Hemodynamic Effects of Combining Epinephrine with Nitroglycerin or Nitroprusside During Group B Streptococcal Sepsis in Piglets

ABSTRACT

Septic shock in young children is often characterized by clinical findings consistent with a reduction in cardiac index (Cl) and elevation of systemic vascular resistance index (SVRI). In this context, infusion of inotropic agents, alone or in combination with vasodilators, has been recommended. We have utilized group B streptococcal (GBS) infusion in piglets to develop a model of low-CI/high-SVRI septic shock, and report here the effects of the combination of epinephrine (EPI) plus either nitroglycerin (NG) or nitroprusside (NP) in this model of infant sepsis. Piglets were anesthetized, intubated, and ventilated. All piglets received GBS continuously for 90 minutes and were further divided into three experimental groups. Group 1 received NG 16 μg/kg·min plus EPI 2 μg/kg·min; group 2 received NP 10 μg/kg·min plus EPI 2 μg/kg·min, and group 3 received 0.9% sodium chloride (saline) only. Cl, which fell for all three groups at the onset of GBS infusion, rose significantly in group 2 animals (but not in groups 1 and 3). This effect was mediated entirely by an increase in myocardial stroke volume. Aortic blood pressure, initially unaffected by GBS infusion, rose significantly in both group 1 and 2 compared with group 3. SVRI, which rose for all three groups at the onset of GBS infusion, was further markedly elevated in group 1 (but not in groups 2 and 3). Pulmonary artery pressure and pulmonary vascular resistance index, both significantly increased after GBS infusion, were reduced in group 2 but not groups 1 and 3. These observations illustrate the potential for unexpected, and possibly detrimental, hemodynamic consequences when vasoactive agents are combined in young septic animals. In so doing, they may help to provide a basis for the choice of pharmacologic agents in the context of low-CI/high-SVRI states in childhood illness.