Co-administration of ephedrine prevents reductions in cardiac output and systemic oxygen delivery secondary to lung compression maneuvers during one-lung ventilation, without reducing arterial oxygenation

Abstract

We previously showed that compression of the nondependent lung during one-lung ventilation (OLV) in patients undergoing esophagectomy improves arterial oxygenation but impairs cardiac output (CO) and systemic oxygen delivery (DO(2)). The objective of this study was to test the hypothesis that the combination of nondependent lung compression and ephedrine improves arterial oxygenation without compromising DO(2). Twenty patients undergoing esophagectomy through a right thoracotomy were studied. Under general anesthesia, a left-sided double-lumen tube was placed, and the dependent lung was mechanically ventilated with a tidal volume of 8ml/kg and a fraction of inspiratory oxygen of 0.8 during OLV. When nondependent lung was compressed by surgeons to improve surgical exposure, a randomly determined intravenous bolus of either ephedrine 4mg (group E) or an identical volume of saline (group S) was administered. Arterial blood was sampled during two-lung ventilation (TLV), at 10min of OLV (OLV1), and 5min after nondependent lung compression (OLV2). The initiation of OLV resulted in a significant drop in PaO(2) at OLV1 (group E, 136±69mmHg; group S, 138±83mmHg; P<0.01) compared with TLV (group E, 404±44mmHg; group S; 367±51mmHg) and tended to improve at OLV2 (group E, 170±63mmHg; group S; 196±121mmHg). However, although CO and DO(2) significantly decreased in group S at OLV2 (4.0±0.8l/min, 621±116ml/min; P<0.01) compared with OLV1 (5.1±0.7l/min, 811±140ml/min), there was no significant difference in these parameters in group E for the two time points. Although arterial oxygenation was not significantly improved by the nondependent lung compression, the addition of intravenous ephedrine to nondependent lung compression prevented the decrease in systemic oxygen delivery without deterioration of arterial oxygenation during OLV in patients undergoing esophagectomy.