Published cases of MH in young children are not common. That’s why this report out of Japan caught my eye this week. Tsutsumi et al. reported a 16-day-old female who was undergoing laparoscopic repair of a congenital diaphragmatic hernia under general anesthesia with sevoflurane and rocuronium. Thirty minutes after induction, the infant developed abdominal wall rigidity, and the anesthesiologist simultaneously noted her body temperature to rise quickly from 36.7 °C to 39.4 °C. Over the next hour, her ETCO2 increased from 42 to 100 mmHg despite hyperventilation, and she became tachycardic to 203 bpm. Her SpO2 dropped to 85% and her trunk and limbs were noted to be rigid. The team then initiated their MH treatment protocol: They discontinued the sevoflurane, hyperventilated with 100% O2, instituted cooling measures, and administered dantrolene, 1 mg/kg loading dose, followed by 7 mg/kg/h for 10 min. Following these measures, the patient’s vital signs soon normalized and the muscular rigidity resolved. The procedure was aborted, and she was then returned to the PICU where she recovered, although additional doses of dantrolene were not reported. The CDH was eventually repaired uneventfully using a non-triggering anesthetic technique.
The most interesting aspect of this case is the genetic analysis for MH-causative variants. On subsequent testing, the patient was found to harbor two known MH-causative variants, one of which was inherited from each parent. Talk about bad luck!
I have some minor quibbles with the reported management. First of all, the authors report that dantrolene was not administered until 30 minutes after noting the abdominal rigidity, while all other signs were indicative of MH. Remember, rigidity during neuromuscular blockade is essentially pathognomonic for MH. It’s certainly OK to investigate the cause of the rigidity at first, but if the ETCO2 and body temp are rising rapidly, it’s MH until proven otherwise and should be treated immediately. Second, they used a loading dose of dantrolene of 1 mg/kg then an infusion of 7 mg/kg/h for 10 min, presumably until the rigidity and ETCO2 normalized, but it’s hard to tell from the report. MHAUS currently recommends a loading dose of 2.5 mg/kg, followed by additional boluses of 1 mg/kg until signs of MH begin to resolve. We then recommend additional boluses of 1 mg/kg for at least 24 hours after the acute episode to prevent recrudescence. Dantrolene infusions are no longer recommended because of unknown IV solution compatibility issues. Fortunately, this child had a good outcome.
Is this the youngest confirmed case of MH ever reported? It seems so, although another unconfirmed case seems pretty convincing. In 1980, Sewall reported a newborn who developed severe rigidity soon after delivery by emergency Caesarean section under general anesthesia with halothane and succinylcholine. The infant’s blood gas and CK values were markedly abnormal and supported the diagnosis of MH. It doesn’t appear from the case that dantrolene was administered, and the infant recovered gradually in the NICU.
So when your attending pimps you and asks what is the youngest reported case of MH, you can say “definitely 16 days, but probably at birth”.
I hope you have a relaxing weekend. For those of you on call, may your days and nights be quiet.
And remember…who ya gonna call? 800-MH-HYPER