Hemorrhagic Shock

Question 1

Discuss transfusion triggers and transfusion targets in shock and non-shock states.

Answer 1

There is high-quality evidence showing that restrictive blood transfusion with a transfusion trigger of haemoglobin of 7-8 g/dl or the presence of symptoms of anaemia is safe and not associated with increased mortality compared with liberal transfusion.

There is moderate evidence for the use of plasma and platelet transfusion in patients receiving massive blood transfusion. There is not enough evidence to support the use of plasma, platelets and cryoprecipitate in any other clinical setting.

Retrospective studies show improved survival after high plasma and platelet to red blood cell ratio of 1:1:1, but this has not been confirmed in randomised trials.

Transfusion trigger is defined as the Hgb threshold which PRBC transfusion is indicated.
Transfusion target is the Hb one aims to achieve after RBC transfusion.
Goal - Traditionally, the rule of “10/30” was followed for RBC transfusion, according to which a Hb level of 10 g/dl or a haematocrit of 30% was recommended in surgical patients.

Over the years, the trigger for transfusion has become more conservative or restrictive. In addition, the decision to transfuse RBCs is based not only on the laboratory values, but also on the objective evaluation of the patient’s clinical condition and her ability to compensate for the blood loss.

Therefore, the patient’s age, co-morbidities, severity of illness, and the rate and amount of haemorrhage are taken into account before transfusion.

Post-operative patients
In haemodynamically stable post-operative surgical patients, the trigger for transfusion is Hb ≤ 8 g/dl or presence of symptoms of inadequate oxygen delivery (chest pain of cardiac origin, orthostatic hypotension or tachycardia unresponsive to fluid resuscitation, or congestive heart failure)

Reasons for transfusion

Plasma is conventionally prescribed to replace coagulation factors in patients receiving massive transfusion (>one blood volume or 70 ml/kg in 24 h or >50% of blood volume in 3 h), for urgent reversal of the effect of warfarin, in known coagulation factor deficiency, and in cases of thrombotic thrombocytopaenic purpura.[17,18] The decision to transfuse is based on both presence of bleeding and abnormal laboratory values of prothrombin time (>1.5), international normalized ratio (>2) and partial thromboplastin time (>2 times). Plasma should not be used to replace intravascular volume.

Platelet transfusion is usually required in a bleeding patient below a platelet count of 50 × 109/L but rarely above 100 × 109/L. If the values fall between these two, transfusion is considered in case of platelet dysfunction (e.g., clopidogrel therapy), on-going bleeding and surgeries in confined spaces such as eye and brain.[10]

Cryoprecipitate is used to increase fibrinogen levels in patients with dysfibrinogenaemia and hypofibrinogenaemia (fibrinogen <80-100 mg/dl), microvascular bleeding in patients receiving massive transfusion when fibrinogen cannot be measured and congenital fibrinogen deficiency.

A high ratio of plasma and platelets to RBC (1:1:1) during MBT has been shown to improve survival in a number of recent studies. However, these studies are retrospective with a high degree of bias, especially survival bias. The AABB guidelines do not recommend for or against a plasma: RBC ratio of 1:3 or greater in trauma patients during massive transfusion due to low QoE.