Massive transfusion

What is a massive transfusion?

A 70-kg male has an average circulating volume of 5 L of whole blood. Assuming a haematocrit of 0.40 to 0.50, this approximates to a red cell volume of just over 2 to 2.5 L. A leucocyte-depleted unit of red blood cells, as distributed by the Australian Red Cross Blood Service, has a volume of 250 to 300 mL with a haematocrit of 0.50 to 0.70. The traditional definition of massive transfusion (MT) of at least 10 units of packed red blood cells (PRBCs) transfused in the first 24 hours was approximated from the total red cell volume in a 70-kg man. More recently, this definition has been challenged as being under-representative of patients during the acute resuscitative phase, as patients who die prior to receiving 10 units of red cells are excluded (mortality bias), as are patients whose transfusion requirements may not reach 10 units, while including patients who may not require transfusion during the acute resuscitative phase but are transfused later, secondary to surgical procedures or complications of management. Definitions using lower volumes of PRBCs in shorter times, such as at least 5 units in 4 hours or greater than 10 units in 6 hours, have also been used.

The definition of MT can be used to alert the clinician and blood bank to a massively haemorrhaging patient. A secondary use of the definition of ‘massive’ transfusion lies in transfusion research for selecting patients for prospective or retrospective studies to establish the guidelines for MT and has little use in clinical practice. Some prospective studies on MT have appropriately selected patients based on perceived need rather than a predetermined definition. However, most retrospective studies of the components of a MT guideline have used the traditional definition of MT as the inclusion criterion. For these guidelines to be useful, a clinician must anticipate the patients who are likely to suffer with a certain level of blood loss over a specified time frame.

The volume of red blood cells transfused is associated with the rate of mortality. There are a number of clinical and ethical reasons for reducing the volume of blood transfusions during resuscitation. Blood is a scarce resource and significant costs are associated with the administration of blood banks. Transfusion of blood has also been associated with multiple adverse effects. Independent of shock severity, blood transfusion is a risk factor for mortality. Blood transfusions are independently associated with an increased incidence of acute respiratory distress syndrome (ARDS), and the volume of transfusion has a dose response with the later development of multi-organ failure. Rarer risks associated with transfusions include minor allergic reaction, blood-borne viral infections, bacterial infection, anaphylactic shock, clinically significant immunosuppression and graft-versus-host disease.

The adverse clinical risks of transfusion and the limited supply of blood have resulted in a trend in modern resuscitation protocols to limit the volume of blood transfused. Appropriate use of blood in the reception and resuscitation of the massively haemorrhaging patient can be achieved by the early definitive control of haemorrhage, restrictive transfusion practice in select patients, external warming and correction of coagulopathy.

Predicting massive transfusion

MT post-injury is relatively infrequent but presents major challenges to emergency departments (EDs) and blood banks. It is important to note that the most common indication for MT in the ED in non-trauma centres is for patients with gastrointestinal haemorrhage. In the hectic phase of reception and resuscitation of patients with critical bleeding, in addition to diagnosis and management of the underlying pathology, the complex processes of rapid checking and delivery of blood products, monitoring of accurate ratios and, later, goal-directed management of coagulopathy must occur. Early prediction of MT and activation of MT protocols can ease some of these challenges, leading to the formulation of several predictive scoring tools ( Table 3.12.1 ).

The primary utility of current predictors of MT is in situations involving mass casualties or combat, although in those scenarios it might result in directing limited resources away from patients with higher scores, just the opposite of its purpose in civilian trauma care. When MT is used clinically, the primary benefit in scoring is the ability to select accurately patients who will receive transfusions because of the high specificity of their scores. This makes it possible for blood and products to be supplied with minimal wastage. However, owing to the current low sensitivity of the scores, a high clinical suspicion must be maintained for all patients and MT protocols promptly activated where clinically indicated.

Preparation

Systems should be instituted for effective prenotification of patients at risk for MT. Pre-hospital staff should be encouraged to contact receiving hospitals as early as possible. Upon notification, relevant staff should be informed. The most senior emergency physician should assume the role of team leader in all cases. Medical and nursing roles should be allocated for management of the airway, breathing and circulation, ensuring flexibility at the discretion of the team leader to reallocate according to patient needs. The role of transfusion specialists to monitor blood and blood-product administration has been reported but has current limited availability. The blood bank, surgical, radiological and theatre staff should be notified. Allied health staff should be on standby to aid in the transport of blood products and equipment, transport of patient and to cater to the needs of relatives.

Reception

On reception, the patient should be managed in a trauma or resuscitation cubicle with full physiological monitoring. The principles of reception of all critically ill patients apply and have been discussed previously. The team leader must prepare the team for specific procedures to assist in the diagnosis and management of the severely haemorrhaging patient. Where relevant, focused assessment with sonography for trauma (FAST) should be performed by staff trained and credentialled in its use. FAST screening in the haemodynamically unstable population has a higher sensitivity and specificity as compared with the stable population. The likelihood ratio for presence of haemorrhage given a positive FAST is about 12.0. Where delays to the operating theatre are expected, preparation should be made for thoracotomy or laparotomy in the ED for appropriate indications.