Partial versus total portacaval shunt in alcoholic cirrhosis. Results of a prospective, randomized clinical trial

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

BACKGROUND

Small-diameter prosthetic H-graft portacaval shunts have been shown to promote preservation of total hepatic blood flow relative to large-diameter H-graft shunts. Nonetheless, specific changes in portal hemodynamics occurring with small-diameter H-graft shunting are unknown. This study was undertaken to evaluate changes in portal flow that occur with these shunts.

METHODS

Portal vein and inferior vena cava (IVC) blood flow were determined intraoperatively in 36 consecutive adults before and after prosthetic H-graft portacaval shunting using color-flow Doppler ultrasound. Postshunt measurements were made immediately cephalad and caudad to the shunt. Comparisons were undertaken using a paired Student's t-test with 95% confidence.

RESULTS

Portal pressures decreased in all (P < 0.001), but never to normal. Postshunt portal flow cephalad and caudad to the shunt were not different from preshunt flow (P = 0.09, P = 0.28, respectively), although they were different from each other (P = 0.004). Postshunt IVC flow cephalad to the shunt was greater than caudad IVC flow (P = 0.004) and greater than preshunt IVC flow (P < 0.001), reflecting high flow through the shunt into the IVC.

CONCLUSIONS

Small-diameter prosthetic H-graft portacaval shunts divert a significant amount of blood from the portal vein and significantly decrease portal pressures. The decreases in portal pressures with shunting are significant whereas changes in portal blood flow into the liver are not. These findings help explain the low incidence of variceal rebleeding and hepatic dysfunction after these shunts.

Surgical management of portal hypertension

Portal hypertension is frequently complicated by upper gastrointestinal tract bleeding and ascites. Hemorrhage from esophageal varices is the most common cause of death from portal hypertension. Medical treatment, including resuscitation, vasoactive drugs, and endoscopic sclerosis, is the preferred initial therapy. Patients with refractory hemorrhage frequently are referred for immediate surgical intervention (usually emergency portacaval shunt). An additional cohort of patients with a history of at least 1 episode of variceal hemorrhage is likely to benefit from elective shunt operations. Shunt operations are classified as total, partial, or selective shunts based on their hemodynamic characteristics. Angiographically created shunts have been introduced recently as an alternative to operative shunts in certain circumstances. Devascularization of the esophagus or splenectomy is done for specific indications. Medically intractable ascites is a separate indication for surgical intervention. Liver transplantation has been advocated for patients whose portal hypertension is a consequence of end-stage liver disease. In the context of an increasingly complex set of treatment options, we present an overview of surgical therapy for complications of portal hypertension.

Analysis of nutrient hepatic blood flow after 8-mm versus 16-mm portacaval H-grafts in a prospective randomized trial

BACKGROUND

In previous unrandomized studies, we demonstrated that patients undergoing 8-mm diameter portacaval H-grafts with collateral ablation (partial shunts) have lower rates of portasystemic encephalopathy (PSE) postoperatively than patients undergoing total portacaval shunts. We postulated that nutrient hepatic blood flow was greater after partial shunts because 8-mm grafts preserved some portal flow.

METHODS

To test this hypothesis, we analyzed hepatic hemodynamics in 18 of 30 randomized patients who consented to be studied after complete operative recovery, grouped according to shunt size. We measured nutrient hepatic blood flow using 99m-Tc-Mebrofenin tracer elimination kinetics, and fractionated it into its portal venous and hepatic arterial components. PSE was assessed by blinded observers. Stepwise logistic regression was used to select the variable that best predicted encephalopathy. From 1989 to 1993, we conducted a randomized, prospective trial of partial (8 mm) versus total (16 mm) portacaval H-grafts. Group differences were compared using one-way analysis of variance (ANOVA).

RESULTS

Hepatic encephalopathy occurred in 2 of 10 patients with partial shunts versus 5 of 8 patients with total shunts. Nutrient hepatic blood flow was significantly higher for partial shunts compared with total shunts (403 +/- 601 versus 243 +/- 17mL/min). Three variables--nutrient hepatic blood flow, portal blood flow, and hepatic arterial flow--were analyzed by stepwise logistic regression. Nutrient hepatic blood flow was selected as the best predictor of hepatic encephalopathy. In this series, PSE did not occur in any patient with more than 325 mL/min of nutrient hepatic blood flow.

CONCLUSION

These findings provide a physiologic basis for clinical observations demonstrating a lower incidence of PSE with partial shunts and indicates the superiority of partial over total shunts. Partial shunts, by preserving portal flow, maintain higher nutrient hepatic blood flow than total shunts and thus minimize PSE rates.