ARTERIAL OXYGENATION DURING ONE LUNG VENTILATION

Purpose: To compare the effects of isoflurane and sevoflurane on arter ial oxygenation and middle cerebral artery blood flow velocity during one lung ventilation. Methods: This was a randomized, crossover study in 20 patients undergoing thoracotomy for oesophageal cancer and sched uled for long term one lung ventilation (OLV): They were randomized to one of two groups: group A, firstly isoflurane was administered follo wed by sevoflurane, and then isoflurane was resumed; group B, the orde r of the administration was reversed, Arterial blood gas samples were drawn at the start of OLV, 30 and 60 min after the initiation of OLV a nd the end of OLV (the change of volatile anesthetic was done 30 and 6 0 min after the start of OLV). Middle cerebral artery (MCA) was monito red continuously with the probe positioned over the temporal bone wind ow. This probe transmitted 2 MHZ wave Doppler signals. Time-averaged M CA blood flow velocity was calculated from the signals. Results: The P aO2 values decreased 30 min after the start of OLV (364.4 +/- 33.4 mmH g vs 179.0 +/- 19.5, and 338.7 +/- 24.8 mmHg vs 139.7 +/- 19.9 in grou ps A and B respectively), but there was no difference between the grou ps. Blood flow velocity of MCA did not change after the start of OLV ( 53.1 +/- 3.2, 55.9 +/- 3.0, 56.4 +/- 2.4, and 54.1 +/- 1.9 vs 50.8 +/- 2.1, 50.7 +/- 2.4, 53.7 +/- 1.5, 50.8 +/- 2.2 cm.sec(-1) in groups A and B respectively): there was no difference between the groups, (P < 0.05). Conclusion: In clinical practice, the selection of either isofl urane and sevoflurane for OLV was of no difference in terms of the art erial blood oxygenation, With bath agents MCA blood flow velocity was maintained during OLV.