Sequential changes of hemodynamics and blood gases in newborn piglets with developing pneumothorax.

Abstract

INTRODUCTION: Little information is available regarding the temporal changes in hemodynamics and blood gases during the development of a moderate pneumothorax in a neonate. In this study, we aim to investigate the temporal changes of hemodynamics and arterial blood gases in a neonatal swine model of unilateral pneumothorax. STUDY DESIGN: Prospective observational controlled animal research. METHODS: Experimental pneumothorax (n = 9) was created by intermittent progressive introduction of 10 ml/kg of room-air every 5 min to a total 40 ml/kg, via a 20G Insyte(R) angiocatheter placed in the fourth intercostal space in line with the right frontal limb. Changes in heart rate, mean arterial pressure, central venous pressure (CVP), common carotid arterial flow (CCAF) and arterial blood gases were measured and compared with the normoxic baseline and a control group (n = 7) (ANOVA). RESULTS: As the pneumothorax developed, SaO2 and PaO2 deteriorated after injecting 20 ml/kg of room-air (P < 0.001 vs. baseline and control), whereas the pH and PaCO(2) remained unchanged. CVP increased after injecting 30 ml/kg of room-air (P < 0.001), with no significant changes in heart rate and mean arterial pressure. Meanwhile, CCAF increased and carotid oxygen delivery declined after 30 ml/kg (P < 0.05). CONCLUSIONS: Deterioration in oxygenation was noted early in the development of pneumothorax in newborn piglets followed by metabolic acidosis. CVP progressively increased despite the lack of significant changes in systemic hemodynamics when moderate pneumothorax developed. Although CCAF increased during a moderate pneumothorax, carotid oxygen delivery decreased.