Prolongation of nerve and epidural anesthetic blockade by bupivacaine in alipid emulsion

We assessed the effect of a lipid emulsion of bupivacaine on prolonging per ipheral nerve and epidural anesthetic blockade in the rat. The intensity an d duration of motor and sensory blockade produced by a single injection of aqueous solution (BPV-as) and lipid emulsion (BPV-em) preparations of 0.5% bupivacaine were evaluated by electrophysiological methods. Both preparatio ns induced complete, reversible motor and sensory blockade after injection. The latency time to the maximal blockade and the duration of anesthetic bl ockade were more prolonged for BPV-em than for BPV-as. The increase in dura tion of maximal blockade was 1.4 times for nerve and 1.3 times for epidural anesthesia. Histological evaluation of spinal roots and spinal cord sectio ns did not show any abnormalities or differences between animals injected w ith BPV-as and those injected with BPV-em. Pharmacokinetic studies showed l ower plasma peak concentration and a longer elimination half-life for BPV-e m than for BPV-as. Thus, BPV-em prolongs the effects of local anesthetics, allows a similar degree of blockade, and reduces the systems toxic effects of anesthetics compared with BPV-as. Implications: We assessed a lipid emul sion containing bupivacaine for peripheral nerve and epidural anesthetic bl ockade in the rat. The emulsion allowed a complete blockade, while increasi ng the duration of the anesthetic effect (by 30%-40%), compared with the st andard bupivacaine aqueous solution.