Anesth Analg 2002;94:876-878
© 2002 International Anesthesia Research Society
AMBULATORY ANESTHESIA
A Comparison of Neuromuscular Effects, Tracheal Intubating Conditions, and Reversibility of Rapacuronium Versus Mivacurium in Female Patients
Bernard F. Vanacker, MD,
Ester Geerts, MD,
Steve Coppens, MD, and
Mathijs van Iersel, MD
Department of Anesthesiology, University Hospitals KULeuven, Leuven, Belgium
Address correspondence and reprint requests to Bernard Vanacker, MD, Department of Anesthesiology, University Hospitals KULeuven, Herestraat 49, B 3000 Leuven, Belgium.
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Abstract
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IMPLICATIONS: Rapacuronium is a new, rapid-onset, short-duration, nondepolarizing neuromuscular blocking drug. We evaluated the intubating conditions at maximum block after the administration of rapacuronium or mivacurium in female patients undergoing laparoscopy. We also evaluated the neostigmine-induced reversibility of neuromuscular block after this single dose of rapacuronium or mivacurium.
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Introduction
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Rapacuronium was introduced as the first nondepolarizing alternative to succinylcholine (1). Mivacurium is a short-acting neuromuscular blocking drug that has been introduced earlier. The purpose of the present study was to compare intubating conditions and the reversibility of muscle paralysis with neostigmine after a single dose of rapacuronium or mivacurium.
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Methods
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Forty consenting adult patients, ASA classification I–II, scheduled for outpatient gynecological laparoscopy were studied according to a protocol approved by the Ethical Committee of our institution. Neuromuscular transmission was monitored with acceleromyography (TOF-Watch-SX Acceleromyograph®, Organon, The Netherlands) applied to the ulnar nerve.
Anesthesia was induced and maintained with propofol and alfentanil. After calibration, the ulnar nerve was stimulated with supramaximal square wave impulses of 0.2 ms duration administered at a frequency of 1 Hz. After a stabilization period of 5 min, patients randomly received rapacuronium 1.5 mg/kg or mivacurium 0.25 mg/kg. The same experienced anesthesiologist, unaware of the relaxant used, attempted orotracheal intubation when maximal neuromuscular block was obtained. The intubation conditions were scored according to the scale proposed by Viby-Mogensen et al. (2) (Table 1).
After intubation train-of-four impulses (0.2 ms duration, 2 Hz, supramaximal intensity, square wave) were applied every 15 s. All acceleromyography data were automatically stored. The time from the end of injection of the neuromuscular blocking drug to the time of maximum block, T1 amplitude at maximum block, and the time to spontaneous recovery of T1 to 25% of baseline were registered. At that moment, neostigmine 0.05 mg/kg IV with glycopyrrolate 0.01 mg/kg IV was administered. The time to recovery of the T4/T1 ratio to 0.7, 0.8, and 0.9 was recorded.
Continuous data were summarized as mean and SD. Categorical data were summarized by frequency distributions. Demographic data were compared using the Student’s t-tests and Fisher’s exact test. Acceleromyography data were compared between the two treatment groups using Student’s t-tests. Intubating scores were compared using the  2 test. Differences were considered statistically significant at P  0.05.
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Results
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Demographic data were similar in both groups. Acceleromyography data are summarized in Table 2. The mean onset time after rapacuronium administration was significantly shorter than after mivacurium. A 100% block was obtained in all but one patient receiving mivacurium, where the maximum block was 96%. Time to recovery of T1 to 25% of baseline was significantly longer after mivacurium. The recovery times of the T4/T1 ratio to 0.7, 0.8, and 0.9 after reversal with neostigmine were not significantly different.
Intubation conditions are summarized in Table 3. For 95% (95% confidence interval 75.1%–99.9%) and 90% (95% confidence interval 68.3%–98.8%) of the subjects in the Rapacuronium and Mivacurium groups respectively, the intubation conditions were clinically acceptable (scores "excellent" and "good"), this difference not being significant. The percentage of patients with intubation score "excellent," however, was higher in the Rapacuronium group (75% versus 25%) (P = 0.006). The incidence of adverse events was infrequent. We did not find signs of bronchospasm in any patient.
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Discussion
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Previous studies have shown that rapacuronium is a rapidly acting drug providing an alternative to succinylcholine (3,4). The delay before obtaining maximum block after the administration of mivacurium was longer, although the relative dose of mivacurium was larger. The ED95 of mivacurium was estimated to be 0.083 mg/kg (5). The dose-response relationship for rapacuronium has not been well established (6). In their preliminary investigation, Wierda et al. (7) reported an ED90 of 1.15 mg/kg for rapacuronium. Kopman et al. (3) found the ED95 to be substantially less (0.75 mg/kg). Based on this value, the dose of mivacurium used was more potent than the dose of rapacuronium.
Intubating conditions were clinically acceptable in most patients. Laryngoscopy and intubation were performed at maximum block measured at the adductor pollicis muscle, occurring later with mivacurium compared with rapacuronium. The ED90 of rapacuronium for blocking the laryngeal muscles has been estimated to be approximately twice the ED90 at the adductor pollicis muscle (8). The relative resistance of the vocal cords to the effects of neuromuscular blocking drugs has been demonstrated with other nondepolarizing neuromuscular blocking drugs. In a dose-ranging study of rapacuronium, doses of 1.5–2.0 mg/kg during propofol anesthesia produced similar good-to-excellent intubating conditions 60–90 seconds after administration (9). In another study, excellent or good intubation conditions were observed in the majority of patients 90 seconds after administration of mivacurium (divided dose), although TOF responses were present in most patients at the start of the intubation attempt (10). In a study by Tang et al. (11), the intubating conditions with mivacurium (0.2 mg/kg) at 90 seconds were clinically acceptable in only 72% of the patients.
Similar results of 25% recovery time after a single dose of rapacuronium have been published by Miguel et al. (4) (15.3 minutes) and Zhou et al. (6) (15 minutes). This time was significantly shorter than after mivacurium. Accordingly, although recovery times for the T1/T4 ratio after neostigmine reversal were not significantly different, increase of the TOF ratio after neostigmine occurred 8 min earlier after rapacuronium, which can be an advantage for short procedures. The number of adverse events was very small.
In conclusion, rapacuronium 1.5 mg/kg exhibited a more rapid onset of action than mivacurium 0.25 mg/kg. Intubating conditions were acceptable in most patients, but excellent in a larger proportion of patients with rapacuronium. Spontaneous recovery of neuromuscular block to 25% of baseline was significantly faster with rapacuronium, but reversal with neostigmine after this degree of spontaneous recovery was equally efficient. Rapacuronium offered an excellent neuromuscular blocking profile for short surgical procedures needing muscle relaxation. Unfortunately, the drug has been withdrawn because of its respiratory side effects.
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Acknowledgments
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Supported, in part, by a grant from Organon Teknika, Dr. M. van Iersel, Boxtel, The Netherlands.
The authors acknowledge Professor J. Van Hemelrijck and Dr. A. Kumar for help with the text and H. Rietbergen for statistical analysis.
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References
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Accepted for publication November 20, 2001.
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Abstract
Introduction
