Effects of fluid challenge on gastric mucosal PCO2 in septic patients

Objective To determine the effects of fluid challenge on systemic hemodynamic variables and gastric intramucosal partial pressure of carbon dioxide (PCO₂) in septic patients.Design Short-term interventional study.Setting Medical-surgical intensive care unit in a university hospital.Patients Twenty-four adult patients with severe sepsis or septic shock requiring volume replacement. All patients were studied within 24 h of onset of severe sepsis or septic shock.Interventions Five hundred milliliters of a 6% hydroxyethyl starch (HES) solution were administered in 30 min.Measurements and results Complete hemodynamic data, blood samples, and gastric mucosal PCO₂ (automatic gas capnometry) determinations were obtained at baseline and 15 min after the end of fluid infusion. After fluid challenge, cardiac index (CI) increased from 3.8 (range 2.9–4.2) to 4.2 (range 3.1–4.9) l/min m^–2 (p<0.05). The PCO₂ gap decreased from 9.8 (range 6.9–26.0) to 8.5 (range 6.6–17.4) mm Hg (p<0.05), but important individual variations were observed. We failed to observe significant relationships between changes in CI and in PCO₂ gap, or between indices of preload (pulmonary artery occluded pressure, right atrial pressure, and pulse pressure variations) and changes in PCO₂ gap. In addition, changes in PCO₂ gap and in (v-a) CO₂ were not related; however, changes in PCO₂ gap were related to baseline PCO₂ gap (p=0.003), PEEP (p=0.02), and cumulative doses of vasopressors (p=0.02).Conclusions The effects of fluid challenge on gastric mucosal PCO₂ are variable and related to baseline PCO₂ gap rather than to systemic variables. In general, rapid volume infusion decreases PCO₂ gap, but this effect is more pronounced in patients with presumably impaired mucosal perfusion.Electronic Supplementary Material Supplementary material is available in the online version of this article at