REVERSAL OF NITROUS OXIDE-INDUCED DEPRESSION OF HYPOXIC PULMONARY VASOCONSTRICTION BY LIGNOCAINE HYDROCHLORIDE DURING COLLAPSE AND VENTILATION HYPOXIA OF THE LEFT LOWER LOBE

Abstract

The blood flow to the left lower lobe (QL), and total (QT) pulmonary blood flow, were measured in 10 open-chest dogs using electromagnetic flowmeters. Ventilation of the left lower lobe with 7% oxygen in nitrogen produced a greater reduction in QL/QT (41%) than lobar ventilation with 7% oxygen in nitrous oxide (33%). Lobar collapse reduced QL/QT by 65%, but there was no change in QL/QT when 50% nitrous oxide was administered to the right lung. The i.v. infusion of lignocaine hydrochloride during ventilation of the lobe with 7% oxygen in nitrogen produced no change in QL/QT. However, lignocaine infusion during lobar ventilation with 7% oxygen in nitrous oxide produced a further reduction in QL/QT to a value which was not significantly different from that observed during ventilation with 7% oxygen in nitrogen. Lignocaine had no effect on QL/QT during lobar collapse whether the right lung was ventilated with 50% oxygen in nitrogen or 50% oxygen in nitrous oxide. It is concluded that lignocaine reverses the depression of hypoxic pulmonary vasoconstriction produced by lobar ventilation with nitrous oxide.