VECURONIUM BROMIDE IN ANAESTHESIA FOR LAPAROSCOPIC STERILIZATION

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1 Br. J. Anaesth. (1985), 57, VECURONIUM BROMIDE IN ANAESTHESIA FOR LAPAROSCOPIC STERILIZATION J. E. CALDWELL, J. M. BRAIDWOOD AND D. S. SIMPSON Although artificial ventilation can be used to avoid hypoventilation and hypercarbia in the spontaneously breathing patient during laparoscopic sterilization (Hodgson, McClelland and Newton, 1970), previously available non-depolarizing neuromuscular blocking drugs were uuitable because of their prolonged duration of action. Although suxamethonium provides good intubating and operating conditio, and although its effects are usually reversed by the end of a short procedure, it does have several disadvantages. The incidence of muscle pain is high in such patients, and is increased if repeated bolus doses are administered (Waters and Mapleson, 1971). In addition, cardiac arryhthmias and prolonged neuromuscular blockade can occur. This study was designed to assess the suitability of vecuronium bromide for use in patients undergoing laparoscopic sterilization. PATIENTS AND METHODS Informed coent was obtained from 52 patients aged between 20 and 40 yr (ASA category 1), scheduled for laparoscopic sterilization with fallope rings following peritoneal iufflation with carbon dioxide. The duration of the procedure was usually less than 15 min. Premedication was with papaveretum mg and hyoscine mg i.m. 1 h before surgery. Before the induction of anaesthesia, monitoring of the ECG and arterial pressure (Dinamap, Critikon) was commenced and a cannula ierted i.v. Anaesthesia was induced with thiopentone 5 mg kg" 1 i.v. and maintained with 67 % nitrous oxide in oxygen. Vecuronium 70 m? kg" 1 was J. E. CALDWELL,* M.B., CH.B., D.R.C.O.G., F.F.A.R.C.S.; J. M. BRAIDWOOD, M.B., CH.B., F.F.A.R.C.S.; D. S. SlMPSON, M.B., CH.B., F.F.A.B.CJ.; Department of Anaesthesia, Falkirk and District Royal Infirmary, Majors Loan, Falkirk. * Present address for correspondence: Department of Anaesthesia, Royal Infirmary, Glasgow, G31 3ER. SUMMARY Vecuronium bromide 70 fig kg ~ x was used to facilitate trachea/ intubation and provide neuromuscular blockade in 52 patients undergoing laparoscopic sterilization. Anaesthesia was maintained with 67% nitrous oxide in oxygen. Patients were monitored clinically and by tactile assessment of the evoked respoe of the adductor pollicis to a supramaximal train-of-four stimulation. Intubating conditio were assessed at 90 s in the first 33 patients, and were poor. They improved significantly in the subsequent 19 patients when intubation was delayed until 150 s (P < 0.05). Operating conditio were good in all except two patients. Residual neuromuscular blockade was antagonized rapidly at completion of surgery by neostigmine 2.5 mg i. v., which was administered provided there was at least one twitch respoe. The mean duration of the procedure was 14.3 min (SD 2.5 min). The mean time from injection of neostigmine to satisfactory spontaneous breathing and neuromuscular recovery was 1.6min (SD 0.7min). administered i.v. and the cnnniiln flushed with physiological saline. Intubating conditio were assessed by a modification of the system described by Lund and Stovner (1970) (table I). The first attempt at intubation was made at 90 s. Conditio were so poor in the first 33 patients that intubation was delayed until 150 s in the subsequent 19 patients. Following trachea! intubation, mechanical ventilation was itituted (14 b.p.m.), minute volume being determined from the Radford nomogram (Radford, 1955). Supramaximal train-of-four stimulation was applied percutaneously to the ulnar nerve at the wrist (Myotest Mk. 2, Biometer). This was commenced immediately before the administration of the vecuronium and repeated every 10 s. Tactile

2 766 BRITISH JOURNAL OF ANAESTHESIA TABLE I. System for scoring intubating conditio. {Modifiedfrom Lund and Stovner {1970)) riiniml criteria Vocal cords well separated and no patient movement in respoe to intubation. Vocal cords moving slightly or slight patient movement in respoe to intubation. Significant patient movement e.g. "bucking" in respoe to intubation. Intubation not possible. TABLE II. System for assessing operating conditio Clinical criteria 1 Good relaxation, no patient movement. 2 Slight resistance to ventilation or slight patient movement not interfering with surgery. 3 Relaxation inadequate to permit procedure to continue. assessments of the evoked respoes of the thumb were recorded before vecuronium was administered, at intubation and at 4-min intervals thereafter. Heart rate and rhythm and the arterial pressure were recorded, before the induction of anaesthesia and at intervals of 3 min thereafter.' Operating conditio were assessed according to the criteria presented in table II. All times were measured from the end of the injection of vecuronium. The times when surgery was started (7^) and completed (7" E ) were recorded. If at least one twitch respoe was present at T E, neostigmine 2.5 mg and atropine 1.2 mg were administered i.v. (7^). If no twitch respoe was present, these agents were withheld until the first respoe had returned (7^). When the patient had clinically adequate spontaneous breathing and there were four twitch respoes with no detectable fade, the time was recorded (7" A ). Train-of-four respoes and cardiovascular variables were recorded at all the above times. The patients breathed 100% oxygen before extubation of the trachea, following which they were traferred to the recovery room. Clinical assessment of recovery was made at 7" A + 5 and 7" A +10 min. Patients were asked to give their name and age, to open their eyes, to protrude their tongue, to cough and to raise their head for 5 s. If TABLE III. Intubating conditio. Number of patients (%) achieving particular scores at the time of initial attempt at intubation. Conditio improved significantly at 150 s (P < 0.05) Total Initial attempt at 90s 0(0) 8(24) 13 (39) 12(37) 33 (100) Initial attempt at 150 s 2(10.5) 9(47.5) 4(21) 4(21) 19(100) they made no respoe to these requests and to painful pressure on the nail bed, a further train-of-four respoes was elicited. No formal follow-up was made after their return to the ward. Statistical analysis of the results was by Student's t test or Chi square, as appropriate. RESULTS Intubating conditio (table III) In the first 33 patients (assessed at 90 s) none had ideal conditio (score 1), in addition 25 (76 %) had clinically unacceptable scores of 3 or 4. Conditio at 150 s improved significantly (P < 0.05). However, even at this time, conditio were uatisfactory in 42 % of patients. It was our impression that conditio were better in the heavier patients who had received a larger dose of vecuronium; however, there was no statistically significant difference between those who weighed less or more than 60 kg (P = 0.05). Operating conditio Forty-five patients scored 1 and five scored 2. Two patients scored 3; one of these two remained apparently unblocked after the initial dose of vecuronium and required supplements of vecuronium and the administration of halothane to permit tracheal intubation and surgery. The other was completely blocked initially, but the surgery lasted 20.5 min and halothane was required near the end as she was resisting ventilation. Both were excluded from study of recovery. Evoked respoes There was great individual variation in the train-of-four respoes during the procedure. In 18 patients all respoes were lost, while in seven all four respoes were maintained although fade was evident. At the completion of surgery, 12

3 VECURONIUM BROMIDE IN ANAESTHESIA FOR STERILIZATION 767 TABLE IV. Duration of procedure, time to recovery and dose ofvecuronium (mean values ±SEM). 7* B = time to end of surgery (mm); T & = time when neostigmine was administered (mm); 7* A = time when clinical and tram-of-four recovery was satisfactory (min) Group 1 All patients Group 2 Group 3 Patients with a twitch respoe at T E Patients with no twitch respoe at T E Significance (Groups 2 and 3 compared) Dose (mg) ± ± ± ± ± ± O± ± ± ± ± ± ± ± ±0.21 P<0.05 P<0.05 patients had no respoe, 20 had one, 11 had two or three and 7 had all four. Recovery Results were analysed in three groups (table IV). Twelve patients had no respoe at T E, but there was no difference in the duration of surgery or the dose of vecuronium between these patients and those with some respoe at this time. Recovery was rapid and uneventful in all patients after the administration of the neostigmine. In the recovery room, 23 patients could perform all the tasks at r A + 5min, and 41 could do so at 7^+10 min. Eight patients could not co-operate because of drowsiness or abdominal pain. One patient had a train-of-four stimulus applied and had four respoes with no detectable fade. Cardiovascular respoes One patient developed a nodal rhythm and one had occasional ventricular extrasystoles: both resolved spontaneously. One patient required atropine i.v. to treat a sinus bradycardia. At 6 min from induction, the approximate mid point of the procedure, the mean heart rate increased to 87 beat min" 1 from a pre-induction value of 73 beat min" 1. Similarly, mean arterial pressure increased to 134 mm Hg from 122 mm Hg. In nine patients the maximum systolic arterial pressure exceeded 160 mm Hg. DISCUSSION Operating conditio were satisfactory and the duration of action of vecuronium seemed suitable for the procedure. In contrast, intubating conditio using the anaesthetic technique described, were poor. Vecuronium 70ugkg~ 1 was used in this study as this had been found to permit intubation at s and to have a suitable duration of action (Agoston et al., 1980). If only scores of 1 or 2 (table II) are regarded as clinically acceptable, then some modification of the technique should be coidered. In no patient in this study was neuromuscular blockade complete at the time of the initial attempt at intubation. However, recent papers have described satisfactory intubating conditio before the oet of complete neuromuscular blockade (Agoston et al., 1980; Kreig et al., 1980). However, the respoe of a patient to tracheal intubation will depend, not only on the degree of neuromuscular blockade, but also on the central reflex suppression by the anaesthetic agents. Volatile agents potentiate neuromuscular blocking drugs and halothane has been shown to decrease the oet time of maximum neuromuscular blockade (Fahey et al., 1980). It would have been impossible to standardize the effect of a volatile agent without prolonging the procedure and, therefore, none was used. If halothane were used in the pre-intubating period only, it is likely that intubating conditio would improve without a prolongation of the action of the vecuronium. Alternatively, intubation could be delayed until 300 s, when maximum blockade will have been attained in most patients (Agoston et al., 1980; Fahey et al., 1980). Doses of vecuronium between 100 and 200 ug kg" 1 would permit more rapid and reliable tracheal intubation, but would have an unacceptably long duration of action (Fahey et al., 1980; Kerr and Baird, 1982; Mirakhur et al., 1983). The dose of vecuronium used was approximately 1.6 times the ED«(Robertson et al., 1983), and a wide variation in individual respoe might have

4 768 BRITISH JOURNAL OF ANAESTHESIA been expected. This was confirmed by the evoked respoes recorded during surgery. However, operating conditio were acceptable, which suggests that profound neuromuscular blockade is not necessary for laparoscopy. The minor movements of facial and limb muscles which occurred reflected the "light" nature of the anaesthesia. No formal assessment of awareness was made although, using an anaesthetic technique similar to that in this study, Terrell and colleagues (1969) specifically sought evidence of awareness during surgery and found none. Tactile assessment of the evoked respoe of the adductor pollicis to train-of-four stimulation is a technique which is feasible for routine clinical use (Viby-Mogeen, 1982). The presence of a single twitch is easily identified and quantifies spontaneous recovery from neuromuscular blockade (Lee, 1975). A wide variation in the degree of recovery existed at the end of surgery. Post-tetanic count (Viby-Mogeen et al., 1981) was not used to quantify the degree of recovery in those who had no evoked respoe at this time, since no further assessment can be made at the same site for at least 5 min, and this could delay the administration of neostigmine. Train-of-four can be repeated every 10 s and, therefore, the return of the first respoe can be detected rapidly. When this study was designed it was coidered possible to identify adequate recovery from neuromuscular blockade (train-of-four > 0.7), when no fade was felt in the train-of-four respoes (Kerr and Baird, 1982). It has since been shown that this is unreliable and that the degree of recovery is likely to be overestimated (Viby- Mogeen et al., 1983). At present there is no accurate method to assess the fade of evoked respoes without sophisticated recording equipment. In this study the mean time to satisfactory recovery in the patients given neostigmine when the first twitch returned (Group 3, table IV) was 1.78 min. Although clinical recovery was judged adequate, it is likely that neuromuscular recovery was incomplete. This will not cause problems if the patients are monitored in a theatre recovery area as neuromuscular function will be satisfactory within a few minutes. Vecuronium bromide and its metabolites have no significant cardiovascular side-effects (Crul and Booij, 1980; Marshall, Gibb and Durant, 1983). Both the heart rate and arterial pressure increased during the procedure. However, the anaesthesia was "light", the trachea intubated and the patients placed in the lithotomy and steep Trendelenburg positio. We coider that these factors accounted for the cardiovascular changes. In conclusion, vecuronium is a suitable drug for this procedure. The anaesthetic technique could be improved by the use of a volatile agent in the initial stages to improve intubating conditio. The degree of neuromuscular blockade, although showing wide individual variation, was adequate for the surgical requirements. Clinical recovery was rapid after the administration of neostigmine. ACKNOWLEDGEMENTS We are grateful to Organon Laboratories for supplies of vecuronium and Dr S. Agoston and his colleagues at the University of Gronigen for their advice and assistance. The co-operation of our colleagues in the Department of Gynaecology in Falkirk and District Royal Infirmary is much appreciated. REFERENCES Agoston, S., Salt, P., Newton, D., Bencini, A., Boomsma, P., and Erdmann, W. (1980). The neuromuscular blocking action of Org NC 45, a new pancuronium derivative, in anaesthetized patients. Br. J. Anaesth., 52, 53S. Crul, J. F., and Booij, L. H. D. J. (1980). First clinical experience* with Org NC 45. Br. J. Anaesth., 52, 49S. Fahey, M. 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5 VEGURONIUM BROMIDE IN ANAESTHESIA FOR STERILIZATION 769 Terrell, R. K., Sweet, W. O., Gladfelter, J. H., and Stephen, C. R. (1969). Study of recall during anesthesia. Anesth. Analg., 48, 86. Viby-Mogeen, J. (1982). Clinical assessment of neuromuscular tramission. Br. J. Anatsth., 54, 209. Engbaek, J., Jeen, N. H., Chraemmer-Jorgeen, B., and Ording, H. (1983). New developments in clinical monitoring of neuromuscular tramission: monitoring without equipment; in Clinical Experiences with Norcuron, p. 66. Amsterdam: Excerpta Medica. Viby-Mogeen, J., Howardy-Haen, P., Chraemmer- Jorgeen, B., Ording, H., Engbaek, J. and Nielsen, A. (1981). Post-tetanic count (PTQ. A new method of evaluating an intee non-depolarising neuromuscular blockade. Anesthesiology, 55, 458. Waters, D. J., and Mapleson, W. W. (1971). Suzamethonium pai: hypothesis and observation. Anaesthesia, 26, 127.