The effect of small diameter H-graft portacaval shunts on portal blood flow

Abstract

BACKGROUND: Small-diameter prosthetic H-graft T he traditional end-to-side portacaval shunt is assoportacaval shunts have been shown to promote ciated with a prohibitive risk of severe hepatic dyspreservation of total hepatic blood flow relative to function and, therefore, has been abandoned as a large-diameter H-graft shunts. Nonetheless, spefirst choice treatment option in the management of variceal cific changes in portal hemodynamics occurring hemorrhage due to portal hypertension.’ This shunt diverts with smalldiameter H-graft shunting are unknown. all portal blood flow from the liver and achieves complete This study was undertaken to evaluate changes in portal decompression. Partial portal decompression incomportal flow that occur with these shunts. pletely decompresses the portal vein and allows prograde porMETHODS: Portal vein and inferior vena cava (IVC) tal blood flow.* Different extremes of partial portal decomblood flow were determined intraoperatively in 36 pression have been compared through study of largeand consecutive adults before and after prosthetic Hsmall-bore prosthetic H-graft portacaval shunts.3*4 Compared graft portacaval shunting using color-flow with large-bore shunts, small-bore shunts less completely deDoppler ultrasound. Postshunt measurements compress the portal vein and divert less nutrient hepatic were made immediately cephalad and caudad to blood flow. The relative maintenance of nutrient hepatic the shunt. Comparisons were undertaken using a blood flow by small-diameter prosthetic H-graft portacaval paired Student’s t-test with 95% confidence. shunts is presumed to be the basis by which these shunts RESULTS: Portal pressures decreased in all (P lead to superior clinical outcomes.’ <O.OOl), but never to normal. Postshunt portal Surprisingly, hemodynamic changes in the portal system ocflow cephalad and caudad to the shunt were not curring with small-diameter prosthetic H-graft portacaval different from preshunt flow (P = 0.09, P = 0.26, . shunts are poorly understood. Studies have been undertaken respectively), although they were different from to determine changes in portal and hepatic blood flo~,~ each other (P = 0.004). Postshunt IVC flow changes in the direction of portal blood flow:” and changes cephalad to the shunt was greater than caudad in portal pressures with small-diameter H-graft shunting.*s IVC flow (P = 0.004) and greater than preshunt The results of these studies are often conflicting and difficult IVC flow (P <O.OOl), reflecting high flow through to correlate with clinical outcomes, leaving many questions the shunt into the IVC. about portal hemodynamic changes with H-graft shunting. CONCLUSIONS: Small-diameter prosthetic H-graft This study was undertaken to measure portal vein and inportacaval shunts divert a significant amount of ferior vena cava (IVC) blood flow to determine the size of blood from the portal vein and significantly dethe reduction in portal blood flow that occurs with partial crease portal pressures. The decreases in portal portal decompression attained through small-diameter prospressures with shunting are significant whereas thetic H-graft portacaval shunting and to determine the volchanges in portal blood flow into the liver are ume of blood shunted from the portal system. Our hypotheses not. These findings help explain the low inciin undertaking this study were that portal blood flow into dence of variceal rebleeding and hepatic dysthe liver was well maintained after partial portal decomfunction after these shunts. Am J Surg. 1996; 171 :154-l 57. pression achieved by small-diameter prosthetic H-graft shunting, that loss of portal blood flow into the liver was small compared with reduction in portal pressures, and that the volume of blood shunted from the portal system was large, although compensated for by an increase in blood flow into the portal system.