Effect of an acute increase in PCO2 on splanchnic perfusion and metabolism.

Abstract

To evaluate the acute effects of an increase in PCO2 on splanchnic tissue perfusion and metabolism. Clinical prospective study in the intensive care unit in a university clinic. Six patients with severe acute lung injury requiring mechanical ventilation. All patients had bilateral infiltrates on chest radiography, a PaO2/FIO2 ratio less than 200 mmHg, and stable hemodynamics without vasoactive drugs. PCO2 was increased 5-20% by an added dead space from baseline, followed by a return to baseline. Splanchnic blood flow was measured using primed continuous infusion of indocyanine green dye with hepatic venous sampling and systemic hemodynamics by routine monitoring; we also determined the gastric mucosal-arterial PCO2 difference and splanchnic lactate/pyruvate exchange. PCO2 was increased by an added dead space; after 60 min all measurements were repeated; after return to baseline a third measurement followed. The increase in PCO2 had no significant effect on splanchnic blood flow or indices of perfusion and metabolism. Our results suggest that acute moderate changes in PCO2 have no major effect on splanchnic perfusion and metabolism.