Suspected case of Malignant Hyperthermia during resection of a sacrococcygeal teratoma

Rita Banoub MD. Roby Sebastian MD, FRCA.

Nationwide Children’s Hospital and Ohio State University, Columbus, OH

Introduction

Malignant hyperthermia (MH) is an inherited disorder of skeletal muscle characterized by a hypermetabolic crisis when a susceptible individual receives a halogenated inhalational anesthetic agent or a depolarizing muscle relaxant. The incidence of MH reactions has been reported as 1:50000 anesthetics administered in adults to 1:15000 in children. MH is inherited as an autosomal dominant disease with variable penetrance or may also arise de novo. The pathophysiologic changes of MH are due to uncontrolled rise of myoplasmic calcium, which activates biochemical processes related to muscle activation. In most cases, the syndrome is caused by a defect in the ryanodine receptor. Over 90 mutations have been identified in the RYR-1 gene located on chromosome 19q13.1, and at least 25 are causal for MH. Case report We report a 37 weeks gestational age female neonate with a prenatal diagnosis of a large sacrococcygeal teratoma measuring 14x15 cms detected on ultrasonography. She was delivered by cesarean section, and follow up MRI demonstrated the tumor with an intraspinal extension up to the level of T4 vertebra, and formation of a posterior fossa arachnoid cyst. The patient was scheduled to undergo excision of the tumor on day of life 5. Patient arrived intubated to the operating room, standard ASA monitoring was applied, an arterial line was established and anesthesia induced with inhaled sevoflurane via endotracheal tube and a bolus of fentanyl. Anesthesia was maintained on sevoflurane and intermittent boluses of fentanyl. Patient remained hemodynamically stable during the first 4 hours of surgery, except for one episode of bradycardia and hypotension requiring a fluid bolus to which she responded appropriately.

During drain placement and defect closure, there was a sudden increase in heart rate reaching 235 bpm with stable blood pressure. This was associated with an elevated end-tidal carbon dioxide of 80 mmHg and temperature of 38.6° C which had increased from a baseline of 36.6° C. Patient was immediately treated with two successive doses of adenosine for diagnosis and treatment of supraventricular tachycardia with no change in heart rate. Malignant hyperthermia (MH) was suspected and treatment was immediately initiated as per the protocol. Sevoflurane was discontinued and anesthesia was maintained with intravenous midazolam, propofol and fentanyl. Patient was actively cooled with ice packs, hyperventilation was initiated and 2 doses of dantrolene 2.5mg/kg was administered. Within 20 minutes of treatment, both the heart rate and temperature decreased to base line values. Initial arterial blood gases revealed profound metabolic acidosis with the following values: pH-7.24/ PCO2-37/ PO2- 299/ base deficit-11/ HCO3-17. The acidosis resolved gradually on repeat testing. The patient remained stable and was transferred to intensive care unit (ICU) intubated and multiple blood samples were sent for creatinine phosphokinase (CPK) measurement. The follow up CPK levels were 165u/l,109u/l,113 u/l and 112u/l at 0, 6, 12 and 24 hours respectively. The postoperative course was uneventful and was extubated after 24 hours of observation in ICU.

Discussion

The diagnosis of MH is based on clinical presentation and/or laboratory testing. The main clinical diagnostic features of MH are unexplained elevation of end-tidal carbon dioxide (ETCO2) concentration, muscle rigidity, tachycardia, acidosis, hyperthermia, and hyperkalemia. The "gold standard" for diagnostic testing for MH is currently the in vitro contracture test (IVCT), which is based on contracture of muscle fibers in the presence of halothane or caffeine. There have been several case reports of MH in infants, however in majority of these cases the patients either did not undergo in vitro contracture testing (IVCT) or the test was proven to be negative. Also, IVCT performed in children less than 10 years often proved to be inconsistent due to immature muscle cells. Pyrexia, supraventricular tachycardia and sudden onset hypercapnia led to a clinical suspicion of MH in this case. Although a true incidence of MH in neonates has not been reported, survival from a malignant hyperthermia (MH) crisis is highly dependent on early recognition and prompt action and hence, treatment with dantrolene which is the cornerstone of successful MH treatment was instituted early. Although there has been no known association between sacrococcygeal teratoma and MH, the release of tumor necrosis factor or other mediators which have a thermogenic potential could explain the sudden onset of the symptoms seen. It is important that once a case of MH is suspected which resolved on stopping any trigger agents, the patient and their relatives should be further investigated whenever possible.

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