Neuromuscular blocking effects and train-of-four fade with cisatracurium: comparison with other nondepolarising relaxants

A comparison of haemodynamic responses between clinical assessment-guided tracheal intubation and neuromuscular block monitoring-guided tracheal intubation: A prospective, randomised study

BACKGROUND AND AIMS

Haemodynamic responses to laryngoscopy and endotracheal intubation and their hazards are well documented. The purpose of the study was to compare the effects of laryngoscopy and intubation on cardiovascular responses when the appropriate moment for intubation was directed by either clinical judgment or train-of-four assessment.

METHODS

A total of 68 patients, posted for laparoscopic cholecystectomy, were randomised into two groups. In Group M patients, the trachea was intubated after train of four counts became zero in adductor pollicis muscle, whereas in Group C patients, the trachea was intubated after the clinical judgment of jaw muscle relaxation. Changes in heart rate (HR) and mean arterial pressure, intubating conditions and the time between the administration of a neuromuscular blocking agent and endotracheal intubation were recorded. Results were analysed by the Analysis of variance and chi-square tests.

RESULTS

HR and mean arterial pressure were significantly higher in Group C as compared to Group M after laryngoscopy and tracheal intubation (P < 0.05). The mean time required for intubation was significantly shorter in Group C compared to Group M (175 ± 7 s vs. 385 ± 101 s). Excellent and good intubation conditions were observed in all Group M patients, whereas 24 out of 34 patients (70%) in Group C showed excellent and good intubation conditions.

CONCLUSION

Haemodynamic responses to laryngoscopy and tracheal intubation can be significantly attenuated if tracheal intubation is performed following complete paralysis of laryngeal muscles, detected by neuromuscular monitoring of adductor pollicis muscle.

Implementing Protocol-Based Therapy of Continuous Neuromuscular Blockade Provides Cost Minimization

Objective:

To compare empiric and protocol-based therapies of neuromuscular blockade in terms of cost and control of paralysis.

Methods:

Data were prospectively collected for nine months before and five months after a protocol was implemented in the 24-bed medical/surgical/neurologic intensive care unit as a physician-initiated, doublesided medication order form. Pancuronium was the preferred agent and vecuronium was an alternative for patients with renal dysfunction, hepatic dysfunction, or hemodynamic instability.

Results:

Twenty-nine empiric-therapy patients and 17 protocol-based therapy patients were comparatively evaluated. Length of stay in the intensive care unit and duration of neuromuscular blockade were similar between groups. Protocol adherence rate was 76.5%. Protocol-based therapy increased the hourly dose of pancuronium (0.29 ± 0.37 mg vs. 0.02 ± 0.10 mg; p < 0.005) and reduced the mean hourly cost of neuromuscular blockade compared with empiric therapy ($5.11 ± 4.76 Canadian [CDN] vs. $9.03 ± 7.03 CDN; p < 0.05). Vecuronium use did not change, but rocuronium and atracurium were not given after protocol implementation. The proportion of recorded train-of-four measurements representing adequate neuromuscular blockade increased (52.3% vs. 32.7%; p < 0.05) with protocol-based therapy.

Conclusions:

Compliance with a neuromuscular blocking protocol reduces drug costs and improves control of neuromuscular blockade.

Sugammadex in clinical practice

The availability of sugammadex allows greater flexibility in the use of rocuronium and vecuronium during anaesthesia and surgery. The neuromuscular block induced by both drugs can be reversed from both superficial and deep levels of block by adjusting the dose of sugammadex. The dose of sugammadex for reversal of shallow block produced by these neuromuscular blocking drugs is approximately 2 mg.kg(-1) and for deep block the dose is 4 mg.kg(-1). A larger dose of sugammadex (16 mg.kg(-1)) administered 3 min after the neuromuscular blocking drug allows rapid reversal of a neuromuscular block induced by 1-1.2 mg.kg(-1) of rocuronium, thereby raising the possibility of using rocuronium as a replacement for suxamethonium. The use of sugammadex has not been reported to be associated with recurrence of block provided a dose that is adequate for reversal has been used. Sugammadex appears to have an acceptable safety profile. There are no requirements for dose adjustment for age or the use of potent volatile anaesthetic agents.

The undesirable effects of neuromuscular blocking drugs

Neuromuscular blocking drugs are designed to bind to the nicotinic receptor at the neuromuscular junction. However, they also interact with other acetylcholine receptors in the body. Binding to these receptors causes adverse effects that vary with the specificity for the cholinergic receptor in question. Moreover, all neuromuscular blocking drugs may cause hypersensitivity reactions. Often the symptoms are mild and self-limiting but massive histamine release can cause systematic reactions with circulatory and respiratory symptoms and signs. At the end of anaesthesia, no residual effect of a neuromuscular blocking drug should be present. However, the huge variability in response to neuromuscular blocking drugs makes it impossible to predict which patient will suffer postoperative residual curarization. This article discusses the undesirable effects of the currently available neuromuscular blocking drugs including the definitions, diagnosis and causes of hypersensitivity reactions and postoperative residual curarisation.

Xylazine Premedication does not Modify the Onset and Duration of Cisatracurium Blockade in Anaesthetized Dogs

The purpose of this study was to evaluate the effect of xylazine as premedication on the onset time and duration of cisatracurium neuromuscular blockade in anaesthetized dogs. This study was carried out on 12 healthy dogs aged 0.5-6 years and weighing 9-26 kg undergoing various elective surgical procedures. The dogs were randomly divided into two groups of t (test) and c (control), with six dogs each. In group t, premedication was conducted using acepromazine maleate 0.3 mg kg(-1) and xylazine 0.3 mg kg(-1) and in group c only acepromazine (same dose) was injected intramuscularly 20 min before general anaesthesia. After induction with thiopental, anaesthesia was maintained with halothane in oxygen to deliver an end-tidal halothane concentration of 1.1%. Neuromuscular blockade was induced with cisatracurium 0.2 mg kg(-1) and monitored using the train-of-four (TOF) stimulation pattern applied at the ulnar nerve. The onset time of cisatracurium blockade was 195 +/- 85.44 s in test and 153.3 +/- 38.16 s in control group. The duration of neuromuscular blockade was 24.8 +/- 4.79 min in t and 28.3 +/- 5.46 min in the c group. Statistical analysis of the data showed no significant difference between groups in terms of onset and duration of neuromuscular blockade.

Modeling of Twitch Fade Based on Slow Interaction of Nondepolarizing Muscle Relaxants with the Presynaptic Receptors

Nondepolarizing muscle relaxants (MRs) diminish the indirectly evoked single twitch due to their binding to the postsynaptic receptors. Additionally, the MRs produce progressive diminution of successive twitches upon repetitive stimulation (fade). Our study addresses the generation of fade as observed under clinical situation. The study was conducted in two phases. In the clinical part, we have evaluated the time course of twitch depression and fade following the administration of several doses of three MRs (rocuronium, pancuronium, and cisatracurium). In the second part, we have modified our model of neuromuscular transmission to simulate the time course of twitch depression and fade. The MR was assumed to bind to a single site on the presynaptic receptor to produce fade. The rates of interaction with the presynaptic receptors were characterized in terms of the arbitrarily assigned equilibrium dissociation constant and the half-life for dissociation of the presynaptic complex. A method was developed to relate the release of acetylcholine to the occupancy of the presynaptic receptors. The strength of the first and the fourth twitch was calculated from the peak concentration of the activated postsynaptic receptors, i.e., of those receptors with both sites occupied by acetylcholine. Our results indicate that, while the affinity of the MR for the presynaptic receptor plays little role in the time course of fade, the rate of dissociation of the complex between the presynaptic receptors and the muscle relaxant may be critical in determining the time course of fade. Tentative estimates of this parameter are offered.

META-ANALYSIS OF THE DIFFERENCES IN THE TIME TO ONSET OF ACTION BETWEEN ROCURONIUM AND VECURONIUM

1. The aim of the present study was to conduct a meta-analysis of the magnitude of differences in the onset of action (T(max)) between rocuronium and vecuronium. 2. A search was made in PubMed, EMBASE Drugs and Pharmacology, Cochrane Controlled Trials Register and Cochrane Database on Systematic Reviews. Studies comparing the T(max) at the adductor policies between rocuronium and vecuronium administered as an intravenous bolus were included in the study. Twenty-nine effect sizes obtained from 21 studies were included. 3. The result of the meta-analysis of differences was -57.9 s (95% confidence interval -71.4 to -44.3 s), favouring rocuronium over vecuronium. The smallest difference in T(max) between these neuromuscular-blocking agents was observed in children (-19.1 s). The difference in T(max) between rocuronium and vecuronium in female patients was -38.7 s. The difference in T(max) between rocuronium and vecuronium measured by electromyography was approximately 50% shorter than that determined by acceleromyography or mechanomyography. In a subanalysis between rocuronium 600 mg/kg versus vecuronium 100 mg/kg, the difference in T(max) between them was very similar to that obtained in the general meta-analysis. 4. According to subanalyses of patient age and sex, drug dose and neuromuscular monitoring systems, the T(max) of rocuronium was approximately 20-70 s faster than that of vecuronium.

Time course and train-of-four fade of mivacurium block during sevoflurane and intravenous anaesthesia

BACKGROUND AND OBJECTIVE

Volatile anaesthetics inhibit nicotinic acetylcholine receptors at clinically relevant concentrations with higher affinity for the neuronal nicotinic receptor. The inhibitory effects of propofol on nicotinic receptors have only been documented at supraclinical concentrations. The aim of this study was to determine recovery properties and train-of-four (TOF) fade of mivacurium during sevoflurane and propofol anaesthesia, in order to examine any differences both in the enhancement of the neuromuscular block (postjunctional effects) and in TOF fade (prejunctional effects).

METHODS

Twenty ASA I-II adult patients were randomly allocated to maintenance of anaesthesia with sevoflurane (end-tidal concentration 2%) or propofol. Neuromuscular block was assessed by acceleromyography and a single dose of mivacurium (0.15 mg kg(-1)) was administered (in the sevoflurane group after 30 min of exposure to sevoflurane). We measured time for recovery of the first twitch of the TOF (T1) from 25-75%, time from 25% recovery of T1 to achieving a TOF ratio (TOFR) of 0.8, TOFR at 50%, 75% and 90% recovery of T1, and height of T1 at TOFR of 0.7 and 0.9. Data were tested using t-test for independent samples.

RESULTS

Recovery times (mean (95% confidence interval, CI)) of mivacurium in the sevoflurane group (T1 25-75%, 11.3 (8.1-14.5) min; T1 25%-TOFR0.8, 19.1 (15.7-22.5) min) were significantly longer (P < 0.05) than in the propofol group (T1 25-75%, 6.5 (5.2-7.7) min; T1 25%-TOFR0.8, 11.3 (7.8-10.3) min). No differences were found in the relations between TOFR and T1 or vice versa, between the groups.

CONCLUSIONS

Recovery times after a single dose of mivacurium were prolonged by sevoflurane compared with propofol but no differences in TOF fade were observed between the two anaesthetics.

Newer neuromuscular blocking agents: how do they compare with established agents?

Rapacuronium bromide (rapacuronium; ORG-9487) is a nondepolarising muscle relaxant (NMBA) with a low potency [90% effective dose (ED90) 1 mg/kg], which to some extent is responsible for its rapid onset of action. Because of the high plasma clearance (5.3 to 11.1 mg/kg/min) of rapacuronium, its clinical duration of action following single bolus doses up to 2 mg/kg in adults is short (i.e. <20 minutes). Rapacuronium forms a pharmacologically active 3-desacetyl metabolite, ORG-9488, which may contribute to a delay in spontaneous recovery after repeat bolus doses or infusions. After rapacuronium 1.5 mg/kg clinically acceptable intubating conditions are achieved within 60 to 90 seconds in the majority of adult and elderly patients undergoing elective anaesthesia. However, in a rapid-sequence setting. intubating conditions are less favourable after rapacuronium 1.5 to 2.5 mg/kg than after succinylcholine. The most prominent adverse effects of rapacuronium (tachycardia, hypotension and bronchospasm) are dose-related, and in particular pulmonary adverse effects are observed more frequently under conditions of a rapid-sequence induction in adults. Therefore, it seems worthwhile to consider only doses of rapacuronium < or = 1.5 mg/kg to facilitate rapid tracheal intubation, and to use succinylcholine or rocuronium rather than rapacuronium in a rapid-sequence setting. Rapacuronium, however, is a suitable alternative to mivacurium chloride (mivacurium) and succinylcholine for short procedures (e.g. ambulatory anaesthesia). Rocuronium bromide (rocuronium) is a relatively low-potent, intermediateacting NMBA. Its main advantage is the rapid onset of neuromuscular block whereby good or excellent intubating conditions are achieved within 60 to 90 seconds after rocuronium 0.6 mg/kg (2 x ED95), and within 60 to 180 seconds after smaller doses (1 to 1.5 x ED95). Larger doses of rocuronium (> or = 1 mg/kg) seem to be suitable for rapid-sequence induction under relatively light anaesthesia. However, it is still a matter of controversy whether, in the case of an unanticipated difficult intubation, the long duration of rocuronium administered in such large doses outweighs the many adverse effects of succinylcholine. Rocuronium has mild vagolytic effects and does not release histamine, even when administered in large doses. Rocuronium is primarily eliminated via the liver and its pharmacokinetic profile is similar to that of vecuronium bromide (vecuronium). Unlike vecuronium, rocuronium has no metabolite. Cisatracurium besilate (cisatracurium), the IR-cis, 1'R-cis isomer of atracurium besilate (atracurium) is approximately 4 times more potent than atracurium. The onset time of cisatracurium is significantly slower than after equipotent doses of atracurium. The recommended intubating dose is 0.15 to 0.2 mg/kg (3 to 4 times ED95). Over a wide range of clinically relevant doses the recovery properties of cisatracurium are affected by neither the size of the bolus dose nor by the duration of infusion. Unlike atracurium, cisatracurium does not trigger histamine release. Like atracurium, cisatracurium undergoes Hofmann elimination. In contrast to atracurium, cisatracurium does not undergo hydrolysis by nonspecific plasma esterases. Moreover, about 77% of the drug is cleared by organ-dependent mechanisms.

Desflurane reduces the effective therapeutic infusion rate (ETI) of cisatracurium more than isoflurane, sevoflurane, or propofol

PURPOSE

The present study investigated the interaction between the cumulative dose requirements of cisatracurium and anesthesia with isoflurane, sevoflurane, desflurane or propofol using closed-loop feedback control.

METHODS

Fifty-six patients (18-85 yr, vitrectomies of more than one hour) were studied. In the volatile anesthetics groups, anesthesia was maintained by 1.3 MAC of isoflurane, sevoflurane or desflurane; in the propofol group, anesthesia was maintained by a continuous infusion of 6-8 mg.kg(-1).hr(-1) propofol. After bolus application of 0.1 mg.kg(-1) cisatracurium, a T1%-level of 10% of control level (train-of-four stimulation every 20 sec) was maintained using closed-loop feedback controlled infusion of cisatracurium. The effective therapeutic infusion rate (ETI) was estimated from the asymptotic steady-state infusion rate Iss. The Iss was derived from fitting an asymptotic line to the measured cumulative dose requirement curve. The ETI of the different groups was compared using Kruskal-Wallis- test, followed by rank sum test, corrected for the number of comparisons, P <0.05 was regarded as showing significant difference.

RESULTS

ETI in the isoflurane group was 35.6 +/- 8.6 microg.m(-2).min(-1), in the sevoflurane group 36.4+/- 11.9 microg m(-2).min(-1), in the desflurane group 23.8 +/- 6.3 microg.m(-2).min(-1). The ETI of the volatile anesthetic groups were all significantly lower than the ETI in the propofol group at 61.7 +/- 25.3 microg.m(-2).min(-1) (P <0.002). The ETI in the desflurane group was significantly lower than in all other groups (P <0.02).

CONCLUSION

In comparison to propofol, isoflurane, sevoflurane and desflurane reduce the cumulative dose requirements of cisatracurium to maintain a 90% neuromuscular blockade by 42%, 41% and 60%, respectively.

Recovery from neuromuscular blockade after either bolus and prolonged infusions of cisatracurium or rocuronium using either isoflurane or propofol-based anesthetics

We examined the recovery characteristics of cisatracurium or rocuronium after bolus or prolonged infusion under either isoflurane or propofol anesthesia. Sixty patients undergoing neurosurgical procedures of at least 5 h were randomized to receive either isoflurane with fentanyl (Groups 1 and 2) or propofol and fentanyl (Groups 3 and 4) as their anesthetic. Groups 1 and 3 received cisatracurium 0.2 mg/kg IV bolus, spontaneously recovered, after which time an infusion was begun. Groups 2 and 4 received rocuronium 0.6 mg/kg IV, spontaneously recovered, and an infusion was begun. Before the end of surgery, the infusion was stopped and recovery of first twitch (T(1)), recovery index, clinical duration, and train-of-four (TOF) recovery was recorded and compared among groups by using appropriate statistical methods. Clinical duration was shorter for rocuronium compared with cisatracurium using either anesthetic. Cisatracurium T(1) 75% recovery after the infusion was shorter with propofol compared with isoflurane. Cisatracurium TOF 75% recovery was similar after either bolus or infusion, but rocuronium TOF 75% recovery after the infusion was delayed. Infusion rates decreased for cisatracurium but remained relatively constant for rocuronium regardless of the anesthetic used. Isoflurane enhances the effect of both muscle relaxants but prolonged cisatracurium recovery more than rocuronium. Of the two muscle relaxants studied, rocuronium's recovery was most affected by length of the infusion. Cisatracurium may be a more desired muscle relaxant for prolonged procedures because recovery was least affected by prolonged infusion.

IMPLICATIONS

This study describes the effect of different anesthetic techniques on the recovery of two different muscle relaxants, cisatracurium and rocuronium, when administered as either a single bolus or prolonged infusion during neurosurgery. This study demonstrates the feasibility of using these relaxants for these prolonged procedures.

Recovery from neuromuscular blockade after either bolus and prolonged infusions of cisatracurium or rocuronium using either isoflurane or propofol-based anesthetics

We examined the recovery characteristics of cisatracurium or rocuronium after bolus or prolonged infusion under either isoflurane or propofol anesthesia. Sixty patients undergoing neurosurgical procedures of at least 5 h were randomized to receive either isoflurane with fentanyl (Groups 1 and 2) or propofol and fentanyl (Groups 3 and 4) as their anesthetic. Groups 1 and 3 received cisatracurium 0.2 mg/kg IV bolus, spontaneously recovered, after which time an infusion was begun. Groups 2 and 4 received rocuronium 0.6 mg/kg IV, spontaneously recovered, and an infusion was begun. Before the end of surgery, the infusion was stopped and recovery of first twitch (T(1)), recovery index, clinical duration, and train-of-four (TOF) recovery was recorded and compared among groups by using appropriate statistical methods. Clinical duration was shorter for rocuronium compared with cisatracurium using either anesthetic. Cisatracurium T(1) 75% recovery after the infusion was shorter with propofol compared with isoflurane. Cisatracurium TOF 75% recovery was similar after either bolus or infusion, but rocuronium TOF 75% recovery after the infusion was delayed. Infusion rates decreased for cisatracurium but remained relatively constant for rocuronium regardless of the anesthetic used. Isoflurane enhances the effect of both muscle relaxants but prolonged cisatracurium recovery more than rocuronium. Of the two muscle relaxants studied, rocuronium's recovery was most affected by length of the infusion. Cisatracurium may be a more desired muscle relaxant for prolonged procedures because recovery was least affected by prolonged infusion.

IMPLICATIONS

This study describes the effect of different anesthetic techniques on the recovery of two different muscle relaxants, cisatracurium and rocuronium, when administered as either a single bolus or prolonged infusion during neurosurgery. This study demonstrates the feasibility of using these relaxants for these prolonged procedures.