Anesth Analg 1999;89:1332
© 1999 International Anesthesia Research Society
LETTERS TO THE EDITOR
Arterial Oxygenation During One-Lung Ventilation: Combined Versus General Anesthesia
W. Anton Visser, MD,
Tiong H. Liem, MD, PhD, and
Mathieu J. M. Gielen, MD, PhD
Department of Anesthesia , University Hospital Nijmegen , 6500 HB Nijmegen, The Netherlands
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we have also observed in patients undergoing coronary artery bypass grafting using high TEA at the T1-T2 level (T.H.L., unpublished data, 1998).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.
References
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Garutti I, Quintana B, Olmedilla L, et al. Arterial oxygenation during one-lung ventilation: combined versus general anesthesia. Anesth Analg 1999;88:494–9.[Abstract/Free Full Text]
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Liu S, Carpenter RL, Neal JM. Epidural anesthesia and analgesia: their role in postoperative outcome. Anesthesiology 1995;82:1474–506.[Web of Science][Medline]
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Liem TH, Hasenbos MAWM, Booij LHDJ, Gielen MJM. Coronary artery bypass grafting using two different techniques. Part 2. Postoperative outcome. J Cardiothorac Vasc Anesth 1992;6:156–61.[Medline]
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Benumof JL. Anesthesia for thoracic surgery. Philadelphia:WB Saunders, 1987.
Response
Ignacio Garutti, MD,
Begoña Quintana, MD,
Luis Olmedilla, MD,
Alberto Cruz, MD,
Mónica Barranco, MD, and
Elvira Garcia de Lucas, MD
Service of Anesthesiology and Reanimation , Hospital General "Gregorio Marañón" , Madrid, Spain
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.
References
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1. Eisenkraft JB, Cohen E, Kaplan JA. Anesthesia for thoracic surgery. In: Clinical anesthesia. Barash PG, Cullen BF, Stoetling RK, eds. Philadelphia: JB Lippincott, 1989:905–46.
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Liem TH, Hasenbos MAWM, Booij LHDJ, Gielen MJM. Coronary artery bypass grafting using two different anesthetic techniques. Part 2. Postoperative outcome. J Cardiothorac Vasc Anesth 1992;6:156–61.
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