Dexmedetomidine and fentanyl combination for procedural sedation in a case of Duchenne muscular dystrophy.

Duchenne muscular dystrophy, an X-linked disorder characterized by progressive muscle weakness, is the most common muscular dystrophy among children leading to death before the end of third decade. Anesthesia in such patients pose a great challenge due to various complications associated with it. The dreaded metabolic and clinical complications occur due to various inhalational anesthetics and succinylcholine in this subset of patients. We are reporting a child with diagnosed Duchenne muscular dystrophy who underwent excision of dentigerous cyst in oral cavity under procedural sedation with combination of dexmedetomidine and fentanyl and thus administration of general anesthesia was avoided.

INTRODUCTION

Neuromuscular diseases and muscular dystrophies have always been challenging to the attending anesthesiologist whenever such patients present for surgery. These disorders are invariably associated with various co-morbid diseases that further heighten the degree of difficulty for the concerned anesthesiologist. Duchenne muscular dystrophy is one of the most common muscular dystrophy in children with an incidence of 1 in 3500 live births and is transmitted by X-linked inheritance.[1] The patients invariably develop cardio respiratory complications during growth that can ultimately prove to be fatal. The affected children start developing the progressive degeneration of skeletal, cardiac, and smooth muscles as early as third year of life. Administration of anesthesia in such patients is associated with numerous challenges and can result in varied spectrum of metabolic and clinical complications such as rhabdomyolysis, metabolic derangements, malignant hyperthermia, cardiac arrhythmia and death. These adverse effects are usually associated with general anesthesia and the implicated pharmacological agents being succinylcholine and inhalational anesthetic agents. We are reporting a 12-year-old male child suffering from Duchenne muscular dystrophy who presented to the oral and maxillofacial department for possible excision of symptomatic and painful dentigerous cyst. The case was managed with a combination of dexmedetomidine and fentanyl for procedural sedation and thus avoided the need for general anesthesia by a thorough pre-operative counseling of the mother and the child.

CASE REPORT

A 12-year-old boy presented to the oral and maxillofacial surgery department of our institution with swelling in lower jaw since 6 months, which progressively increased in size and was painful. It was diagnosed to be dentigerous cyst that required excision due to its painful symptomatology. He was an established case of Duchenne muscular dystrophy since childhood and was confined to wheel chair since then. The child had no history of recent upper respiratory tract infection or previous anesthetic exposures. On physical examination, the weight of the child was measured to be 48 kg and he had wasting of muscles in both the lower limbs with motor power of grade II. Airway examination revealed mouth opening of >3 cm with modified Mallampati grade of II, normal thyromental and mento-hyoid distance and normal range of neck movements [Figure 1]. Examination of the back revealed a mild scoliosis involving the thoraco-lumbar region with convexity toward the right side. Cardiovascular and respiratory system examination was unremarkable. The laboratory investigations were all within normal limits except for raised creatine kinase levels of 1823 IU/L (normal 75–230). The electrocardiography showed sinus tachycardia and biventricular hypertrophy and findings of echocardiography revealed an ejection fraction of 32% with moderate depression of the left ventricular systolic function. The child was planned for excision of dentigerous cyst. During the preoperative visit, the child and the parents were highly anxious about the procedure but after careful counseling and discussion of various implications and the risks associated with general anesthesia, the parents and the child agreed to undergo the procedure under procedural sedation. The child was given nil per oral instructions according to the standard protocol and was advised tab. ranitidine 150 mg PO and tab. metoclopramide 10 mg PO in the night and in the morning 2 h before the planned procedure. On the day of procedure, the anesthesia machine was properly checked and flushed to remove any traces of inhalational agents and all vaporizers were removed. The child was shifted to the operating room and an intravenous line was secured and preloading done with 400 mL of the normal saline solution. The monitoring included five lead electrocardiography, noninvasive blood pressure (NIBP) and pulse oximetry. The child was then premedicated with glycopyrrolate 0.2 mg intravenously (IV) and fentanyl 1 μg/kg was given IV to achieve analgesia. Dexmedetomidine was administered slowly with a loading dose of 1 μg/kg over 15 min followed by a continuous infusion at 0.5 μg/kg/h throughout the surgical procedure. Lignocaine with 1 in 2 lakh adrenaline was used for local infiltration and the child was given supplemental oxygen through nasal prongs at 3 L/min. The child remained calm and comfortable throughout the procedure which lasted for 40 min and did not complain of any pain. At the end of procedure, the dexmedetomidine infusion was discontinued and the child remained sedated but arousable to verbal commands. Postoperatively, the child was observed in a high dependency unit for 2 h. The recovery period was uneventful and the child was discharged after 6 h when fully awake and responding.

Figure 1

Frontal view of the face showing the mouth opening and oral cavity

DISCUSSION

Duchenne Muscular Dystrophy is an X-linked, progressive neuromuscular disease affecting 1in 3500 live male births.[1] It is thought to occur due to mutation in dystrophin gene located on X chromosome leading to formation of abnormal or low levels of dystrophin protein that is an integral part of skeletal muscles, thus causing muscular weakness. Those affected usually dies before the end of third decade due to widespread involvement of respiratory and cardiac muscles.[2] These patients develop multisystem involvement leading to cardiomyopathy, decreased lung volumes, sleep apnoea, weak pharyngeal muscles, gastric hypo-motility, kyphoscoliosis and muscle contractures. These patients are highly prone to perioperative metabolic reactions and complications when they are exposed to nondepolarising muscle relaxants and/or inhalational anesthetic agents leading to rhabdo-myolysis and hyper-metabolic reactions resembling malignant hyperthermia.[34] In addition, these patients are also vulnerable to adverse effects of general anesthesia and procedural sedation for example upper airway obstruction due to macroglossia and weak upper airway dilator muscles, inability in maintaining patency of upper airway due to limited mobility of mandible and cervical spine and postoperative atelectasis and hypoxemia due to reduced functional residual capacity. Our patient had an established diagnosis of Duchenne muscular dystrophy since childhood and was restricted to wheel chair with the involvement of the cardiovascular system. As the procedure involved a common area for surgeons and anesthesiologist, that is, oral cavity, there was a dilemma so as how to administer general anesthesia and to secure the airway to prevent complications associated with loss of airway and a possible risk of aspiration of blood. Considering the fatal complications of general anesthesia in such patients and after thorough discussion with the surgeons and the parents of the child, it was decided to perform the procedure under sedation. The requirements were calm and comfortable, spontaneously breathing patient who can maintain upper airway patency as well as preserved airway reflexes. Thus, dexmedetomidine and fentanyl were selected as preferred agents. There have been several reports in literature about successful use of dexmedetomidine in conjunction with ketamine, benzodiazepines and opioids.[5-8] However, there are no reports of any oral cavity procedures done under procedural sedation using dexmedetomidine. As co-operative and awake state was desired during surgical procedure, so ketamine was not chosen for this procedure as it would have diminished the consciousness level and an ability to maintain a continuous verbal contact with the patient. Moreover, administration of ketamine is associated with copious oral secretions and it would have interfered with a smooth surgical procedure. Dexmedetomidine, a potent α2-agonist, does not cause any respiratory depression, maintains airway reflexes, potentiates analgesia by other agents and induces arousable sleep thus invasive procedures can easily be performed even inside oral cavity. The sole use of dexmedetomidine have been found to have limited utility in procedural sedation in patients with Duchenne muscular dystrophy for painful invasive procedures and is recommended to use in conjunction with other drugs like benzodiazepines, opioids and ketamine.[9] The surgical procedure was performed in this patient in accordance with the guidelines formulated by American College of Chest Physicians for successful management of patients with Duchenne muscular dystrophy undergoing general anesthesia or procedural sedation with the back-up facility of intensive care unit.[10]

In conclusion, this case report suggests that dexmedetomidine can successfully be used for sedation in invasive procedures involving oral cavity due to its minimal respiratory depression, ability to maintain airway reflexes and stable hemodynamic parameters. However, a good preoperative consultation with the surgeon and proper counseling of patient and the parents is essential for a better co-operation of patient intraoperatively.