The Duration of Immobilization Causes the Changing Pharmacodynamics of Mivacurium and Rocuronium in Rabbits

Extravascular leakage of induction doses of rocuronium: four cases in which both depth of neuromuscular block and plasma concentration of rocuronium were assessed

The duration of action of extravasated rocuronium varies depending on the patient's comorbidities. In patients who receive high doses of non-depolarizing neuromuscular blocking agents subcutaneously, anesthesiologists should be aware of unexpected prolongation of the progress and recovery of neuromuscular block. In such cases, the depth and recovery of neuromuscular block should be objectively monitored to avoid residual neuromuscular block and recurarization.

Reversal with sugammadex for rocuronium-induced deep neuromuscular block after pretreatment of magnesium sulfate in rabbits

Background

Magnesium sulfate (MgSO₄) has been used in the treatment of pre-eclampsia, hypertension and arrhythmia. Magnesium enhances the neuromuscular block of rocuronium. This study has been conducted to evaluate the reversal efficacy of sugammadex from deep rocuronium-induced neuromuscular block (NMB) during consistent pretreatment of MgSO₄ in rabbits.

Methods

Twenty-eight rabbits were randomly assigned to four groups, a control group or study groups (50% MgSO₄ 150–200 mg/kg and 25 mg/kg/h IV), and received rocuronium 0.6 mg/kg. When post-tetanic count 1–2 appeared, sugammadex 2, 4, and 8 mg/kg was administered in the 2-mg group, control and 4-mg group, and 8-mg group, respectively. The recovery course after reversal of sugammadex administration was evaluated in each group.

Results

The mean serum concentration of magnesium was maintained at more than 2 mmol/L in the study groups, and the total dose of MgSO₄ was more than 590 mg. The reversal effect of sugammadex on rocuronium-induced NMB in pretreated MgSO₄ was not different from that in the group without MgSO₄. The recovery time to train-of-four ratio 0.9 after sugammadex administration in the 2-mg group was longer than in the other groups (P < 0.001); there were no other significant differences among the groups.

Conclusions

The reversal of sugammadex from a deep rocuronium-induced NMB during large pretreatment of MgSO₄ was not affected. However, we should consider that the reversal effect of sugammadex varied depending on the dose.

The pharmacodynamics of mivacurium in the rabbit with carbon tetrachloride-induced liver disease

BACKGROUND AND OBJECTIVE

Neuromuscular blocking effects according to the severity of liver dysfunction have not been evaluated. We assessed the neuromuscular effects of mivacurium in carbon tetrachloride (CCl4)-treated rabbits with toxic hepatitis in vivo.

METHODS

We compared the dose-response relationships and the neuromuscular blocking effects of mivacurium in 66 rabbits randomly treated with 0.3 mL kg(-1) of corn oil, 0.3 mL kg(-1) of CCl4 or 0.6 mL kg(-1) of CCl4 for 11 weeks, respectively. Train-of-four stimuli were applied every 10 s to the common peroneal nerve and the force of contraction of the tibialis anterior muscle was measured.

RESULTS

Severe hepatitis was associated with a rightward shift of the mivacurium dose-response curves, but mild hepatitis had no effect. The calculated ED50 values for the control, mild and severe hepatitis were 17.1+/-2.6, 18.2+/-2.7 and 31.8+/-3.2 microg kg(-1), respectively. Rabbits with severe hepatitis had a significantly prolonged recovery time from neuromuscular blockade compared with other rabbits. Cholinesterase activity had a negative correlation with recovery indices of mivacurium even in severe hepatic injury. Severe hepatitis induced a prolongation of action duration of repeated doses, but maintained the constant intervals.

CONCLUSIONS

The dose-response and the time course of neuromuscular blockade of mivacurium differ in mild hepatitis compared with severe hepatitis, but required no adjustments of different doses for repeated injection after the desired depth of neuromuscular block, and had a negative correlation with the activity of plasma cholinesterase in both hepatic injuries.