53. Blood transfusion

Question 1

What is the definition of a massive blood transfusion?

Answer 1

Replacement of total blood volume, with stored homologous bank blood,
within 24 hours

Acute administration of more than 1.5 times the patient’s blood volume

Question 2

What problems are associated with a massive transfusion?

Answer 2

1. Clotting abnormalities
2. Biochemical complications
3. Metabolic complications
4. Delayed complications

Question 3

Clotting abnormalities

Answer 3

1. Blood loss causing reduced levels of platelets, coagulation factors and inhibitors.
2. Dilution of these factors with volume replacement
   dilutional thrombocytopaenia
   dilutional coagulopathy
3. DIC may occur in 30% of patients who have a massive transfusion.
   Lab results: Increased PT, APTT and FDPs
   Decreased platelet count
   Decreased fibrinogen
   DIC is generally due to hypoperfusion, etc. and not to transfusion itself

Question 4

Biochemical complications

Answer 4

1. Hyperkalaemia
   K+ conc. in stored blood = 30 mmol/l after 3 weeks storage
2. Citrate toxicity
   Metabolised to bicarbonate in the liver resulting in metabolic alkalosis

Patients who have liver disease or who are hypothermic are more prone to this

> 1 unit / 5 min needed to overwhelm citrate metabolism

Citrate binds to ionized calcium → hypocalcaemia

3. Hypocalcaemia Causing decreased cardiac output – rare
4. Acid–base disturbance

Lactate from red cells
Citric acid (the anticoagulant in donor blood)
Acid–base balance depends on rate of blood
administration, rate of citrate metabolism and the
perfusion of the patient

Question 5

Other problems

Answer 5

1. Hypothermia
   Left shift of O2 dissociation curve
   Platelet and clotting dysfunction

Haemoglobin dysfunction
Low temperature – left shift of O2 dissociation curve
Acidosis – right shift of O2 dissociation curve.
Decreased levels of 2,3-DPG (especially after 14 days) –
left shift of O2 dissociation curve

Haemolysis
Due to osmotic fragility

Incompatibility
Errors occur more easily in extreme clinical situations

Air embolism
Potential hazard with the use of pressure bags

Anaphylaxis 3%–5%

Question 6

Delayed complications

Answer 6

Delayed complications
Disease transmission HIV/hepatitis/malaria/bacteria → sepsis
Immunosuppression Ca bowel recurrence, infection
ARDS
Pulmonary oedema

Question 7

How would you manage a patient requiring a massive transfusion?

Answer 7

The aim is to restore:

Circulating volume – mortality is increased with prolonged shock.

Oxygen carrying capacity – packed cell volume >0.20

Haemostasis

Colloid osmotic pressure

Biochemical balance

Question 8

Points to mention are:

Answer 8

ABC approach
High flow O2
Large bore peripheral venous access with fluid warmers
Keep the patient warm (warming blankets)

Get help Senior assistance
Haematologist-communicate with the lab!
Surgical help -? required to stop bleeding

Monitoring
Amount of blood loss – suction, weighing swabs
Invasive arterial blood pressure
CVP/PAWP
Blood gases (repeated at intervals)
Frequent clotting studies
ECG
Urinary catheter
SaO2
ETCO2
Temperature (central and peripheral)
A thromboelastography may prove useful if available

Equipment
Rapid infusion device
Cell saver
Sengstaken–Blakemore tube
MAST suit

Question 9

Ongoing Mx

Answer 9

HDU/ICU
FFP and platelets 2 units of FFP and 5 units of platelets have been
recommended in the past for every 8–10 units of blood
transfused. However, the need for supplements must be
judged by clinical assessment and lab tests.
FFP should be given if the PT is prolonged by more than
5 seconds.

Microvascular bleeding due to thrombocytopaenia is
more likely to occur if the platelet count is <50 × 109/l.
Treat with 6–8 units of platelets.

Cryoprecipitate Contains more fibrinogen and Factor VIII
15 packs can be used to help treat DIC, which should be
suspected if thrombin time is doubled.

Question 10

Drugs

Answer 10

Drugs

Aprotinin – serine protease inhibitor to inhibit fibrinolysis

Tranexamic acid –
antifibrinolytic agent that binds to
plasminogen and plasmin and
interferes with their ability
to split fibrinogen.

Desmopressin/vasopressin – affects circulatory endothelial cells

Calcium chloride

Question 11

Blood filters – a contentious issue

Answer 11

Designed to remove microaggregates:

Micropore filters: 2 types (20–40 μm)

Depth filters (impaction and adsorption)

Screen filters (direct interception principle)

Problems: Impede blood flow, become blocked and activate complement
Haemolysis and platelet depletion (depth filters)

Standard blood filters (170 m)