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

Isoflurane has been reported to inhibit hypoxic pulmonary vasoconstric tion. However, the effects of one-lung ventilation and isoflurane on r egional pulmonary blood flow (Or) have not been investigated in detail . Therefore, using radionuclide labelled microspheres we measured Or i n rabbits (n = 8) in the left lateral decubitus position during two- a nd one-lung ventilation under i.v. baseline anaesthesia and during add itional administration of 1.5% isoflurane. Macrohaemodynamic variables were recorded continuously. Isoflurane increased non-dependent lung b lood flow during two-lung ventilation. One-lung ventilation caused a h omogeneous decrease in Or throughout the hypoxic lung, irrespective of isoflurane administration (P < 0.001). However, isoflurane significan tly augmented Or of the hypoxic lung during one-lung ventilation (P < 0.05). During all phases, Or of the upper lobe was higher compared wit h that in the lower lobe in isogravitational slices of both lungs; a v entrodorsal perfusion gradient was found in the left upper lobe. We co nclude that 1.5% isoflurane increased perfusion of the non-dependent l ung, inhibited hypoxic pulmonary vasoconstriction-induced redistributi on of pulmonary blood flow and did not influence isogravitational perf usion gradients.