[The effects of ephedrine and phenylephrine on arterial partial pressure of oxygen during one-lung ventilation]

We investigated the effects of ephedrine (EP) and phenylephrine (PH) on partial pressure of oxygen and intra-pulmonary shunt during one-lung ventilation under general anesthesia with enflurane, fentanyl and oxygen. When systolic blood pressure decreased to less than 80% of the resting values, 30 adult patients who were randomly assigned into 2 groups, received either EP 0.15 mg.kg-1 or PH 2 micrograms.kg-1. In group-EP, PaO2 increased significantly from 187 +/- 112 to 205 +/- 114 mmHg (FIO2 = 1.0, P < 0.05), while in group-PH, PaO2 changed from 209 +/- 129 to 248 +/- 84 mmHg without statistical significance. Intra-pulmonary shunts were essentially unchanged in both groups. Neither dysrhythmia, ST-T changes on electrocardiography, congestive heart failure, nor severe hypoxemia were observed in any patient during the study. These results indicate that EP and PH in above doses can be safely administered to treat arterial hypotension during one-lung ventilation.