The effect of long-term oral dantrolene on the neuromuscular action of rocuronium: a case report
A 52-year-old male patient with a height of 163 cm and a weight of 65 kg was admitted to the hospital due to right femoral edema, and following a diagnosis of right femoral abscess, an incision and drainage procedure was performed.\nWith regard to medical history, the patient was paraplegic from the level of the fourth thoracic vertebra due to a T2-level spinal cord injury from a car accident 4 years previously. Due to tetany symptoms in both lower limbs, he had been regularly taking an oral dantrolene formula of 50 mg (Anorex® Cap. 25 mg, Yooyoung Pharmaceutical, Seoul, Korea) every night for the previous 3 years.\nPrior to the operation, the patient's blood pressure was 100/60 mmHg, and his heart rate was 94 beats per minute. There was a systemic inflammation response due to the right femoral abscess, accompanied by an increase in body temperature (38.3℃); in addition, the prothrombin time was outside the normal range (INR 1.21). Hence, the decision was made to perform the operation under general anesthesia.\nAs pretreatment for anesthesia, 0.2 mg of i.m. glycopyrrolate was administered 30 minutes prior to entering the operating room. When the patient entered the operating room, the standard anesthetic monitoring devices were applied, and the blood pressure and heart rate were 123/78 mmHg and 86 beats per minute, respectively.\nThe neuromuscular monitoring device (TOF-Watch®, Organon, Boxtel, Netherlands) was attached to the ulnar nerve of the left forearm flap. Propofol 2 mg/kg was intravenously administered for induction of anesthesia, and i.v. rocuronium 0.3 mg/kg (ED95) was administered while ventilating with 5 L/min of oxygen and 4 vol% of sevoflurane.\nThe TOF ratio did not fall under 0.25 2 minutes after rocuronium administration, and 10 mg (0.15 mg/kg) of i.v. rocuronium was additionally administered. After 2 minutes, the TOF count still had not decreased to 0, and 0.15 mg/kg of i.v. rocuronium was repetitively administered. Thereafter, the TOF count decreased to 0, and endotracheal intubation was carried out.\nThe mandible was sufficiently relaxed at the time of endotracheal intubation; there was no movement of the vocal cord, and coughing or movement was not observed after intubation. The anesthesia was maintained with 1.2-1.5 vol% of sevoflurane and 50% N2O during the operation.\nThe TOF ratio was 0.37 at the end of the operation, which was 35 minutes after the last dose of the muscle relaxant had been administered. Intravenous pyridostigmine 0.15 mg/kg and glycopyrrolate 0.003 mg/kg were administered as antagonists of the muscle relaxant. Extubation was carried out; the TOF ratio was maintained above 0.9 at around 55 minutes after the last dose of the muscle relaxant had been administered. No sign of respiratory depression was observed after extubation, and no particular signs and symptoms were observed in the recovery unit.\nThree months later, the patient was diagnosed with chronic osteomyelitis, and an incision and drainage operation was planned. It was decided to perform general anesthesia in consideration of the state of systemic inflammation and the patient's preference.\nAs pretreatment for anesthesia, 0.2 mg of i.m. glycopyrrolate was administered 30 minutes prior to entering the operating room. When the patient entered the operating room, the standard anesthetic monitoring devices and the neuromuscular monitoring device were applied in the same manner as in the previous operation.\nThe blood pressure was 112/70 mmHg, and the heart rate was 93 beats per minute. The neuromuscular monitoring device (TOF-Watch® SX, Organon, Netherlands) was attached to the ulnar nerve of the right forearm flap. Loss of consciousness was confirmed after administration of 2 mg/kg of i.v. propofol, and then 2.5 vol% of sevoflurane was administered as an inhalation anesthetic.\nAfter the loss of consciousness, stabilization and calibration were carried out to establish the initial value of the spasm height prior to the administration of rocuronium. For the calibration of the spasm reaction, a 50 Hz tetanic stimulation was conducted for 5 seconds, which was then changed to a 2 Hz TOF stimulation with 15-second intervals, and the calibration was initiated by pressing the CAL switch on the TOF-Watch®SX (CAL 2 mode). The TOF response change was within 10% 2 minutes after the calibration, and this was considered as the stabilization of the spasm response. The muscle relaxant was then administered.\nAt 180 seconds following the i.v. administration of rocuronium 0.3 mg/kg (ED95), a block of more than 80% of T1 failed; therefore, additional i.v. rocuronium 0.3 mg/kg was administered, and a 100% block of T1 was achieved at just past 300 seconds. Endotracheal intubation was then carried out. The anesthesia was maintained with 1.5-2.0 vol% of sevoflurane and 50% of N2O during the operation. The time taken to recover T1 to 25% after the administration of the second dose of the muscle relaxant was 4 minutes and 36 seconds.\nTwenty-five minutes after endotracheal intubation, T1 had recovered more than 25%; hence, an additional 7.5 mg of rocuronium was administered. With the recovery of the muscle relaxation, the time taken for T1 to recover from 25% to 75% was 9 minutes and 1 second.\nThe TOF ratio was 0.33 5 minutes after ceasing sevoflurane administration on completion of the operation. Neostigmine 0.05 mg/kg and glycopyrrolate 0.005 mg/kg were administered to antagonize the muscle relaxation.\nAt 5 minutes and 30 seconds after administration of the antagonist, T1 had recovered more than 95%, and the TOF ratio had recovered to more than 0.9. Therefore, extubation was carried out. There was no sign of respiratory depression after extubation in the recovery unit.