Retrospective Comparative Study on Differences in Presence of Gas in the Aneurysm Sac after Endovascular Aortic Aneurysm Repair in Early Postoperative Period between Carbon Dioxide Flushing Technique and Saline Flushing of the Delivery System

BACKGROUND: Presence of gas is a frequent finding on early postoperative computed tomography angiography (CTA) after endovascular aortic aneurysm repair (EVAR) with unclear clinical relevance. The aim of this study is to examine and compare the presence of gas within the aneurysm sac following EVAR on early postoperative CTA after the use of carbon dioxide (CO2) flushing technique with saline flushing alone.

METHODS: A retrospective analysis of patients undergoing standard, fenestrated EVAR (fEVAR) or branched EVAR (bEVAR) with flushing of the delivery system with CO2 between January 2016 and August 2018 was undertaken. Data of a previous report using standard saline flushing were included. Patients were classified into 2 main groups: group 1 with saline flushing and group 2 with CO2 flushing and 3 subgroups according to the type of endograft. The presence, position, and volume of gas in the postoperative CTA (within 10 days) was examined and analyzed in terms of anatomical and procedural risk factors.

RESULTS: Group 1 included 210 patients (mean age 73 ± 8, 84% males), while group 2 included 300 patients (mean age 70 ± 11, 68% males). Presence of gas was more common in group 1 (83, 39% vs. 64, 21%, P = 0.000). Volume of gas was larger in group 1 [0.41 mL (0.01-2.7) vs. 0.2 mL (0.02-1), P = 0.001). In standard EVAR with saline flushing (subgroup 1a), 59 patients (45%) had presence of gas with CO2 flushing (subgroup 2a); 35 patients (25%) had presence of gas (P = 0.005). The mean gas volume was larger in subgroup 1a compared to 2a (0.40 ± 0.47 vs. 0.15 ± 0.17 mL, P = 0.000). The location of the gas was more frequent in contact with the anterior wall of the aorta in both groups, standard EVAR subgroups and fEVAR subgroups. The presence of gas in group 2 was associated with larger preoperative size of the aortic diameter (P = 0.03) and larger perfused lumen diameter (P = 0.05). The type of the graft was not associated with the presence of gas in the aneurysm sac on postoperative CTA. However, the presence of gas was more frequent in standard EVAR than fEVAR and bEVAR. Endoleak type II was not associated with the presence of gas.

CONCLUSIONS: CO2 flushing of stent grafts during standard and complex EVAR prior to deployment reduces the frequency and volume of gas on postoperative CTA. This study indicates that the CO2 flushing technique may effectively exchange trapped air for a less harmful gas in endografts.