In Response

Abstract

Dr. Setzer-Saade1 questions a malignant hyperthermia (MH) episode in a child without exposure to volatile anesthetics or succinylcholine. We now have the patient data reported to the North American Malignant Hyperthermia Registry of MHAUS via the AMRA (adverse metabolic/musculoskeletal to anesthesia) from 2004 and new information from the patient’s anesthesiologist, whose contact information was still accurate. This 2-year-old, 12.7-kg girl with a lean build presented for elective dental restorations due to dental caries (without known abscesses). She had a positive family history of MH but no personal history of muscle weakness, cramps, cola-colored urine, heat stroke or intolerance to heat, unexplained fevers, generalized infection, or exercise intolerance due to muscle pain, weakness, or fever. She did not have increased or decreased muscle tone, generalized muscle weakness, myopathy, ptosis, strabismus, hernia, clubbed foot, joint hypermobility, kyphosis, pectus carinatum, winged scapulae, skeletal fractures, or laryngeal papillomas. Her preoperative vital signs were arterial blood pressure 90/50 mm Hg, PR 115 beats per minute (bpm), respiratory rate 20 per minute, and oral temperature 98.2°F. This was her first anesthetic and the Ohmeda Excel 210 machine (not a workstation) was prepared by removing all anesthetic vaporizers, changing the soda lime in the carbon dioxide absorber, and flushing overnight with oxygen at 10 L/min. Monitoring included blood pressure, electrocardiograph, stethoscope, end-tidal PCO2, pulse oximeter, and both a skin liquid crystal temperature probe and an esophageal temperature probe. No forced air or IV warming device was used. She was well sedated with oral midazolam and accepted IV cannulation while breathing 30% nitrous oxide and 70% oxygen. Anesthetic drugs included IV propofol, IV morphine, nitrous oxide, and IV glycopyrrolate. Her trachea was intubated before the development of her adverse reaction. Fifteen minutes after induction, she developed an inappropriate rapidly increasing temperature with a maximum temperature of 41.6°C observed 25 minutes after induction. Thirty minutes after induction, her maximum expired CO2 was considered by the reporting anesthesiologist to be inappropriately increased to 52 mm Hg, despite assisted manual ventilation. Twenty-eight minutes after induction (13 minutes after her first adverse sign), she was given a dantrolene dose of 2.5 mg/kg and received a total of 3.9 mg/kg before her transfer to a children’s hospital. Other treatment included hyperventilation with 100% oxygen, active cooling, fluid loading, and IV sodium bicarbonate. Less than 5 minutes after dantrolene, her temperature began to decrease. After the adverse reaction, she had received midazolam and rocuronium, but her trachea was extubated with stable vital signs before transport. Forty-two minutes after induction, breathing 100% oxygen, arterial blood gas was pH 7.18, PCO2 52 mm Hg, PO2 515 mm Hg, BE −8.4 mEq/L, bicarbonate 19 mEq/L, and potassium 3.9 mEq/L. There was no bleeding tendency. Creatine kinase values were not reported because they were obtained at the facility to which she was transferred. Scheduled dental restorations were not completed. Additional adverse signs associated with MH did not recur. Sepsis workup was negative, and she was discharged the next day with an MH diagnosis. Diagnostic muscle biopsy and molecular genetic analysis were not performed. The clinical grading scale ranking for this patient’s event was “almost certain” MH.2 Did she really have MH instead of iatrogenic warming or sepsis? She had a brief anesthetic without external warming, her teeth were not abscessed, her sepsis workup was negative, and she was discharged on postoperative day 1. We judge that the most likely diagnosis was MH. If it was MH, what triggered this episode? Given the preparation of the anesthesia machine preoperatively, it is unlikely due to trace volatile anesthetics. Most likely, this episode was triggered by unknown factors. This has happened in known MH-susceptible individuals who receive “non-MH triggering” anesthetics.3,4 “Until we understand the mechanism of human MH triggering, no anesthetic regimen can guarantee safety”5 underscoring the need for vigilance. Marilyn Green Larach, MD, FAAP The North American Malignant Hyperthermia Registry of MHAUS and Penn State College of Medicine Hershey, Pennsylvania [email protected] Gerald A. Gronert, MD The North American Malignant Hyperthermia Registry of MHAUS and University of California at Davis Davis, California Gregory C. Allen, MD, FRCPC The North American Malignant Hyperthermia Registry of MHAUS and Olympia Anesthesia Associates Olympia, Washington Barbara W. Brandom, MD The North American Malignant Hyperthermia Registry of MHAUS and Children's Hospital and the University of Pittsburgh Pittsburgh, Pennsylvania Erik B. Lehman, MS Penn State College of Medicine Hershey, Pennsylvania