Can a patient with a history of Malignant Hyperthermia (MH) who previously tolerated inhalation gas anesthesia safely receive inhalational gas for subsequent anesthetics?

Patients with History of Malignant Hyperthermia Should Not Receive Inhalational Anesthetics Even If They Previously Tolerated Them

Patients with a history of malignant hyperthermia (MH) must not be exposed to inhalational anesthetics or succinylcholine, regardless of whether they previously tolerated these agents without incident. 1

Rationale for Avoiding Inhalational Anesthetics in MH-Susceptible Patients

Understanding MH Risk

• MH is a potentially fatal pharmacogenetic disorder affecting skeletal muscle when susceptible individuals are exposed to triggering agents 2
• Triggering agents include all potent inhalation anesthetics (desflurane, sevoflurane, isoflurane, halothane) and succinylcholine 1
• Previous uneventful exposure to triggering agents does not guarantee future safety:
  • MH can manifest with delayed onset, even after previous uneventful exposures 3
  • The syndrome has variable penetrance and expressivity 4

Scientific Basis

• The European Malignant Hyperthermia Group (EMHG) provides a strong recommendation that "only trigger-free anesthesia should be used in all MH-susceptible patients" 1
• The Association of Anaesthetists guidelines (2021) clearly state that "patients at increased risk of developing MH must not be exposed to potent inhalational anesthetics or suxamethonium" 1
• The lowest vapor concentration of volatile anesthetic that can trigger MH in humans remains unknown, making any exposure potentially dangerous 1

Safe Anesthetic Management for MH-Susceptible Patients

Anesthetic Options

1. Regional or local anesthesia is preferred when appropriate 1
2. Total intravenous anesthesia (TIVA) is the recommended approach when general anesthesia is required 1
   • Avoid all volatile anesthetics and succinylcholine
   • Follow established guidelines for safe TIVA practice

Preparation of Anesthetic Workstation

When preparing for an MH-susceptible patient, the anesthetic machine must be properly prepared:

If adequate preparation time is available:

• Remove vaporizers from anesthetic workstation
• Change anesthetic breathing circuit and soda lime canister
• Flush circuit with oxygen or air at maximum flow rate for workstation-specific time 1

If time is limited:

• Remove vaporizers from anesthetic workstation
• Flush circuit with oxygen or air at maximum flow rate for 90 seconds
• Insert activated charcoal filters (ACFs) on both inspiratory and expiratory limbs
• Change anesthetic breathing circuit and soda lime canister 1

Common Pitfalls and Caveats

Key Misconceptions to Avoid

• Previous uneventful exposure does not guarantee safety: A patient may have an MH reaction even after previously tolerating triggering agents 3
• Severity is unpredictable: MH reactions can range from mild to fulminant and potentially fatal 5
• Delayed onset is possible: MH can manifest after a significant delay from anesthetic induction 3

Important Clinical Considerations

• The mortality from MH has decreased from over 80% thirty years ago to less than 5% with proper management 6
• This reduction in mortality is largely due to avoiding triggering agents in susceptible individuals and prompt treatment with dantrolene when MH occurs 2
• Even if a patient previously tolerated inhalational anesthetics, the risk of a potentially fatal MH reaction outweighs any benefit of using these agents when safe alternatives exist 1

Conclusion

The scientific evidence and expert guidelines are clear: patients with a history of MH should never receive inhalational anesthetics or succinylcholine, regardless of previous tolerance. Safe alternatives such as regional anesthesia or TIVA with a properly prepared anesthetic workstation should always be used to minimize morbidity and mortality risk.