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

Abstract

We would like to thank Dr. Visser et al. for their comments regarding our paper. The main intraoperative concern during endobronchial anesthesia is the possibility of the appearance of arterial hypoxemia, a situation that is very difficult to anticipate before selective ventilation to the dependent lung. Therefore, it seems logical to move away from anesthesia techniques that worsen the physiological defense mechanisms (hypoxic pulmonary vasoconstriction). In our study, we demonstrate that using thoracic epidural anesthesia (TEA) with local anesthetics, combined with general anesthesia, increases intrapulmonary shunt and decreases arterial oxygen tension during one-lung ventilation (OLV). Of course, only a few patients suffer from hypoxemia, and we are aware that efficient treatments can be used to amend this. Moreover, we must bear in mind that a high FiO2 may cause absorption atelectasis and, potentially, further increase the degree of shunt because of the collapsed alveoli (1). Therefore, its reasonable to use anesthesia techniques that allow us to keep suitable oxygenation maintaining an inspired oxygen concentration of <60%. We are not contraindicating the use of TEA in such surgical procedures; we are suggesting that such a technique could not be recommended during OLV. We agree that using TEA intra- and postoperatively for thoracotomy can result in fewer postoperative complications than other techniques such as that used by Liem et al. (2) (general anesthesia combined with nicomorphine postoperative analgesia every 6 h). However, it has never been demonstrated that TEA intra- and postoperative is superior to general anesthesia intraoperative followed by postoperative epidural analgesia in thoracic or upper abdominal surgery. It is probable that the advantages of TEA are fundamentally in its postoperative benefits. The fact that we do not advise its usage during the short period of OLV (120–180 min) does not mean that we ignore the basic advantages of TEA during the 3 to 5 postoperative days. Several experimental investigations demonstrate that isofluorane has an inhibitory effect on hypoxic pulmonary vasoconstriction. Nevertheless, it has not been proven that this drug alters, clinically or statistically, oxygenation during OLV. On the contrary, our study on TEA demonstrated this clinical effect. In conclusion, we still believe that TEA during OLV cannot be recommended. The increase of shunt could be acceptable only when some advantage is demonstrated from the intraoperative TEA. Naturally, we believe that the epidural analgesia is clearly indicated in thoracotomies from the end of OLV and during the first 3–5 days of postoperative period. Ignacio Garutti MD Begoña Quintana MD Luis Olmedilla MD Alberto Cruz MD Mónica Barranco MD Elvira Garcia de Lucas MD