The effects of increasing concentrations of desflurane on systemic oxygenation during one-lung ventilation in pigs.

Abstract

During one-lung ventilation (OLV), hypoxic pulmonary vasoconstriction reduces venous admixture and attenuates the decrease in arterial O2 tension by diverting blood from the nonventilated to the ventilated lung. In vitro, increasing concentrations of desflurane depresses hypoxic pulmonary vasoconstriction in a dose-dependent manner. Accordingly, we investigated the effects of increasing concentrations of desflurane on oxygenation during OLV in vivo. Thirteen pigs (25-30 kg) were anesthetized (induction: propofol 2-3 mg/kg IV; maintenance: N2O/O2 50%/50%, desflurane 3%, propofol 50 microg x kg(-1) min(-1), and vecuronium 0.2 mg x kg(-1) x h(-1) IV), orotracheally intubated, and mechanically ventilated. After placement of femoral arterial and thermodilution pulmonary artery catheters, a leftsided, 28F, double-lumen tube was placed via tracheotomy. After double-lumen tube placement, N2O and desflurane were discontinued, propofol was increased to 200 microg x kg(-1) x min(-1), and the fraction of inspired oxygen was adjusted at 0.8. Anesthesia was then continued in random order with desflurane 5%, 10%, or 15% end-tidal concentrations while propofol was discontinued. Whereas mixed venous PO2, mean arterial pressure, cardiac output, and shunt fraction decreased in a dose-dependent manner, PaO2 remained unchanged with increasing concentrations of desflurane during OLV. These findings indicate that, in vivo, increasing concentrations of desflurane do not necessarily worsen oxygenation during OLV. Oxygenation during one-lung ventilation depends on reflex vasoconstriction in the nonventilated lung. In vitro, desflurane inhibits this reflex dose-dependently. Our results indicate that, in vivo, this does not necessarily translate to dose-dependent decreases in oxygenation during one-lung ventilation.