Blood transfusion

Red Blood Cells

ABO blood type (O, A, B, or AB)
- Most important antigen group
RhD group (positive or negative)
- Second most important antigen group
There are more than 30 minor blood group antigens, including Kell (K and k), Kidd (Jk^a^ and Jk^b^), Duffy (Fy^a^ and Fy^b^) and MNS (S and s)
Group and screen
- Group tests recipient for ABO and RhD status
- Screen tests the recipient plasma for unexpected and clinically significant minor antigen incompatibility
- Takes about 45 minutes, but if the screen is positive then can take days to determine which specific antibodies are causing the problem
Crossmatch confirms that a specific unit of RBCs is safe to give to the recipient
- If screen was negative, an abbreviated crossmatch is done either as immediate spin or as electronic
- If screen was positive, then a full antiglobulin crossmatch is done

Each unit is about 300 mL with a hematocrit of 65 to 70%, and raises the recipient's hemoglobin by about 10 g/L
Usually transfused over 2 hours
- Can do up to 3 or 3.5 hours in elderly over 70 years old, heart failure, LV dysfunction, prior MI, renal dysfunction, or volume overload (usually with concurrent diuretics at the start of the transfusion)

Acute blood loss
- Maintain hemoglobin above 70 g/L during active bleeding
- Maintain hemoglobin higher (e.g. above 80 g/L) during active bleeding in patients with:
  - Unstable or acute coronary syndrome
  - Coronary artery disease
  - Uncontrolled or unpredictable bleeding
Anemia
- Consider for hemoglobin below 70 g/L in stable patients
- Consider for hemoglobin below 80 g/L in patients undergoing orthopedic or cardiac surgery or with cardiovascular disease

Caution in prothrombotic thrombocytopenia syndromes like HIT, TTP, and catastrophic antiphospholipid syndrome
Of limited utility in ITP

In non-immune thrombocytopenia, it is reasonable to maintain platelets over 10
For procedures with low risk of blood loss (e.g. appendectomy, cholecystectomy, vaginal delivery)
- Platelets less than 20: transfuse 1 dose
- Platelets 20 to 50: transfuse 1 dose if significant bleeding occurs
For procedures with high risk of blood loss, transfuse 1 dose for platelets less than 50
For neurosurgery, ophthalmologic procedures, or significant head trauma with high risk of intracranial hemorrhage, maintain platelets above 100 (may need multiple doses)
For bleeding from platelet dysfunction (e.g. post-cardiopulmonary bypass, or congenital platelet defect), transfusion may be required regardless of platelet count

Each unit has a volume of 250 mL and requires 30 minutes to thaw
It must be ABO compatible
The usual dose is 10 to 15 mL/kg (3 to 4 units for average human)
Units are transfused over 30 minutes to 2 hours (maximum 3.5 hours)
A single dose (10 to 15 mL/kg) should normalize the INR and PTT if within 1.3 to 1.8 times normal, and lasts 6 hours (the half-life of factor VII)

Before a procedure or during active bleeding where the INR, PT, or PTT is at least 1.8 times normal, and no other therapies are available
During massive transfusion protocols (6 to 10 units of RBCs expected within 6 hours)
Before a procedure or during active bleeding in patients with severe liver disease and INR greater than 2 times normal
Not useful when INR less than 1.8, when used 1:1 with RBCs, if there is no pending surgery or bleeding, for the reversal of warfarin, for the reversal of other anticoagulants, or as nutritional support

Risk	Event
1 in 13	Red cell sensitization, increasing risk of hemolytic transfusion reaction and hemolytic disease of the fetus and newborn
1 in 20	Febrile non-hemolytic transfusion reaction, per pool of platelets
1 in 100	Transfusion-associated circulatory overload
1 in 100	Minor allergic reaction (urticaria)
1 in 300	Febrile non-hemolytic transfusion reaction, per unit of RBCs
1 in 7,000	Delayed hemolytic transfusion reaction
1 in 10,000	Transfusion-related acute lung injury (TRALI)
1 in 10,000	Symptomatic bacterial infection, per pool of platelets
1 in 40,000	ABO mismatch, per unit of RBCs
1 in 40,000	Anaphylaxis
1 in 100,000	Post-transfusion purpura
1 in 200,000	Death from bacterial infection, per pool of platelets
1 in 250,000	Symptomatic bacterial infection, per unit of RBCs
1 in 500,000	Death from bacterial infection, per unit of RBCs
<1 in 1,000,000	Transmission of West Nile virus
1 in 4,000,000	Transmission of Chagas disease
1 in 7,500,000	Transmission of hepatitis B virus
1 in 7,600,000	Transmission of HTLV
1 in 13,000,000	Transmission of hepatitis C virus
1 in 21,000,000	Transmission of HIV

Differential diagnosis includes bacterial infection, acute hemolytic transfusion reaction, and febrile non-hemolytic transfusion reaction
Stop transfusion, check vitals, compare patient name to name on blood product
If severe:
- Collect blood bank samples to recheck ABO group
- Send unit to blood bank for bacterial cultures and compatibility testing
- Send blood cultures
If mild: give acetaminophen 325 mg and continue transfusion

Differential includes transfusion-related acute lung injury, transfusion-associated circulatory overload, and anaphylaxis
Stop transfusion, check vitals q15min, compare patient name to name on blood product
Chest x-ray

Minor reactions may include urticaria, flushing, erythema, pruritis, cough, wheeze, nausea, vomiting, abdominal pain, and diarrhea
For minor reactions
- Stop the transfusion
- Give diphenhydramine 25 to 50 mg p.o. or IV
- If urticarial rash is less than 2/3 BSA and no other concerning symptoms, restart the transfusion slowly
For recurrent urticarial reactions, consider premedication with diphenhydramine, cetirizine, and/or steroids

Anaphylaxis usually starts immediately or up to 45 minutes of starting the transfusion
Symptoms include:
- Urticaria and flushing are usually present
- May have airway obstruction with dyspnea, chest pain, wheezing, and stridor
- Hypotension
- Nausea and vomiting
For severe allergic reactions:
- Stop the transfusion and do not restart
- Diphenhydramine 25 to 50 mg IV
- For anaphylaxis, epinephrine and steroids