A tributary of the superior mesenteric vein was catheterized in dogs. The diameters of the opacified portal vein (PV) were determined on biplane cineangiograms. Droplets of lipiodol were injected and cinefluorography performed. The mean linear velocity of portal blood was calculated from the velocity of droplets observed during apnea, using correction factors obtained from previous model experiments. The portal vein flow (PVF) was calculated from the mean linear velocity and the mean cross-sectional area of PV. Portal and systemic blood pressures (PVP, BP), cardiac output (CO), and respirations were recorded. Measurements were taken before lowering the CO and BP and after the restitution of normal values. The cross-sectional area of PV is elliptical in shape and becomes smaller after bleeding, regaining its shape after replacement of blood. PVP varied from 3–12 mmHg and was not affected by the injection of lipiodol droplets. Hemorrhage had no effect on PVP and PVF in its early stage, but further bleeding (30 ml/kg) produced a fall in both. After restitution of BP and CO, PVP and PVF returned to normal values. PVF, on the average, represented 23 of CO (range 1.2 – 3.5 l/min.). While the CO was lowered, PVF as per cent of CO was increased. Extremely low CO produced a decrease in PVF as per cent of CO. An application of the method is suggested in man where the portal vein can be catheterized via a recanalized umbilical vein.
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