Effect of prone position on hepato-splanchnic hemodynamics in acute lung injury

Objective: To evaluate the effects of prone position on hepatosplanchnic hemodynamics, metabolism and gut mucosal energy balance. Design: Prospective clinical study. Setting: Medical intensive care unit in a university hospital. Patients: Eleven hemodynamically stable patients with acute lung injury (ALI) requiring mechanical ventilation. Intervention: Patients were studied in the supine position, after 90 min in the prone position and after 90 min of supine repositioning. Measurements and results: In addition to global hemodynamics we measured intra-abdominal pressure (IAP, bladder), hepato-splanchnic blood flow (HSBF, steady state indocyanine green technique using a hepatic vein catheter) and gastric mucosal-arterial PCO2 gap (PCO2 gap, automated air tonometry). Systemic hemodynamics did not change during the whole study. Prone positioning did not significantly affect IAP. HSBF as well as splanchnic oxygen consumption remained unaltered, too. Similarly, neither liver lactate uptake nor indocyanine green extraction were influenced by positional changes. Finally, stable regional hemodynamics were accompanied by an unchanged PCO2 gap. Conclusion: We conclude that if IAP and systemic hemodynamics remain unaffected, the prone position in ALI patients compromises neither hepato-splanchnic perfusion nor gastric mucosal energy balance.