Effects of thoracic epidural anesthesia on pulmonary venous admixture and oxygenation with isoflurane or propofol anesthesia during one lung ventilation

ABSTRACT

Thoracic epidural anesthesia [TEA] with local anesthetics during OLV is increasingly being combined with general anesthesia [GA] in our clinical practice for thoracic surgery. A combination of TEA with GA might maximize the benefits of each form of anesthesia. Furthermore, epidural anesthesia and postoperative epidural analgesia may improve outcome in high-risk patients. The present study was designed to compare the effects of thoracic epidural anesthesia on oxygenation and pulmonary venous admixture [Qs/Qt], when combined with isoflurane or propofol anesthesia, during one lung ventilation and to compare also between the effects of propofol with isoflurane on oxygenation and pulmonary venous admixture [Qs/Qt], during one lung ventilation. This study was carried out on 60 patients, [ASA classification I-II-III] in Tanta University Hospitals, scheduled for thoracotomies for pulmonary resections in the lateral decubitus position and one-lung ventilation. The patients were randomized into one of four groups, 15 patients in each group Group I propofol group [TIVA group], Group II propofol combined with thoracic epidural anesthesia [TIVA-TEA group], Group III isoflurane group [ISO group] and Group IV isoflurane combined with thoracic epidural. The trachea was intubated with a doublelumen tube and its position was confirmed with auscultation. Anesthesia was maintained with propofol at continuous infusion in [Group I and Group II], and with isoflurane in [Group III and Group IV] and with increments of fentanyl and vecuronium. PaO[2], PaCO[2], SaO[2], PvO[2], SvO[2] and Hb, as well as the hemodynamic variables [HR and MAP] were measured. A right atrial blood sample was used to calculate the pulmonary venous admixture [Qs/Qt]. In epidural groups [Group II and Group IV] a 10-ml bolus of a solution of bupivacaine 0.1%+ 0.1 mg/ml morphine in saline was administered at least 30 min before the induction, followed by a 7 ml/h infusion of the same solution during the operation. In the other two groups [Group III and Group IV], no medication was applied via the epidural catheter in the preoperative and the intraoperative period. After preoxygenation, anesthesia was induced with fentanyl 3 microg/kg and propofol 2 mg/kg; tracheal intubation was facilitated with vecuronium 0.1 mg/kg. As regards PaO[2], it was significantly higher in Group I and Group II [propofol groups] than Group III and Group IV [isoflurane], in contrary, no significant effect of TEA [between Group I and Group II] nor between [Group III and Group IV] on PaO[2]. However; PaO[2] significantly decreased during OLV in all groups. As regards Qs/Qt, it was significantly lower in Group I and Group II [propofol groups] than Group III and Group IV [isoflurane], in contrary, no significant effect of TEA [between GI and GII] nor between [GIII and GIV] on Qs/Qt. However; Qs/ Qt significantly increased during OLV in all groups. The administration of thoracic epidural anesthesia, either combined with propofol or isoflurane, was not associated with a relevant impairment of oxygenation during OLV. Therefore Pre-emptive analgesia via an epidural thoracic catheter can be used safely as a standard in lung surgery, decreasing the anesthesia requirements when combined with GA, maximizing the benefits of each form of anesthesia and improving the outcome in patients with cardiopulmonary diseases, hence it was found that it has no effect on oxygenation during OLV, and it is associated with stable hemodynamics