Effects of lidocaine on pulmonary circulation during hyperoxia and hypoxia in the dog
Yukioka, H.; Hayashi, M.; Tatekawa, S.; Fujimori, M.
Regional Anesthesia 21(4): 327-337
1996
ISSN/ISBN: 0146-521X PMID: 8837191 Document Number: 457971
Background and Objectives: High concentrations of lidocaine have been found to cause pulmonary vasoconstriction and low concentrations (0.5-0.9 mu-g/mL) to cause reversal of nitrous oxide-induced depression of hypoxic pulmonary vasoconstriction. This study was under-taken to examine the effects of high concentrations of lidocaine on pulmonary circulation during hyperoxic and hypoxic ventilation. Methods: With use of cross-circulation consisting of ventilation and constant-flow perfusion of the left lower lobe (LLL) independently of 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 either 5, 10, 20, 40, 70, or 140 gg/mL during ventilation with 50% oxygen or 3% oxygen. Mean arterial and venous pressures in the LLL (PAP-LLL and PVP-LLL), airway pressure of the LLL, and blood gas in LLL inflow and outflow were measured. Results: High plasma concentration of lidocaine (140 mu-g/mL) in the LLL inflow produced a significant increase in PAP-LLL during hyperoxia, while PAP-LLL did not change significantly at the 5-70-mu-g/mL lidocaine concentration. In LLL outflow blood, PO-2 increased significantly following a 140 mu-g/mL lidocaine infusion during hyperoxia, while in LLL inflow blood, Po-2 did not change. The airway pressure of LLL also did not change. During hypoxia, hypoxic pulmonary vasoconstriction did not occur, and lower plasma concentrations of lidocaine (40-70 mu-g/mL) significantly constricted the lobar vessels. in addition, lidocaine at the 140-mu-g/mL concentration constricted the upstream vessels (presumably the lobar arteries) more strongly than the lobar veins during hypoxia. Conclusions: Extremely high concentrations (140 mu-g/mL) but not low concentrations (5-70 mu-g/mL) of lidocaine produced pulmonary vasoconstriction and reduced shunt. Lower concentrations of lidocaine constricted the hypoxic lobar vessels.