The Journal of the Arkansas Medical Society Med Journal Aug 2019 Final 2 | Page 18

Malignant Hyperthermia: When You Least Expect It Benjamin K. Woodle, MD; Daniel Bingham, MD; Tolga Suvar, MD; Jill Ramsey, MD; Alvin Stewart, MD Background M alignant hyperthermia (MH) is a rare genetic condition that predisposes 1:15,000 pediatric patients and 1:40,000 adult patients to a hyper-metabolic state resulting in abnormal muscle contraction predominant after exposure to an offending agent such as volatile anesthetics or succinylcholine. Other manifestations of MH include rising EtCO 2 , acidosis, hyperkalemia, rhabdomyolysis, myoglobinuria (“Coca-Cola colored urine”), and hyperpyrexia. Onset of symptoms vary, from immediate to several hours after exposure. Early efforts attempting to determine the mechanisms of MH focused on the gene for the ryanodine (Ryr1) receptor. This particular receptor is an ion channel responsible for calcium release from the sarcoplasmic reticulum, and it plays an important role in muscle depolarization. Subsequent genetic studies in humans have revealed at least five different chromosomes and more than 180 individual mutations associated with MH. Most patients with an episode of MH have an indicative family history that includes a relative who has an “anesthetic allergy” or possible death resulting from a reaction to anesthesia. Thus, a pre-op evaluation consisting of a family history There are not many side effects to treating MH with dantrolene; whereas, the end result of not treating MH promptly is death. of anesthetic complications is always important prior to surgery. With high clinical suspicion, a proper diagnosis can be made with a muscle biopsy and a halothane-caffeine contracture test. In many of the early reported cases, both succinylcholine and a halogenated anesthetic agent were used. Of note, and interestingly, nearly 50% of patients who experience an epi- sode of MH have had at least one previous un- eventful exposure to anesthesia, during which they received a recognized triggering agent. MH is most commonly triggered by inhaled, haloge- nated volatile anesthetics such as sevoflurane, isoflurane, desflurane, and halothane; but it can also be triggered by the depolarizing muscle re- laxant succinylcholine. A halogenated anesthetic agent alone may trigger an episode of MH; how- ever, the prevalence of MH with exposure to suc- cinylcholine only, has been controversial. There has been doubt that succinylcholine, alone, causes MH crisis in susceptible individuals. 1,2 However, data from the MH registry and new data from the Canadian MH experience show that MH crisis can be induced by succinylcholine administration alone. 3-5 Case Report A 20-year-old Caucasian male, with an un- known past medical history, was a restrained driver involved in a MVC. Upon EMS arrival, his GCS was 5, interosseous access was obtained, and the patient was intubated with succinylcho- line and ketamine for airway protection at the scene. A level-one trauma was activated, and the patient was transported to the trauma center via med flight. On arrival to the trauma bay, vital signs were GCS 6T, HR 163, BP 70/32, sp02 99% and EtCO2 45, with no obvious injuries on pri- 42 • THE JOURNAL OF THE ARKANSAS MEDICAL SOCIETY mary or secondary survey. Vital signs were Temp 40.8C, HR 130, BP 144/34, spO2 100, etCO2 53. iSTAT showed a pH of 7.30, PCO2 28, and HCO3 of 14.3. The patient was given 650mg Tylenol via NG tube and started on Propofol and fentanyl for sedation. A CT scan was then obtained and showed no intracranial or intraabdominal injury and was only significant for a transverse fracture of L1 vertebrae. Patient was taken back to the trauma bay, where a Foley catheter was inserted revealing dark urine. The patient’s temperature continued to rise to 41.3C. The first set of labs returned and were significant for potassium of 6.0, Cr 2.2, Lactate 6.0, CK 1688, and tropo- nin 2.99. ABG 7.06/58/92/16.8 on (SIMV 90% 600/20/11). A cooling blanket was placed over the intubated patient, with ice packs placed around his head and extremities; cold intrave- nous fluids were started. The patient continued to have hypercarbia, with EtCO2 peak at 100. The decision was made to initiate dantrolene therapy for suspected malignant hyperthermia. The patient received a total of four doses of dan- trolene, dosed at 2.5mg/kg, with improvement in both temperature and etCO2. The patient was transferred to the ICU, where dantrolene admin- istration was continued at 1mg/kg/hr. The pa- tient later developed multi-system organ failure due to rhabdomyolysis and severe acidosis. The family elected to make the patient DNR, and he was pronounced shortly thereafter. Discussion Attributing to the rarity of malignant hyper- thermia, most health care providers do not have a high clinical suspicion to make this diagnosis. However, in the presence of an offending agent such as succinylcholine and/or halogenated-vol- VOLUME 116