Background and methods: Hepatic dysfunction after severe hemorrhagic shock is common and may be a consequence of visceral tissue hypoxia. Peripheral tissue PO2 has been suggested to correlate with the development of visceral hypoxia. To test the hypothesis that changes in peripheral tissue PO2 reflect changes in hepatic PO2, we measured subcutaneous PO2, transcutaneous PO2, transconjunctival PO2, and liver tissue PO2, and their relationship with changes in mean arterial blood pressure (MAP) and systemic oxygen transport (DO2), during progressive bleeding in pigs (n = 23). In addition to the tissue PO2, portal vein PO2 and circulating lactate concentrations were also measured in six of the animals. The animals were anesthetized and bled to an MAP of 50 mm Hg within 1 hr.
Results: After an induced 10% reduction of MAP, only the DO2 decreased significantly (p less than .05). After a 20% reduction of MAP, the DO2 decreased further and was associated with a significant (p less than .05) reduction of all peripheral tissue PO2 values. A significant (p less than .05) reduction of liver tissue PO2 was observed later during bleeding, after induction of a 30% reduction in MAP. In the subgroup with portal venous PO2 and lactate measurements, reductions of all peripheral tissue PO2 and portal venous PO2 values occurred after a 20% reduction (p less than .05) of MAP. An increase (p less than .05) in the portal venous lactate concentration was observed after a 50% reduction of MAP, and a decrease (p less than .05) in liver tissue PO2 was noted after a 60% reduction of MAP.
Conclusions: Reductions of both peripheral and portal venous PO2 values occur early during hemorrhage. The liver tissue PO2, though initially low, appears to be better defended, suggesting either redistribution of splanchnic blood flow or adaptation in hepatic oxygen demand.