From the Guidelines
Malignant hyperthermia can occur up to several hours after exposure to triggering agents, with the latest reported onset being 72 minutes after discontinuation of the inhalational agent 1. The timing of MH reactions is highly variable, and the onset may be delayed, especially with the use of certain anesthetics like desflurane 1. Some key points to consider:
- The diagnosis of an MH reaction has been made after the discontinuation of inhalational anaesthesia, with some cases reported to start during the anaesthetic but others clearly beginning after the discontinuation of the inhalational agent 1.
- The speed of progression of an MH reaction tends to be more rapid in those reactions that occur soon after administration of the triggering agents 1.
- The more florid reactions tend to occur when both suxamethonium and a potent inhalational anaesthetic have been administered 1. If malignant hyperthermia is suspected, even late, immediate treatment is crucial:
- Discontinue all triggering agents
- Administer dantrolene sodium (dosage as per clinical guidelines)
- Provide supportive care (cooling measures, manage acidosis, treat hyperkalemia) Healthcare providers should remain vigilant for signs of malignant hyperthermia, including rapid heart rate, increased body temperature, muscle rigidity, and elevated end-tidal CO2, even after patients leave the immediate post-operative period, especially in those with a family history or previous suspicious reactions 1.
From the Research
Latest Onset Time for Malignant Hyperthermia (MH)
- The latest onset time for malignant hyperthermia (MH) can vary, but according to the provided studies, it can occur up to 2 hours after exposure to triggering agents 2.
- A case report published in 2024 described a patient who developed MH 2 hours after electroconvulsive therapy (ECT) with succinylcholine, with symptoms reaching their peak in less than 24 hours 2.
- Another study published in 2019 reported a case of MH that occurred 70 minutes after induction of anesthesia with succinylcholine and desflurane, with treatment commencing 120 minutes after induction 3.
- A case report from 2007 described a patient who developed delayed-onset MH 90 minutes after exposure to sevoflurane, with gradual elevation in heart rate observed during the second exposure to the anesthetic agent 4.
- These cases highlight the importance of continuous monitoring and prompt diagnosis of MH, even after the initial exposure to triggering agents 5, 6.