ELEVATED CARDIAC OUTPUT (CO) WITHOUT ELEVATED O2 DELIVERY (QO2) DOES NOT PROTECT AGAINST METABOLIC ACIDOSIS DURING SEPSIS IN PIGLETS

Abstract

Infants infected with Group B Streptococcus (GBS) develop reduced CO, reduced QO2, and metabolic acidosis. We investigated whether reduced CO is a necessary prerequisite for acidosis during GBS sepsis. Piglets (n=16) were anaesthetized and ventilated. Blood pressure, left atrial pressure (LAP), and CO were measured. Blood gases and O2 contents were determined q. 30 min × 4 hours from aorta and PA. Group 1 (GBS, n=6) received GBS X 4 hours. Group 2 (GBS/DEX, n=6) received GBS + 6% Dextran sufficient to raise LAP from 5 to 12 mm Hg. Group 2 piglets were phlebotomized to maintain QO2 equal to Group 1 during every 30-minute interval. Group 3 piglets (SAL, n=4) received 0.9% NaCl. After 240 minutes of GBS, CO and QO2 fell from 104.4 to 42.5 cc/min/kg and 14,2 to 5.7 cc O2/kg/min (both p<.01). After 240 minutes of GBS/DEX, QO2 fell from 16.8 to 7.3 cc O2/kg/min (p<0.01, 0 vs 240 mins; p=N.S. at each 30-minute interval vs GBS), while CO did not fall significantly (119.9 to 105 co/kg/min p=N.S. vs SAL; p<0.01 vs GBS). Both GBS and GBS/DEX developed lower pH (7.20; 7.22) and greater base deficit (-14.0; -9.7) than SAL (7.44, -2.7) (p<0.05 GBS S GBS/DEX vs SAL; p=N.S. GBS vs GBS/DEX). No differences in VO2 or O2 extraction were noted between GBS and GBS/DEX. Conclusions: 1. GBS infusion reduced CO, QO2, & pH in piglets. 2. Dextran raised LAP and CO during GBS sepsis. 3. Elevation of CO (but not QO2) during GBS did not protect against the development of metabolic acidosis. Reduced CO is not a hemodynamic prerequisite for acidosis during GBS sepsis in piglets.