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