Lung uptake of lidocaine during hyperoxia and hypoxia in the dog

Lidocaine has been shown to accumulate in the lung following its administration. This study was undertaken to determine effects of dose of lidocaine on lung uptake during hyperoxic and hypoxic ventilation.

Using cross-circulation 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 anesthesia, lidocaine was infused into the inflow system, so that plasma lidocaine concentrations in the inflow blood were maintained at 5, 10, 20, 40 and 70 micrograms/ml respectively during ventilation with 50% O2 or 3% O2. During 20 micrograms/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 maintained at 20 micrograms/ml. Actual plasma lidocaine and ICG concentrations in blood drawn from the inflow ([Lid]pa,[ICG]pa) and the outflow ([Lid]pv,[ICG]pv)systems were measured, 1, 3, 5, 7 and 10 minutes after the beginning of lidocaine infusion. Percent lung uptake of perfused lidocaine was calculated as ¿1-([Lid]pv/[Lid]pa)/([ICG]pv/[ICG]pa)¿ x 100.

During ventilation hyperoxia, mean percent lung uptakes of lidocaine were 41-52% 1 minute after the beginning of lidocaine infusion, and decreased in time-dependent fashion to 7-12% 10 minutes later. Curves of percent lung uptake of lidocaine over time were similar for the 5 predetermined lidocaine concentration groups (5-70 micrograms/ml). There were no significant differences in percent lung uptakes of lidocaine between the ventilation hyperoxia and hypoxia conditions.

These findings suggest that percent lung uptake of lidocaine is unaffected by hypoxic ventilation and by varying the concentration of lidocaine in the perfusion through the recipient dog lung lobe.