Myotonic Dystrophy Foundation

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Neal Campbell, M.D.1, Barbara Brandom, M.D. 2, John W. Day, M.D., Ph.D. 3, Richard Moxley, M.D. 4
1 Fellow, Pediatric Anesthesiology, Department of Anesthesiology, University of Pittsburgh School of Medicine, Children’s Hospital of Pittsburgh, UPMC, Pittsburgh, PA
2 Professor, Department of Anesthesiology, University of Pittsburgh School of Medicine, Children’s Hospital of Pittsburgh, UPMC, Pittsburgh, PA
3 Professor, Department of Neurology, University of Minnesota School of Medicine, University of Minnesota Medical Center, Fairview, Minneapolis, MN
4 Professor, Department of Neurology, University of Rochester School of Medicine and Denistry, University of Rochester Medical Center, Rochester, NY
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FOREWORD:

The anesthetic management of patients with myotonic dystrophy (dystrophia myotonica, DM) can be challenging. “Complications are not proportional to the severity of the disease; they often arise in mildly affected patients” (15). Indeed, there are multiple reports within the medical literature that detail poor outcomes related to the following complications: loss of airway secondary to medication-induced respiratory depression; aspiration of stomach contents; sudden death that is usually secondary to cardiac conduction delays and dysrhythmias. One must consider if, in light of these complications, “regional anesthesia is a viable alternative or if the surgical procedure is really necessary” (15).

The following points about myotonic dystrophy in this foreword can help a vigilant anesthesiologist avoid complications and provide safe anesthesia care to DM patients presenting for surgery:

1. General: “Myotonia” is described as muscle contraction (voluntary or otherwise) with abnormal, prolonged relaxation (3). Triggers for myotonia include certain medications, potassium, hypothermia, shivering, or any mechanical or electrical stimulus (2, 3, 4). Patients also exhibit profound skeletal muscle weakness secondary to muscle degeneration.

2. Medications: DM patients are exquisitely sensitive to the respiratory depressant effects of anesthetic medications (3). Be sure to have appropriate airway and monitoring equipment available when using these medications, and prepare for the likelihood of postoperative mechanical ventilation until strict extubation criteria are met. In addition, postoperative pain control should be managed with NSAIDs, regional techniques using local anesthetics, and acetaminophen when possible. If opioids are employed (systemic or neuraxial), then ICU care and continuous pulse oximetry must be considered given the high risk for respiratory depression and aspiration.

3. Airway: Rapid sequence induction with cricoid pressure is recommended. Weakness of the pharyngeal muscles and a delayed gastric emptying time predispose DM patients to aspiration (3, 21). Also, succinylcholine effects are unpredictable in DM patients: one case report describes jaw rigidity and impossible intubation after succinylcholine administration (19); prolonged laryngospasm and cyanosis has been reported in myotonia congenita, but could theoretically also occur in DM (20). Avoid succinylcholine when possible.

4. Respiratory System: The effects of myotonic dystrophy on the respiratory system are profound and common (1, 24). Respiratory muscle weakness predisposes DM patients to restrictive lung disease with concurrent dyspnea and ineffective cough (3). Moreover, arterial hypoxemia and a diminished ventilatory response to hypoxia and hypercapnia are frequent associations (3). Accordingly, these factors place DM patients at an increased risk for pneumonia and other perioperative pulmonary complications (1). Ventilatory weakness contributes to the complex sleep disorders of DM, which frequently results in profound pre-operative sleep deprivation that further complicates post-anesthetic care.

5. Cardiac System: DM patients can have cardiac abnormalities that may lead to sudden death secondary to various cardiac conduction delays or other dysrhythmias (3, 6). Thoroughly evaluate the cardiac system – including echocardiogram, 12-lead EKG, and interrogation of the internal cardiac rhythm device (if present) – before any anesthetic care is given.

6. Central Nervous System: The many CNS effects of DM further complicate perioperative care. For example, behavioral and cognitive problems in the patient and other family members can complicate pre-operative preparation. Hypersomnia is a common and sometimes the primary manifestation of DM that can result from a narcolepsy-like central hypersomnia as well as sleep-related ventilatory insufficiency or obstructive sleep apnea, any of which can lead to profound sleep deprivation in the pre-operative period as well as multiple management difficulties post-anesthesia. Also, DM subjects have heightened CNS sensitivity to sedatives, anxiolytics and analgesics, further impeding ventilatory drive and airway protection. Perioperative casualties often develop several days post-operatively due to aspiration or inadequate monitoring of hypoxia, during the period in which DM patients become increasingly encephalopathic due to sleep deprivation or the unintended effects of medication.

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