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 tracheal intubation with vecuronium: the priming principle

Following the administration of a single 0.1 mg/kg dose of vecuronium bromide, satisfactory conditions for tracheal intubation developed in 156 +/- 12 s (mean +/- SEM), and the clinical duration of the initial dose was 36 +/- 2 min. When the initial dose of vecuronium was administered in two increments, a 0.015 mg/kg "priming" dose, followed 6 min later by a 0.050 mg/kg "intubating" dose, intubation time decreased to 61 +/- 3 s and clinical duration to 21 +/- 1 min. The priming dose that had no unpleasant effect on premedicated, awake patients could be administered 3-4 min before, and the intubating dose 2 to 3 min after induction of anesthesia. With the described technique, comparable intubating conditions could be obtained just as rapidly with vecuronium as with succinylcholine chloride, without subjecting the patients to the side effects of and the complications occasionally encountered with succinylcholine. An added advantage of the use of a priming dose is that it will reveal undiagnosed, pathologic, or idiopathic increase of sensitivity to nondepolarizing muscle relaxants.     

Rapid induction sequence with vecuronium: should we intubate after 60 or 90 seconds?

The purpose of the study was to determine intubating conditions after administration of either succinylcholine or vecuronium in a rapid induction sequence. Patients received either succinylcholine 1.5 mg.kg-1 (Groups I and II) after d-tubocurarine 0.05 mg.kg-1 four minutes earlier, or vecuronium (Groups III and IV) in an initial dose of 0.01 mg.kg-1 followed four minutes later by 0.1 mg.kg-1. In Groups I and III an apnoeic delay of one minute was allowed before intubation whereas in Groups II and IV the delay was 90 sec. There was no significant difference in intubating conditions between Groups I and IV. Intubating conditions in Group III (vecuronium-delay of one minute) were statistically worse than in any of the three other groups. A delay of 90 sec after succinylcholine improved intubating conditions in male patients. Considering that intubating conditions obtained after 90 sec in patients given a priming sequence with vecuronium (Group IV) were not different from those obtained 60 sec after succinylcholine (Group I), the authors conclude that vecuronium is an acceptable alternative for rapid tracheal intubation. In the doses used in this study, intubating conditions 60 sec after vecuronium were unacceptable for rapid induction of anaesthesia.     

Pharmacodynamics of high-dose vecuronium in children during balanced anesthesia.

To compare the speed of onset, intubating conditions, duration of action, and recovery from neuromuscular blockade with vecuronium to those with succinylcholine, 40 ASA physical status 1 or 2 children (ages 2-9 yr) were studied during N2O-O2-opioid anesthesia. Each child was randomly assigned to receive a bolus dose of one of the following muscle relaxants: succinylcholine 2.0 mg/kg (n = 10), vecuronium 0.1 mg/kg (n = 10), vecuronium 0.2 mg/kg (n = 10), or vecuronium 0.4 mg/kg (n = 10). The evoked electromyogram of the abductor digiti minimi to train-of-four stimulation was monitored. We found that with succinylcholine, the time to 95% twitch depression (speed of onset, mean +/- SD), 24 +/- 7 s, was significantly less than that with each dose of vecuronium: 0.1 mg/kg, 83 +/- 21 s; 0.2 mg/kg, 58 +/- 17 s; and 0.4 mg/kg, 39 +/- 11 s, respectively (P less than 0.05). The time to laryngoscopy and intubation did not differ significantly between succinylcholine (48 +/- 10 s) and vecuronium 0.4 mg/kg (57 +/- 13 s); however, both were significantly less than than with vecuronium 0.1 and 0.2 mg/kg (P less than 0.005). The intubating conditions were excellent in 100% of patients. The duration of action was least with succinylcholine (5.7 +/- 1.5 min) and increased with increasing doses of vecuronium: 0.1 mg/kg, 23.9 +/- 5.1 min; 0.2 mg/kg, 55.2 +/- 11.6 min; and 0.4 mg/kg, 74.6 +/- 9.9 min, respectively (P less than 0.001). The recovery index was most rapid with succinylcholine (1.6 +/- 0.4 min) and was slowest with vecuronium 0.4 mg/kg (22.6 +/- 2.1 min) (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Onset and duration of neuromuscular blockade following high-dose vecuronium administration

To determine the onset time and duration of high doses of vecuronium, 40 ASA Physical Status 1 and 2 patients were randomly assigned to receive either 100, 200, 300, or 400 micrograms/kg of vecuronium bromide for muscle relaxation during elective general surgery. Neuromuscular blockade was continuously quantitated by recording the electromyographic response to stimulation of the ulnar nerve train-of-four. The rate of onset of neuromuscular blockade, endotracheal intubating conditions, duration of neuromuscular blockade, and hemodynamic effects of vecuronium at each dose were evaluated and compared. The time from vecuronium administration to complete abolition of twitch tension (T1 = 0%) decreased from 208 +/- 41 to 106 +/- 35 s as the vecuronium dose was increased from 100 to 400 micrograms/kg (P less than 0.01). Corresponding times to endotracheal intubation (T1 less than 20%) also decreased from 183 +/- 24 to 96 +/- 31 s with increasing doses (P less than 0.01). Recovery time (T1 = 25%) increased from 37 +/- 13 to 138 +/- 24 min with increasing doses (P less than 0.01). No significant hemodynamic differences between the four groups were observed. Endotracheal intubating conditions were good or excellent in all patients. High doses of vecuronium may, therefore, be a useful alternative to succinylcholine when a rapid onset of neuromuscular blockade is required.     

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.     

Duration of action of vecuronium after an intubating dose of rapacuronium, vecuronium, or succinylcholine

Rapacuronium (RAP) is a new, rapid-onset, short-duration, nondepolarizing neuromuscular blocker. If RAP is used to facilitate endotracheal intubation, what will the duration of a subsequent maintenance dose of vecuronium (VEC) be? We investigated the duration of action of a maintenance dose of VEC after intubation with RAP, VEC, or succinylcholine (SUC). Adult surgical patients under general anesthesia were randomly allocated to receive a tracheal intubating dose of RAP 1.5 mg/kg, VEC 0.1 mg/kg, or SUC 1 mg/kg. The anesthetic was induced with propofol and maintained with propofol, nitrous oxide, and oxygen. Neuromuscular function was monitored with electromyography. Recovery of the intubating dose of neuromuscular blocker was allowed to occur spontaneously until the first twitch of the train-of-four (T1) reached 50% of baseline, and then VEC 0.025 mg/kg (0.5 x 95% effective dose [ED(95)]) was administered. The onset, duration, and recovery to T1 = 25% and 50% were recorded. The durations of action (recovery of T1 25%) after intubating doses of RAP, VEC, and SUC were 13.7 +/- 5.3, 43.2 +/- 13.2, and 9.2 +/- 3.7 min (mean +/- SD), respectively (P < 0.0001). The times to maximum depression of T1 after a maintenance dose of VEC (0.5 x ED(95)) were 5.4 +/- 2.9, 5.1 +/- 2.5, and 5.3 +/- 2.8 min (mean +/- SD) for the RAP, VEC, and SUC groups, respectively. Recoveries to T1 25% after VEC for the RAP, VEC, and SUC groups were 18.9 +/- 11.5, 21.5 +/- 8.03, and 12.8 +/- 8.4 min, and at T1 50% they were 21.5 +/- 9.1, 30.8 +/- 9.5, and 15.5 +/- 9.7 min (mean +/- SD), respectively (P < 0.001, RAP and VEC versus SUC). The duration of action of a maintenance dose of VEC was similar after an intubating dose of RAP or VEC but was shortened when preceded by an intubating dose of SUC. IMPLICATIONS: The duration of action of a maintenance dose of vecuronium was longer after an endotracheal intubating dose of rapacuronium compared with succinylcholine.     

Dose-response relation, neuromuscular blocking action, intubation conditions, and cardiovascular effects of Org 9273, a new neuromuscular blocking agent.

The ED50 and the ED90, the time-course of the neuromuscular block, the intubation conditions, and the cardiovascular effects of Org 9273, a new steroidal nondepolarizing neuromuscular blocking agent, have been evaluated in 41 anesthetized patients. From cumulative dose-response curves the ED50 and ED90 were calculated to be 175 and 300 micrograms/kg, respectively. The time-course of neuromuscular blockade after 300- and 500-micrograms/kg doses of Org 9273 appeared to be similar to that of equipotent doses of vecuronium. The neuromuscular block was characterized by a fast initial rate of block development. High-dose Org 9273 (1 mg/kg = 3-4 times the ED90) had a clinical duration comparable to an intubating dose of pancuronium, but a considerably more rapid onset and recovery index. Three hundred micrograms per kilogram and 500 micrograms/kg Org 9273 produced good to excellent intubation conditions 1 min after administration. Org 9273 in a dose of 0.5-2 times the ED90 produced no cardiovascular changes; however, 3-4 times the ED90 increased heart rate 20%-25% (P less than 0.001), probably due to a vagolytic effect.     

Variability of onset times within and among relaxant regimens.

STUDY OBJECTIVE: To evaluate the consistency of times to 95% twitch height depression (T95%) in groups of patients receiving identical induction and relaxant regimens. DESIGN: Prospective, noncontrolled, blinded study. SETTING: Ambulatory surgical unit at a university medical center. PATIENTS: Seventy-five ASA physical status I and II patients undergoing general endotracheal anesthesia. INTERVENTIONS: Patients received succinylcholine 1.5 mg/kg or a nondepolarizing regimen with doses ranging from approximately 1.5 to 6 times the ED95, with or without a priming dose. MEASUREMENTS AND MAIN RESULTS: For each of the eight relaxant regimens used in five or more patients, the intraregimen variability of T95% (at the adductor pollicis muscle upon ulnar stimulation at 0.1 Hz) was expressed as SD and range, and the individual data points were displayed. There was wide intraregimen variability. For each regimen, the slowest T95% was at least 73% longer than the fastest T95%. For the 16 patients receiving a priming dose plus an intubating dose 5 or more times the ED95, the median T95% was 95 seconds; however, T95% was beyond 120 seconds in 5 of the 16 cases. CONCLUSIONS: The wide variability in onset times among subjects receiving the same regimen indicates that monitoring of neuromuscular response, preferably to a relatively slow rate of neurostimulation, is essential if one elects to use moderate to high doses of atracurium and/or vecuronium for rapid-sequence induction in a patient in whom movement or coughing is unacceptable. Since onset times were not symmetrical about the mean, the magnitude and frequency of unacceptable onset times would not be fully appreciated unless the individual data points were displayed. Such information may be critical when reporting the suitability of a neuromuscular blocking drug for rapid intubation.     

Effects of alfentanil and lidocaine on the hemodynamic responses to laryngoscopy and tracheal intubation

This study was undertaken to determine whether lidocaine and/or alfentanil can effectively abolish or attenuate the increase in mean arterial pressure (MAP), heart rate (HR), and rate pressure product (RPP) associated with rapid sequence induction of anesthesia. Sixty patients were randomly divided into four groups. Group 1 received saline 10 ml, group 2 received lidocaine 2 mg/kg, group 3 received alfentanil 15 micrograms/kg, and group 4 received alfentanil 30 micrograms/kg. All patients were induced with sodium thiopental 4 mg/kg and succinylcholine 1.5 mg/kg to facilitate tracheal intubation. The study drug was given after sodium thiopental was administered, and the investigator was blinded to it. Blood pressure (BP) and HR were recorded at the following times: before induction; after induction but before laryngoscopy and intubation; and 1, 3, and 5 minutes after intubation. Alfentanil 15 and 30 micrograms/kg given in rapid sequence fashion with thiopental and succinylcholine effectively blunted the hemodynamic responses to laryngoscopy and tracheal intubation. Lidocaine 2 mg/kg and saline were found to be ineffective in blunting these same responses.     

维库溴铵预注复合麻黄素预处理对麻醉诱导时维库溴铵的起效时间的影响

目的 探讨丙泊酚、芬太尼全麻诱导前预注射麻黄素和维库溴铵对维库溴铵的起效时间和诱导后血流动力学的影响.方法 48例全麻下行择期手术的成年患者,ASA分级Ⅰ或Ⅱ级,按随机数余数分组法分成4组,每组12例.在麻醉诱导前预先静注:Ⅰ组麻黄素70μg/kg和0.01 mg/kg维库溴铵、Ⅱ组0.01 mg/kg维库溴铵、Ⅲ组麻...     

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.     

Priming with vecuronium and atracurium--a comparison

Vecuronium (V) and atracurium (A) were compared in a randomised study in premedicated patients undergoing laparoscopy for gynecological pathology. Both groups contained ten patients. Anesthesia was induced with fentanyl (0.1 mg) and thiopentone (1 mg/kg initially and subsequently 4 mg/kg). A priming dose of vecuronium (20 micrograms/kg) or atracurium (100 micrograms/kg) was given one minute before the intubating dose (60 micrograms/kg for vecuronium and 300 micrograms/kg for atracurium). Ninety seconds thereafter intubation was performed. Maintenance of anesthesia consisted of isoflurane at an inspiratory concentration of 1% in a mixture of O2/N2O (50%/50%) with small supplements of fentanyl. Neuromuscular block was monitored with the Datex Relaxograph. Results show that neither drug offers major clinical advantages over the other: there is no difference in speed of onset (V:T190sec 14.6 +/- 4.3%; A:T190sec 23.5 +/- 6.5%; Mean +/- SEM) and duration of neuromuscular block (V:T150sec 34.2 +/- 3.5 min; A:T150sec 41.3 +/- 2.8 min; Mean +/- SEM) and intubation conditions are almost identical.     

Comparison of tracheal intubating conditions and neuromuscular blocking profiles after intubating doses of mivacurium chloride or succinylcholine in surgical outpatients

Thirty ASA physical status I or II outpatients scheduled to undergo short procedures (less than 1 hr in duration) requiring tracheal intubation received either 1.0 mg/kg succinylcholine or 0.20 mg/kg (2.5 x ED95) or 0.25 mg/kg (3 x ED95) mivacurium. A N2O/O2/narcotic anesthetic technique was utilized and the ulnar nerve was stimulated with subcutaneous electrodes placed at the wrist. Tracheal intubation was attempted in all patients either 2 min after mivacurium or 1 min after succinylcholine. Intubation conditions were not different between the succinylcholine and mivacurium groups or between the two mivacurium groups. The onset and duration of neuromuscular blockade were shorter with succinylcholine than with mivacurium. Suppression of the T1 response to 90% of baseline occurred in 0.9 min with 1.0 mg/kg succinylcholine and at 2.2 and 1.5 min respectively, with 0.20 mg/kg and 0.25 mg/kg mivacurium. Initial recovery of the T1 response occurred at 6.4 min after 1.0 mg/kg succinylcholine and 12.7 and 13.6 min respectively after 0.20 mg/kg and 0.25 mg/kg mivacurium. Subsequent to initial recovery from the intubating dose of relaxant, infusions of mivacurium or succinylcholine were administered to maintain approximately 95% block. The mean infusion rates were 6.6 micrograms.kg-1.min-1 mivacurium and 41.2 micrograms.kg-1.min-1 for succinylcholine. Spontaneous recovery from neuromuscular blockade occurred more quickly after succinylcholine than after mivacurium: the time from cessation of infusion to recovery of T1 to 95% of baseline was 6.5 min in patients given succinylcholine and 16.7 min in patients given mivacurium. When reversal was in order, residual mivacurium-induced blockade was readily antagonized by 0.045 mg/kg neostigmine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Optimal dose of succinylcholine revisited

BACKGROUND: The authors reappraised the conventional wisdom that the intubating dose of succinylcholine must be 1.0 mg/kg and attempted to define the lower range of succinylcholine doses that provide acceptable intubation conditions in 95% of patients within 60 s. METHODS: This prospective, randomized, double-blind study involved 200 patients. Anesthesia was induced with 2 mug/kg fentanyl and 2 mg/kg propofol. After loss of consciousness, patients were randomly allocated to receive 0.3, 0.5, or 1.0 mg/kg succinylcholine or saline (control group). Tracheal intubation was performed 60 s later. A blinded investigator performed all laryngoscopies and also graded intubating conditions. RESULTS: Intubating conditions were acceptable (excellent plus good grade combined) in 30%, 92%, 94%, and 98% of patients after 0.0, 0.3, 0.5, and 1.0 mg/kg succinylcholine, respectively. The incidence of acceptable intubating conditions was significantly greater (P < 0.05) in patients receiving succinylcholine compared with those in the control group but was not different among the different succinylcholine dose groups. The calculated doses of succinylcholine (and their 95% confidence intervals) that were required to achieve acceptable intubating conditions in 90% and 95% of patients at 60 s were 0.24 (0.19-0.31) mg/kg and 0.56 (0.43-0.73) mg/kg, respectively. CONCLUSIONS: The use of 1.0 mg/kg of succinylcholine may be excessive if the goal is to achieve acceptable intubating conditions within 60 s. Comparable intubating conditions were achieved after 0.3, 0.5, or 1.0 mg/kg succinylcholine. In a rapid-sequence induction, 95% of patients with normal airway anatomy anesthetized with 2 mug/kg fentanyl and 2 mg/kg propofol should have acceptable intubating conditions at 60 s after 0.56 mg/kg succinylcholine. Reducing the dose of succinylcholine should allow a more rapid return of spontaneous respiration and airway reflexes.     

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.     

Intubation conditions following rocuronium: influence of induction agent and priming

A small priming dose of rocuronium can shorten the onset time of neuromuscular blockade. Induction agents with less cardiovascular depression also reduce the onset time. We hypothesized that ketamine, compared to thiopentone, would reduce onset time and improve intubating conditions following priming. Sixty patients ASA I to II, randomized by computer-generated sequence to four groups were investigated in a double-blind controlled trial. In the two groups with priming, 0.04 mg/kg of rocuronium was followed by three minutes of priming interval. Induction was followed by an intubation dose of 0.4 mg/kg of rocuronium. After 30 seconds, intubation was attempted within a further 20 seconds. In the two control groups, the same sequence was repeated except sham priming (saline) was given. For induction, S-ketamine (1 mg/kg) or thiopentone (4 mg/kg) were administered. Intubating conditions were graded as excellent, good, poor, or not possible. Neuromuscular transmission was monitored by acceleromyography of the thumb. There were no measured differences in onset time of neuromuscular block or in haemodynamics between the groups. The proportion of good to excellent intubating conditions was higher when ketamine was preceded by priming compared to ketamine without priming (87% vs 20%; P<0.05). In both priming and control groups intubating conditions were improved when using ketamine compared to thiopentone (P<0.05). The mechanism of this effect was not clear from this study.     

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.     

Facilitation of rapid-sequence intubation with large-dose vecuronium with or without priming.

STUDY OBJECTIVES: To determine the effect of priming on the intubation and onset times of vecuronium 0.3 mg/kg. DESIGN: Randomized, unblinded study. SETTING: Operating rooms and postanesthetic recovery unit of a university-affiliated general hospital. PATIENTS: Thirty female ASA physical status I and II patients scheduled for intraperitoneal surgery divided into two groups of 15 each. INTERVENTIONS: Anesthesia was induced and maintained with sufentanil, droperidol, thiopental sodium, and nitrous oxide in oxygen. Patients in Group 1 were given vecuronium 0.015 mg/kg 4 minutes before induction and vecuronium 0.285 mg/kg 1 minute after induction. Patients in Group 2 received a single 0.3 mg/kg dose of vecuronium 1 minute after thiopental sodium. The ulnar nerve was stimulated every 10 seconds with train-of-four supramaximal impulses of 0.2 millisecond duration at 2 Hz. The compound electromyogram (EMG) of the adductor pollicis was continuously recorded. The trachea was intubated when the amplitude of the EMG decreased to 15% to 25% of control. At the end of surgery, residual neuromuscular block was reversed with edrophonium 0.75 mg/kg. MEASUREMENTS AND MAIN RESULTS: All patients in Group 1 could be intubated in 80 seconds or less, and the longest onset time was 120 seconds. In Group 2, the longest intubation time was 140 seconds, and the longest onset time was 200 seconds. Clinical durations in both groups were unpredictable, ranging from 47 to 185 minutes in Group 1 and from 63 to 160 minutes in Group 2. Ten of the 30 patients required an additional 0.5 mg/kg of edrophonium for antagonism of the residual neuromuscular block. There were no significant changes in heart rate or blood pressure attributable to vecuronium. CONCLUSIONS: Seventy-five percent to 85% neuromuscular block of the adductor pollicis, required for atraumatic tracheal intubation, developed in 80 seconds or less when vecuronium 0.3 mg/kg was administered in divided doses and in 140 seconds or less when it was injected as a single bolus dose. Clinical duration of vecuronium 0.3 mg/kg is long and unpredictable, and reversal of residual neuromuscular block may require larger doses of anticholinesterases. It is recommended that an intubating dose of vecuronium 0.3 mg/kg be used only in patients undergoing long surgical procedures that require prolonged postanesthetic mechanical ventilation.