Continuous intravenous infusion of rocuronium (ORG 9426) in patients receiving balanced, enflurane, or isoflurane anesthesia

Infusion dose requirement of rocuronium in patients on phenytoin therapy - A prospective comparative study

Background and Aims:

Patients with intracranial tumour are usually on anticonvulsants. Patients on phenytoin therapy demonstrate rapid metabolism of nondepolarising muscle relaxants secondary to enzyme induction. Infusion dose requirement of rocuronium in such patients has been sparingly studied. We studied the continuous infusion dose requirement of rocuronium bromide in patients on phenytoin therapy and its correlation with serum levels of phenytoin.

Methods:

Seventy-five patients scheduled for supratentorial tumour surgery were included in the study. Patients not on phenytoin were taken as control. The primary outcome variable studied was the infusion dose requirement of rocuronium in patients on phenytoin. Based on pre-operative serum phenytoin levels, study group patients were divided into two groups: sub-therapeutic level group (phenytoin level <10 μg/mL) and therapeutic level group (phenytoin level >10 μg/mL). Following anaesthesia induction, rocuronium bromide 0.6 mg/kg was administered to achieve tracheal intubation. Rocuronium infusion was titrated to maintain zero response on the train-of-four response.

Results:

Demographic data were comparable. Patients receiving phenytoin required higher infusion dose compared to the control group (0.429 ± 0.2 mg/kg/h vs. 0.265 ± 0.15 mg/kg/h, P < 0.001). The serum phenytoin level had no correlation to infusion dose requirement of rocuronium (0.429 ± 0.205 mg/kg/h vs. 0.429 ± 0.265 mg/kg/h (P = 0.815). The recovery was faster in the phenytoin group compared to the control group. Haowever, it was not clinically significant.

Conclusion:

The infusion dose requirement of rocuronium bromide in patients on phenytoin is higher and the serum levels of phenytoin does not influence the dose required.

Effective method of continuous rocuronium administration based on effect-site concentrations using a pharmacokinetic/pharmacodynamic model during propofol-remifentanil anesthesia

BACKGROUND

Rocuronium bromide (Rb) is a rapid onset, intermediate-acting neuromuscular blocking agent that is suitable for continuous administration. The appropriate rate of rocuronium administration is, however, difficult to determine due to large interindividual differences in sensitivity to rocuronium. The aim of this study was to clarify whether the simulated rocuronium concentration at the time of recovery to %T1 > 0 % after the initial administration of rocuronium is a good indicator of optimal effect-site concentrations during continuous rocuronium administration.

METHODS

Twenty-one patients were anesthetized with propofol. After induction, Rb 0.6 mg/kg was administered intravenously, and nerve stimulation using the single stimulation mode was conducted every 15 s. When %T1 recovered to >0 % after the initial administration of Rb, the effect-site concentration of rocuronium, calculated by pharmacokinetic simulation with Wierda's set of parameters, was recorded and defined as the recovery concentration (Rb r.c.). The administration rate of rocuronium was adjusted to maintain the Rb r.c. during surgery. Rb administration was discontinued just before the end of surgery, and the recovery time until %T1 > 25 % was recorded. Plasma Rb concentrations were measured at 1 and 3 h after the initiation of continuous Rb administration.

RESULT

The mean Rb r.c. was 1.56 ± 0.35 μg/ml, with minimum and maximum values of 1.09 and 2.08 μg/ml, respectively. The %T1 did not increase above 10 % in any of the patients during continuous administration of Rb, and the recovery period to %T1 > 25 % ranged from 9 to 29 min. The effect-site concentrations of Rb calculated with Wierda's parameters significantly correlated with plasma concentrations (P < 0.01) at both 1 and 3 h after the initial administration of Rb.

CONCLUSION

The results suggest that our method may be one of the most reliable protocols for the continuous administration of Rb described to date for maintaining suitable muscle relaxation during surgery without excessively prolonged effects.

The effects of propofol, isoflurane and sevoflurane on vecuronium infusion rates for surgical muscle relaxation in dogs

OBJECTIVE

To compare the constant rate infusion (CRI) of vecuronium required to maintain a level of neuromuscular blockade adequate for major surgeries, e.g. thoracotomy or laparotomy, in dogs anaesthetized with a CRI of fentanyl and either propofol, isoflurane or sevoflurane.

STUDY DESIGN

Prospective, randomized, cross-over study.

ANIMALS

Thirteen male beagles (age, 9-22 months; body mass 6.3-11.3 kg).

MATERIALS AND METHODS

Dogs were anaesthetized with propofol (24 mg kg(-1) hour(-1) IV CRI; group P), isoflurane (1.3% end-tidal concentration; group I) or sevoflurane (2.3% end-tidal concentration; group S) with fentanyl (5 microg kg(-1) hour(-1) IV, CRI). Sixty to seventy minutes after induction of anaesthesia, vecuronium was administered at a rate of 0.4, 0.3 and 0.2 mg kg(-1) hour(-1) in groups P, I and S respectively. To determine the degree of neuromuscular block, a peripheral nerve was stimulated electrically using the train-of-four (TO4) stimulus pattern. Evoked muscle contractions were evaluated using a neuromuscular monitoring device. Once the TO4 ratio reached 0, the continuous infusion rate was decreased and adjusted to maintain a TO4 count of 1. Continuous infusion was continued for 2 hours. The infusion rate of vecuronium was recorded 20, 40, 60, 80, 100 and 120 minutes after the start of infusion.

RESULTS

The mean continuous infusion rates of vecuronium during stable infusion were 0.22 +/- 0.04 (mean +/- SD), 0.10 +/- 0.02 and 0.09 +/- 0.02 mg kg(-1) hour(-1) in groups P, I and S respectively. There were statistically significant differences between the rates in groups P and I and between the rates in groups P and S. Conclusions and clinical relevance In healthy dogs, the recommended maintenance infusion rate of vecuronium is 0.2 mg kg(-1) hour(-1) under CRI propofol-fentanyl anaesthesia and 0.1 mg kg(-1) hour(-1) during CRI fentanyl-isoflurane or sevoflurane anaesthesia.

The relationship of the anthropometric variables to the infusion rate of rocuronium in the elderly

We have determined the infusion rates of rocuronium in the elderly and young adult patients during sevoflurane and nitrous oxide anesthesia. The correlation of some anthropometric predictors with infusion rate of rocuronium was also investigated for both elderly and young adult. Participating patients were assigned to one of two groups: 1) young adult patients aged 20 to 50 years (n = 30); 2) elderly patients aged over 65 years (n = 30). The anthropometric variables such as height, weight, ratio of weight to body surface area, subscapularis and suprailiac skin folds, body surface area, body mass index and % ideal body weight were evaluated as predictors for infusion rate. The infusion rate in elderly patients was significantly less compared with that in young adult patients (p < 0.05). In elderly patients, no anthropometric predictor was related to the infusion rate of rocuronium. This suggests that the infusion rate of rocuronium for an elderly patient needs to be individualized by monitoring neuromuscular transmission to avoid excessive dose.

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.

Neostigmine antagonism of rocuronium block during anesthesia with sevoflurane, isoflurane or propofol

PURPOSE

To examine the influence of continuing administration of sevoflurane or isoflurane during reversal of rocuronium induced neuromuscular block with neostigmine.

METHODS

One hundred and twenty patients, divided into three equal groups, were randomly allocated to maintenance of anesthesia with sevoflurane, isoflurane or propofol. Neuromuscular block was induced with rocuronium and monitored using train-of-four (TOF) stimulation of the ulnar nerve and recording the force of contraction of the adductor pollicis muscle. Neostigmine was administered when the first response in TOF had recovered to 25%. At this time the volatile agent administration was stopped or propofol dosage reduced in half the patients in each group (n = 20 in each group). The times to attain TOF ratio of 0.8, and the number of patients attaining this end point within 15 min were recorded.

RESULTS

The times (mean +/- SD) to recovery of the TOF ratio to 0.8 were 12.0 +/- 5.5 and 6.8 +/- 2.3 min in the sevoflurane continued and sevoflurane stopped groups, 9.0 +/- 8.3 and 5.5 +/- 3.0 min in the isoflurane continued and isoflurane stopped groups, and 5.2 +/- 2.8 and 4.7 +/- 1.5 min in the propofol continued and propofol stopped groups (P < 0.5-01). Only 9 and 15 patients in the sevoflurane and isoflurane continued groups respectively had attained a TOF ratio of 0.8 within 15 min (P < 0.001 for sevoflurane).

CONCLUSIONS

The continued administration of sevoflurane, and to a smaller extent isoflurane, results in delay in attaining adequate antagonism of rocuronium induced neuromuscular block.

The influence of halothane, isoflurane and sevoflurane on rocuronium infusion in children

BACKGROUND

Rocuronium is a non-depolarizing neuromuscular blocking agent with intermediate duration of action and without significant cumulative properties, suitable for continuous infusion. This study was designed to determine the infusion requirements in children under nitrous oxide and fentanyl, halothane, isoflurane or sevoflurane anaesthesia.

METHODS

Forty children, 3-11 years old, ASA physical status group I or II were studied. They were randomly allocated to receive fentanyl-nitrous oxide, 1 MAC halothane-nitrous oxide, 1 MAC isoflurane-nitrous oxide or 1 MAC sevoflurane-nitrous oxide anaesthesia. Rocuronium, 0.6 mg(-1) was used to facilitate endotracheal intubation. Electromyographic response of adductor pollicis to train-of-four (TOF) stimulation, 2 Hz for 2 s, applied to the ulnar nerve at 10-s intervals was recorded using Relaxograph (Datex, Helsinki, Finland). Once the first twitch response (T1) returned to 5%, muscle relaxation was maintained by continuous infusion of rocuronium, adjusted automatically in a closed-loop system to maintain a stable 90-99% T1 depression. The block was considered stable if it changed by no more than 2% over a 10-min observation period.

RESULTS

Halothane, isoflurane and sevoflurane groups had ower infusion requirements than the fentanyl-nitrous oxide group (P<0.00075). Rocuronium requirement (mean +/- SD) at one hour from the commencement of anaesthesia was 16.7+/-2.3, 13.6+/-3.7, 13.1+/-5.1 and 8.4+/-1.6 microg x kg(-1) x min(-1) for children receiving fentanyl-nitrous oxide, halothane, isoflurane and sevoflurane anaesthesia, respectively.

CONCLUSIONS

The rocuronium infusion rate required to maintain stable 90-99% T1 depression was reduced by approximately 20% with halothane and isoflurane anaesthesia, and by 50% with evoflurane anaesthesia when compared to fentanyl-nitrous oxide anaesthesia. Significant patient-to-patient variability of infusion rate makes monitoring of neuromuscular transmission necessary.

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.

Cumulation characteristics of cisatracurium and rocuronium during continuous infusion

PURPOSE

The dissimilar pharmacokinetic properties of cisatracurium (CIS) and rocuronium (ROC) predict different potential for drug cumulation when these drugs are administered by continuous infusion. A study was therefore undertaken to compare cumulation potential of CIS and ROC during surgical procedures of relatively long duration (2-4 hr).

METHODS

Sufentanil/propofol-N2O anesthesia was administered to 40 ASA I and II adults. In a double-blind protocol, patients were randomly allocated to receive a continuous i.v. infusion of either CIS or ROC, titrated in progressive increments or decrements as required to achieve and maintain 95 +/- 5% depression of the T1 response of the adductor pollicis muscle, using a Datex NMT-100 Relaxograph EMG monitor applied at the wrist. At the end of surgery, 60 microg x kg(-1) neostigmine plus 15 microg x kg(-1) atropine were administered for reversal.

RESULTS

The duration of infusion was 104 +/- 33 min in group CIS and 110 +/- 23 min in group ROC (P=NS). In both groups, a progressive decrease in potency-adjusted infusion rates was observed after 30 min, then stabilized beyond 60 min. When allowing for an initial period of stabilization, mean potency-adjusted infusion requirements were: CIS 0.81 +/- 0.02 microg x kg(-1) x min(-1) and ROC 5.58 +/- 1.94 microg x kg(-1) x min(-1). There were no differences between groups at any time with regard to potency-adjusted infusion requirements necessary to maintain 90-99% block (P=NS). However, drug costs/hr for maintenance of neuromuscular block were less with CIS ($3.57 +/- 0.09) than with ROC ($6.03 +/- 0.27), P < 0.001.

CONCLUSION

When adjusted to equipotency, infusion requirements of CIS and ROC vary at similar rates during general anesthesia. Despite pharmacokinetic differences, neither drug demonstrates cumulation for infusion lasting up to 3.5 hr.

Rapacuronium recovery characteristics and infusion requirements during inhalation versus propofol-based anaesthesia

We examined the effect of four maintenance anaesthetics on the neuromuscular blocking activity and spontaneous recovery characteristics after a short-term infusion of rapacuronium. Eighty ASA I-III adult patients undergoing elective surgery were studied at four centres. Anaesthesia was induced with propofol 1.5-2.5 mg kg-1 and fentanyl 1-2 micrograms kg-1, followed by a bolus of rapacuronium 1.5 mg kg-1. The patients were randomized to receive either desflurane (2-4% end-tidal, ET), sevoflurane (0.75-1.5% ET), isoflurane (0.4-0.8% ET), or a propofol infusion (75-150 micrograms kg-1 min-1) for maintenance of anaesthesia in combination with nitrous oxide (60-70%) in oxygen. When the first twitch (T1) of a train-of-four stimulus (using the TOF Guard accelerometer) returned to 5%, an infusion of rapacuronium was started at 3 mg kg-1 h-1 and adjusted to maintain T1/T0 at 10%. The duration of infusion lasted between 45 and 60 min, and the average infusion rates of rapacuronium were similar in all groups, ranging from 1.6 to 2.5 mg kg-1 h-1. There were no significant differences among the groups in the times for T1/T0 to return to 25%, 75% or 90%, or for T4/T1 to return to 70% and 80% upon discontinuation of the infusion. When potent inhalation anaesthetics are used in clinically relevant concentrations for maintenance of anaesthesia, the neuromuscular recovery profile of rapacuronium administered as a variable-rate infusion for up to 1 h is similar to that found with a propofol-based anaesthetic technique.

Pharmacokinetics of rocuronium bromide in obese female patients

Following administration of 0.6 mg kg-1 rocuronium, the pharmacokinetics and the pharmacodynamics were studied in six obese and six control (normal weight) patients receiving balanced anaesthesia. Twelve gynaecological patients were allocated into two groups, according to body mass index (normal weight: body mass index: 20-24, obese weight: body mass index > 28). Venous plasma concentrations were determined by high-pressure liquid chromatography before administration of rocuronium, at 1, 2, 4, 6, 8, 10, 15, 20, 25, 30, 35, 40, 48, 60, 75, 120, 180, 240, 300, 360 and 420 min after administration of rocuronium and at recovery of single twitch to 25% and 75% of control twitch height. Onset time was shorter (NS) in the obese compared with normal weight (obese weight: 65 +/- 16, normal weight: 100 +/- 39 s, mean +/- SD). Duration 25% (obese weight: 29.5 +/- 5.3, normal weight: 28.4 +/- 5.3 min) and spontaneous recovery time (obese weight: 12.6 +/- 2.7, normal weight: 12.5 +/- 2.3 min) did not show any differences between the two groups. The pharmacokinetics of rocuronium were comparable in the two groups. The volume of distribution at steady state Vss (mL kg-1) was 208 +/- 56 in normal weight and 169 +/- 37 in obese weight. Distribution (T1/2 alpha) and elimination half-life (T1/2 beta) as well as mean residence time were 15.6 +/- 3.7, 70.3 +/- 23.9 and 53.2 +/- 9.8 min in normal weight and 16.9 +/- 3.8, 75.5 +/- 25.5 and 51.1 +/- 18.9 min in obese weight, respectively. Also, no differences were observed in plasma clearance (3.89 +/- 0.58 in normal weight and 3.62 +/- 1.42 mL kg-1 min-1 obese weight). This study indicates that the pharmoacodynamics and pharmacokinetics of rocuronium are in female patients not altered by obesity.

Dosage of neostigmine for reversal of rocuronium block from two levels of spontaneous recovery

Spontaneous recovery, and recovery following neostigmine 20, 35 or 50 microgram.kg-1 administered at 10 or 25% of recovery of the first twitch of the train-of-four, was assessed in 80 patients after rocuronium administration under continued isoflurane anaesthesia. In an additional 40 patients, isoflurane administration was discontinued and neostigmine 35 or 50 microgram.kg-1 was given at 10 or 25% recovery. The administration of neostigmine reduced the recovery times significantly. A neostigmine dose of 20 microgram.kg-1 resulted in slower recovery compared with the higher doses, particularly when reversal was attempted at a first twitch height of 10%. Higher doses of neostigmine given at a first twitch height of 25% resulted in rapid reversal of block [mean (SD) times of 7.0 (4.8) and 6.4 (1.9) min with the 35 and 50 microgram.kg-1 doses, respectively, for attaining a train-of-four ratio of 0.8]. Discontinuing isoflurane did not alter recovery times. The incidence of emetic symptoms did not differ between groups, including one group that received atropine instead of glycopyrronium in combination with neostigmine. We conclude that rocuronium block can be antagonised safely using a neostigmine dose of 35 microgram.kg-1, although recovery may be slightly slower if administered at a first twitch of 10% of control.

Rocuronium administration in children during isoflurane anesthesia: neuromuscular effects

BACKGROUND

The time-course of the effect of rocuronium during isoflurane anesthesia in children has rarely been evaluated. Forty-five children, aged 2-14 years, ASA 1, undergoing elective surgery and receiving isoflurane anesthesia, were studied.

METHODS

Patients randomly received a dose of 400, 600, or 800 micrograms/kg of rocuronium. The first response to the control height (T1:T0) was fitted to time in order to obtain times to onset of action (TOA) including time to 90 (B90) and 99.9% (B100) of relaxation and to spontaneous recovery of 10 (T10), 25 (T25), 50 (T50), 75 (T75), and 90% (T90) of neuromuscular function (NMF). Each time was compared among groups. Linear regression analysis between the TOA or the times to spontaneous recovery of NMF (TSRNMF) and age or weight were also performed.

RESULTS

The TOA were similar among the three groups while TSRNF in children receiving 600 or 800 micrograms/kg were longer (p < 0.05) than children receiving 400 micrograms/kg. The T10 and T25 were related to age (p = 0.05), whereas T10, T50, T75, and T90 were related to weight (p < 0.01). These relationships were stronger in males than females.

CONCLUSIONS

Maximal relaxation was reached in all children receiving 600 or 800 micrograms/kg of rocuronium. The TSRNMF were mainly related to the weight of the children, and gender affected each relationship. Widely variable responses were observed with all three doses.

Comparison of neuromuscular effects, efficacy and safety of rocuronium and atracurium in ambulatory anaesthesia

PURPOSE

To compare the neuromuscular effects, efficacy, and safety of equi-effective doses of rocuronium and atracurium in ambulatory female patients undergoing surgery.

METHODS

Forty-one patients undergoing laparoscopic gynaecological surgery were randomized to receive 2 X ED90 rocuronium (0.6 mg.kg-1; n = 20) or atracurium (0.5 mg.kg-1; n = 21) during intravenous propofol/alfentanil anaesthesia with N2O/O2 ventilation. Neuromuscular block was measured with a mechanomyogram eliciting a train-of-four (TOF) response at the wrist. Intubation conditions 60 sec after administration of muscle relaxant and immediate cardiovascular disturbances or adverse events during the hospital stay were noted by blinded observers.

RESULTS

Compared with atracurium, rocuronium was associated with a shorter onset time (59.0 +/- 22.2 vs 98.6 +/- 41.4 sec; P < 0.001) and clinical duration of action (33.3 +/- 7.1 vs 44.7 +/- 7.2 min; P < 0.001), but longer spontaneous recovery index (9.6 +/- 2.41 vs 6.9 +/- 1.89 min; P = 0.023) and a similar time to spontaneous recovery to TOF 70%; 53 +/- 6.31 vs 59.2 +/- 7.59 min; P = 0.139). Tracheal intubation was accomplished in < 90 sec in all patients receiving rocuronium but in only 14 of 21 patients receiving atracurium. The incidence of adverse events and the cardiovascular profiles for the two drugs were similar, although one patient receiving atracurium experienced transient flushing of the head and neck.

CONCLUSION

Rocuronium has minimal side effects, provides conditions more suitable for rapid tracheal intubation, and is associated with a shorter clinical duration than atracurium. Once begun, the spontaneous recovery profile of rocuronium is slightly slower than that of atracurium.

Evaluation of intubating conditions with rocuronium and either propofol or etomidate for rapid sequence induction

We have assessed the effect of two induction agents on tracheal intubating conditions after rocuronium 0.6 mg.kg-1 in unpremedicated patients undergoing simulated rapid sequence induction. Following pre-oxygenation, anaesthesia was induced with propofol up to 2.5 mg.kg-1 (n = 35) or etomidate 0.3 mg.kg-1 (n = 36), and further increments as required. After loss of verbal contact, cricoid pressure was applied and rocuronium was injected. Laryngoscopy was performed at 45 s and intubation attempted at 60 s after rocuronium had been given. Ninety-four per cent of patients in the propofol group had clinically acceptable (good or excellent) intubating conditions compared to only 75% in the etomidate group (p = 0.025). Owing to coughing, one patient in the etomidate group could not be intubated on the first attempt. A greater pressor response also followed intubation after induction with etomidate. We conclude that etomidate and rocuronium alone cannot be recommended for intubation at 60 s under rapid sequence induction conditions.

Neuromuscular blocking effects of rocuronium during desflurane, isoflurane, and sevoflurane anaesthesia

PURPOSE

To determine the magnitude of the potentiation of rocuronium by desflurane, isoflurane and sevoflurane 1.5 MAC anaesthesia.

METHODS

In a prospective, randomised, study in 80 patients, the cumulative dose-effect curves for rocuronium were determined during anaesthesia with desflurane, sevoflurane and isoflurane (with N2O 70%, 15 min steady state) or total intravenous anaesthesia (TIVA) using propofol/fentanyl. Neuromuscular block was assessed by acceleromyography (TOF-Guard) after train-of-four (TOF) stimulation of the ulnar nerve (2 Hz every 12 sec, 200 microseconds duration). Rocuronium was administered in increments of 100 micrograms.kg-1 until first twitch (T1) depression > 95%.

RESULTS

Rocuronium led to more pronounced T1 depression with desflurane or sevoflurane anaesthesia than with TIVA. The ED50 and ED95 were lower during desflurane (95 +/- 25 and 190 +/- 80 micrograms.kg-1) and sevoflurane (120 +/- 30 and 210 +/- 40 micrograms.kg-1) than with TIVA (150 +/- 40 and 310 +/- 90 micrograms.kg-1) (P < .01), while the difference was not significant for isoflurane (130 +/- 40 and 250 +/- 90 micrograms.kg-1). Following equi-effective dosing (T1 > 95%) the duration to 25% T1 recovery, recovery index (25/75), and TOF0.70 was: 13.2 +/- 1.8, 12.7 +/- 3.4, and 26.9 +/- 5.7 min during anaesthesia with desflurane; 15.5 +/- 5.0, 11.4 +/- 3.8, and 31.0 +/- 6.0 min with sevoflurane; 13.9 +/- 4.7, 10.7 +/- 3.3, and 26.3 +/- 8.9 min with isoflurane; and 13.9 +/- 3.9, 11.3 +/- 5.7, and 27.5 +/- 8.2 min with TIVA anaesthesia (P: NS).

CONCLUSION

Interaction of rocuronium and volatile anaesthetics resulted in augmentation of the intensity of neuromuscular block but did not result in significant effects on duration of or recovery from the block.

Interactions between P-glycoprotein substrates and other cationic drugs at the hepatic excretory level

1. In the present study it was tested whether known P-glycoprotein (P-gp) substrates/MDR reversal agents interact with small (type 1) and bulky (type 2) cationic drugs at the level of biliary excretion in the rat isolated perfused liver model (IPRL). The studies were performed with model compounds tri-n-butylmethylammonium (TBuMA) (a relatively small type 1 organic cation), rocuronium (Roc) (a bulky type 2 organic cation) and the classical P-gp substrate doxorubicin (Dox). 2. Inhibitors were given in a 4 fold molar excess to the substrate studied. To minimize an interaction of the substrates at the hepatic uptake level, the competing compounds were added when over 55% to 85% of the administered dose of the model compounds had been removed from the perfusate and taken up by the liver. 3. We found a mutual interaction between TBuMA and procainamidethobromide (PAEB), both type 1 cationic compounds during biliary excretion. Interestingly, type 2 compounds, such as rocuronium, clearly inhibited type 1 cationic drugs as well as Dox secretion into bile, whereas type 1 compounds did not significantly inhibit type 2 drug excretion into bile. The type 1 cations PAEB and TBuMA only moderately inhibited Dox biliary excretion. Dox did not inhibit the biliary excretion of the type 2 agent rocuronium whereas rocuronium reduced Dox biliary excretion by 50% compared to controls. 4. MDR substrates/reversal agents like verapamil, quinine, quinidine and vinblastine strongly reduced both type 1 and type 2 organic cation excretion into bile. Dox secretion into bile was also profoundly reduced by these drugs, vinblastine being the most potent inhibitor in general. 5. The lack of mutual inhibition observed in some combinations of substrates may indicate that major differences in affinity of the substrates for a single excretory system exist. Alternatively, multiple organic cation transport systems with separate substrate specificities may be involved in the biliary excretion of amphiphilic drugs. Furthermore, the present study revealed a clear positive correlation between the lipophilicity of the potential inhibitors studied and their respective inhibitory activity on the biliary excretion of the model drugs investigated. 6. Our data are compatible with a potential involvement of P-glycoprotein in the hepatobiliary excretion of doxorubicin as well as of some type 1 and type 2 organic cations. Furthermore we postulate that the hydrophobic properties of the amphiphilic cationic drugs studied play a crucial role in the accommodation of these agents by P-glycoprotein and/or other potential cationic drug carrier proteins in the canalicular membrane.

Dose-response and time-course of the effect of rocuronium bromide during sevoflurane anaesthesia

To evaluate the influence of sevoflurane on the dose-response relationship and on the time-course of the effect of rocuronium, 60 adult patients undergoing elective plastic surgery were randomly allocated to either the control or the sevoflurane group. Anaesthesia was maintained with 60% nitrous oxide in oxygen and thiopentone in the control group and with 60% nitrous oxide in oxygen and an end-tidal concentration of 1.75% sevoflurane in the sevoflurane group. Neuromuscular function was assessed mechanomyographically with train-of-four stimulation at the wrist every 12s and the percentage depression of the first twitch of the train-of-four was used as the study parameter. The dose-response relationship of rocuronium in the two groups was determined by the cumulative dose-response technique. The dose-response curve of rocuronium in the sevoflurane group was shifted to the left compared to the control group, indicating a potentiation of rocuronium-induced neuromuscular block. The effective doses of rocuronium required to produce 50%, 90% and 95% twitch depression in the sevoflurane group were decreased by 30.5%, 26.7% and 25.2%, respectively, compared to the control group. Following the administration of a total dose of rocuronium of 400 micrograms.kg-1, the duration of action of, and the recovery from, rocuronium were both significantly prolonged by sevoflurane. There were significant differences in the duration of peak effect, clinical duration, recovery index and the total duration of action between the control and the sevoflurane groups.

Rocuronium in infants, children and adults during balanced anaesthesia

We studied 20 infants, 20 children and 20 adults during balanced anaesthesia to compare the neuromuscular blocking effects of rocuronium in these age groups. Neuromuscular function was recorded by adductor pollicis emg and a cumulative log-probit dose-response curve of rocuronium was established. Thereafter, full spontaneous recovery of the neuromuscular function was recorded. Onset time of the first dose of rocuronium was shorter in children than in infants or adults. The potency of rocuronium was greatest in infants and least in children; the ED50 doses (mean +/- SD) being 149 +/- 36 micrograms.kg-1 in infants, 205 +/- 52 micrograms.kg-1 in children and 169 +/- 47 micrograms.kg-1 in adults (P < 0.05 between infants and children) and the ED95 doses being 251 +/- 73 micrograms.kg-1, 409 +/- 71 micrograms.kg-1 and 350 +/- 77 micrograms.kg-1, respectively (P < 0.05 between all groups). The emg recovery following an average 94.5 +/- 4.8% neuromuscular blockade established by rocuronium was roughly similar in all study groups. Thus, one ED95 dose of rocuronium, unlike vecuronium, acts as an intermediate-acting agent in all age groups.

Quantifying the interaction of vecuronium with enflurane using closed-loop feedback control of vecuronium infusion

The influence of different levels of enflurane anaesthesia on infusion requirements of vecuronium was studied in 40 adult surgical patients. Ninety percent neuromuscular block was maintained by computer controlled infusion of vecuronium. During the first 90 min study period all patients received fentanyl-nitrous oxide-oxygen (2:1) anaesthesia. For the following 90 min the patients were randomly assigned to receive enflurane at different end-tidal concentrations: group I, control, fentanyl-nitrous oxide anaesthesia; group II, enflurane 0.3%-nitrous oxide; group III, enflurane 0.6%-nitrous oxide; group IV, enflurane 0.9%-nitrous oxide. Every patient served as his/her own control and the changes of vecuronium infusion requirements were determined individually. When the administration of enflurane was started, vecuronium infusion requirements decreased progressively until 90 min. In group II the infusion rate lowered from 80 +/- 28 to 56 +/- 20 micrograms.kg-1.h-1, in group III from 61 +/- 29 to 34 +/- 17 micrograms.kg-1.h-1 and in group IV from 65 +/- 20 to 30 +/- 14 micrograms.kg-1,h-1. In the control group the infusion rate decreased during the three hour study period from 69 +/- 17 (first 90 min period) to 59 +/- 16 micrograms.kg-1.h-1 (second 90 min period). Enflurane reduces the dose requirements of vecuronium administered by continuous infusion in a dose- and time-dependent manner.

The pharmacokinetics and neuromuscular effects of rocuronium bromide in patients with liver disease

To determine the effect of liver disease on the pharmacokinetics of rocuronium, the authors administered 0.6 mg/kg (twice the ED95) to 10 patients with liver disease and compared these results to values in 10 healthy surgical patients. Anesthesia was induced with thiopental and maintained with isoflurane (0.9%-1.1% end-tidal concentration) and nitrous oxide (60%). Venous blood samples were obtained for 6 h after rocuronium injection and plasma concentrations were measured using gas chromatography. Pharmacokinetic differences between groups were determined using a population-based pharmacokinetic analysis (NONMEM). Hepatic impairment did not alter the plasma clearance of rocuronium (217 +/- 21.8 mL/min, mean +/- SE, for both groups), but did increase the volume of the central compartment (5.96 +/- 1.01 L for controls, 7.87 +/- 1.33 L for patients with liver disease) and volume of distribution at steady state (16.4 L for controls, 23.4 L for patients with liver disease). In turn, elimination half-life was longer in patients with liver disease (111 min) compared to controls (75.4 min). The authors conclude that liver disease alters the pharmacokinetics of rocuronium by increasing its volume of distribution. The longer elimination half-life might result in a longer duration of action of rocuronium in patients with liver disease, particularly after prolonged administration.

Quantifying the effect of enflurane on atracurium infusion requirements

The present study was designed to evaluate the interaction between atracurium and enflurane in 40 adult surgical patients using closed-loop feedback control of infusions of atracurium. Anaesthesia was induced with thiopentone and fentanyl and intubation was facilitated with atracurium 0.5 mg.kg-1 lean body mass. During the first 90 min, anaesthesia was maintained with nitrous oxide in oxygen (2:1) and fentanyl. For the following 90 min the patients were randomly assigned to receive enflurane at different end-tidal concentrations: Group I, control, fentanyl-nitrous oxide anaesthesia; Group II, enflurane 0.3%-nitrous oxide; Group III, enflurane 0.6%-nitrous oxide; Group IV, enflurane 0.9%-nitrous oxide. The possible interaction of atracurium with enflurane was quantified by determining the asymptotic steady-state rate of infusion (ISS) of atracurium necessary to produce a constant 90% neuromuscular block. This was accomplished by applying nonlinear curve fitting to data on the cumulative dose requirements. Every patient served as his/her own control and the changes in the infusion rates were determined individually. Patient characteristics and controller performance, i.e., the ability of the controller to maintain the neuromuscular blockade constant at the setpoint, did not differ among groups. In Group II ISS decreased from 0.33 +/- 0.12 to 0.26 +/- 0.08 mg.kg-1.hr-1 (P < 0.01), in Group III from 0.32 +/- to 0.12 to 0.24 +/- 0.08 mg.kg-1.hr-1 (P < 0.001) and in Group IV from 0.29 +/- 0.09 to 0.21 +/- 0.09 mg.kg-1.hr-1 (P < 0.001). In the control group atracurium requirements remained unchanged throughout the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration of rocuronium (Org 9426) by continuous infusion and its reversibility with anticholinesterases

The use of rocuronium (Org 9426) as a single bolus followed by an infusion was assessed in 50 patients under anaesthesia with nitrous oxide-oxygen and halothane. Neuromuscular block was monitored using train-of-four stimulation and recording the force of contraction of the adductor pollicis muscle. Rocuronium was administered in an initial bolus dose of 0.45 mg.kg-1 followed by an infusion adjusted manually to maintain the T1, the first response in the train-of-four, at 10% of control. Following cessation of rocuronium infusion the patients were either allowed to recover spontaneously (n = 10) or were given neostigmine 50 micrograms.kg-1 or edrophonium 1 mg.kg-1 at 10 or 25% recovery of the T1 (n = 10 for each group). Adequate antagonism was defined as attaining a sustained train-of-four ratio of 0.7. Rocuronium requirements showed marked variation among individual patients but were relatively constant in individual patients. The mean (SD) time to attain stable infusion rates was 17.4 (10.9) min. The mean (SD) requirement of rocuronium for steady state 90% block of T1 was 572 (190) micrograms.kg-1.h-1 (range 242-1104 micrograms.kg-1.h-1). The mean (SD) time to attain a train-of-four ratio of 0.7 in the group allowed to recover spontaneously was 36.1 (7.3) min. This interval was 7.5 (1.9), 9.3 (7.0), 4.6 (1.9) and 1.9 (0.9) min respectively in the groups receiving neostigmine at T1 of 10%, edrophonium at T1 of 10%, neostigmine at T1 of 25% and edrophonium at T1 of 25%. The antagonism was significantly faster in those reversed at 25% (p < 0.05). Three patients in the group receiving edrophonium at T1 of 10% and one in the group receiving neostigmine at T1 of 25% failed to attain a train-of-four ratio of 0.7. It is concluded that rocuronium can be administered as a continuous infusion for stable neuromuscular block. Neostigmine may be a more reliable antagonist of deep block, whereas edrophonium is advantageous when there is a greater spontaneous recovery.

Newer neuromuscular blocking agents

Four neuromuscular blocking drugs, doxacurium, mivacurium, pipecuronium, and rocuronium have been or are about to be introduced into clinical practice. The purpose of this MiniReview is to describe their pharmacology, to consider their place in clinical anaesthetic practice, and to examine whether the needs of the clinician have been met. Two of the agents (doxacurium, mivacurium) are benzylisoquinolines resembling atracurium and two (pipecuronium, rocuronium) are aminosteroids related to pancuronium and vecuronium. Two (doxacurium, pipecuronium) are long-acting compounds, similar in duration of action to pancuronium, although the need for such a profile is questionable. Rocuronium has an intermediate duration of action and produces its maximum effect within two minutes which is much more rapid than any other non-depolarizing relaxant and this is probably a result of its poor potency. However, the onset of paralysis is not as quick as after succinylcholine. Mivacurium is unique because it is metabolized by plasma cholinesterase which produces a rapid recovery although slower than succinylcholine. All of the new drugs are devoid of serious cardiovascular or other side effects. The anaesthetist is now presented with an armamentarium of safe, nondepolarizing muscle relaxants with varying durations of action. However, the rapid onset and recovery associated with succinylcholine are unique and important in the urgent control of a patient's airway and respiration. The indications for succinylcholine will not disappear and the search for a non-polarizing replacement will continue.

Nondepolarizing relaxants: new concepts and new drugs

Less than a decade ago, the only nondepolarizing neuromuscular blocking drugs available to the anesthetist were traditional long-acting drugs such as pancuronium and d-tubocurarine. The revolution that began 10 years ago in our use of relaxants promises to continue unabated into the next decade. Changes in our clinical use of these drugs will be sparked not just by the introduction of new drugs but also by a greater understanding of the pharmacokinetic/pharmacodynamic principles that govern onset and recovery.