Intravenous lipids in newborn lungs: thromboxane-mediated effects

Abstract

Lipid infusions can interfere with oxygenation and cause pulmonary hypertension. We studied the effects of iv lipid infusions on pulmonary hemodynamics and oxygen transport to investigate whether the vasoconstrictor, thromboxane (Tx), mediates resulting changes. Newborn piglets were instrumented to observe cardiopulmonary hemodynamics, blood gases, and oxygen contents. Oxygen delivery (DO2), oxygen consumption, and extraction ratios were calculated. All piglets received continuous 1-g/kg.h iv lipid infusions. After one hour, and as the lipid infusion continued, six piglets were given placebo (PL) and six others were given the Tx antagonist SQ 29548 (SQ). Pulmonary vasoconstriction occurred in both groups after one hour of lipid infusion (pulmonary artery pressure [PAP] 28 +/- 6 mm Hg in the PL piglets and to 31 +/- 13 mm Hg in the SQ piglets. After intervention, PAP remained elevated only in the PL group (32 +/- 2 vs. 23 +/- 8 mm Hg) (p less than .02). PaO2 and DO2 fell significantly with iv lipid and improved after intervention in SQ animals only (p less than .02). TxB2 increased in all animals with iv lipid (276 +/- 295 to 1481 +/- 716 in PL; 228 +/- 110 to 1402 +/- 580 in SQ), and fell with intervention in the SQ animals only (2632 +/- 1236 vs. 964 +/- 305, respectively; p less than .02). In conclusion, interference with DO2 associated with pulmonary hypertension and increased TxB2 occurred with iv lipid infusion in piglets. Tx antagonism ameliorated these changes.