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(1/306) Effects of an intubating dose of succinylcholine and rocuronium on the larynx and diaphragm: an electromyographic study in humans.

BACKGROUND: Paralysis of the vocal cords is one objective of using relaxants to facilitate tracheal intubation. This study compares the neuromuscular blocking effect of succinylcholine and rocuronium on the larynx, the diaphragm, and the adductor pollicis muscle. METHODS: Electromyographic response was used to compare the neuromuscular blocking effect of succinylcholine and rocuronium on the laryngeal adductor muscles, the diaphragm, and the adductor pollicis muscle. Sixteen patients undergoing elective surgery were anesthetized with propofol and fentanyl, and their tracheas were intubated without neuromuscular blocking agents. The recurrent laryngeal and phrenic nerves were stimulated at the neck. The electromyographic response was recorded from electrodes placed on the endotracheal tube and intercostally before and after administration of 1 mg/kg succinylcholine or 0.6 mg/kg rocuronium. RESULTS: The maximum effect was greater at the adductor pollicis (100 and 99%) than at the larynx (96 and 97%) and the diaphragm (94 and 96%) after administration of succinylcholine and rocuronium, respectively (P < or = 0.05). Onset time was not different between the larynx (58+/-10 s), the diaphragm (57+/-8 s), and the adductor pollicis (54+/-13 s), after succinylcholine (all mean +/- SD). After rocuronium, onset time was 124+/-39 s at the larynx, 130+/-44 s at the diaphragm, and 115+/-21 s at the adductor pollicis. After succinylcholine administration, time to 90% recovery was 8.3+/-3.2, 7.2+/-3.5, and 9.1+/-3.0 min at the larynx, the diaphragm, and the adductor pollicis, respectively. Time to 90% recovery after rocuronium administration was 34.9+/-7.6, 30.4+/-4.2, and 49.1+/-11.4 min at the larynx, the diaphragm, and the adductor pollicis, respectively. CONCLUSION: Neuromuscular blocking effect of muscle relaxants on the larynx can be measured noninvasively by electromyography. Although the larynx appears to be resistant to muscle relaxants, we could not demonstrate that its onset time differed from that of peripheral muscles.  (+info)

(2/306) Comparison of intubating conditions after rapacuronium (Org 9487) and succinylcholine following rapid sequence induction in adult patients.

We have assessed intubating conditions provided by rapacuronium (Org 9487) and succinylcholine after rapid sequence induction of anaesthesia in adult patients undergoing elective surgery. We studied 335 patients, ASA I and II, in five centres. Two hundred and thirty-four subjects with normal body weight and 101 obese subjects were allocated randomly to one of four treatment groups differing in the neuromuscular blocking drug administered (rapacuronium 1.5 mg kg-1 or succinylcholine 1 mg kg-1) and in the technique used for induction of anaesthesia (fentanyl 2-3 micrograms kg-1 with thiopental 3-6 mg kg-1 or alfentanil 20 micrograms kg-1 with propofol 1.5-2 mg kg-1). Intubation was started at 50 s by an anaesthetist blinded to the drugs used. Intubating conditions were clinically acceptable (excellent or good) in 89.4% of patients after rapacuronium and in 97.4% after succinylcholine (P = 0.004), the estimated difference being 8.1% (95% confidence interval (CI) 2.0-14.1%). Neither anaesthetic technique nor subject group had an influence on intubating conditions. After intubation, the maximum increase in heart rate averaged 23.1 (SD 25.4%) and 9.4 (26.1%) after rapacuronium and succinylcholine, respectively (P < 0.001). Pulmonary side effects (bronchospasm and increased airway pressure) were observed in 10.7% (95% CI 5.8-17%) and 4.1% (95% CI 1.3-8.8%) of patients given rapacuronium and succinylcholine, respectively (P = 0.021). We conclude that after rapid sequence induction of anaesthesia in adults, clinically acceptable intubating conditions were achieved less frequently after rapacuronium 1.5 mg kg-1 than after succinylcholine.  (+info)

(3/306) Quantal evoked depolarizations underlying the excitatory junction potential of the guinea-pig isolated vas deferens.

1. The effects of a putative gap junction uncoupling agent, heptanol, on the intracellularly recorded junction potentials of the guinea-pig isolated vas deferens have been investigated. 2. After the stimulation-evoked excitatory junction potentials (EJPs) had been suppressed by heptanol (2.0 mM) to undetectable levels, a different pattern of evoked activity ensued. This consisted of transient depolarizations that were similar to EJPs in being stimulus locked and in occurring at a fixed latency, but differed from EJPs in that they occurred intermittently and had considerably briefer time courses. 3. Analysis of the amplitudes and temporal parameters of the rapid residual depolarizations revealed a close similarity with spontaneous EJPs (SEJPs). There was no statistically significant difference between the rise times, time constants of decay and durations of the rapid residual depolarizations and of SEJPs. 4. Selected evoked depolarizations were virtually identical to SEJPs occurring in the same cell. Evoked depolarizations of closely similar amplitude and time course also occurred, usually within a few stimuli of each other. 5. These depolarizations appear to represent the individual quantal depolarizations that normally underlie the EJP and are therefore termed 'quantal excitatory junction potentials' (QEJPs) to distinguish them from both EJPs and SEJPs. 6. We examined the possibility that heptanol revealed QEJPs by disrupting electrical coupling between cells in the smooth muscle syncytium. Heptanol (2.0 mM) had no effect on the amplitude distribution, time courses, or the frequency of occurrence of SEJPs. Intracellular input impedance (Rin) of smooth muscle cells was left unaltered by heptanol. 7. 'Cable' potentials of the vas deferens, recorded using the partition stimulation method, also remained unchanged in the presence of heptanol. Thus, heptanol appeared not to modify syncytial electrical properties of the smooth muscle in any significant way. 8. Our observations show directly that the quantal depolarizations underlying the EJP in syncytial smooth muscle are SEJP-like events. However, no unequivocal statement can be made about the mechanism by which heptanol unmasks QEJPs from EJPs.  (+info)

(4/306) Effect of rocuronium compared with succinylcholine on intraocular pressure during rapid sequence induction of anaesthesia.

We have compared the effect of rocuronium and succinylcholine on intraocular pressure (IOP) during rapid sequence induction of anaesthesia using propofol and fentanyl, in a randomized double-blind study. We studied 30 adult patients, allocated to one of two groups. Anaesthesia was induced with fentanyl 2 micrograms kg-1 and propofol until loss of verbal response. This was followed by succinylcholine 1.5 mg kg-1 (group S; n = 15) or rocuronium 0.9 mg kg-1 (group R; n = 15). Laryngoscopy was performed 60 s later. IOP, mean arterial pressure (MAP) and heart rate (HR) were measured before induction, immediately before intubation and every minute after intubation for 5 min. A Keeler Pulsair air impulse tonometer was used to measure IOP and the mean of two readings obtained in the right eye at each measurement time was recorded. Intubating conditions were evaluated according to a simple scoring system. IOP in the succinylcholine group was significantly greater than that in the rocuronium group (mean 21.6 (SEM 1.4) mm Hg vs 13.3 (1.4) mm Hg; P < 0.001). Intubating conditions were equally good in both groups. We conclude that with rapid sequence induction of anaesthesia using propofol and fentanyl, rocuronium did not cause as great an increase in IOP as succinylcholine and may be an alternative in open eye injury cases.  (+info)

(5/306) Intramuscular rapacuronium in infants and children: dose-ranging and tracheal intubating conditions.

BACKGROUND: Intravenous rapacuronium's rapid onset and short duration suggest that intramuscular rapacuronium might facilitate tracheal intubation without prolonged paralysis. Accordingly, the authors injected rapacuronium into the deltoid muscle to determine the optimal dose and time for intubation in pediatric patients. METHODS: Unpremedicated patients (aged, 2 months to 3 yr) were studied. Part I: Spontaneous minute ventilation (V(E)) and twitch tension were measured during N2O/halothane anesthesia. Rapacuronium (2.2-5.5 mg/kg, given intramuscularly, n = 23), succinylcholine (4 mg/kg, given intramuscularly, n = 12), or vecuronium (0.1 mg/kg, given intravenously, n = 15) was given. Time to 50% depression of V(E) and 10% recovery of twitch were measured. Dose for each patient was changed 10-20% according to the previous patient's response. Part II: In 22 patients anesthetized with 0.82-1.0% halothane, the optimal rapacuronium dose determined in part I (infants, 2.8 mg/kg; children, 4.8 mg/kg) was given intramuscularly. Laryngoscopy was scored. Time to laryngoscopy was increased or decreased 0.5 min according to the previous patient's response. RESULTS: Part I: Rapacuronium typically depressed ventilation in < or = 2 min with 10% twitch recovery in 20-60 min. With succinylcholine, median time to ventilatory depression was 1.3 and 1.1 min for infants and children, respectively; for vecuronium, 0.7 and 0.6 min. Part I: Intubating conditions were good-excellent at 3.0 and 2.5 min in infants and children, respectively; time to 10% twitch recovery (mean +/- SD) was 31 +/- 14 and 36 +/- 14 min in the two groups. CONCLUSIONS: This pilot study indicates that deltoid injection of rapacuronium, 2.8 mg/kg in infants and 4.8 mg/kg in children, permits tracheal intubation within 2.5-3.0 min, despite a light plane of anesthesia. Duration of action is intermediate.  (+info)

(6/306) Effects of non-depolarizing neuromuscular blocking agents on norepinephrine release from human atrial tissue obtained during cardiac surgery.

We have studied the effect of non-depolarizing neuromuscular blocking agents, at concentrations present in serum during anaesthesia, on release of [3H]-norepinephrine ([3H]NE) from superfused atrial appendage obtained during cardiac surgery from 48 patients. Three of the neuromuscular blocking agents (pancuronium, gallamine and rocuronium), which are known to cause an increase in heart rate during anaesthesia, increased stimulation-evoked release of [3H]NE. In contrast, (+)tubocurarine and pipecuronium, neuromuscular blocking agents that do not cause tachycardia, did not affect release of NE. Org 9487 significantly enhanced release while SZ1677 was ineffective, even at concentrations higher than those expected after administration of a 2 x ED95 dose. Atropine enhanced release. These data suggest that the axon terminals of sympathetic nerves in human heart have muscarinic heteroreceptors whose activation by acetylcholine (ACh) released from the vagal nerve reduces release of NE. This action contributes to lowering of heart rate. Therefore, any neuromuscular blocking agent with antimuscarinic actions and capable of increasing the release of NE may produce tachycardia.  (+info)

(7/306) Evaluation of neuromuscular and cardiovascular effects of two doses of rapacuronium (ORG 9487) versus mivacurium and succinylcholine.

BACKGROUND: This study compares the neuromuscular blocking and cardiovascular effects of rapacuronium (ORG 9487), a new aminosteroid nondepolarizing muscle relaxant, to recommended intubating doses of succinylcholine and mivacurium. METHODS: Adult patients were randomized in an open-label fashion to receive 1-5 microg/kg fentanyl before 1.5 mg/kg propofol induction followed by 1.5 or 2.5 mg/kg rapacuronium, 1.0 mg/kg succinylcholine, or 0.25 mg/kg mivacurium (i.e., 0.15 mg/kg followed by 0.1 mg/kg 30 s later). RESULTS: Patient neuromuscular blockade status was monitored by measuring the train-of-four response to a supramaximal stimulus at the ulnar nerve every 12 s. Percentage of the first twitch of the train-of-four (T1) at 60 s was similar in patients receiving 1.5 mg/kg rapacuronium, 2.5 mg/kg rapacuronium, and succinylcholine and was significantly less than in patients in the mivacurium group (26, 16, and 18%, respectively, vs. 48%; P < 0.01). Times to 80% T1 depression were also similar among patients in the 1.5 mg/kg rapacuronium, 2.5 mg/kg rapacuronium, and succinylcholine groups and significantly longer in the mivacurium group (62, 54, and 54 s, respectively, vs. 112 s; P < 0.01). Clinical duration was longer in all groups compared with the succinylcholine group; however, clinical duration in the 1.5 mg/kg rapacuronium group was shorter compared with the mivacurium group (15 vs. 21 min, respectively; P < 0.01). Heart rate changes were mild in the 1.5 mg/kg rapacuronium, succinylcholine, and mivacurium groups. The patients in the 2.5 mg/kg rapacuronium group had significantly higher heart rates compared with patients in the mivacurium group. No differences were found in blood pressure changes among patients in the four groups. CONCLUSIONS: Rapacuronium, 1.5 and 2.5 mg/kg, produced neuromuscular blockade as rapidly as succinylcholine and significantly faster than mivacurium. Although succinylcholine continued to show the shortest duration, 1.5 mg/kg rapacuronium used a rapid onset and a relatively short duration and may be considered an alternative to succinylcholine.  (+info)

(8/306) Neuromuscular blocking agents in paediatric anaesthesia.

Neuromuscular blocking agents are used commonly in paediatric anaesthesia, both to facilitate tracheal intubation and during surgery. Paediatric patients differ from adults in certain pharmacokinetic and pharmacodynamic characteristics. However, because maturational changes in certain of these characteristics counterbalance, dosing requirements do not differ markedly with age. In general, onset is more rapid in paediatric patients than in adults. Succinylcholine is still used commonly in children, despite restrictions by regulatory authorities, because of its rapid onset and offset. However, newer non-depolarizing neuromuscular blocking agents, particularly mivacurium, rocuronium and rapacuronium, offer many of the advantages of succinylcholine without its severe adverse effects: rocuronium and rapacuronium have an onset comparable with that of succinylcholine whereas the onset of mivacurium is slightly longer. In addition, recovery from an intubating dose of either mivacurium or rapacuronium is nearly comparable with that of succinylcholine. If rapacuronium i.m. proves to have a rapid onset without prolonged duration, the remaining value of succinylcholine will diminish.  (+info)