Erythrocyte osmotic fragility testing and the prediction of canine malignant hyperthermia susceptibility.

A Doberman-German Shepherd cross-bred male dog, previously diagnosed as malignant hyperthermia susceptible, was mated to an unrelated nonsusceptible German Shepherd cross-bred female. The resultant litter was subjected to hematological, biochemical and erythrocyte osmotic fragility testing in an endeavor to predict the susceptibility of individuals to malignant hyperthermia. Laboratory evaluations were repeated at one year of age and the litter subjected to the halothane challenge test. No significant difference in erythrocyte osmotic fragility was found between malignant hyperthermia susceptible and nonsusceptible siblings at six weeks or at one year of age. Erythrocyte osmotic fragility, in both malignant hyperthermia susceptible and nonsusceptible animals, increased between six weeks and one year of age. Dantrolene sodium was an effective treatment for malignant hyperthermia in the dog when administered early in an episode and in adequate dosage. The initial sign of a malignant hyperthermia episode was a very rapid increase in end tidal partial pressure of carbon dioxide. This finding reinforces the value of capnographic monitoring in anesthesia.