Pre-Transfusion Testing
Group and Screen (Type and Screen)
Antigens that are not present in screened cells are unlikely to cause significant hemolytic reactions (0.2% risk of transfusion reaction if only type and screen is done). They can be safely transfused with negative-type specific blood if there is a negative screen.
| Test | Description |
|---|---|
| Group | Tests ABO-Rh antigens on RBCs. Recipient RBCs are tested with anti-A, anti- B and anti-D (Rh) antibodies to determine blood type |
| Screen | Indirect Coomb’s test to assess for antibodies in the recipient’s serum. The recipient serum is mixed with RBCs of known antigens. No agglutination = negative screen. If the screen is positive serum is tested further. |
- What is a Bombay Phenotype:
- A rare blood group was discovered in Bombay, India in 1952.
- Lacks A, B and H antigens and has anti-A, anti-B, and anti-H antibodies making blood incompatible with most blood groups.
- Bombay phenotype recipients can only be transfused with Bombay phenotype donors
Weak D vs partial D
| Partial D | Weak D | |
|---|---|---|
| Location of mutation | External (Exposed) | Internal |
| Anti-Rho (D) | Positive | Negative |
| All epitopes present | Yes | No |
| Rhesus group | Rh D- | Rh D+ |
| Can receive blood from Rh D+ | No | Yes |
| Isolated using DU testing | Difficult | Yes |
Group and Cross-Match (Type and Cross-Match)
Group and cross-match is used when there is a high likelihood of transfusion. Can be an electronic or serologic cross-match.
| Test | Description |
|---|---|
| Immediate phase (5min) | Checks ABO typing errors and incompatibilities caused by naturally occurring antibodies to the MN, P and Lewis system |
| Incubation phase (45 min) | Immediate-phase reaction products are incubated to detect incomplete antibodies to the Rh system that did not cause agglutination in the first phase |
| Indirect Antiglobulin Test | Antigloulin serum is added to products of the first two tests to look for incomplete recipient antibodies to Rh, Kell, Duffy and Kidd |
Screening for Infectious Disease
- Infectious agents screened for in the blood include:
- HIV-1, HIV-2
- Syphilis
- HBV core Ab
- HCV
- CMV
- HTLV
- Zika
Blood Products
Methods for separating blood products
| Method | Description |
|---|---|
| Centrifugation | Light and heavy spins (1700 rpm) separate pRBC and platelet-rich plasma; heavy spins (3000rpm) obtain platelets from platelet-rich plasma |
| Apharesis | A machine isolates products from the donor’s blood (eg, platelets), and the remaining components are returned to the donor |
| Gravity | Whole blood settles for 12 hours, causing pRBC to settle at the bottom. Plasma and buffy coats are obtained by decanting. pRBCs remain in the container |
Some Blood Products with some of their indications
| Product | Indication |
|---|---|
| Whole Blood | Massive Hemorrhage, Exchange transfusion, pRBC unavailable |
| Packed Red Blood Cells | Anaemia |
| Leukocyte-depleted Red Blood Cells | Reduce HLA alloimmunization, reduce allergic reactions, reduce CMV transmission |
| Frozen Red Blood Cells | Storage of rare blood types |
| Irradiate Red Blood Cells | Prevent Transfusion-associated graft versus host disease |
| Washed Red Blood Cells | Reduce allergic reactions and anaphylaxis in IgA deficiency |
| Granulocytes | Sepsis in neutropenic patients |
| Platelets (Aphaeretic or Pooled) | Bleeding in thrombocytopenia, Prevent bleeding in thrombocytopenia |
| Fresh Frozen Plasma | Bleeding due to multiple factor deficiency, Disseminated Intravascular Coagulation, Liver Disease, Warfarin Overdose, Factor Depletion in Large Transfusions, Bleeding in Thrombotic Thrombocytopenic Purpura |
| Cryoprecipitate | Low fibrinogen, Von Willebrand Disease, Hemophilia A, Factor VIII deficiency |
| Factor VIII | Hemophilia A |
| Factor IX | Hemophilia B |
| Albumin | Hypovolemia with hyperproteinemia |
| IVIg | Disease prophylaxis, Autoimmune diseases, Immunodeficiency |
Blood Products and Storage Temperature
| Blood Product | Storage Temperature |
|---|---|
| Whole Blood | 2-6 °C refrigeration for 35 days |
| pRBC | 2-6 C refridgeration for 35 – 42 days |
| FFP | -18 °C freeze for 1 year |
| FFP thawed | 2-6 °C refrigeration |
| Platelets | 20 – 24 °C incubated and agitated for 5 days |
| Cryoprecipitate | -18 °C frozen for 1 year |
| Cryoprecipitate thawed | 0 – 24 °C at controlled room temperature |
Packed Red Blood Cells (pRBCs)
pRBCs from a single donor have a volume of 250-350ml (1 unit) with a Hematocrit of 60-70%. pRBCs are stored at 4 C in CPD, CPDA, or Adsol. pRBC is usually given with NS through a Y-type tubing.
Nota Bene: 1 unit pRBC increases adult Hb by ~ 1g/dL or Hct by ~ 3% (10ml/kg pRBC increases Hct by 10%)
RBC anticoagulants and preservatives
| Anticoagulant | Shelf-life of RBC |
|---|---|
| Citrate Phosphate Dextrose (CPD) | 21 days |
| Citrate Phosphate Dextrose Adenine (CPDA) | 35 days |
| Adenine Dextrose Sorbitol Sodium Chloride Mannitol (ADSOL) | 42 days |
Components of CPDA and their functions
| Component | Function |
|---|---|
| Citrate | Anticoagulant. Metabolized by the liver into bicarbonate. At high transfusion rates, excess citrate binds to calcium, resulting in hypocalcemia |
| Phosphate | Buffer |
| Dextrose | Energy source |
| Adenine | precursor to ATP synthesis |
- Changes to RBCs that occur during storage
- Decreased 2,3-BPG
- Decreased ATP
- Decreased intracellular K+, increased plasma K+
- Distorted RBCs and membrane rigidity
- Decreased plasma pH
- Decreased RBC glucose
- Indications for Packed Red Blood Cells
- Hemoglobin < 7 g/dL in young, healthy patients (usually unnecessary when Hb > 10 g/dL)
- For Hb 6 – 10 g/dL:
- Ongoing indications of organ ischemia
- Potential for ongoing blood loss
- Volume status
- Risk factors for complications of inadequate oxygen, e.g., myocardial infarction
- Solutions not compatible with pRBC
- Lactated Ringer’s (theoretical clot formation due to calcium in LR)
- D5W (a hypotonic solution that hemolyzes RBCs)
Fresh Frozen Plasma (FFP)
FFP contains all clotting factors, fibrinogen, plasma proteins (particularly albumin), electrolytes, physiologic anticoagulants (protein C, protein S, antithrombin), and added anticoagulants (citrate). AB blood type is the universal donor (Uses ABO compatible; Rh-incompatible is OK to give). FFP is stored frozen for up to 1 year, takes 30 minutes to thaw, and is used within 24 hours of thawing.
Nota bene: 10 – 20 ml/kg of FFP will raise factors by 20-30% (2.5-4.5 units for a 70kg patient)
FFP has an INR of 1.6 – 1.8.
| Starting INR | FFP units needed to reach an INR of 1.5 |
|---|---|
| 2.5 | 4 |
| 2.0 | 3 |
| 1.8 | 2 |
- Indications for FFP (ASA guidelines)
- Correct excessive microvascular bleeding with INR > 2
- During a massive transfusion (before lab results are available)
- Urgent reversal of Warfarin overdose (or can use Prothrombin Complex Concentrate)
- Correction of known factor deficiency (when specific factor concentrate is unavailable)
- Heparin resistance (Antithrombin III deficiency) in patients requiring Heparinization
Warfarin reversal, Urgent Surgery
| INR | Reversal |
|---|---|
| 1.5 – 1.9 | FFP |
| 1.9 – 5 | FFP + 1-3 mg of IV Vitamin K |
| 5 – 9 | FFP + 2-5 mg IV Vitamin K |
Warfarin reversal, Surgery 24 – 48 hours later
| INR | Reversal |
|---|---|
| 1.5 – 1.9 | 1mg PO Vitamin K |
| 1.9 – 5 | 1 – 2.5 mg PO Vitamin K, if INR is still elevated 24 hours after dose, give 1- 2 mg PO Vitamin K |
| INR 5 – 9 | 2.5 – 5 mg PO Vitamin K, if INR is still elevated 24 hours after dose, give 1 – 2 mg PO vitamin K |
- Warfarin reversal for non-surgical patients
Platelets
Platelets can be given to ABO-incompatible individuals. They are Rh tested only (a small amount of RBCs are present, so Rh sensitization can occur for some individuals). They are stored at room temperature for ≤ 5 days.
Platelet concentrate: volume of 50-70 ml per unit.
Nota bene: 1 unit of platelet concentrate increases PLT by 5,000 – 10,000
“6-pack”: 6 pooled platelet concentrates from different donors
**Apheresis unit platelets: volume of 200-400 ml
Nota bene: 1 unit raises platelets by 30,000 – 50,000
- Indications (ASA guidelines)
- Rarely used for platelets > 100,000
- For platelets < 50,000 and undergoing surgery/procedure (spontaneous bleed can occur at <10K)
- When the platelet count is 50,000, based on the risk of bleeding
- When the platelet count is < 100,000, there is a concern for CNS bleeding
- With platelet dysfunction, e.g. cardiopulmonary bypass, platelet inhibitors, renal dysfunction
Cryoprecipitate
Cryoprecipitate is a fraction of plasma that precipitates when FFP is thawed. It contains factor I (fibrinogen), factor VIII, factor XIII and vWF. 1 unit contains 200 – 250 mg of Fibrinogen (10 units = 2g of fibrinogen). Once thawed, they are stored at room temperature and given within 6 hours. Can be stored at -18 – 20 C for 1 year. Not screened for ABO incompatibility due to limited antibody concentration.
Nota bene: 0.1 units/kg raises fibrinogen by 100 mg/dl. 10 units of cryoprecipitate raise a 70kg patient’s fibrinogen by 70 mg/dL (60-100).
- Indications (ASA guidelines)
- Rarely, when fibrinogen > 150 mg/dL.
- When fibrinogen is < 100 mg/dL with microvascular bleeding
- During massive transfusion, when fibrinogen levels are not available
- Bleeding patients with Von Willebrand Disease
- Congenital fibrinogen deficiency
Prothrombin Complex Concentrate (PCC)
| Unactivated PCCs | Description |
|---|---|
| 4 factor (Kcentra) | Contains inactive form of factor II, factor VII, factor IX, and factor X. Also contains Heparin |
| 3 factor (Profinine) | Contains inactive forms of Factor II, Factor IX and Factor X |
| Activated PCCs | |
| 4 factor (FEIBA) | Contains factor II, factor VII, factor IX, and factor X. Only factor VII is mostly the activated form. Does not contain Heparin |
Alternative Strategies for Managing Blood Loss During Surgery
Autologous transfusion
- Blood is taken 4-5 weeks before surgery and self-donated if the patient’s HCT is > 34
- Reduces risk of infection and transfusion reaction
Cell saver
- Blood shed during surgery is aspirated into a reservoir, mixed with heparin, concentrated, and debris is removed
- Used for blood loss > 1000 – 1500 mL
- Contraindicated for septic wounds and cancer
- Patients may still require transfusion of other products for coagulopathy (heparinized and provides pRBCs only)
Normovolemic hemodilution
- 1 – 2 units of blood are removed and stored in a CPD bag and replaced with crystalloid for a goal HCT of 20-25%
- Blood is then given back after loss