Background: There are no pharmacologic strategies to prevent embolism bubble-induced blood clot formation. The authors conducted experiments to measure thrombin production in sheared whole blood in the presence and absence of bubbles and three surface-active compounds.
Methods: Blood samples were obtained from six volunteers seven times. The thrombin-specific substrate Boc-VPR-MCA was added to citrated blood diluted with HEPES-buffered saline. Experimental groups were as follows: sparging (air microbubble embolization) with surfactant present; sparging alone; surfactant alone; and neither surfactant nor sparging. The surfactants were Dow Corning Antifoam 1510US, Perftoran, and Pluronic F-127. Blood was sheared by a cone-plate viscometer at 100 and 500 s-1 for 5, 10, and 20 min at 37 degrees C, pipetted into excess stop buffer, and evaluated fluorimetrically. Mean values of fluorescence intensity +/- SDs for each group were compared using ANOVA. Differences were considered significant at P < 0.05 using the Bonferroni correction.
Results: For fixed shear rate, thrombin production increased 2.3- to 5.7-fold (P < 0.05) as shear duration lengthened. For fixed shear duration, thrombin production increased 1.9- to 3.9-fold (P < 0.05) with increasing shear rate. For fixed shear rate and duration, sparging increased thrombin production 2.1- to 3.7-fold (P < 0.05). Surfactant addition without sparging did not change thrombin production (P > 0.05). Surfactants attenuated thrombin production in sparged samples 31.8-70.9% (P < 0.05).
Conclusions: Thrombin production is shear rate and duration-dependent. Sparging increases thrombin production. Surfactants added before sparging attenuate thrombin production. Surfactants may have a clinical application to attenuate gas embolism-induced clotting.