Transfusion medicine handbook

6. Special Circumstances

6.1 Management of Acute Blood Loss

There are four main causes of major haemorrhage: trauma, surgery, obstetrics and medical (e.g. gastrointestinal bleeding, anticoagulants) [1]. It may jeopardise patients and challenge laboratory and blood transfusion resources. A successful outcome requires prompt action and good communication between clinical specialties, diagnostic laboratories, blood banks and NZBS.

Major haemorrhage is difficult to define because it has a spectrum of severity and presentation, at one extreme it is seen as acute major blood loss associated with haemodynamic instability and risk of shock, but also those in whom the bleeding appears controlled but still require 'massive' transfusion. Various definitions of major haemorrhage continue to be used in the literature based on volumes of blood loss, or volume of blood transfused over a period. These are retrospective definitions and difficult to apply in the acute situation. The current trend is towards the use of a more anticipatory or dynamic definition for major haemorrhage, based on the clinical status of the patients, their physiology and response to resuscitation therapy [2].

The aim of treatment is the rapid and effective restoration of an adequate blood volume and to maintain blood composition within safe limits with regard to haemostasis, oxygen carrying capacity and biochemistry.

The essential features of management are [1]:

• Restore blood volume to maintain tissue perfusion and oxygenation
• Maintain and regularly monitor haemostasis
• Avoid the triad of hypothermia, acidaemia and coagulopathy.

Table 6.1: Transfusion Requirements in Response to Loss of Blood Volume shows likely crystalloid and blood transfusion requirements in response to acute blood loss, based on estimation of lost circulating volume.

If bleeding continues after attempted surgical haemostasis and when the coagulation tests are abnormal or the platelet count reduced, then platelets, FFP, cryoprecipitate or a combination of these products may also be required.

In the setting of trauma-induced bleeding, early initiation of blood transfusion support with optimal ratios of plasma and platelets to red cell units may help achieve haemostasis and reduce the risk of exsanguination.

In trauma patients, use of the antifibrinolytic tranexamic acid is considered standard of care as an adjunct in arresting bleeding and should be administered as early as possible and within three hours of the trauma. The CRASH-2 trial included over 20,000 trauma patients, at least 16 years old, with significant haemorrhage (or at risk of) who were within 8 hours of initial injury [3]. Compared to placebo, administration of tranexamic acid 1 g loading dose over 10 minutes followed by 1 g infusion over 8 hours reduced hospital mortality and death due to haemorrhage within 4 weeks of injury. No increase in the rate of vascular occlusion (myocardial infarction, stroke, pulmonary embolism) was seen with the use of tranexamic acid. For further information on the use of this antifibrinolytic agent see Section 8.6: Tranexamic Acid 

Table 6.1: Transfusion Requirements in Response to Loss of Blood Volume

Clinical trials in humans have not demonstrated albumin solutions or other colloids to be superior to crystalloid in resuscitation, but larger quantities of crystalloid may be required. Hydroxyethyl starch solutions must not be used in patients with sepsis or kidney impairment or in critically ill patients [5].

Aggressive volume resuscitation may cause problems with interstitial oedema, compartment syndrome, acute lung injury and, subsequent to haemodilution, exacerbations of anaemia, thrombocytopaenia and coagulopathy. A strategy of permissive hypotension, with minimal volume resuscitation and tolerating systolic blood pressures of 80-100 mmHg, is generally preferable while active bleeding is being controlled. Permissive hypotension is contraindicated in patients with traumatic brain injury and should be used with caution in the elderly.

Large quantities of saline may cause hyperchloraemic metabolic acidosis with subsequent complications and this has increasingly led to the use of physiologically buffered fluids such as Plasmalyte 148 and compound sodium lactate (Hartmann's or Ringer-Lactate).

Avoid saline in patients with severe liver disease for whom sodium overload is a risk. Specialist advice is recommended. For the same reason care should be taken with albumin solutions in these patients.

Table 6.2: Transfusion Support for Major Bleeding should be referred to in conjunction with a local massive haemorrhage pathway (MHP).

Table 6.2: Transfusion Support for Major Bleeding