A 28-year-old woman with a family history of malignant hyperthermia (MH) is scheduled for elective cosmetic surgery under general anesthesia. She has never undergone surgery before and has no personal history of anesthetic complications. Preoperative workup is unremarkable. The anesthesiologist plans to use a non-triggering anesthetic technique. Which of the following is the MOST appropriate anesthetic induction and maintenance regimen for this patient?

Explanation

## Prevention of MH Crisis in Susceptible Patients ### Risk Stratification **Key Point:** Family history of MH or unexplained perioperative death/complications in relatives = presumed MH susceptibility until proven otherwise. These patients require a non-triggering anesthetic technique. **High-Yield:** MH susceptibility is inherited in an autosomal dominant pattern with variable penetrance (mutations in RYR1 ~70%, CACNA1S ~20%). A positive family history warrants avoidance of ALL volatile anesthetics and succinylcholine. ### Classification of Anesthetic Agents | Agent Category | Triggering? | Safe in MH? | Examples | |---|---|---|---| | **Volatile anesthetics** | YES | NO | Isoflurane, desflurane, sevoflurane, halothane | | **Depolarizing agents** | YES | NO | Succinylcholine | | **IV induction agents** | NO | YES | Propofol, thiopental, etomidate, ketamine | | **Non-depolarizing NMBs** | NO | YES | Rocuronium, vecuronium, cisatracurium, atracurium | | **Opioids** | NO | YES | Fentanyl, remifentanil, morphine | | **Benzodiazepines** | NO | YES | Midazolam | | **Nitrous oxide** | NO | YES | N₂O | | **Local anesthetics** | NO | YES | Lidocaine, bupivacaine | **Clinical Pearl:** Nitrous oxide is NOT triggering and is safe in MH-susceptible patients. However, modern practice often avoids N₂O due to other concerns (PONV, neurotoxicity); TIVA is preferred. ### Optimal Non-Triggering Technique (TIVA) ```mermaid flowchart TD A["MH-Susceptible Patient"]:::outcome --> B["Induction: Propofol or Etomidate IV"]:::action B --> C["Intubation: Non-depolarizing NMB<br/>Rocuronium or Vecuronium"]:::action C --> D["Maintenance: TIVA<br/>Propofol + Remifentanil"]:::action D --> E["Avoid ALL volatile anesthetics"]:::urgent E --> F["Avoid succinylcholine"]:::urgent F --> G["Safe alternatives:<br/>N₂O + TIVA acceptable"]:::action G --> H["Monitor: ETCO₂, temp, K⁺"]:::action H --> I["Dantrolene on standby in OR"]:::action ``` ### Why TIVA (Total Intravenous Anesthesia) is Gold Standard 1. **Propofol** (induction and maintenance) — non-triggering, rapid offset, antiemetic. 2. **Remifentanil** (opioid infusion) — ultra-short acting, allows rapid emergence. 3. **Non-depolarizing NMB** (rocuronium or vecuronium) — safe, no triggering. 4. **Nitrous oxide** (optional) — safe but often omitted in modern TIVA. **Mnemonic: "TIVA = Total Intravenous Anesthesia = Trigger-free Anesthesia"** - **T**otal = all drugs IV, no volatile - **I**ntravenous = propofol + remifentanil - **V**oid = volatile anesthetics - **A**void = succinylcholine ### Preoperative Counseling & Precautions - Inform patient of MH risk; discuss non-triggering plan. - Ensure dantrolene (36 vials, 20 mg each) is available in OR. - Use fresh CO₂ absorbent (volatile anesthetic residue can linger in old absorbent). - Have MH emergency protocol posted in OR. - Consider MH testing (caffeine halothane contracture test, genetic testing) if patient desires definitive diagnosis. **High-Yield:** Even with a non-triggering technique, maintain vigilance for signs of MH (↑ETCO₂, muscle rigidity, tachycardia, fever). MH can rarely occur with TIVA alone if patient is homozygous for RYR1 mutation, but risk is <1%. ### Why NOT the Other Options - **Option 1:** Isoflurane is a volatile anesthetic (TRIGGERING); succinylcholine is a depolarizing agent (TRIGGERING). Both are contraindicated. - **Option 3:** Desflurane is a volatile anesthetic (TRIGGERING); succinylcholine is TRIGGERING. Both contraindicated. - **Option 4:** Sevoflurane is a volatile anesthetic (TRIGGERING). Etomidate and vecuronium are safe, but the volatile agent makes this plan unsafe.