Early physiologic changes in canine fecal peritonitis

Oxygen delivery (DO2) and related variables were studied in eight dogs during severe untreated peritonitis induced by cecal ligation and perforation. The development of peritonitis was accompanied by abdominal fluid sequestration and significant increases in hemoglobin (Hgb), arterial oxygen content (CaO2), and P50. Changes in mixed venous PO2 (P-vO2), mixed venous saturation (S-vO2), DO2, oxygen uptake (VO2), cardiac index (CI), and arteriovenous O2 difference (C[a--v]O2) were not significant. When blood volume was returned to normal levels with dextran, CI rose and C(a--v)O2 decreased; P-vO2 increased and Hgb returned to baseline levels. In this animal model, sepsis and fluid sequestration produced an increase in blood O2 capacity and CaO2, which sustained DO2 and VO2. No changes were observed in P-vO2 or S-vO2. The hyperdynamic state of severe sepsis became evident only after reversing hemoconcentration by colloid infusion. The increase in P-vO2 and S-vO2 after volume loading is possibly related to primary septic mechanisms and/or to changes in DO2.