(3) All cases are not reported to MH registries such as the North American Malignant Hyperthermia Registry (NAMHR). The initial symptoms of MH are not specific. These and other factors lead to under reporting.

Registries such as the NAMHR are one method of disease monitoring. Recently, it has been appreciated that applying the same approach used in wildlife biology can be used to estimate the frequency of disease occurrence in humans. This method is called capture-recapture (9).

(4) Triggering of MH even in susceptible patients may not occur

- There were MH susceptible patients who had no problems during one or more anesthetics only to have MH triggered on a subsequent anesthetic. The reason for this is unclear.

(5) Lack of uniform criteria for the clinical diagnosis of MH

- First published in 1994, the clinical grading scale for MH was developed to overcome this problem (10).