EFFECTS OF GROUP B STREPTOCOCCI ON LUNG FLUID BALANCE QUO IN UNANESTHETIZED SHEEP

Abstract

Sepsis and pneumonia with group B streptococci (GBS) has become an increasingly important cause of morbidity and mortality among newborn infants. Because the associated clinical syndrome resembles endotoxemia with respiratory distress as a prominent feature, the effects of infusing GBS on lung fluid balance were studied in unanesthetized sheep. Sheep were prepared as described previously (J. Clin. Invest. 54:792, 1974) and during each experiment, lung vascular pressures, lung lymph flow, lymph and plasma protein concentrations and arterial blood gases and pH were measured. After a steady baseline period, 109-1011 GBS suspended in 100ml saline was infused over 30 minutes. GBS caused chills, fever, a 45% increase in pulmonary artery pressure, a 75% increase in lung lymph flow and a 10% decrease in lymph: plasma (L/P) protein concentration. GBS also caused PaO2 and PaCO2 to fall and pHa to increase. Heat killed and live organisms had similar effects. The increase in lung lymph flow with decreased L/P protein concentration is like the previously reported response to mechanically increased lung vascular pressures (Circ. Res. 37:271, 1975). It is concluded that intravenous GBS causes increased fluid filtration from lung mlcrovessels primarily by increasing microvascular pressure. This effect could be an important part of the GBS septicemic syndrome in neonates, and may be mediated by an “endotoxin-like” substance.