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

Increased Renal Clearance of Rocuronium Compensates for Chronic Loss of Bile Excretion, via upregulation of Oatp2

Requirement for rocuronium upon surgery changes only minimally in patients with end-stage liver diseases. Our study consisted of both human and rat studies to explore the reason. The reduction rate of rocuronium infusion required to maintain neuromuscular blockade during the anhepatic phase (relative to paleohepatic phase) was examined in 16 children with congenital biliary atresia receiving orthotopic liver transplantation. Pharmacodynamics and pharmacokinetics of rocuronium were studied based on BDL rats. The role of increased Oatp2 and decrease Oatp1 expressions in renal compensation were explored. The reduction of rocuronium requirements significantly decreased in obstructively jaundiced children (24 ± 9 vs. 39 ± 11%). TOF50 in BDL rats was increased by functional removal of the kidneys but not the liver, and the percentage of rocuronium excretion through urine increased (20.3 ± 6.9 vs. 8.6 ± 1.8%), while that decreased through bile in 28d-BDL compared with control group. However, this enhanced renal secretion for rocuronium was eliminated by Oatp2 knock-down, rather than Oatp1 overexpression (28-d BDL vs. Oatp1-ShRNA or Oatp2-ShRNA, 20.3 ± 6.9 vs. 17.0 ± 6.6 or 9.3 ± 3.2%). Upon chronic/sub-chronic loss of bile excretion, rocuronium clearance via the kidneys is enhanced, by Oatp2 up-regulation.

Update on neuromuscular pharmacology

Since the introduction of d-tubocurarine into clinical practice, neuromuscular relaxants have been widely used in anaesthesia. Although their clinical use is easy, several points still require further attention and research. There is still a need for a drug with the clinical profile of succinylcholine but fewer unwanted side-effects. A better understanding of the effects of muscle relaxants on different muscles could help in their clinical use during the perioperative period. Much knowledge is needed about residual neuromuscular block and its detection in order to improve the quality of recovery from neuromuscular blockade. If some questions remain to be answered, several recent articles have increased our knowledge and should improve our clinical practice.

Dose-response relationship of rocuronium: a comparison of electromyographic vs. acceleromyographic-derived values

BACKGROUND

Acceleromyography (AMG) is being employed with increasing frequency as a research tool. However, there is almost no information available regarding the accuracy of values for drug potency obtained using AMG. This study was an attempt to determine if AMG-derived ED(50/95) values are interchangeable with those measured with a more traditional neuromuscular monitor.

METHODS

Thirty adult patients were studied. Anesthesia was induced and maintained with N20, propofol, and supplementation opioid. Tracheal intubation was accomplished without muscle relaxants. Simultaneous ipsilateral AMG and EMG responses to 0.10 Hz stimulation was recorded. Following instrument calibrations, a single dose of rocuronium was administered. The first patient received a bolus of 0.17 mg kg(-1) of rocuronium. Using the Hill equation with a postulated slope of 4.50, the ED(50) was calculated. The second subject received a dose which approximated the calculated ED(50) for patient no. 1. Successive subjects were given a dose based on the running average of the estimated ED(50).

RESULTS

The AMG-derived ED50/95 values for rocuronium (0.163 +/- 0.055 and 0.314 +/- 0.105 mg mg(-1)) were virtually identical to those established using EMG (0.159 +/- 0.043 and 0.306 +/- 0.084 mg kg(-1)). While mean peak twitch depression (Delta T1) was the same in both groups for individual subjects Delta T1 differed by +/- 20% (95% confidence interval).

DISCUSSION

Acceleromyography-derived twitch heights for individual patients are not necessarily interchangeable with information obtained using electromyography. Nevertheless, acceleromyography appears to be a valid methodology for determining the drug potency when a population rather than an individual subject is being studied.

Rocuronium infusion requirements and plasma concentrations at constant levels of neuromuscular paralysis during three phases of liver transplantation

STUDY OBJECTIVE

To develop a rapid online test of graft liver function during liver transplantation.

DESIGN

Prospective, observational study.

SETTING

University hospital transplant unit.

PATIENTS

17 adult patients with end-stage liver disease who underwent liver transplantation surgery.

INTERVENTIONS

Rocuronium infusion dose requirements and plasma concentrations to maintain constant levels of neuromuscular paralysis during three phases of liver transplantation and their relationship with early postoperative liver function tests were studied.

MEASUREMENTS

Infusion dose requirements of rocuronium, assay of rocuronium plasma concentrations using gas chromatography-mass spectrometry, and intensity of neuromuscular blockade were measured.

MAIN RESULTS

A 24% decrease in rocuronium infusion requirements was observed during the an-hepatic phase. Rocuronium requirement during the neohepatic phase was increased only modestly or remained unchanged in 14 of the 16 patients who had normal graft function in the immediate postoperative period. Rocuronium plasma concentrations for maintaining constant levels of paralysis were significantly lower during the neohepatic phase than during the paleohepatic and anhepatic phases, indicating that there is likely to be a change in pharmacodynamics during this phase. Significant reduction in rocuronium infusion requirements during the neohepatic phase was observed in the only patient who had poor graft function in the early postoperative stage, suggesting that the reduced infusion requirement to maintain a constant neuromuscular paralysis may be related to the functional state of the graft liver after reperfusion.

CONCLUSIONS

A significant reduction in rocuronium infusion requirement during the neohepatic phase may be suggestive of impaired organ function after reperfusion of the graft liver. Rocuronium may serve as a potential online indicator of graft liver function during liver transplantation by measurement of its infusion requirements during transplantation.

Effect of maintenance bolus on the recovery profile of a short-acting nondepolarizing muscle relaxant

STUDY OBJECTIVE

To evaluate the effect of different maintenance boluses of a short-acting nondepolarizing neuromuscular blocking drug on its spontaneous recovery profile during anesthesia.

DESIGN

Prospective, randomized, double-blind, dose-ranging study.

SETTING

University-based medical center.

PATIENTS

69 ASA physical status I and II consenting adult outpatients undergoing general anesthesia with an anticipated duration of at least 2 hours.

INTERVENTIONS

Patients were randomized to one of three study groups. Following induction of anesthesia with propofol and fentanyl, rapacuronium 1.5 mg x kg(-1) intravenously (i.v.), was administered to facilitate tracheal intubation. Anesthesia was maintained with desflurane 4% end-tidal in combination with nitrous oxide 67% in oxygen. When the first twitch (T(1)) in the train-of-four (TOF) returned to 25% of its baseline value, a maintenance dose of rapacuronium 0.25 mg x kg(-1) i.v. (Group 1), 0.5 mg. kg(-1) i.v. (Group 2), or 0.75 mg. kg(-1) i.v. (Group 3) was administered. The time course of neuromuscular block was monitored at the wrist using standard electromyography.

MEASUREMENTS AND MAIN RESULTS

The times for recovery of the T(1) to 25% of the baseline value following different maintenance doses of rapacuronium were only 6.3 +/- 2.2, 7.5 +/- 2.3, and 9.6 +/- 2.5 minutes, in Groups 1, 2 and 3, respectively. However, the times for the TOF ratio to return to 0.7 were 44 +/- 15, 53 +/- 20, and 66 +/- 30 minutes in Groups 1, 2, and 3, respectively. Although recovery times were significantly longer after rapacuronium 0.75 mg x kg(-1) i.v. (Group 3), there were no significant differences in any of the recovery variables between Groups 1 and 2.

CONCLUSIONS

Spontaneous recovery of the T(1) to 25% of the baseline value occurred 6 to 10 minutes after a maintenance bolus dose of rapacuronium 0.25 to 0.75 mg x kg(-1) i.v. However, recovery to a TOF>0.7 required 44 to 66 minutes during desflurane anesthesia.