A 6-year-old child has had repeated episodes of otitis media. She undergoes an uneventful surgical placement of pressure-equalization (PE) tubes. In the recovery room, she develops a fever of 40degC (104degF), rigidity of her muscles, dark colored urine, and metabolic and respiratory acidosis. Which of the following therapies is most likely to be beneficial for this child's condition?

In addition to the findings listed in the question, patients experiencing malignant hyperthermia (MH) also have clinical findings of tachycardia, arrhythmia, tachypnea, and cyanosis, as well as laboratory findings of myoglobinuria, elevated serum creatine kinase levels, and evidence of acute renal failure. This myopathy is usually inherited as an autosomal dominant trait; the gene is on chromosome 19 and codes for the ryanodine receptor, a calcium release channel. A family history of similarly affected relatives would suggest the need to evaluate all family members for this condition; prevention (or treatment) is with dantrolene sodium. The test of choice to identify a patient at risk for this condition is the caffeine contracture test, in which a muscle biopsy tissue specimen is attached to a strain gauge and then exposed to caffeine. Patients at risk for MH have a diagnostic muscle spasm. Ryanodine receptor (RYR1) gene sequencing is also available.Acidification of the urine might be helpful for an aspirin overdose, but the child has no history of having aspirin ingestion. The findings in the question do not support tetanus (immunoglobulins not helpful) nor seizure activity (diazepam not indicated). The rapid nature of this child's change in status makes septicemia unlikely; antibiotics and blood cultures likely are not warranted.