Epidural Anesthesia and Pulmonary Function in a Patient with Amyotrophic Lateral Sclerosis

Abstract

Amyotrophic lateral sclerosis (ALS) is a degenerative disease of motor ganglia in the anterior horn of the spinal cord and spinal pyramidal tracts. Since the disease often involves atrophy and weakness of respiratory muscles resulting in respiratory failure and death, the anesthetic management of patients with ALS has been a controversial subject. General anesthesia may cause ventilatory depression due to abnormal responses to muscle relaxants [1-3]. Regional anesthesia such as spinal and epidural anesthesia is also relatively contraindicated in patients with a motor neuron disease, including ALS, for the fear of exacerbating the disease [4,5]. Although successful use of epidural anesthesia in the management of patients with this disease was reported recently [6], its effects on pulmonary function have not been discussed. We describe a case of ALS in which epidural anesthesia was successfully used for inguinal herniorrhaphy. Pulmonary function was examined, and no neurologic exacerbation was noted except for a temporal decrease in vital capacity (VC). Case Report A 69-yr-old, 43-kg, 152-cm male patient was scheduled for inguinal herniorrhaphy for right inguinal hernia. At age 63, muscle weakness of the upper and lower extremities and fasciculation in the upper extremities developed and the diagnosis of ALS was made. His previous surgery included gastrectomy for gastric ulcer performed at the age of 48. Preoperative evaluation revealed muscle atrophy, weakness, and fasciculation of the upper and lower extremities. His grasp power was 1 kg of the right hand and 4 kg of the left hand, and he was not able to walk. He had no difficulty in speaking and swallowing. Blood pressure was 110/80 mm Hg, and heart rate was 70 bpm and regular. No abnormalities were found in the heart. He showed no clinical signs of autonomic dysfunction. Chest radiograph showed no abnormalities. pHa was 7.39, PaO2 89 mm Hg, and PaCO2 44 mm Hg while breathing room air. After discussion of options, he elected to have an epidural anesthetic. The day before surgery pulmonary function tests were performed with the patient in a 30 degrees head-up comfortable position so that the tests could be repeated after surgery in the same position. The results of the tests showed a VC of 87% of predicted value and a one second forced expiratory volume (FEV1.0)/forced vital capacity (FVC) of 84%. No preanesthetic medication was given on the day of surgery. With the patient in the lateral decubitus position, an epidural puncture was performed at L1-2 intervertebral space using a 17-gauge Tuohy needle, and, after injection of 8 mL of 2% mepivacaine, an epidural catheter was inserted. The catheter was taped in place, the patient was turned supine, and 2 L/min oxygen was started via an aerosol face mask. Fifteen minutes later, the level of analgesia as determined by pinprick was T5-L2. pHa was 7.44, PaO2 114 mm Hg, and PaCO2 36 mm Hg just before surgery. No medication was given during surgery but additional increments of 4 and 5 mL of 2% mepivacaine epidurally and ephedrine 5 mg to treat hypotension which occurred approximately 10 min after the epidural injection. The patient was fully alert during the procedure. The surgical procedure was uneventful and lasted 1 h and 45 min. Immediately after surgery, the level of anesthesia was T5-S2. The patient had no respiratory discomfort with pHa 7.48, PaO2 119 mm Hg, and PaCO2 33 mm Hg. Pulmonary function tests were performed 20 min after surgery with the patient in the head-up position and revealed a VC of 58% of predicted value and a FEV1.0/FVC of 76%. The postoperative course was uneventful. Only nonsteroidal antiinflammatory drugs were used for postoperative pain control. On 8th postoperative day, repeated pulmonary function tests showed a VC of 82% of predicted value and a FEV1.0/FVC of 85%. No exacerbation of neurologic signs or symptoms were noted. There was no worsening of extremity weakness, fasciculations, or dysphagia. The patient was discharged 14 days after surgery. Discussion Respiratory involvement is a common feature of ALS, and thus there has been great concern regarding the effects of anesthetic management on respiratory function. In the present case, epidural anesthesia was used in a patient who underwent inguinal herniorrhaphy. The patient did not incur any respiratory deterioration except for a temporal decrease in VC according to the pulmonary function tests performed during the perioperative period. This is the first case report describing the successful use of epidural anesthesia in connection with pulmonary function. The present case could have been managed with infiltration anesthesia, which seems free of an association with ventilatory depression. However, after careful consideration, both the patient and the surgeons opted for an epidural anesthetic, as is usual with a case of inguinal herniorrhaphy at our institution. We measured pulmonary function during the perioperative period, since it has been recognized that the progression of ALS is not well correlated with blood gas exchange but with pulmonary function. Patients with severe ALS have characteristic abnormalities in pulmonary function, including reduced VC [7,8]. However, gas exchange is usually well maintained until the loss of lung volume becomes severe, and a reduction in VC to as low as 50% is commonly missed [7]. We believe, therefore, that spirometry is valuable for detecting a possible progress of pulmonary dysfunction during postoperative period in ALS patients. In the present case, the surgical procedure and/or epidural anesthesia caused the patient to have reduced VC in the immediate postoperative period, while gas exchange was well maintained and he had no respiratory discomfort. On the eighth postoperative day, however, the pulmonary function returned completely to the preoperative values. The postoperative period is often associated with pulmonary dysfunction, even in normal patients [9,10]. VC decreases approximately 10% after superficial surgery such as herniorrhaphy [10]. In addition, epidural anesthesia, with which sensory level extends to T-5, decreases VC by about 13% [11]. In view of the fact that the present patient had epidural anesthesia extending to T-5 level in the postoperative period when the pulmonary function tests were conducted, the reduction seen in VC does not seem to have resulted from acute progression of this disease. Regional anesthesia may cause exacerbation of preexisting neurologic damage [5,12]. This concern may be reinforced by recent reports of major and minor neurologic sequelae after spinal anesthesia, indicating that neurologic damage after regional anesthesia is not restricted to patients with neurological disease and can occur more commonly [13-15]. It seems prudent, therefore, to use epidural anesthesia, of which the concentration of local anesthetic in the cerebrospinal fluid is smaller as compared to that of spinal anesthesia, in a patient with neurological disease. Gradual onset of block produced by epidural anesthesia can be another advantage over spinal anesthesia, which may change hemodynamics precipitously in patients with autonomic dysfunction such as ALS. In summary, we present a patient with ALS who underwent inguinal herniorrhaphy under epidural anesthesia. Postoperatively, the patient developed only a temporal decrease in VC without any neurologic exacerbation. Epidural anesthesia appears useful and safe for patients with ALS undergoing lower abdominal or lower extremity surgery. However, careful postoperative management is important, since mild pulmonary dysfunction might occur without hypoxemia or any clinical symptoms, regardless of the anesthesia method used.