COMPARISON OF STAGNANT VERSUS ANEMIC HYPOXIA DURING GROUP-B STREPTOCOCCAL SEPSIS IN PIGLETS

The relationships between cardiac index (CI), oxygen delivery (DO2), oxygen consumption, and pH are not well characterized in human newborn sepsis or its models. In this experiment we attempted to discern whether reductions in CI, as distinct from reductions in DO2 were related to the development of metabolic acidosis during group B streptococcal (GBS) sepsis. Eighteen piglets, 2 to 4 weeks old, were anesthetized, paralyzed, and mechanically ventilated. One group, SALINE (n = 6), did not receive GBS. The other two groups received identical, graded, continuous infusions of live GBS organisms for 4 hours. Piglets in the STAGNANT group (n = 6) suffered reduction of DO2 due to GBS-induced reduction of CI (stagnant hypoxia). Piglets in the ANEMIC group (n = 6) received intravenous dextran and phlebotomy during GBS infusion to preserve CI at baseline while DO2 was reduced (anemic hypoxia) to levels comparable to the STAGNANT group. By 240 minutes of GBS infusion, CI was significantly reduced in the STAGNANT piglets (104 to 43 mL/kg/min), but did not change significantly in the ANEMIC (120 to 105 mL/kg/min) or SALINE piglets (109 to 124 mL/kg/min). Oxygen delivery fell significantly in both the STAGNANT (14.2 to 5.7 mL O2/kg/ min) and ANEMIC piglets (16.8 to 7.3 mL O2/kg/min), but not in the SALINE group (15.0 to 15.6 mL O2/kg/min). Despite the differences in CI, pH fell equally and significantly over 4 hours of GBS infusion for STAGNANT (7.47 to 7.20) and ANEMIC piglets (7.45 to 7.22), but did not change for SALINE piglets (7.46 to 7.45). Likewise, base deficit rose equally and significantly for STAGNANT (-1.5 to 1 4.0 mEq/L) and ANEMIC (0.1 to 9.7 mEq/L) piglets, but did not change for SALINE piglets (1.2 to 2.4 mEq/L). Oxygen consumption did not change significantly for any group, and the oxygen extraction ratio rose significantly and equally for both STAGNANT (32% to 73%) and ANEMIC piglets (33% to 69%), but not for SALINE piglets (48% to 55%). These data suggest that changes in CI, independent of changes in DO2 have little effect in the development of acidosis during GBS sepsis in piglets. © 1991.