Malignant hyperthermia is rare...but there’s no time to waste when it happens.
It occurs from exposure to anesthetic gases (sevoflurane, etc) or succinylcholine...in patients at risk due to a genetic mutation.
These patients can have muscle rigidity, hyperthermia, tachycardia, or hypercapnia from uncontrolled calcium release in the muscle. This can lead to rhabdomyolysis, arrhythmias, and death.
Keep in mind, it’s not just a risk in surgery. It can happen up to an hour after exposure and anywhere succinylcholine is given.
Start treatment within 10 minutes of symptom onset. Give dantrolene 2.5 mg/kg IV push to stop calcium release.
Repeat every 5 minutes prn for ongoing muscle rigidity or other symptoms. Patients rarely need more than 10 mg/kg total.
Ensure turnaround times can be met by using kits and routinely performing mock drills. Regulatory agencies may ask about these.
Keep enough dantrolene in-house to manage a crisis. Most guidance recommends at least 36 vials of dantrolene 20 mg (Revonto, etc) or 3 vials of 250 mg (Ryanodex) to treat one patient who’s about 70 kg.
Ryanodex costs about $8,500...versus $2,500 for the 20 mg vials. But Ryanodex is faster to prep, since it requires fewer vials and less diluent.
In your kits, include sterile water vials to prep dantrolene. Avoid 1 L bags due to potential mix-ups with other IV fluids.
Also include the 24-hour hotline (800-MH-HYPER) in your kit to reach malignant hyperthermia specialists for guidance.
Cool patients with temps above 39°C with a protocol (cooled IV saline, external cooling devices, etc) until temp falls below 38°C.
Check labs and treat other complications as needed...such as hyperkalemia, acidosis, or arrhythmias.
Don’t treat tachycardia with verapamil or other CCBs. Using them with dantrolene may cause hyperkalemia and cardiac arrest.
Once the patient stabilizes, give dantrolene 1 mg/kg every 4 to 6 hours for at least 24 hours...since malignant hyperthermia symptoms recur in about 1 in 5 patients.
If a patient with a history of malignant hyperthermia presents for surgery, don’t pretreat with dantrolene. Expect other anesthetic strategies, such as IV agents instead of volatile gases.
- https://www.mhaus.org/healthcare-professionals/ (3-1-23)
- Anesth Analg. 2019 Apr;128(4):652-659
- Anesth Analg. 2019 Aug;129(2):347-349
- J Am Coll Clin Pharm. 2023 Jan 30. doi: 10.1002/jac5.1762
- Medication pricing by Elsevier, accessed Feb 2023