Evaluating fibrin polymerization dynamics in three dimensions peri-operatively in cardiac surgical patients using spectrally encoded confocal microscopy (SECM) (Conference Presentation)

Abstract

The polymerization dynamics and microstructure of the fibrin network is vital to hemostasis. During cardiac surgery, heparin is administered to prevent bleeding and reversed using protamine at the end of surgery. Residual heparin and inadequate reversal following surgery impair fibrin integrity, likely associated with major postoperative blood loss. In this study, we apply a recent approach, SECM, to evaluate fibrin integrity in blood clots during heparin administration and protamine reversal in cardiac surgery patients. SECM’s capability for video rate microscopy over large fields of view with a spatial resolution of 0.4x1.0µm permits the dynamic assessment of fibrin polymerization and 3D microstructure. Plasma from 10 patients was collected during cardiac surgery at baseline and following protamine reversal. In addition, the dose-dependent response of heparin was studied by spiking 6 normal plasma samples at heparin doses of 0.1-2USP/mL. All samples were tested using SECM and clot polymerization parameters including fibrin time (FT) and fibrin density (FD) were derived. In cardiac surgical patients, FD was lower after protamine reversal (p<0.05) compared to baseline despite similar FT, suggesting that fibrin microstructure is not restored immediately after surgery. In spiked samples, fibrin polymerization was delayed with higher FT (p<0.05), fibrin strands were longer, and the FD was lower (p<0.05) with increasing heparin dose. Similar to surgical samples, FD was not restored following protamine reversal (p<0.01) in spiked samples. These studies show that the loss of fibrin integrity following cardiac surgery can be quantified using SECM, which may provide new insights on mechanisms of postoperative bleeding.