Anesthetic Considerations in a Patient with Myotonic Dystrophy for Hip Labral Repair
Introduction Myotonic muscular dystrophy (dystrophia myotonica) (DM) is a rare musculoskeletal disease with a prevalence of 1 in 8,000. This genetic disease requires significant considerations for patients in the perioperative period. Here we discuss the case of a patient with DM for labral hip repair and review the literature on the management and anesthetic concerns of DM.
Case Report Our patient is a 58-year-old Caucasian man weighing 92.9 kg, 175 cm tall, with a history of type 1 DM who presented for repair of a hip labral tear. His past medical history was significant for obstructive sleep apnea (OSA), gastroesophageal reflux disease, bicuspid aortic valve, bipolar disorder, obsessive-compulsive disorder, and cataracts.
His only prior anesthetic exposure was for cataract surgery and he had no complications. However, the patient's daughter, who also had DM, experienced severe respiratory depression following general anesthesia, requiring intensive care unit (ICU) admission postoperatively.
Primary considerations in relation to anesthesia include the disease's association with cardiomyopathy and cardiac conduction abnormalities, sensitivity to respiratory depression and ventilatory weakness, prolonged gastric emptying, and myoclonus triggered by stimuli such as hypothermia and specific medications.
Treatment Following the application of standard ASA monitors, a combined spinal and epidural anesthetic technique was performed successfully. Fifteen mg of isobaric bupivacaine was injected into the subarachnoid space at the L4-L5 interspace and an epidural catheter was inserted immediately. The spinal level was tested and found to be at a T10 dermatomal level. External pacer/defibrillator pads were applied and an arterial line was used for continuous blood pressure monitoring and to facilitate arterial blood gas measurements in the event of pulmonary compromise. A thermometer was placed in the patient's axilla for continuous monitoring. The operating room's ambient temperature was increased, a forced-air warming blanket was applied to the patient, and a fluid warmer was connected to his intravenous line. Intraoperatively, the patient received small (0.5 to 1 mg) boluses of midazolam titrated for a Richmond Agitation-Sedation Scale (RASS) of −3. For the 3 hour and 43 minute procedure, the patient received a total of 10 mg of midazolam and 50 mcg of fentanyl. Forty-five minutes into the surgical procedure the surgeon requested further relaxation of the patient's hip muscles and the epidural catheter was subsequently bolused with 5 mL of 2% lidocaine. Two hours into the procedure, another 5 mL of 2% lidocaine was bolused into the epidural. No complications were noted in the intraoperative period. The patient was transported to the postanesthesia care unit (PACU) with continuous SpO2, ECG, and blood pressure monitoring. A written consent was obtained from the patient for this case report.
Discussion Two genes have been identified as playing a role in the development of DM. A CTG expansion in DMPKgene results in type 1 (DM1), while an expansion in the ZNF gene results in type 2 (DM2).Although the functions of these genes are unknown, the CTG expansion of either gene results in faulty communication within the cell. The severity of the disease appears to correlate with the expansion repeats. DM affects multiple organ systems and patients may present with different symptomatology. A thorough assessment of the patient is critical to successful perioperative management. Poor preoperative assessment or undiagnosed DM in a surgical patient can lead to morbidity and mortality in the perioperative period.
Keywords Myotonic Dystrophy, Hip Labral Repair