Akuter Blutverlust und Verbrennungen in der operativen Medizin

Plasma and plasma products in the treatment of massive haemorrhage

Massive haemorrhage requires the use of plasma products when it is accompanied by a coagulopathy or when the more than one blood volume has been lost and intractable bleeding continues. The coagulopathy results from haemorrhagic shock, hypothermia, and activation, consumption and dilution of coagulation factors. Plasma products have a critical role in maintaining sufficient levels of coagulation proteins to ensure haemostasis can occur. Fresh frozen plasma is a source of all coagulation proteins and is required when the prothrombin time and activated partial thromboplastin time exceed 1.5 times the normal control. Cryoprecipitate is the plasma product of choice if fibrinogen, the most critical coagulation protein, is required rapidly and to maintain levels at >1g/L. Prothrombin complex concentrates, monocomponent factor therapy and fibrin sealants each have a role in specific clinical settings. Recombinant factor VIIa has now been shown to have a role in massive haemorrhage. Randomised controlled trials are currently underway to determine the optimal dose and timing of its administration. The physiology and management of the coagulation disturbance using plasma products in the massive haemorrhage of specific clinical situations are described.

Extracorporeal blood volume of donors during automated intermittent-flow plasmapheresis and its relevance to the prevention of circulatory reactions

BACKGROUND

Intermittent-flow plasmapheresis often involves a large extracorporeal blood volume of the donor during the procedure with the concomitant risk of circulatory reactions. Guidelines governing donor recruitment often apply an arbitrary threshold of 15 percent of the donors' blood volume not to be exceeded during hemapheresis procedures. No data demonstrating the suitability of this approach exist.

STUDY DESIGN AND METHODS

The blood volumes of 1204 plasmapheresis donors were calculated with different formulae that utilized either body weight or body surface area. Extracorporeal blood volumes of these donors were determined for a commonly used intermittent-flow plasmapheresis machine known to result in a large extracorporeal blood volume. A validated model was employed that calculated the fluid volume shifts occurring during the procedure. The records of all plasmapheresis procedures of these donors were retrospectively reviewed for circulatory reactions.

RESULTS

The median extracorporeal volumes ranged from 14 to 17 percent of the blood volume at a donor Hct level of 0.40 to 0.48 L per L for men and from 17 to 20 percent at a Hct level of 0.36 to 0.44 L per L for women. In more than 60 percent of male and more than 90 percent of female donors, extracorporeal volumes exceeded 15 percent of the blood volume during plasmapheresis. In this subgroup, 65 percent of male and 75 percent of female donors never presented with any signs of circulatory reactions.

CONCLUSION

Application of an arbitrary threshold of 15 percent of the donors' blood volume not to be exceeded during hemapheresis procedures is expected to lead to an unjustified deferral rate in plasmapheresis donors.

Massive blood transfusion in the elective surgical setting

Massive haemorrhage in elective surgery can be either anticipated (e.g. organ transplantation) or unexpected. Management requires early recognition, securing haemostasis and maintenance of normovolaemia. Transfusion management involves the transfusion of packed red cells, platelet concentrates and plasma (fresh frozen plasma and cryoprecipitate). Blood product support should be based on clinical judgment and be guided by repeated laboratory tests of coagulation. Although coagulation tests may not provide a true representation of in vivo haemostasis, they do assist in management of haemostatic factors. Below critical levels (prothrombin time or activated partial thromboplastin time >1.8; fibrinogen <1.0 g/l; platelet count < 80 x 10(9) 1(-1)) it is difficult to achieve haemostasis. Despite seemingly adequate blood component therapy there remain situations where haemorrhage is uncontrollable. In this setting, alternative approaches must be considered. These include the use of other blood products (e.g. prothrombin complex concentrates; fresh whole blood; fibrin glue) and pharmacological agents (e.g. aprotinin). Complications of massive transfusion result in significant morbidity and mortality. These may be secondary to the storage lesion of the transfused blood products, disseminated intravascular coagulation, hypothermia or hypovolaemic shock. The use of fresh blood products and leucocyte-reduced packed red cells and platelets, may minimise some of the adverse clinical sequelae.