198 THE EFFECT OF NALOXONE (N) ON THE HEMODYNAMICS OF THE NEWBORN PIGLET WITH SEPTIC SHOCK

Abstract

To investigate the effect of N in the septic newborn, we instrumented 8 piglets (1–5 days old) for continuous measurement of mean arterial pressure (MAP), pulmonary artery pressure (PAP), central venous pressure, heart rate (HR), left ventricular (LV) pressure, LV contractility (dP/dt), cardiac output (CO), and O₂ content. O₂ consumption (VO₂), systemic vascular resistance (SVR), and pulmonary vascular resistance (PVR) were calculated. Following a stabilization period, Group B streptococci (GBBS), 3–9 × 10¹⁰ org/kg, were infused over 30 minutes. Following the infusion, N (1/mg/kg) was given followed by a continuous infusion of 1/mg/kg/hr (n=4). Control pigs (n=4) were given an equal volume of saline. Both groups developed significant increases in PAP, SVR, and PVR followed by a return toward baseline. VO₂, CO, and dP/dt declined in both groups throughout the study, but in the N treated animals the decreases in CO and dP/dt were ameliorated and the MAP was restored toward baseline. The N group had significantly improved survival (p<.05) with 3/4 N pigs and 0/4 C pigs alive > 4 hr. We speculate that naloxone may reverse the hemodynamic sequelae and improve survival in newborns with septic shock.

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