The mechanism of pancuronium potentiation of mivacurium block: use of the isolated-arm technique

The effect of defasciculating doses of pancuronium and atracurium on succinylcholine neuromuscular blockade

Background:

A defasciculating dose of non-depolarizing muscle relaxant administered prior succinylcholine decrease its side effects including fasciculations and postoperative myalgias; however it is believed that the dosage of succinylcholine should be increased when such a pre-treatment is used.

Objectives:

We hypothesized that a defasciculating dose of pancuronium as a pre-treatment could prolong its duration of effect.

Patients and Methods:

Forty patients scheduled for elective orthopaedic surgery were consecutively assigned into 5 groups, a first group without pre-treatment (succinylcholine 1 mg/kg) and 4 subsequent groups of pretreatment with atracurium 0.05 mg/kg + succinylcholine 1 or 1.5 mg/kg and pancuronium 7.5 µg /kg + succinylcholine 1 and 1.5 mg/kg. The muscle relaxant effect of succinylcholine was assessed with a force transducer using train of four stimulations every 12 seconds. Kruskall Wallis Anova test was used to compare results.

Results:

The duration of succinylcholine induced paralysis (1 and 1.5 mg/kg) was significantly prolonged with pre-treatment with pancuronium but succinylcholine 1mg/kg did not reached maximum blockade after pre-treatment with atracurium. After pancuronium, full recovery after succinylcholine 1.5 and 1 mg/kg occurred respectively after 18 and 15 minutes. P < 0.05 vs. 12 minutes for succinylcholine 1mg/kg alone.

Conclusions:

This study highlights potentiation effect of a defasciculating dose of pancuronium on succinylcholine paralysis suggesting the lack of justification to increase succinylcholine dosage.

Dose-response effect of serum butyrylcholinesterase activity after clinical doses of pancuronium

INTRODUCTION

Low-dose pancuronium is known to affect serum cholinesterase activity (BChE); however, the dose-response effect of clinical doses of pancuronium on BChE has not been investigated.

METHODS

Thirteen ASA I-II patients scheduled for elective surgery requiring muscle relaxation were enrolled in this study. All patients had normal BChE before surgery. Incremental doses of pancuronium (10, 20, 50, and 100 microg/kg) were injected in accordance with surgical needs every 45 min. BChE was measured 3 min after injection by an automatic colorimetric method.

RESULTS

BChE decreased significantly in all except one patient in comparison to the baseline (P < 0.05). However all values remained within normal clinical range. A dose of 100 microg/kg yielded significant decrease in comparison to 10 microg/kg but not to other dosages. Linear regression was not significant for the dose-response relationship (P = 0.05).

CONCLUSION

After clinical incremental doses of pancuronium, BChE remained within clinical range.

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.