Pulmonary uptake of ropivacaine and levobupivacaine in rabbits.

Abstract

Local anesthetic toxicity produced by an inadvertent IV injection is attenuated by the pulmonary uptake of local anesthetics. We compared the pulmonary uptake of ropivacaine and levobupivacaine after a bolus injection in rabbits. Sixteen anesthetized rabbits were randomly assigned to either a ropivacaine group or a levobupivacaine group. A bolus containing ropivacaine or levobupivacaine 0.5 mg/kg and indocyanine green (an intravascular indicator) 0.25 mg/kg was injected rapidly into the vena cava. Arterial blood samples were collected serially at 1.2-s intervals for 30 s. Concentrations of local anesthetic and indocyanine green in each sample were determined for the calculation of first-pass uptake of a local anesthetic in the lung. The first-pass uptake of levobupivacaine (31.4% +/- 8.3%; mean +/- SD) was larger than that of ropivacaine (22.9% +/- 5.6%), and the maximum arterial concentration of ropivacaine (21.2 +/- 2.8 micro g/mL) was larger than that of levobupivacaine (18.6 +/- 1.9 micro g/mL). We conclude that the pulmonary uptake of levobupivacaine is larger than that of ropivacaine after a bolus injection. Therefore, the advantages of ropivacaine over levobupivacaine in terms of less cardiovascular toxicity may be offset by the smaller pulmonary uptake after an inadvertent IV injection.