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Background: Abnormal gastric tonometric variables, a surrogate for splanchnic ischemia, occur in approximately 50% of patients at the end of routine cardiac operations and are associated with postoperative morbidity. We sought to determine whether gastric tonometric variables deteriorate after left ventricular assist device insertion and to explore the association between abnormal gastric tonometric variables and vasoconstrictor use., Methods: Nineteen patients who had insertion of a left ventricular assist device were enrolled in a prospective, observational study. Automated air tonometry was used to determine the difference between gastric and arterial partial pressure of carbon dioxide (CO2 gap) at five time points perioperatively., Results: Compared with baseline, systemic blood flow was significantly increased at the end of operation (1.9 +/- 0.6 versus 2.9 +/- 0.7 L x min(-1) x m(-2), p < 0.0001). Tonometric variables, which were normal at baseline, became abnormal in 90% of patients (baseline CO2 gap 4 +/- 2 mm Hg versus end of operation CO2 gap 24 +/- 15 mm Hg, p < 0.0001). Elevated CO2 gaps correlated with larger doses of norepinephrine (r = 0.69, p = 0.001) and vasopressin (r = 0.88, p < 0.0001). Abnormal gastric tonometric variables at the end of operation correlated with postoperative intensive care unit length of stay (r = 0.70, p = 0.0009) and multiple organ dysfunction score (r = 0.64, p = 0.0033)., Conclusions: Despite a significant increase in systemic blood flow after left ventricular assist device implantation, abnormal gastric tonometric variables developed and were associated with larger vasoconstrictor dose. These data provide evidence that gastric ischemia can develop independently of changes in systemic blood flow and support the potential role of vasoconstrictors as a cause of splanchnic ischemia.

Objective: It has been postulated that splanchnic ischemia, as manifested by gastric hypercarbia, helps to trigger excessive systemic inflammation, which has been linked to the development of adverse postoperative outcome. This study examined whether gastric PCO(2) values are associated with adverse outcome in cardiac surgical patients., Design and Setting: Prospective cohort study in a tertiary-care hospital., Patients: 43 patients undergoing elective cardiac surgery., Interventions: Simultaneous measurements of gastric PCO(2) (using automated air tonometry) and arterial PCO(2) were obtained at the beginning and end of surgery. The difference (gap) between regional PCO(2) and arterial PCO(2) (corrected for temperature) was calculated. Adverse outcome was defined as in-hospital death or prolonged (>10 days) postoperative hospitalization., Measurements and Results: Fourteen patients fulfilled the predefined definition for adverse outcome. Postoperative ICU stay and postoperative hospital length of stay were significantly longer in these patients. At the end of surgery gastric minus arterial PCO(2) gap was significantly larger in patients with adverse outcome. Global hemodynamic and perfusion related variables were not associated with adverse outcome (cardiac index, mean arterial pressure, mixed venous oxygen saturation, arterial lactate, arterial base excess)., Conclusions: Gastric minus arterial PCO(2) gap after surgery is larger in patients with adverse postoperative outcome, which supports the theory that gastrointestinal reduced perfusion is relevant to the pathogenesis of postoperative morbidity.

Unlabelled: Low gastric intramucosal pH (pHi) and an increased gastric-arterial PCO2 difference (CO2 gap) are markers of tissue hypoperfusion. Perfluorocarbons (PFCs) have a large oxygen-carrying capacity and release oxygen when encountering low tissue oxygen tension. Nine cardiac surgical patients instrumented for gastric tonometry were enrolled as part of a multicenter, randomized, single-blinded study of a PFC emulsion (perflubron emulsion [Oxygent]). Patients were randomized to receive PFC (n = 4) or placebo (n = 5) after intraoperative autologous blood harvesting by acute normovolemic hemodilution. At baseline there were no intergroup differences in tonometric-, hemodynamic-, or oxygen delivery-derived variables, e.g., Control group (pHi, 7.37 +/- 0.06; CO2 gap, 6.4 +/- 1.3 mm Hg) versus PFC group (pHi, 7.38 +/- 0.06; CO2 gap, 6.7 +/- 1.5 mm Hg). After acute normovolemic hemodilution, pHi was significantly lower (P < 0.01) in the Control group (7.22 +/- 0.25) than in the PFC group (7.44 +/- 0.25), and CO2 gap was significantly higher (P < 0.001) in the Control group (23.4 +/- 5.1 mm Hg) than in the PFC group (1.8 +/- 0.8 mm Hg). These differences in tonometric variables persisted during surgery. The PFC group showed a significantly (P < 0.007) shorter time to first bowel movement postoperatively (2.0 +/- 0.8 vs 5.4 +/- 1.6 days). Time to consumption of solid food was also shorter in the PFC group and almost achieved statistical significance (P = 0.056)., Implications: This study suggests that the administration of perflubron emulsion prevents gastrointestinal tract ischemia in cardiac surgical patients and may preserve postoperative gastrointestinal tract function.