Pressure measurements in closed aneurysmal sac during abdominal aortic aneurysm resection

Purpose: This study determined the relationship between closed aneurysmal sac pressure (ASP) and mean blood pressure (BP) during open abdominal aortic aneurysm (AAA) resection and evaluated the contribution of inferior mesenteric and lumbar artery blood flow to ASP after proximal and distal clamping. Methods: We measured ASP after proximal and distal clamping by placing an 18-gauge needle connected to a BP transducer into the excluded aneurysmal sac in 25 consecutive patients from April 1999 to August 2000. Simultaneous measurement of the mean systemic BP was also recorded. The ratio of ASP to mean BP in relation to the number of actively bleeding lumbar arteries (N-LA), diameter of the AAA (D-Cm), and volume of the thrombus in the AAA (Vol-TA) were recorded. Results: The mean ASP was 43.32 +/- 15.19 nim Hg, with an ASP to mean BP ratio of 0.47 +/- 0.15. The N-LA in the closed aneurysmal sac ranged from 0 to 6 (mean, 3.4 +/- 1.78). The D-Cm as determined by means of computed tomography (CT) scan of the aorta ranged from 5 to 8 cm in its largest anteroposterior/transverse diameter. The average Vol-TA was 6.15 +/- 4.49 mL. Inferior mesenteric artery blood flow contributed to ASP in three patients (12%). There was no correlation between ASP to mean BP ratios and the N-LA (P = .127), D-Cm (P = .882), or Vol-TA (P = .252). Conclusion: Closed ASP and ASP ratios are highly variable and do not correlate with N-LA, D-Cm, or the Vol-TA.