We describe an anesthetic in a patient having symptoms of both cerebral palsy (CP) and hemiplegia (HP). This case report illustrates the comparative resistance to vecuronium between the CP and HP sides.
Our patient was a 44-yr-old man whose spastic CP had been diagnosed when he was a neonate. The range of motion of the patient’s limbs was severely limited because of spastic quadriplegia; however, he could walk by himself, although with difficulty. He was admitted to the hospital with a sudden immobilization of his left arm and leg and was found, by computed tomography, to have a cerebral tumor in the right cerebral hemisphere. The patient was scheduled for removal of the tumor during general anesthesia approximately 1 mo after the onset of HP. Laboratory examinations of blood and electrocardiogram were within normal range. Until the day before surgery, the patient took phenytoin 300 mg daily for prevention of seizure disorders.
The patient was premedicated with atropine 0.25 mg IM approximately 45 min before the induction of anesthesia. An IV cannula was inserted into the right saphenous vein, and an infusion of lactated Ringer’s solution was started. A blood pressure cuff was placed on the left lower limb to minimize interference with arm blood flow and neuromuscular monitoring. Anesthesia was induced with fentanyl 4 μg/kg and thiamylal 5 mg/kg IV, followed by controlled ventilation with 2.0% inspired sevoflurane in oxygen via a face mask. Immediately after the induction of anesthesia, bilateral ulnar nerves were stimulated simultaneously at the wrists with square-wave supramaximal stimuli of 0.2-ms duration, delivered in a twitch mode at 0.1 Hz, and the contraction of adductor pollicis muscles were measured by using accelerometrys. After evoked responses were stable, the patient was given vecuronium 0.1 mg/kg IV. Figure 1 shows that onset times were very slow in both the CP side (7.5 min) and the HP-combined side (8.3 min). The maximum blockade was 86% of control in the HP side, although complete block was achieved in the CP side. We administered additional vecuronium 0.05 mg/kg; however, a complete neuromuscular block was not obtained in the HP side (96% of control). Tracheal intubation was performed after maximal depression of twitch tension. Anesthesia was maintained by using 1.0%–2.0% sevoflurane, 50% nitrous oxide in oxygen, and supplemental IV fentanyl. Ventilation was adjusted to keep the end-tidal carbon dioxide within the range of 28–32 mm Hg. Esophageal temperature was maintained above 35°C with a heating mattress. Further incremental doses of vecuronium were not administered, and spontaneous recovery of neuromuscular function was allowed to occur.
Clinical duration from the first injection of vecuronium to recovery of twitch to 25% of control (DUR25) and time to recovery from 25% to 75% of control were remarkably shorter in the HP side (33.3 min and 20.8 min) compared with the CP side (47.5 min and 32.2 min). Each surgical procedure and anesthesia were completed uneventfully.
In a previous study (1), we showed that complete neuromuscular blocks were obtained after IV vecuronium 0.1 mg/kg in all patients without neuromuscular disorders, and that mean onset time and DUR25 were 2.6 min and 44.2 min, respectively. In comparison with the results, resistance to vecuronium was demonstrated in both the HP and CP sides. However, the degree of resistance in the HP side was more pronounced, as evidenced by a less intense maximum neuromuscular block, slower onset, and a more rapid recovery of twitch responses.
Denervation of lower motor neurons (2) and proliferation of acetylcholine receptors (AchR) (3–5) are recognized even after upper motor neuron injury. Upregulation of AchR results in resistance to nondepolarizing muscle relaxants (NDMRs) as early as three to seven days after motor neuron injury (3–5). Therefore, we reasoned that there had been sufficient time for AchR proliferation in this patient. Resistance to NDMRs in CP patients has also been reported (6). Moorthy et al. (6) concluded that CP patients showed resistance to vecuronium and rapid recovery from neuromuscular block, compared with non-CP patients. The resistance may be secondary to AchR proliferation. However, CP patients do not exhibit hyperkalemia to depolarizing blockade that often occurs in cases of upper or lower motor neuron diseases (7). Perhaps there is a difference in the degree or type of proliferation of AchR between CP and HP patients. There is a possibility that the difference contributes to the magnitude of resistance to vecuronium observed in the CP and HP sides.
Furthermore, we should consider possible interactions between vecuronium and anticonvulsant drugs. Chronically administered anticonvulsants, such as phenytoin (8–10), valproic acid (10) and carbamazepine (10–13), are relatively resistant to NDMRs, as seen by mechanisms that may include upregulation of AchR (8), increased α1-acid glycoprotein, which binds NDMRs in serum (8), increased metabolism of NDMRs via hepatic enzyme induction (14), increased clearance of NDMRs (13), and increased endplate anticholinesterase activity (10,11). Resistance to NDMRs after anticonvulsant therapy occurs after two weeks (8). Our patient had received long-term phenytoin therapy, which may have contributed to resistance to vecuronium. However, it was reported previously that mean DUR25 obtained after IV vecuronium 0.1 mg/kg was approximately 19 (9) to 28.1 (13) min in patients receiving chronic anticonvulsants therapy. In comparison with the results, a DUR25 of 47.5 min obtained in the CP side seemed to be long, even with 0.15 mg/kg. Additionally, it is impossible to explain the differences in recovery from neuromuscular block observed in the CP and HP sides by the mechanisms described above. From these points of view, chronic phenytoin therapy was unlikely to have influenced resistance to vecuronium in our patient.
In conclusion, the resistance to vecuronium observed in the HP side was more remarkable than in the CP side. The mechanism is not clear, but the difference is thought to relate to different degrees of AchR proliferation between the CP and HP sides. Clinically, our results suggest that complete recovery from neuromuscular block should be assessed adequately in the CP side that shows a delayed recovery, compared with the HP side.
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