EFFECTS OF ISOFLURANE ON REGIONAL PULMONARY BLOOD-FLOW DURING ONE-LUNG VENTILATION

Isoflurane has been reported to inhibit hypoxic pulmonary vasoconstriction. However, the effects of one-lung ventilation and isoflurane on regional pulmonary blood flow (Or) have not been investigated in detail. Therefore, using radionuclide labelled microspheres we measured Or in rabbits (n = 8) in the left lateral decubitus position during two- and one-lung ventilation under i.v. baseline anaesthesia and during additional administration of 1.5% isoflurane. Macrohaemodynamic variables were recorded continuously. Isoflurane increased non-dependent lung blood flow during two-lung ventilation. One-lung ventilation caused a homogeneous decrease in Or throughout the hypoxic lung, irrespective of isoflurane administration (P < 0.001). However, isoflurane significantly augmented Or of the hypoxic lung during one-lung ventilation (P < 0.05). During all phases, Or of the upper lobe was higher compared with that in the lower lobe in isogravitational slices of both lungs; a ventrodorsal perfusion gradient was found in the left upper lobe. We conclude that 1.5% isoflurane increased perfusion of the non-dependent lung, inhibited hypoxic pulmonary vasoconstriction-induced redistribution of pulmonary blood flow and did not influence isogravitational perfusion gradients.