Hepatosplanchnic blood flow control and oxygen extraction are modified by the underlying mechanism of impaired perfusion.

OBJECTIVE

To assess the effects of low hepatosplanchnic blood flow on regional blood flow control and oxygenation.

DESIGN

Three randomized, controlled animal experiments.

SETTING

Two university experimental research laboratories.

SUBJECTS

Pigs of either gender.

INTERVENTIONS

Isolated abdominal blood flow reduction: An extracorporeal shunt with reservoir and roller pump was inserted between proximal and distal aorta in 11 pigs. Abdominal aortic blood flow was reduced by 50% by activating the shunt. Mesenteric ischemia: In seven pigs, superior mesenteric arterial flow was reduced to 4 mL.kg.min for 4 hrs. Cardiac tamponade: In 12 pigs, aortic blood flow was reduced by cardiac tamponade to 50 mL (moderate tamponade) and further to 30 mL.kg.min (severe tamponade) for 1 hr each. In each experimental condition, the same number of control animals was used.

MEASUREMENTS AND MAIN RESULTS

Abdominal blood flow reduction, acute mesenteric ischemia, and moderate tamponade resulted in a portal venous flow (QPV) reduction to 51 +/- 23%, 52 +/- 18%, and 61 +/- 25% (mean +/- sd) of baseline flow, respectively. During abdominal blood flow reduction, QPV and hepatic arterial flow (QHA) decreased proportionally, whereas in moderate tamponade and acute mesenteric ischemia QPV reduction was associated with an increase in QHA of 30 +/- 39% and 102 +/- 108%, respectively (p = .001 and .018). Prolonged mesenteric ischemia restored total hepatic blood flow (Qliver) completely. During all conditions, decreasing mesenteric oxygen consumption was partly prevented by increased mesenteric oxygen extraction (p < .001 for all conditions). In contrast, decreasing hepatic oxygen delivery was associated with increased oxygen extraction in tamponade (p = .009) but not in abdominal blood flow reduction.

CONCLUSIONS

Blood flow redistribution can restore Qliver totally when mesenteric blood flow is reduced selectively, partially when cardiac output is reduced, and not at all during abdominal blood flow reduction. Since hepatic oxygen extraction does not increase in abdominal blood flow reduction, hepatic oxygenation is at risk in this condition.