LUNG UPTAKE OF LIDOCAINE DURING HYPEROXIA AND HYPOXIA IN THE DOG

Background: Lidocaine has been shown to accumulate in the lung followi ng its administration. This study was undertaken to determine effects of dose of lidocaine on lung uptake during hyperoxic and hypoxic venti lation. Methods: Using cross-circulation consisting of ventilation and constant-flow perfusion of the left lower lobe independently from all other lobes of the dog lung under nitrous oxide and halothane anesthe sia, lidocaine was infused into the inflow system, so that plasma lido caine concentrations in the inflow blood were maintained at 5, 10, 20, 40 and 70 mu g/ml respectively during ventilation with 50% O-2 or 3% O-2. During 20 mu g/ml lidocaine infusion, indocyanine green (ICG), an intravascular marker, was mixed with the lidocaine solution, in such a fashion that plasma ICG concentration in the inflow blood was mainta ined at 20 mu g/ml. Actual plasma lidocaine and ICG concentrations in blood drawn from the inflow ([Lid]pa, [ICG]pa) and the outflow ([Lid]p v, [ICG]pv) systems were measured 1, 3, 5, 7 and 10 minutes after the beginning of lidocaine infusion. Percent lung uptake of perfused lidoc aine was calculated as {1-([Lid]pv/[Lid]pa)/([ICG]pv/[ICG]pa)} x100. R esults: During ventilation hyperoxia, mean percent lung uptakes of lid ocaine were 41-52% 1 minute after the beginning of lidocaine infusion, and decreased in time-dependent fashion to 7-12% 10 minutes later. Cu rves of percent lung uptake of lidocaine over time were similar for th e 5 predetermined lidocaine concentration groups (5-70 mu g/ml). There were no significant differences in percent lung uptakes of lidocaine between the ventilation hyperoxia and hypoxia conditions. Conclusions: These findings suggest that percent lung uptake of lidocaine is unaff ected by hypoxic ventilation and by varying the concentration of lidoc aine in the perfusion through the recipient dog lung lobe.