Mivacurium in patients with myasthenia gravis undergoing video-assisted thoracoscopic thymectomy

Abstract

Editor—Video-assisted thoracoscopic thymectomy is widely used in patients with myasthenia gravis (MG) as an option of minimally invasive surgery. Thoracoscopic approach provides reduced pain scores, early mobilization, and diminished length of stay.1Toker A Tanju S Sungur Z et al.Videothoracoscopic thymectomy for non-thymomatous myasthenia gravis: results of 90 patients.Surg Endosc. 2008; 22: 912-916Crossref PubMed Scopus (19) Google Scholar Different strategies have been adopted regarding the use of neuromuscular blocking drugs in these patients. We report our experience of thoracoscopic thymectomies in myasthenic subjects. With IRB approval and informed consent, 112 patients with MG were enrolled for video-assisted thoracoscopic surgery from 2002 to 2007. All subjects were evaluated before operation according to Osserman and Leventhal scales. All patients received their morning dose of pyridostygmine on the day of surgery (Table 1). No other premedication was used. Anaesthesia was induced with propofol (2–2.5 mg kg−1) and fentanyl (1–1.5 µg kg−1). After measurement of initial train-of-four (TOF) value, a dose of mivacurium 0.1 mg kg−1 (ED95) was injected. The trachea was intubated when TOF was zero. The quality of intubation (Goldberg score), time to intubation, and need for supplemental doses (25% of initial dose) were recorded. Anaesthesia was maintained with a propofol infusion (8–10 mg kg−1). One-lung ventilation was used throughout the thoracoscopic procedure. At the end of surgery, neuromuscular recovery was assessed according to TOF values, sustained head lift, and inspiratory efforts.Table 1Demographic, preoperative and operative data of 112 patients. Data are mean (range) or mean (sd)Age (yr)33.3 (18–55)BMI24.1 (13.2)Operation time (min)64.2 (27.2)Osserman I–II/III–IV100/12Leventhal <11/≥1191/21Pyridostigmine dose (mg)229.89 (110.5)Initial mivacurium dose (mg)7 (0.9)Intubation time (s)151 (68) Open table in a new tab Intubation conditions were mostly excellent (96%). Mean cumulative mivacurium dose was 10.9 (4.6) mg and 94 (84%) patients needed at least one supplemetal dose of neuromuscular blocking agent, indicating rapid recovery of neuromuscular junction with these mivacurium doses. Of the 112 patients, two required prolonged mechanical ventilation in the intensive care unit (ICU). The use of neuromuscular blocking agent in this population is quite rare.2Patterson IG Hood JR Russell SH Weston MD Hirsch NP Mivacurium in the myasthenic patients.Br J Anaesth. 1994; 73: 494-498Abstract Full Text PDF PubMed Scopus (48) Google Scholar, 3Seigne RD Scott RP Mivacurium chloride and myasthenia gravis.Br J Anaesth. 1994; 72: 468-469Abstract Full Text PDF PubMed Scopus (30) Google Scholar, 4Tripathi M Kaushik S Dubey P The effect of use of pyridostigmine and requirement of vecuronium in patients with myasthenia gravis.J Postgrad Med. 2003; 49: 311-315PubMed Google Scholar The most important reason for avoiding neuromuscular blocking agents in myasthenic patients is that the effect and duration of action of these drugs cannot be predicted. This can lead to a prolonged apnoea after the operation and cause an unpredicted and unwarranted ICU admission and prolonged hospital stay. Mivacurium seems a good alternative as a short-acting agent, especially with neuromuscular monitoring. It achieves excellent intubation conditions with double-lumen tubes, and provides a silent lung at operative side which improves surgical exposure in thoracoscopic procedures. In a preliminary study, we tried to use either no or a dose of half an ED95 mivacurium, but found intubation with a double-lumen tube very difficult or impossible in some patients. Our experience of more than 100 patients suggests that the use of neuromuscular blocking agents need not be avoided during thoracoscopic thymus surgery in myasthenic subjects. The use of a reduced dose of mivacurium with neuromuscular monitoring allows safe extubation in myasthenic patients undergoing thoracoscopic surgery.