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
Basics
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)
Indications
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
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
Plasma
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)
Indications
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
