EFFECT OF SODIUM BICARBONATE ON THE KINETICS OF BUPIVACAINE IN I.V. REGIONAL ANAESTHESIA IN DOGS

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Abstract
Changes in pH studied in vitro affected considerably the distribution of bupivacaine between the erythrocytes and incubation medium: in an acidic medium, the uptake of bupivacaine by erythrocytes was decreased. The acidosis induced in vivo in dogs' limbs during i.v. regional anaesthesia (IVRA) with bupivacaine was corrected by injecting sodium bicarbonate into the occluded limb. The concentration of bupivacaine in the cephalic vein was measured in dogs under IVRA. After removal of the tourniquet, the drug concentration-time relationship showed a biexponential pattern of decline. Injection of sodium bicarbonate into the limb 10 min before the release of the tourniquet suppressed the rate at which the concentration of bupivacaine decreased during the second phase. This slower rate of drug release from the tissues may prolong residual analgesia.