Rapid tracheal intubation with atracurium--a comparison of priming intervals

To determine the optimal interval between the administration of the priming dose and the intubating dose, atracurium was given to 44 patients either in a single dose of 0.5 mg X kg-1 or in an initial dose of 0.06 mg X kg-1 followed two, three or five minutes later with 0.44 mg X kg-1. When atracurium was given as a single bolus of 0.5 mg X kg-1 the time to 100 per cent twitch suppression (onset time) was 90.9 +/- 36 (mean +/- SD) seconds. When the priming interval was two minutes, the onset time of the intubating dose was 76.6 +/- 42.2 seconds (p = NS). But when the priming interval was three or five minutes, the onset times were 42.2 +/- 16.5 (p less than 0.01) and 52.6 +/- 28.8 (p less than 0.05) seconds respectively. Waiting for five minutes after the administration of the priming dose did not improve the intubating conditions. It is concluded that three minutes appears to be the optimal time interval for the administration of atracurium in divided doses. When a priming dose of atracurium is given three minutes before the intubating dose, it can provide an alternative to succinylcholine for rapid endotracheal intubation.     

Rapid tracheal intubation with atracurium - a comparison of priming intervals

determine the optimal interval between the administration of the priming dose and the intubating dose, atracurium was given to 44 patients either in a single dose of 0.5 mg.kg^-1 or in an initial dose of0.06mg.kg^-1 followed two, three or five minutes later with 0.44 mg.kg^-1. When atracurium was given as a single bolus of 0.5 mg. kg^-1 the time to 100 per cent twitch suppression (onset time) was90.9 ± 36 (mean ± SD) seconds. When the priming interval was two minutes, the onset time of the intubating dose was 76.6 ± 42.2 seconds (p = NS). But when the priming interval was three or five minutes, the onset timeswere42.2 ± 16.5(p<0.01)and52.6 ± 28.8(p < 0.05) seconds respectively. Waiting for five minutes after the administration of the priming dose did not improve the intubating conditions. It is concluded that three minutes appears to be the optimal time interval for the administration of atracurium in divided doses. When a priming dose of atracurium is given three minutes before the intubating dose, it can provide an alternative to succinylcholine for rapid endotracheal intubation.     

The optimal priming dose for atracurium

To determine the optimal priming dose for administration in divided doses, atracurium was given to 77 patients either in a single dose of 0.5 mg X kg-1 or in an initial dose of 0.04, 0.05, 0.06, 0.07, 0.08 or 0.09 mg X kg-1, followed three minutes later by the remainder of the 0.5 mg X kg-1 dose. Patients were anaesthetized throughout the study. When atracurium was given as a single bolus of 0.5 mg X kg-1, the mean time to complete neuromuscular block was 141.5 seconds. Administration in divided doses accelerated the onset time (p less than 0.01), that is the time from the intubating dose to the complete suppression of train-of-four (TOF) response. The TOF ratio decreased slightly but statistically significantly following the priming doses. When the priming dose was 0.05 mg X kg-1, the mean onset time was 70.9 seconds and priming with larger doses did not add any further advantage. It is concluded that 0.05 mg X kg-1 appears to be the optimal priming dose for the administration of atracurium in divided doses. When 0.05 mg X kg-1 is given three minutes before the intubating dose, tracheal intubation can be accomplished in less than 90 seconds.     

Intubationsbedingungen nach Gabe von Atracurium und Vecuronium Bolusmethode vs. Primingtechnik

Prompted by the ongoing discussion of the pros and cons of using succinylcholine, this study was conducted to compare the responses to bolus injections of atracurium or vecuronium with those after sequential injection of these drugs (priming principle). We evaluated the earliest possible intubation times, intubating conditions, and the onset times (i.e. times from the end of injection to the maximum blockade) under conditions approaching real use as closely as possible. Methods. The randomized and double-blind study was carried out with 80 ASA risk class 1 and 2 patients. Approval of the institutional ethics committee was obtained, and each patient gave informed consent. Patients were randomly allocated to four study groups of 20 patients each. Isotonic saline was administered to those patients assigned to the atracurium or vecuronium bolus groups, whereas the patients assigned to the other two groups received a priming injection of either atracurium (0.05 mg/kg) or vecuronium (0.01 mg/kg). We observed the patients for signs of incipient muscular weakness before the induction of anaesthesia. Anaesthesia was induced with thiopental 3.5 min after the first injection (5 mg/kg and 50–100?mg before intubation). After a further 1 min during which adequate mask ventilatin with oxygen was assured, corresponding to a priming interval of 4.5?min, 0.5 mg/kg of atracurium or 0.1 mg/kg of vecuronium was administered to the patients in the bolus groups and 0.45 mg/kg of atracurium or 0.09 mg/kg of vecuronium as intubating doses to those in the priming groups. Intubation was attempted at 90, 120, 150 and 180?s thereafter. Intubating conditions were evaluated on the basis of laryngoscopy, vocal cord movement and coughing or bucking of the patients. Neuromuscular function was monitored via accelerometry at the adductor pollicis muscle (TOF stimulation of the ulnar nerve every 15?s). Results. The priming doses did not diminish the elicited twitches of the adductor pollicis muscle, but led to heavy eyelids and double vision in 35% of the atracurium patients and 47% of the vecuronium patients; these symptoms were well tolerated by the patients. At the time of intubation the adductor pollicis muscle was relaxed to approximately the same degree in all groups (mean±SD for the TOF ratios in the bolus groups was 0.46±0.37 for atracurium, 0.45±0.4 for vecuronium; in the priming groups 0.52±0.39 for atracurium, 0.53±0.36 for vecuronium). The administration of the relaxants in divided doses significantly shortened the intubating time after atracurium (100 vs 124?s) and improved the intubating conditions of vecuronium (good vs tolerable), but had no effect on the time course of the neuromuscular blockade (onset times in the bolus groups 224±84?s for atracurium and 209±64 s for vecuronium; in the priming groups 249±112?s for atracurium and 205±52 s for vecuronium). Conclusions. The priming technique presented here is clinically superior to the bolus method and therefore should be preferred in all elective cases and in those patients in whom succinylcholine is contraindicated.     

Evaluation of the timing principle with small priming doses of vecuronium]

The intubating conditions using the timing principle combined with small priming doses of vecuronium were evaluated in forty patients who underwent elective surgery. They were randomly assigned to one of two groups: 1) timing, 2) timing with priming. In timing group, vecuronium 0.15 mg.kg-1 was administered, and at the onset of clinical muscle weakness, thiopental 4-5 mg.kg-1 was given promptly. Sixty seconds after thiopental, patients were intubated. In the timing with priming group, vecuronium 0.005 mg.kg-1 was administered as priming doses. Four minutes later vecuronium 0.15 mg.kg-1 was given. The administration of thiopental and the intubation were done in the same way as in timing group. The time to onset of clinical weakness after the administration of vecuronium 0.15 mg.kg-1 was significantly shorter in the timing with priming group than that in the timing group (46.1 +/- 4.8 vs. 57.6 +/- 7.8, P < 0.01). There were no significant differences in intubating score, T1, TR, onset time, and duration between the two groups. We conclude that the timing principle combined with small priming doses of vecuronium might be safe and useful for rapid tracheal intubation.     

Rapid tracheal intubation with vecuronium: The timing principle

A method of administration of vecuronium for intubation that allows excellent intubating conditions in 60 seconds after the induction of anesthesia is described. Patients were divided into three groups based on the dose of vecuronium given. These patients were given either 0.10 mg/kg, 0.15 mg/kg, or 0.20 mg/kg, of veruronium intravenously. Intubating doses of vecuronium were given prior to the induction of anesthesia with sodium thiopental. Administration of the sodium thiopental was timed to the onset of clinical weakness in each patient.     

Is the priming principle both effective and safe?

This study determined the priming dose of vecuronium (V), pancuronium (P) and atracurium (A) that resulted in the most rapid onset of neuromuscular blockade (NMB) in 150 patients given either V 0.08 mg/kg, P 0.1 mg/kg or A 0.6 mg/kg. Patients were further divided (n = 10 per group) to receive no prime or 5%, 10%, 15% or 20% of the total dose as a prime followed 5-7 minutes later by the remaining (intubating) dose. A further 10 patients received 0.04 mg/kg d-tubocurarine followed by 1.5 mg/kg succinylcholine (S). Priming significantly shortened the onset of NMB. The priming doses producing the most rapid onset were 0.012 mg/kg for V, 0.015 mg/kg for P and 0.09 mg/kg for A. The S resulted in significantly greater NMB at 60 sec than any priming dose of A, V or P. There was no difference between the three nondepolarizing neuromuscular blockers in shortening the onset of NMB produced by priming. To evaluate both the effect of the "optimal" priming dose in awake patients and the effect of increasing intubating doses on NMB an additional 40 patients were given V 0.012 mg/kg followed by V 0.08, 0.1, 0.12 or 0.15 mg/kg. Increasing the intubating dose did not improve onset of NMB. The "optimal" priming dose, however, resulted in a high incidence of symptoms of muscle weakness. We conclude that priming shortens the onset of NMB similarly between V, P and A but the priming dose producing the most rapid onset of NMB also results in a high incidence of side effects and therefore the priming principle should be used with caution.     

Influence of the priming technique on pharmacodynamics and intubating conditions of cisatracurium

STUDY OBJECTIVES: To determine the effects of the priming technique on the intubating conditions and pharmacodynamics of different doses of cisatracurium. DESIGN: Open-label, randomized study. SETTING: Operating room of a university-affiliated hospital. PATIENTS: 60 ASA physical status I, II, and III female patients. INTERVENTIONS: Patients were randomly assigned to one of four groups. Patients from Groups 1, 2, and 3 received 0.01 mg/kg cisatracurium as a priming dose, and patients from Group 4 received placebo. Four minutes later, patients from Groups 1, 2, 3, and 4 received the following intubating doses of cisatracurium: 0.09 mg/kg, 0.14 mg/kg, 0.19 mg/kg, and 0.2 mg/kg, respectively. Anesthesia was induced with thiopental sodium, sufentanil, droperidol, and nitrous oxide (N2O; 6 L/min) in oxygen (O2; 4 L/min) and maintained with isoflurane up to 0.7%, N2O in O2, and sufentanil. Mechanomyography assessed the neuromuscular function of the adductor pollicis with train-of-four supramaximal impulses. The trachea was intubated when the amplitude of the first twitch decreased to 10% to 15% of control. MEASUREMENTS AND MAIN RESULTS: There were no significant differences among the groups regarding the demographic data, the value of the first twitch at 60 seconds, the time to 90% block, and the onset time. Clinical duration of cisatracurium was significantly different between Group 3 and Groups 1 and 2, whereas Group 4 differed significantly from Group 1. Intubating conditions did not differ significantly among the groups. CONCLUSION: When primed, cisatracurium 0.09 mg/kg and 0.14 mg/kg produced an onset time comparable with that of 0.2 mg/kg and allowed an earlier spontaneous recovery (p < 0.05). In this study, there was no benefit in priming cisatracurium 0.19 mg/kg.     

The pattern of train-of-four fade after atracurium: influence of different priming doses

This study was designed to investigate the effect of three different priming doses of atracurium--0.06, 0.07, and 0.08 mg/kg--followed 3 min later by the remainder of a 0.5 mg/kg dose on the relationship between the depression in the first twitch of the train-of-four (T1) and train-of-four (TOF) fade. This relationship was studied after the administration of the full dose of the relaxant in all groups. Of all the priming doses, 0.08 mg/kg atracurium, when followed 3 min later by 0.42 mg/kg atracurium, had a significantly greater fade in the TOF ratio at any given T1 value. This may indicate significant prejunctional activity. Acceleration of the onset of neuromuscular blockade was, however, evident in all groups that received atracurium in divided doses. The implication is, therefore, that prejunctional activity may not contribute significantly to the acceleration of onset of neuromuscular blockade after administration of atracurium in divided doses, as described in this study.     

Intubating conditions after vecuronium and atracurium given in divided doses (the priming technique)

Intubating conditions have been assessed at 60 s following administration of vecuronium 0.1 mg kg-1 or atracurium 0.5 mg kg-1 given either as a single dose after induction of anaesthesia with thiopentone or in divided doses; vecuronium 0.015 mg kg-1 followed 4 or 6 min later by 0.085 mg kg-1, or atracurium 0.075 mg kg-1 followed 4 or 6 min later by 0.425 mg kg-1. In the divided dose groups the smaller initial (priming) dose was given prior to induction of anaesthesia. Onset and duration of clinical relaxation were assessed using a peripheral nerve stimulator. The intubating conditions at 60 s improved significantly, with the use of relaxants in divided doses being acceptable in 80 and 70% of patients, respectively, with vecuronium and atracurium, but the conditions are not as good as those commonly found using suxamethonium. Priming at 6 min has no advantage over priming at 4 min. The onset of complete block was accelerated with priming, but the difference was not significant. The duration of clinical relaxation of vecuronium was significantly prolonged by giving it in divided doses. Unpleasant awareness of muscle weakness was observed in 15 patients, requiring early induction of anaesthesia in five of them.     

Refining the priming principle for vecuronium during rapid-sequence induction of anesthesia

Administration of a subparalyzing dose of a nondepolarizing muscle relaxant (priming dose) prior to its intubating dose hastens the onset time (time from muscle relaxant administration to 100% depression of twitch tension) of neuromuscular blockade. This study was undertaken to determine the optimal priming and intubating doses and time interval between these doses (priming interval) of vecuronium during rapid-sequence induction of anesthesia. The authors measured single-twitch tension in 79 healthy, awake, premedicated (fentanyl, 50-150 mu iv, and/or diazepam, 5-10 mg iv) patients. In Part A of the study, the priming dose was varied (0.0, 0.005, 0.01, 0.0015, or 0.02 mg/kg iv). Decrement of twitch tension and symptoms were recorded 3 min later. Four minutes after the priming dose, thiopental, 4-6 mg/kg iv, and vecuronium, 0.1 mg/kg iv, were given. Onset times for the 0.01, 0.015, and 0.02 mg/kg groups were significantly shorter than for 0.005 and 0.0 mg/kg groups. No breathing difficulties were encountered in any of the groups. Decrement of twitch tension greater than 25% of control only occurred in the 0.02 mg/kg group (4 of 11 patients). In Part B, the priming interval was varied (2, 4, or 6 min) after giving the optimal priming dose (0.01 mg/kg). Anesthesia was induced as in Part A. Onset times for the 4-min group were significantly faster than the 2- or 6-min groups. In Part C, the intubating dose was varied (0.07, 0.1, or 0.15 mg/kg iv) after the optimal priming dose and optimal priming interval (4 min). Onset times for the 0.1 mg/kg and 0.15 mg/kg groups were significantly faster than the 0.07 mg/kg group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rapid-sequence orotracheal intubation: a comparison of three techniques

The authors compared tracheal intubating conditions using three techniques for rapid-sequence orotracheal intubation. Sixty patients were randomly assigned to one of three groups: priming with vecuronium (0.01 mg/kg priming dose, 4-min priming interval, 0.14-mg/kg intubating dose along with thiopental 4-6 mg iv); timing with vecuronium (0.15-mg/kg intubating dose given before thiopental and timed to weakness of hand grip); and succinylcholine (1.5 mg/kg). Blinded intubators graded intubating conditions 60 s after the induction of anesthesia with thiopental. Intubation scores in the succinylcholine group were significantly better than in the priming group (P = 0.009). Intubation scores of the succinylcholine and the timing groups were not significantly different. Use of the timing principle for rapid-sequence orotracheal intubation is a reliable alternative in cases where succinylcholine is contraindicated.     

Rapid onset of the action of vecuronium by administration of a precurarizing dose

The administration of vecuronium in divided doses with respect to onset of action and intubating conditions was investigated. This study was conducted in 3 parts. In part 1 the maximal precurarizing dose of 0.015 mg/kg vecuronium was found. In the second part we showed that the optimal time interval between divided doses was 3 min. In the third part we made a comparative investigation between the effect of 0.015 + 0.085 mg/kg body wt. at a 3 min interval and that of a single dose of 0.1 mg/kg body wt. vecuronium. --Neuromuscular function was assessed in semiquantitative manner, using the train of four (TOF) stimulation of ulnar nerve. Administration of vecuronium in divided doses, compared with a single dose of 0.1 mg/kg body wt., resulted in a more than 1 min earlier onset time of 1.5-2.5 min and facilitated early intubation. As soon as twitch tension had completely disappeared uniform by excellent intubating conditions were available in all cases. The administration of vecuronium in divided doses enabled better intubating conditions than the same single dose of vecuronium.     

Thiopental--ketamine association and low dose priming with rocuronium for rapid sequence in duction of anaesthesia for elective cesareum section

Obstetric patients undergoing caesarean section under general anaesthesia require rapid induction due to high risk of aspiration. Rocuronium provides the shortest onset of action of nondepolarizing blocking agents. Onset time can be shortened by the priming principle. Ketamine has been shown to improve intubating conditions when used in association with rocuronium. Even if ketamine crosses the placenta rapidly, it does not produce neonatal depression unless used in doses above 1-1.5 mg x kg(-1). We present a case of elective caesarean section due to pelvic disproportion managed in general anaesthesia. Following 5 min of preoxygenation, a priming dose of 0.04 mg x kg(-1) of rocuronium was administered. The patient was maintained on spontaneous breathing with 100% oxygen by face mask for 3 min and then induced in rapid sequence with thiopental 2 mg x kg(-1), ketamine 1 mg x kg(-1) and 0.4 mg x kg(-1) or rocuronium. Intubation was performed 30 s after induction (twitch tension 17%) with an excellent clinical intubating score. No adverse events such as muscle weakness or patient discomfort were observed or reported by the patient. Time from injection of the intubating does of rocuronium to recovery of 25% of single twitch was 26 min. Recovery index (T25-75) was, instead, of 3 min and 25 s. The combination of the induction agents thiopental and ketamine, associated with low dose priming with rocuronium, have guaranteed excellent intubating conditions in this clinical context.     

Facilitation of rapid endotracheal intubations with divided doses of nondepolarizing neuromuscular blocking drugs

The authors sought to determine whether prior administration of a small, subparalyzing dose of nondepolarizing muscle relaxant would shorten the onset time of an intubating dose of muscle relaxant. Initially, in 60 anesthetized patients, twitch response of adductor pollicis to ulnar nerve stimulation was studied after a small dose of pancuronium 0.015 mg . kg-1, metocurine 0.03 mg . kg-1, or d-tubocurarine 0.04 mg . kg-1, followed 3 min later by pancuronium 0.08 mg . kg-1 or atracurium 0.4 mg . kg-1 administered iv. After 60 s, the minimum neuromuscular block, in all patients was 79.0 +/- 5.0%. A 95% depression or twitch tension occurred between 59.1 +/- 5.3 and 86.1 +/- 5.9 s. In another 60 patients, intubating conditions under similar regimen were studied, except the small dose of muscle relaxant was given immediately prior to induction of anesthesia. At the end of 60 s, good to excellent intubating conditions were present in 100% of the patients following the second dose of pancuronium and in 83% of the patients following atracurium. In 17% of the patients, after atracurium intubating conditions were fair. When nondepolarizing neuromuscular blocking drugs are administered in divided doses, neuromuscular blockade adequate for endotracheal intubation is achieved in less than 90 s. This facilitates rapid endotracheal intubation in a time comparable to using succinylcholine, without undesirable effects of the depolarizing neuromuscular blocking drugs.     

Intubation with low-dose atracurium in children

The objective of this study was to compare intubating conditions and neuromuscular effects using smaller doses of atracurium (0.25 mg/kg and 0.3 mg/kg) with the recommended dose of 0.4 mg/kg for intubation in children anesthetized with halothane, N2O and oxygen undergoing strabismus repair. All patients (10 in each group) had good or excellent intubating conditions at 80% depression of twitch height [T1 of train-of-four (TOF) stimulation]. Mean times to intubation were 2.6 +/- 0.2 minutes following 0.25 mg/kg and 2.2 +/- 0.2 minutes following 0.3 mg/kg. These times were significantly longer (P less than 0.05) than the mean intubation time of 1.5 +/- 0.2 minutes following 0.4 mg/kg. Mean times to recovery, defined as times from injection of atracurium to return of T1 of TOF to 10%, 25%, and 95% of control measurements, were significantly shorter with the smaller doses. Atracurium at these low doses may provide an alternative to succinylcholine for intubating children during halothane anesthesia for surgical procedures lasting 20-30 min.     

Comparative clinical studies of vecuronium, atracurium and pancuronium

The new relaxants vecuronium (Norcuron) and atracurium (Tracrium) have been compared with pancuronium (Pavulon) with respect to onset and duration of action and intubating conditions under clinical situations. A variant of the balanced anaesthesia technique with flunitrazepam, fentanyl and N2O/O2 was used. The following doses were considered equipotent (mg/kg body weight): vecuronium 0.07/0.10; atracurium 0.35/0.50; pancuronium 0.08/0.115. The degree of neuromuscular block was assessed in a semiquantitative manner, using the train of four. No difference between the three relaxants in onset of action was found. After the high doses, however, full paralysis developed 60 s earlier. The same is true of intubating conditions. Good or very good intubating conditions were obtained in the majority of cases 3 minutes after injection of the drug. Following the higher dose, good intubating conditions are achieved approximatively 1/2-1 min sooner. Both new relaxants allow for relatively rapid intubation without the inconvenience of a long duration of action. After a low initial dose the following time for recovery to 25% was noted (means +/- S.D., min): vecuronium 20.3 +/- 7.0; atracurium 28.0 +/- 3.1; pancuronium 53.3 +/- 14.8. The early recovery phase (from 5% to 25% recovery) was 6.1 +/- 2.4 after vecuronium, 8.3 +/- 1.7 after atracurium, 17.2 +/- 10.8 after pancuronium. There is a good correlation between our semiquantitative results, using the train of four, and quantitative recordings of muscle contractions reported in the literature. Both drugs show no cumulative effect after five repeated administrations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of intubating conditions with atracurium, vecuronium and pancuronium

A blind trial, comparing time of onset of satisfactory conditions for tracheal intubation with atracurium 0.6 mg/kg, vecuronium 0.1 mg/kg and pancuronium 0.1 mg/kg is described. Intubation was attempted at 30-second intervals in 60 patients, randomly allocated to receive one of the above muscle relaxants. Patients receiving atracurium 0.6 mg/kg could be intubated from 30 to 120 seconds. Patients receiving either vecuronium 0.1 mg/kg or pancuronium 0.1 mg/kg were able to be intubated between 60 and 240 seconds. The results showed a statistically significant earlier onset of satisfactory intubating conditions with atracurium than with vecuronium or pancuronium in these doses but no difference between vecuronium and pancuronium.     

Rapid sequence induction using vecuronium

The purpose of this study was to determine the ideal priming and total dose of vecuronium when used as the relaxant during rapid sequence induction of anesthesia and tracheal intubation. Seventy patients were studied. Various priming and total dose schedules using vecuronium were compared with succinylcholine, 1.5 mg/kg. The mean onset times, intubating conditions, and mean duration times were compared. A priming dose of 10 micrograms/kg produced good intubation conditions with both 70 micrograms/kg and 150 micrograms/kg (total doses), but the mean onset times remained significantly longer than succinylcholine 1.5 mg/kg (P less than 0.05). A priming dose of 15 micrograms/kg of vecuronium with 100 micrograms/kg total dose, on the other hand, not only produced excellent intubating conditions but also resulted in a mean onset time not significantly different from succinylcholine, 1.5 mg/kg. This latter dose schedule of vecuronium is recommended for rapid sequence induction when succinylcholine is contraindicated. Vecuronium is preferable to pancuronium for rapid sequence induction because of its lack of cardiovascular side effects and short duration.     

Speed and ease of tracheal intubation: priming with mivacurium compared with succinylcholine

This study examined the efficacy of mivacurium priming (0.015 mg · kg^?1) with five minutes between the priming and intubating doses by comparing the effects of one, two and three times the ED₉₅ dose (0.075 mg · kg^?1) of mivacurium after priming (Groups 1, 2 and 3, respectively), with a saline prime and 2 × ED₉₅ mivacurium (Group 4) or 1 mg · kg^?1 dose of succinylcholine (Group 5). The time from the intubating dose injection to intubation was measured and intubating conditions were rated on a five-point scale with 4 being optimal and 0 being failure. Mean times (± SEM) in seconds between the administration of the intubating dose and tracheal intubation were: 106.4 ± 5.1, 89.6 ± 6.7, 81.9 ± 2.7, 169.9 ± 7.8 and 82.9 ± 3.5 for Groups 1–5 respectively. The times for Group 2 (2 × ED₉₅ with priming), Group 3 (3 × ED₉₅ with priming) and Group 5 (succinylcholine with saline) were shorter than the times of Groups 1 (1 × ED₉₅ with priming) and 4 (2 × ED₉₅ with saline) P < 0.05. Mean intubating condition scores (± SD) for the five groups respectively were 3.1 ± 0.6, 3.4 ± 0.6, 3.5 ± 0.5, 3.2 ± 0.6 and 3.8 ± 0.4. Scores for Groups 2, 3 and 5 were higher than those of Group 1 (P < 0.05). The data demonstrated that (1) priming with mivacurium shortens the intubation time and is accompanied by good intubating conditions with doses 2× and 3× ED₉₅, and (2) intubating times and conditions similar to those achieved with succinylcholine can be obtained using mivacurium 2× (total dose 0.150 mg · kg^?1) or3 × ED₉₅ (total dose 0.215 mg · kg^?1) with a five-minute priming interval. Priming provides an alternative technique in those clinical circumstances where succinylcholine is contraindicated.