Page 33 - CASA Bulletin of Anesthesiology 2022, Vol 9, No 1 (1)

Vol. 9, No 1, 2022

side effects (i.e., thrombophlebitis, weakness, nausea) comparable to the older generic versions
of dantrolene.

In most cases of likely MH, signs of hypermetabolism (i.e., hypercarbia) will begin to
decrease shortly after the initial bolus of dantrolene. Some patients will require additional doses
for signs of hypermetabolism to completely abate. MHAUS recommends redosing dantrolene (1
mg/kg following the initial 2.5 mg/kg bolus) as frequently as needed until the patient responds
with a decrease in ETCO2, decreased muscle rigidity, and/or lowered heart rate.

Dantrolene has no effect on cardiac or smooth muscle. Its most common local adverse
reaction is venous irritation or thrombosis at the site of administration due to its high pH; side
effects include nausea, malaise, lightheadedness, and mild to moderate muscle weakness.

Counseling after an MH crisis

Following recovery from a suspected acute MH event, testing for MH susceptibility should
be offered to the patient and family members. Evaluation and management for MH susceptibility
should be performed with necessary testing (i.e., genetic testing, halothane contracture muscle
biopsy).

Until necessary testing has been performed, patients should not have anesthesia with
triggering agents and avoid exercise in excessive heat, particularly with high humidity, as this
may trigger an event. They should wear a conspicuous identifier (i.e., MedicAlert bracelet)
indicating that they are MH susceptible, to inform medical providers in an emergency and should
inform family members of the possible MH episode. MHS is a genetic condition and blood
relatives at risk may need to be evaluated.

American and International resources and society guidelines should be offered to all MH
susceptible patients. These include, but not limited to, MHAUS, European Malignant
Hyperthermia Group (EMHG): Consensus guidelines on perioperative management of malignant
hyperthermia suspected or susceptible patients, Malignant Hyperthermia Group of Australia and
New Zealand (MHANZ): Malignant hyperthermia resource kit, and Japanese Society of
Anesthesiologists (JSA): Guideline for the management of malignant hyperthermia crisis, 2016.

References

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