Intralipid-induced decrease in oxygenation in neonates is related to changes in the respiratory quotient.
Intravenous lipid infusion has been previously reported to be associated with hypoxemia. Different mechanisms have been proposed, but none have explored the decrease in respiratory quotient (RQ) following lipid administration as a possible factor. Ten neonates without respiratory problems, breathing room air and on total parenteral nutrition were studied. Arterialized capillary blood gases, transcutaneous PO2 (TcPO2) measurements and expired gas concentrations were obtained, prior to and 1 g/kg of 10% lipid emulsion was infused over 6 h. Following lipid infusion, the TcPO2 decreased from 72 +/- 8 to 65 +/- 8 mm Hg and the RQ decreased from 0.94 +/- 0.08 to 0.86 +/- 0.5 (p less than 0.05), while the pH, PaCO2 and the alveolar-arterial oxygen tension difference did not change. The decrease in TcPO2 significantly correlated with the decrease in alveolar oxygen tension. Seven of the 10 infants had a significant decrease in TcPO2 with a significant decrease in RQ from 0.98 +/- 0.05 to 0.85 +/- 0.06 (p less than 0.01). In 3 patients with no significant change in TcPO2 following intralipid administration, the RQ was initially significantly lower than the rest of the group (0.85 +/- 0.04; p less than 0.05) and did not change at the end of the infusion (0.88 +/- 0.03). These data suggest that the changes in PaO2 following lipid infusion in neonates without lung disease and breathing room air, are related to the decrease in alveolar oxygen tension secondary to the change in RQ.