P034: ANESTHETIC CONSIDERATIONS IN PATIENTS WITH MYOTONIC DYSTROPHY
Chirag Y Patel, DO; Daniel Perez, MD; University of Miami/Jackson Memorial Hospital
Myotonic dystrophy, specifically type 1 (Steinhart Disease), is an autosomal dominant disorder that prevents individuals from being able to relax voluntary contracted muscles. It occurs as a result of a defect in the CTG repeat on the DMPK gene which causes dysfunctional adenosine triphosphate (ATP). This prevents calcium influx to the sarcoplasmic reticulum. Patients can have a variety of complications including, but not limited to, decreased ventilatory response to hypercarbia; myotonic crisis; delayed recovery from neuromuscular blocking agents; restrictive lung disease; weakened pharyngeal muscles; cardiac conduction abnormalities; and gastrointestinal reflux. Type 1 myotonic dystrophy (DM1) has an incidence of 2.1 to 14.3 per 100,000 with onset occurring at any age of life. Individuals with DM1 have several anesthetic considerations to consider. A report of DM1 in a 30-year-old Hispanic male with obstructive sleep apnea secondary to inferior turbinate hypertrophy and nasal septal deviation underwent septoplasty under general anesthesia. Patient was diagnosed with EMG, without genetic screening. The patient had no other past medical history other than DM1 and obstructive sleep apnea, and had no complications from his myotonic disease. He did have appropriate work up performed preoperatively, however. Patient had echocardiogram completed to evaluate for dilated cardiomyopathy and mitral valve prolapse, both of which are complications of DM1. Echocardiogram showed ejection fraction of 65% with normal wall motion, no evidence of left ventricular hypertrophy, and no evidence of mitral valve prolapse. Electrocardiograph showed no cardiac conduction abnormalities with normal sinus rhythm. He was premedicated with midazolam 2 mg IV. Patients with DM1 normally have RSI performed due to delayed gastric emptying and oropharyngeal muscle weakness, however since this patient had no symptoms of reflux we proceeded with standard induction. He was induced with propofol 150 mg IV, and then given rocuronium 30 mg IV. Individuals with DM1 have prolonged effects to sedation and enhanced muscle weakness, therefore a low dose of rocuronium was used. Succinylcholine was avoided as the fasciculations can prompt worsening myotonia and spasm that could impair ventilation and lead to possible myotonic crisis. Patient was maintained on sevoflurane and dexmedetomidine at a rate of 0.4 mcg/kg/hr during the case, as the goal was to emerge the patient as smoothly as possible to avoid myotonic crisis. He was kept warm during the case with a full body warming device, as well as given IV fluids on a hot line to avoid hypothermia and shivering, which may provoke myotonia. For pain management opioids were avoided in order to decrease prolonged recovery time. Patient was given acetaminophen 1000 mg PO preoperatively and ketorolac 30 mg IV near the end of the procedure. He was reversed with weight dose appropriate sugammadex, because administering neostigmine can cause incomplete reversal and increased postoperative complications. With careful anesthetic considerations applied, patients with DM1 can undergo safe general anesthesia.