Arterial Oxygenation During One-Lung Ventilation: Combined Versus General Anesthesia

Abstract

We read with interest the study by Garutti et al. (1), in which they demonstrated that thoracic epidural anesthesia (TEA) during one-lung ventilation (OLV) in the lateral decubitus position increases intrapulmonary shunt and decreases PaO2. However, we feel that the conclusion that TEA cannot be recommended in patients undergoing OLV is unjustified by their findings. The larger intrapulmonary shunt during TEA is an interesting phenomenon that we have also observed in patients undergoing coronary artery bypass grafting using high TEA at the T1-T2 level (T.H.L., unpublished data, 1998). However, in the study by Garutti et al. (1), subsequent lower PaO2 in the TEA group compared with the general anesthesia (GA) group did not lead to hypoxemia (PaO2 117 ± 57 mm Hg in the TEA group after 30 min). Indeed, three patients in the GA group presented with values of PaO2 < 70 mm Hg compared with two patients in the TEA group. Therefore, although PaO2 values show statistically significant differences, they do not appear to lead to clinically important differences. However, there is significant evidence that using TEA intra- and postoperatively for thoracotomy or sternotomy results in fewer postoperative complications, superior postoperative bloodgasses, and increased patient comfort (2,3). We feel that these factors outweigh decreased PaO2 levels during the operation, for which there are several treatment strategies available (4). In our practice, we usually combine TEA with bupivacaine/morphine and GA with isoflurane, which is known to also attenuate hypoxic pulmonary vasoconstriction, and hypoxemia during OLV is rarely a problem. Although we understand that the combination of GA, TEA, and OLV has many facets, which have to be elucidated one by one, we have to keep our eyes on the big picture. We therefore feel that the conclusion that TEA cannot be recommended in patients undergoing OLV may not be made by looking at only one aspect. W. Anton Visser MD Tiong H. Liem MD, PhD Mathieu J. M. Gielen MD, PhD