The effects of thoracic epidural analgesia on oxygenation and pulmonary shunt fraction during one-lung ventilation: an meta-analysis

BACKGROUND: The aim of our study is to compare the effects of thoracic epidural analgesia combined with general anesthesia (GA) vs. general anesthesia on oxygenation and pulmonary shunt fraction during one-lung ventilation (OLV). METHODS: Literature research was firstly conducted for studies related to comparison of epidural anesthesia combined with GA vs. GA with reporting of hemodynamic and oxygenation variables and published from Jan 1990 to Jan 2014 in EMBAS, MEDLINE and Cochrane Central Register of Controlled Trials databases. The studies were reviewed and data were extracted and analyzed using fixed-effect and random-effect models. RESULTS: There are 14 trials with 60 separate comparisons enrolling 653 patients for analysis. Regarding systemic hemodynamics, thoracic epidural analgesia decreased the mean arterial pressure and mean pulmonary arterial pressure with weighted mean difference 95 % confidence interval (−6.64 [−9.57 to −3.71] vs. -6.33 [−9.25 to −3.41] and −3.18 [−5.07 to −1.28] vs. -2.05 [−3.35 to −0.75]) respectively at the two measurements time, however, only decreasing heart rate and systemic vascular resistance (−3.28 [−5.98 to −0.67] and −319.99 [−447.05 to −192.94]) over the first 30 min after OLV. For oxygenation variables, thoracic epidural analgesia is associated with significant reduction in partial arterial oxygen pressure, mixed arterial saturation of oxygenation and increased pulmonary venous admixture fraction compared to general anesthesia with weighted mean difference 95 % confidence interval (−16.52 [−21.98 to − 11.05] vs. − 14.23 [−20.81 to − 7.65]), (0.74 [0.33 to 1.15] vs. − 0.63 [−1.23 to −0.04]) and (2.53 [1.35 to 3.72] vs. 2.77 [1.81 to 3.74]) respectively before and after 30 min of one-lung ventilation. A decrease in mixed venous saturation of oxygenation occurred after 30 min of OLV (−2.39 [−3.73 to −0.99]). Besides, a higher mean value of airway pressure was found in the thoracic epidural analgesia with weighted mean difference 95 % confidence interval (1.95 [1.61 to 2.28] vs. 0.87 [0.54 to 1.20]) at the measurements. CONCLUSION: Based on the existing limited data puts forward recommendations for cautious usage of thoracic epidural analgesia in case of underlying risks in lower systemic hemodynamics, decreased partial arterial oxygen pressure but increases pulmonary shunt during one-lung ventilation. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12871-015-0142-5) contains supplementary material, which is available to authorized users.