Blood Transfusion and Clotting Factors

Blood Transfusion and Clotting Factors

Red Cell Transfusion

If blood loss is 50% or greater than the blood volume (>2500ml) whole blood or packed red cells in an additive solution should be transfused. Aim for a Hb level of 8.0 g/dl; over-transfusion is unnecessary. O Negative blood can be used in an extreme emergency. Fully cross matched blood is preferable if time allows.

Platelets

The platelet count needs to be maintained above 50 x 10 9/L if haemorrhage is on-going. A fall to this level is typical of a 2 blood volume replacement, or less if there is associated disseminated intravascular coagulation (DIC). An ideal dose of platelets for transfusion is 1 adult therapeutic dose for every 4 units of transfused red cells. Very low platelet counts are associated with placental abruption - early recognition and aggressive is required.

FFP and Cryoprecipitate

Coagulation failure is common in major obstetric haemorrhage. The onset can be very rapid when haemorrhage is caused by antental abruption leading to DIC. Coagulation failure is also caused by giving large quantities of crystalloid, colloid, or stored blood that do not contain clotting factors. This leads to dilutional coagulation failure. The ideal combination is to give 4 units of fresh frozen plasma (FFP) with every 4 units of red cells transfused, if there is ongoing g bleeding. FFP can be given on clinical grounds alone with rapid blood loss or after checking a clotting screen. FFP contains all the coagulation factors but is a relatively poor source of fibrinogen. Cryoprecipitate is relatively poor in some of the clotting factors but has more fibrinogen. Normothemia is essential for haemostasis, therefore use of IV fluid warmers and surface warming devices are essential.

Antifibrinolytics: Drugs to Inhibit Clot Lysis

Tranexamic acid is an anti-fibrinolytic agent, which competitively inhibit the conversion of plasminogen to plasmin, thereby preventing fibrin degradation and stabilizing clot formation. It can be given by slow IV injection at a dose of 0.5 - 1.0 gm and it can be given with other blood products.