Does gastric tonometry monitor splanchnic perfusion?

Objective: To define whether the gastric mucosal-arterial PCO2 gradient (PC O2 gap) reliably reflects hepatosplanchnic oxygenation in septic patients, Design: Prospective observational clinical study, Setting: An adult, 31-bed medical/surgical department of intensive care of a university hospital, Patients: A total of 36 hemodynamically stable, invasively monitored, mecha nically ventilated, sedated, paralyzed patients with severe sepsis, Interventions: In each patient, hepatosplanchnic blood flow was determined by the continuous indocyanine green infusion technique and gastric mucosal PCO2 by the saline tonometry technique, Suprahepatic venous blood oxygen sa turation and PCO2 also were measured, The mesenteric veno-arterial PCO2 gra dient was determined as the difference between the suprahepatic venous bloo d PCO2 and the arterial blood PCO2. Measurements and Main Results: There were significant cor-relations between the hepatosplanchnic blood flow and the suprahepatic venous blood oxygen s aturation (r(2) = .56; p < .01), between the hepatosplanchnic blood flow an d the mesenteric veno-arterial PCO2 gradient (r(2) = .55; p < .01), and als o between the suprahepatic venous blood oxygen saturation and the mesenteri c veno-arterial PCO2 gradient (r(2) = .64; p < .01), There was no statistic ally significant correlation between the PCO2 gap and the hepatosplanchnic blood flow, the suprahepatic venous blood oxygen saturation or the mesenter ic veno-arterial PCO2 gradient. Conclusions: In stable septic patients, the PCO2 gap is not correlated with global indexes of gut oxygenation, The interpretation of PCO2 gap is more complex than previously thought.