Perioperative management of malignant hyperthermia: BJA Consensus Guideline
Delhi: The European Malignant Hyperthermia Group has released consensus guidelines on perioperative management of malignant hyperthermia suspected or susceptible patients.
Malignant hyperthermia (MH) is a potentially fatal condition, in which genetically predisposed individuals develop a hypermetabolic reaction to potent inhalation anaesthetics or succinylcholine. Because of the rarity of malignant hyperthermia and ethical limitations, there is no evidence from interventional trials to inform the optimal perioperative management of patients known or suspected with malignant hyperthermia who present for surgery.
Furthermore, as the concentrations of residual volatile anaesthetics that might trigger a malignant hyperthermia crisis are unknown and manufacturers' instructions differ considerably, there are uncertainties about how individual anaesthetic machines or workstations need to be prepared to avoid inadvertent exposure of susceptible patients to trigger anaesthetic drugs.
The guideline, published in the British Journal of Anaesthesia, are intended to bundle the available knowledge about perioperative management of malignant hyperthermia-susceptible patients and the preparation of anaesthesia workstations.
Key recommendations include:
- Indications for pharmacological premedication are the same for MH-susceptible patients as those not predisposed to MH.
- Only trigger-free anaesthesia should be used in all MH-susceptible patients.
- If trigger-free anaesthesia is provided, then an MH-susceptible patient will not need any extra monitoring during anaesthesia compared with a patient with the same condition and preoperative status, but not predisposed to MH.
- MH-susceptible patients can receive standard care in the recovery room (PACU) after surgery.
- MH-susceptible patients may be anaesthetised in an outpatient setting avoiding all volatile anaesthetics and succinylcholine whilst following national guidelines for ambulatory general anaesthesia.
- Specific pre- or postoperative blood tests are not necessary in MH-susceptible patients.
- Anaesthetic breathing circuit (T-circuit, circle circuit, and reservoir bag) and soda lime should be changed for uncontaminated equipment before the anaesthesia machine is flushed.
- Anaesthesia machine and breathing circuit should be flushed with a maximum fresh gas flow of at least 10 L min−1 (oxygen, air, or any mixture) throughout the preparation period.
- In the absence of specific recommendations from the manufacturer, during machine preparation, the tidal volume can be set at 600 ml and ventilatory frequency at 15 bpm for an adult patient when mechanical ventilation is used.
- Activated charcoal filters licensed for this purpose, which effectively reduce volatile anaesthetic concentrations to <5 ppm, may be used to minimise anaesthesia machine preparation time.
- Reduce fresh gas flow from >10 to 3 L min−1 when activated charcoal filters (ACFs) are placed and breathing circuit and soda-lime canister are changed.
- After ACFs are placed and breathing circuit and soda-lime canister are changed, usual fresh gas flows can be used with a minimum of 1 L min−1.
- Activated charcoal filters should be kept in place during the entire general anaesthesia procedure.
"These guidelines from the EMHG describe how to minimise the risk of triggering an MH reaction when preparing to anaesthetise MH-susceptible patients. This includes preparation of the anaesthetic workstation for safe and trigger-free general anaesthesia, with and without the use of ACFs. The guidelines are based on available evidence and the opinions of MH experts from a large group of laboratories studying MH around the world," wrote the authors.
"Consensus guidelines on perioperative management of malignant hyperthermia suspected or susceptible patients from the European Malignant Hyperthermia Group," is published in the British Journal of Anaesthesia.