We started with work on microaggregate formation in stored blood and progressed to a careful, systematic evaluation of the clinical significance of microaggregates in animals. We evaluated clinical filtering systems for blood administration which removed particles from stored blood. We proved the presence and nature of microaggregates in stored blood. We also showed that quantities of microaggregates were negligible in terms of the effect of pulmonary structure or function repeated blood filter testing showed that blood could be administered rapidly through blood ultra-filters that effectively removed microaggregate debris and not increase cost or flow rate. We then studied blood flow in hemorrhagic shock and showed a prolonged reduction in visceral blood flow after successful hemodynamic resuscitation. Change in blood volume and organ blood flow distribution was unrelated to catecholamines, renin release or thromboxane of prosta-cyclin production during shock. We examined local blood flow regulation in a hind limb perfusion model and showed that the changes induced on the peripheral vasculature by shocked blood was virtually all due to catecholamines.