Learning Objective Recognize nonspecific and delayed presentations of malignant hyperthermia (MH).
Case A 22-year-old male was admitted with drug overdose. He was found to be afebrile and drowsy with shallow respirations in the ER and was intubated for airway protection. CXR showed a right lower lobe infiltrate. Five hours later in the MICU, he was noted to be flushed and tachycardic with a temperature of 104.8°C. Cultures were obtained; Tylenol and antibiotics administered with a cooling blanket applied later. A review of medications given in the ER revealed succinylcholine. A CPK level of 37,789 U/L, elevated urine myoglobin, and high fever suggested malignant hyperthermia with rhabdomyolysis. The patient became normothermic after two doses of dantrolene. He was counseled about MH on discharge.
Discussion MH is a rare genetic disorder due to the mutations of ryanodine receptor in skeletal muscles. It usually occurs after administration of inhaled anesthetics or depolarizing muscle relaxants. Clinical features include marked fever, muscle rigidity, metabolic acidosis, rhabdomyolysis and hemodynamic instability. Hyperthermia develops within minutes to hours following exposure to disease-inducing medications. Many of the early signs are nonspecific and can mimic those of other etiologies. In our case, delayed diagnosis of MH was due to not only late-onset hyperthermia, but also initial attribution of his fever to aspiration pneumonia. Treatment includes discontinuation of triggering agents, oxygenation and use of dantrolene along with cooling measures. This case demonstrates the variability of presentation and underscores the need for continuous monitoring whether in a surgical or medical setting.