Spinal anesthesia for inguinal hernia repair in 8‐year‐old child with myasthenia gravis

SIR—Myasthenia gravis (MG) is an autoimmune disease characterized by weakness and fatigue of the voluntary muscles, because of the presence of acetylcholine receptor antibodies (1). The incidence is 2–10 ⁄ 100 000 cases per year (2). Children account for 11–29% of all patients with MG (3). Anesthesia concerns for MG patients focus on avoiding muscle relaxants and monitoring for postoperative respiratory failure. The use of regional or local anesthesia seems warranted whenever possible. Spinal anesthesia has advantages of reduced drug dosage, profound sensory and motor block, lack of systemic effects, avoidance of tracheal intubation and decreased need for opioid administration (4). Although spinal anesthesia is widely used in the pediatric age group, surprisingly we have not seen any report concerning its use in a myasthenic child. This report describes a pediatric case with MG, who underwent successful inguinal hernia repair under spinal anesthesia. An 8-year-old, 25-kg girl with MG presented for inguinal hernia repair. She had MG for 3 years and was classified as Osserman (5) Grade IIa with obvious ptosis and mild generalized weakness. She was taking pyridostigmine 15 mg five times daily. On the day of surgery, the morning dose of pyridostigmine was continued and no other premedication was given. An infusion of 0.5% dextrose and 0.2% sodium NaCl was given at a rate of 5 mlÆkg hÆ6 h before anesthesia and continued throughout the operation. Following the establishment of routine monitoring, the patient was sedated with 2-mg midazolam i.v. Oxygen was administered at 3 lÆmin by facemask. She was placed in a lateral decubitus position and after an additional doses of 1-mg midazolam, lumbar puncture was performed using a midline approach at the L5-S1 intervertebral space with a 27 gauge 90-mm Whitacare pencil point spinal needle (Becton Dickinson, S. Agustin del Guadalix, Madrid, Spain); 1.6 ml 0.5% hyperbaric bupivacaine was given intrathecally. In the supine position, bilateral motor block occurred within 2 min and sensory block was achieved approaching T6-7 level verified by pin prick test after 5 min. She remained comfortable and hemodynamically stable throughout the 45 min of surgery, which was uneventful. Postoperatively, she was monitored in the recovery room until regression of the sensory block and after complete resolution of the sedation she was transferred to the pediatric surgery ward. Sensory and motor function completely recovered 2 h after the surgical procedure. The patient had only one episode of nausea in the postoperative first hour and was discharged from the hospital 6 h later. Overall no complication occurred. Several studies have been published on the use of spinal anesthesia in high-risk newborns and infants at risk of postoperative apnea (6,7) and also for older children with muscular and neuromuscular disease which increase risk of postoperative respiratory failure (4). Caudal-epidural block with inhalation anesthesia is the most commonly used regional anesthetic technique in children. However, this requires a higher volume of local anesthetic and the use of inhalation anesthesia (8). Potentiation of neuromuscular blocking drugs by local anesthetics has been reported. These agents decrease the sensitivity of the postjunctional membrane to acetylcholine, which causes weakness in myasthenia. Ester anesthetics, which are metabolized by cholinesterase, may cause problems particularly in patients taking anticholinesterases. Regional and local anesthesia should be performed using reduced doses of amide, rather than ester, local anesthetics to avoid high blood levels of drug in circulation (1). Spinal anesthesia produces excellent block with light sedation levels maintaining protective airway reflexes (8) and provides an appropriate alternative regional anesthesia method. However, high-spinal anesthesia should be particularly avoided in patients with MG because it may lead to deterioration of intercostal muscle movement. Using intrathecal opioids should be avoided to minimize the risk of respiratory muscle weakness and central respiratory depression in these patients. It is controversial whether anticholinesterase therapy should be maintained or discontinued before surgery (9,10). Anticholinesterases may potentiate vagal responses and increase bronchial secretions. Anticholinesterase drugs can also inhibit plasma cholinesterase activity with a subsequent decrease in the metabolism of ester local anesthetics (9). We decided to continue anticholinesterase therapy before surgery in this patient. As the block level did not rise higher than the T6 level and respiratory reflexes were intact throughout, we did not need to administer atropine and this prevented any complication that might arise secondary to this drug. In children, sufficient duration of anesthesia for surgery is consistently less than seen in adults. In the report of Dohi et al. (11), motor function returned after a mean of 114 min in children aged over 5 years compared with 336 min in adults. The reasons are unclear but presumably include age-related differences in cerebrospinal fluid volume, diameter and surface area of the spinal cord and nerve roots and rate of absorption of local anesthetic from 1220 CORRESPONDENCE