E. S. Wise1, K. M. Hocking1, P. Komalavilas1,2, J. Cheung-Flynn1, C. M. Brophy1,2 1Vanderbilt University Medical Center,Vascular Surgery,Nashville, TN, USA 2VA TN Valley Healthcare System,Vascular Surgery,Nashville, TN, USA
Introduction:
Human saphenous vein (HSV) remains the most common conduit for CABG. A recent retrospective analysis on the PREVENT IV cohort suggested that normal saline (NS), relative to buffered salt solutions and blood, may be associated with a higher incidence of graft failure. We hypothesized that the acidic pH of NS leads to injury to the conduit.
Methods:
Unmanipulated (UM) HSV samples and a vial of arterial blood were obtained from CABG patients. Two rings were placed into heparinized (10U/mL) solutions for two hours, including control (UM), Plasma-Lyte A (PL), NS, and autologous whole blood (AWB). Smooth muscle (SM) contractility and endothelial-dependent relaxation (EDR) were assessed via potassium chloride (KCl, 110 mM) and carbachol (0.5 µM) following phenylephrine (1-5 µM) pre-contraction, respectively. The colorimetric MTT assay for cellular viability was performed on two additional rings. Finally, rings of rat aorta (RA) were placed into NS, PL and PL adjusted to various pH levels for two hours and endothelial-dependent relaxation responses were determined. Data was analyzed via paired student t-tests; P<0.05 was considered significant.
Results:
HSV preserved in NS demonstrated decreased KCl-induced SM contractility relative to UM and PL (n=16-17, *P<0.03, Figure 1A). AWB SM contractility was decreased relative to PL (n=6, *P<0.03, Figure 1A). NS HSV also demonstrated decreased EDR relative to UM and PL (n=9-10, *P<0.03, Figure 1B). In the MTT assay, NS had decreased cellular viability relative to UM, PL and AWB (n=11-12, *P<0.03, Figure 1C). Using a rat aorta model, pH dependence on endothelial function was determined; pH 5.5-PL and NS were significantly lower than UM, and pH 5.5-PL was significantly lower than PL (n=5; #P<0.05, Figure 1D).
Conclusion:
Preservation of HSV in NS leads to impaired functional responses and viability of the SM and endothelial layer. This may be due to the acidic pH of NS. The use of a pH-balanced, buffered solution for HSV is recommended for storage after harvest.
