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

Objectives: To evaluate the acute effects of an increase in PCO2 on splanchnic tissue perfusion and metabolism Design. Clinical prospective study in the intensive care unit in a university clinic, Patients: 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. Interventions: PCO2 was increased 5-20 % by an added dead space from baseline, followed by a return to baseline. Measurements and results: 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. Conclusion: Our results suggest that acute moderate changes in PCO2, have no major effect on splanchnic perfusion and metabolism.