Plasma as a resuscitation fluid for volume-depleted shock: Potential benefits and risks.

The clinical state of shock constitutes a relative or absolute deficiency of circulating volume for adequate oxygen delivery to meet the metabolic demands.1 Although shock states differ in epidemiology, etiology, and pathophysiologic pathways, a common denominator of shock is endothelial barrier dysfunction.2, 3 Different kinds of shock states, such as occurring after major surgery, trauma, and in sepsis, can result in strong pro‐inflammatory host responses with ensuing endothelial hyperpermeability.4, 5, 6 Loss of endothelial barrier results in leakage of fluid into surrounding tissue, contributing to edema, tissue hypoxia, and organ failure.6 This loss of fluids further aggravates the intravascular circulatory volume deficiency during shock. Obviously, septic and traumatic shock are different entities, with different etiologies and differences in initiation of host response and coagulation response. However, endothelial activation with loss of endothelial barrier integrity is a common finding in both shock states. In trauma‐induced shock, current resuscitation strategies consist of the early transfusion of whole blood or a balanced ratio of plasma, platelets, and red blood cells.7, 8 The aim of resuscitation is to ensure adequate oxygen delivery and to correct coagulopathy. Plasma transfusion may play a key role, as trials point toward improved survival with high dose or early use of plasma transfusion compared to standard care.9, 10, 11 Upon reaching surgical hemostasis, it is general practice to stop transfusion. However, as a result of ongoing inflammation and endothelial activation, patients can continue to be fluid dependent, which is often responded to with crystalloids. However, liberal use of crystalloids in traumatic hemorrhagic shock is associated with increased mortality and increased endothelial permeability, inflammation, and reduced perfusion of vital organs.12, 13, 14 In septic shock, the primary treatment of shock is volume resuscitation with crystalloid or colloids, as advocated in guidelines.15 However, comparable to traumatic hemorrhagic shock, use of a restrictive fluid balance reduces the occurrence of organ failure as well as mortality in sepsis.16, 17, 18 most likely, the association between the amount of infused volume and adverse outcome in shock states is related to increased shedding of the glycocalix, breakdown of adherent junctions, and tight junctions resulting in an increased gradient of leakage over the hyper permeable endothelium.19 Taken together, due to a relative or absolute deficiency of intravascular volume, patients with shock are likely to need volume expansion to maintain perfusion pressure. This poses a challenge to the treatment of shock, as fluid therapy is both a cornerstone of therapy as well as a foe. Different fluids may have differential effects on endothelial integrity. Low‐protein‐content fluids seem to aggravate shedding of glycocalix,20 whereas protein‐rich fluids such as plasma may be superior to normal saline in protecting the glycocalix and endothelial barrier function.21 Transfusion with plasma as a volume expander in shock may seem controversial at first, but one needs to consider that despite the fact that plasma is transfused in millions of patients annually, there currently is limited understanding of its mechanisms of action. In traumatic blood loss, transfusion of plasma may improve survival by decreasing exsanguination.7, 10 The common perception is that plasma is a pro‐coagulant blood product, by replenishing coagulation factors. However, as plasma contains coagulation factors but also anticoagulant proteins, the net effect of plasma on coagulation may be neutral. In line with this, plasma transfusion increases the amount of coagulation factors as well as levels of anti‐coagulant proteins,22 resulting in unchanged thrombin generation, at least in non‐bleeding critically ill patients with an inflammatory‐driven consumption coagulopathy. In patients with traumatic hemorrhagic shock, it is not apparent whether the mechanism of effect of plasma is directly related to the correction of coagulopathy.23 In rats with hemorrhagic shock, deranged thrombin formation was somewhat restored with resuscitation with plasma but not with crystalloids, but whether this relates to prevention of dilutional coagulopathy or to a specific pro‐coagulant effect of plasma is not clear.24, 25 Other mechanisms of the protective effect of plasma may be at hand. These may include preservation of the glycocalix, decreasing inflammation and decreasing endothelial leak. This review aims to discuss the potential of plasma as a resuscitation fluid in shock, with an emphasis on possible mechanisms of benefit on the activated endothelium. Studies comparing plasma with other fluids on (markers of) endothelial integrity have found effects both in (models of) trauma‐induced shock and in septic shock. As loss of endothelial integrity may be a common denominator of shock, we will discuss both these shock states.