepare dantrolene (20 mg vials × 12) at bedside - Use fresh anesthesia circuit; consider using a new machine or flushing the circuit with 100% O₂ for 10 minutes - Monitor core temperature continuously (esophageal or bladder probe) - Monitor ETCO₂ continuously (early sign of MH if unexpectedly elevated) - Maintain normothermia with forced-air warmer 3. **Post-operative:** - Observe in recovery for 30 minutes - Monitor for delayed signs of MH (myoglobinuria, hyperkalemia, rhabdomyolysis) - Consider dantrolene 1 mg/kg IV q4–6h × 24–48 hours if any concern **Mnemonic:** **SAFE agents in MH** = **S**pinal/regional, **A**void triggers, **F**ocus on TIVA, **E**nsure dantrolene ready **Tip:** Inform the patient that regional anesthesia is the preferred option and is safe. Reassure her that if general anesthesia becomes necessary, a trigger-free technique will be used. [cite:Miller's Anesthesia 8e Ch 33; ASA Practice Advisory on MH]