The transfusion service, decoded in a day.
Welcome, Chloe & Matt. This is a working dashboard, not a textbook — three pillars, real cases, and quick checks designed to make you safe and useful on service by this afternoon.
- Pillars
- 3
- Interactive cases
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- Practice questions
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- Glossary terms
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Blood components & blood bank
What each product does, who it’s for, how compatibility works, and how to react when a transfusion goes wrong.
Open pillar → 02Coagulation testing
A reusable way to think: bleeding vs clotting, screening vs special tests, and a clean PT/aPTT algorithm.
Open pillar → 03Apheresis medicine
The consult service: what we remove or exchange, the conditions that need it, and TTP as the can’t-miss emergency.
Open pillar →How to use this dashboard
- Move top-to-bottom, or jump with the left rail.
- Answer the inline questions — feedback is instant and explained.
- Watch for the labeled callouts as you read:
Today’s goal
Understand what transfusion medicine actually does — and how to reason through the common scenarios safely.
You already know anemia, bleeding, and thrombosis clinically. We’re adding the lab framework and the bedside reflexes that sit on top.
The blood bank: the right product, for the right patient, safely.
Transfusion medicine is the clinical specialty that gets the correct blood component to the correct patient — and manages what happens when blood meets the immune system. Start here: what each product is, how compatibility works, and how to recognize a reaction.
What the blood bank actually does
Your mental modelIt is a safety and matching service. Before most transfusions it confirms the patient’s blood type and screens their plasma for antibodies that could destroy donor red cells — then issues compatible units and watches for reactions.
Giving incompatible red cells can cause fatal hemolysis. Almost every safe transfusion rests on one boring, vital step: correct patient identification.
The four products you must know
Everything else is a variationWhole blood is almost always separated into components so each patient gets only what they need:
ABO & Rh — the logic, not the memorization
You make antibodies against the ABO antigens you lack — automatically, from infancy. That single fact drives all red-cell compatibility.
| Blood group | Antigens on RBC | Antibodies in plasma | Can receive RBCs from |
|---|---|---|---|
| O | none | anti-A & anti-B | O only |
| A | A | anti-B | A, O |
| B | B | anti-A | B, O |
| AB | A & B | none | A, B, AB, O |
O is the universal red-cell donor (no antigens to attack). AB is the universal red-cell recipient (no antibodies to do the attacking).
Plasma carries the antibodies, so plasma compatibility is the mirror image of red cells.
AB is the universal plasma donor (its plasma has no anti-A/anti-B). O is the universal plasma recipient. Notice it’s exactly reversed from red cells — that reversal is the whole trick.
Universal red-cell donor = O. Universal plasma donor = AB. Same patient, opposite answer depending on the product.
Rh refers to the D antigen. D-negative people don’t naturally have anti-D, but they can form it after exposure to D-positive blood.
For a D-negative female of child-bearing potential, give D-negative red cells and platelets. Anti-D crosses the placenta and causes hemolytic disease of the fetus/newborn in a future pregnancy. RhIg (RhoGAM) prevents this sensitization.
Ordering: type & screen, crossmatch, emergency release
Type & screen
Determine ABO/Rh and screen the patient’s plasma for unexpected antibodies. The default order when transfusion is possible but not certain. If the screen is negative, compatible blood can be released fast.
Type & crossmatch
Reserve specific units and test donor cells against patient plasma. Order when transfusion is likely (e.g., a bleeding patient or a procedure with expected loss). Units are held for that patient.
Emergency release
No time to wait: issue O red cells (O-negative for women of child-bearing potential) and AB plasma, uncrossmatched. Lifesaving in the trauma bay; the lab catches up afterward.
The product guide
Packed red blood cells (pRBC)
Oxygen-carrying capacityUse it for: symptomatic anemia or acute blood loss. Common restrictive trigger Hgb < 7 g/dL (< 8 in many cardiac patients).
Don’t transfuse treatable iron deficiency or a stable, asymptomatic patient above threshold, and never use blood as a volume expander.
“Why give two when one will do?” Transfuse one unit, then reassess.
Platelets
Primary hemostasisUse it for: thrombocytopenia or platelet dysfunction with bleeding/risk. Prophylaxis < 10×10⁹/L; < 50 for most procedures; < 100 for CNS/neurosurgery.
Avoid in TTP and HIT (can fuel thrombosis) unless there is life-threatening bleeding.
Stored at room temperature → platelets carry the highest bacterial-sepsis risk of any component.
Fresh frozen plasma (FFP)
Many factors at onceUse it for: bleeding with multiple factor deficiencies — DIC, liver disease, massive transfusion; warfarin reversal when PCC is unavailable.
Not a volume expander, and not the best warfarin reversal when 4-factor PCC is available (PCC is faster and smaller volume). Don’t “fix” a mildly high INR in a non-bleeding patient before a low-risk procedure.
Cryoprecipitate
The fibrinogen productUse it for: low fibrinogen — DIC, massive transfusion, obstetric hemorrhage.
Cryo is not a general clotting-factor source. Need broad factors → FFP. Need a specific factor → its concentrate.
Modified products — who needs the “special” blood
Leukoreduced — fewer white cells
Most blood is now leukoreduced by default. Reduces febrile non-hemolytic reactions, HLA alloimmunization, and CMV transmission.
Irradiated — prevents TA-GVHD
Gamma irradiation disables donor lymphocytes so they can’t attack the recipient. For the severely immunocompromised, neonates, and directed/relative donations (HLA-similar blood is paradoxically more dangerous here).
CMV-safe — for CMV-negative at-risk patients
CMV-seronegative units or leukoreduction protect CMV-negative pregnant patients, transplant recipients, and neonates from transfusion-transmitted CMV.
Washed — plasma proteins removed
Saline-washing removes plasma. For IgA-deficient patients with anti-IgA or severe recurrent allergic/anaphylactic reactions.
Product comparison at a glance
| Product | Key content | Core indication | Typical effect / trigger | One safety pearl |
|---|---|---|---|---|
| pRBC | red cells | symptomatic anemia, blood loss | +1 g/dL Hgb | one unit, then reassess |
| Platelets | platelets | thrombocytopenia / dysfunction + bleeding | prophylaxis <10k | highest sepsis risk; avoid in TTP/HIT |
| FFP | all factors | multi-factor deficiency, DIC, liver | 10–15 mL/kg | not a volume expander |
| Cryoprecipitate | fibrinogen, FVIII, vWF, FXIII | low fibrinogen (DIC, OB hemorrhage) | fib <100–150 | the fibrinogen product, not a cure-all |
Transfusion reactions — recognize the buckets, act fast
Stop the transfusion. Keep the line open with normal saline, check the patient and the unit identification, support vital signs, and call the blood bank. Stopping first is never wrong.
Acute hemolytic (AHTR)
ABO incompatibility — almost always a clerical/ID error. Fever, flank/back pain, dark urine, hypotension, DIC. Most feared, fully preventable.
Febrile non-hemolytic
Most common. Fever/chills from cytokines and donor WBCs, no hemolysis. Leukoreduction prevents most.
Allergic → anaphylactic
Mild = hives (antihistamine, often resume). Severe = anaphylaxis, classically IgA-deficient recipients → washed products + epinephrine.
TACO
Circulatory overload: dyspnea, hypertension, pulmonary edema. Transfuse slowly, diurese. Think elderly/cardiac/renal.
TRALI
Acute lung injury within 6 h: hypoxemia, bilateral infiltrates, normal filling pressures. Leading cause of transfusion death. Supportive care.
Septic / bacterial
High fever, rigors, shock soon after starting — think platelets (stored warm). Stop, cultures, broad antibiotics.
TACO is too much volume: hypertensive, responds to diuretics. TRALI is lung injury: normal/low pressures, within 6 hours, supported not diuresed. Same breathless patient — opposite mechanism and management.
TA-GVHD (donor lymphocytes attack the host) and delayed hemolytic reactions are rarer. TA-GVHD is prevented by irradiation; delayed hemolysis appears days later as a quietly falling hemoglobin with a positive DAT.
Massive transfusion — the high-level idea
When a patient is hemorrhaging (≈ one blood volume or ≥ 10 units in 24 h), institutions activate a massive transfusion protocol and resuscitate in a balanced 1 : 1 : 1 ratio of red cells : plasma : platelets to avoid dilutional coagulopathy.
Watch the metabolic cost: stored blood’s citrate binds calcium → hypocalcemia (give calcium), plus hyperkalemia and hypothermia (warm the fluids). Remember the lethal triad: cold, acidotic, coagulopathic.
Beginner FAQ
Why screen for antibodies if we already know the blood type?
ABO/Rh isn’t the whole story. Prior pregnancies or transfusions can create antibodies to other red-cell antigens (Kell, Duffy, Kidd…). The screen finds those so the lab can pick units the patient won’t hemolyze.
If O-negative is universal, why not give it to everyone?
O-negative is scarce. It’s reserved for emergencies and for women of child-bearing potential. Everyone else gets type-specific blood to conserve the universal supply.
Does a patient consent for every transfusion?
Yes — transfusion is a procedure with risks and benefits. Informed consent (outside true emergencies) is standard, and the bedside ID check at hang time is the single most important safety step.
Try it — bedside case
Quick checkpoint
Coagulation: a way of thinking, before a list of tests.
Most students try to memorize the clotting cascade and freeze at the bedside. Flip it: start with three questions about the patient, then let a small number of tests localize the problem. This is the framework to keep.
The three questions that organize everything
Bleeding or clotting?
Is the patient bleeding (deficiency / dysfunction) or clotting (thrombophilia)? They point to opposite work-ups. Most inpatient coagulation questions are about bleeding or an abnormal screening test.
Inherited or acquired?
Inherited = lifelong, family history, since childhood (hemophilia, vWD). Acquired = new, sick patient, on drugs (DIC, liver, warfarin, heparin). Acquired is far more common on the wards.
Screening or specialized?
Screening tests (PT, aPTT, platelets, fibrinogen) localize the problem. Specialized tests (mixing study, factor assays, LA panel) confirm it. Screen first; send special tests with a hypothesis.
What the screening tests actually measure
PT measures the extrinsic + common pathway (factors VII → X, V, II, fibrinogen). The INR standardizes the PT so warfarin can be monitored anywhere.
Prolonged PT: warfarin, vitamin K deficiency, liver disease, early/mild — because factor VII has the shortest half-life, the PT moves first.
aPTT measures the intrinsic + common pathway (XII, XI, IX, VIII → X, V, II, fibrinogen).
Prolonged aPTT: heparin, hemophilia A (VIII) or B (IX), von Willebrand disease, or a lupus anticoagulant. The next move is almost always a mixing study.
Fibrinogen is the final substrate — the brick that thrombin turns into a clot. It falls when it’s consumed or not made.
Low fibrinogen → DIC, severe liver disease, or obstetric hemorrhage. A low fibrinogen in a bleeding patient is a cue for cryoprecipitate.
D-dimer is a fibrin breakdown product — evidence that clot has formed and been lysed. Very sensitive, not specific.
A high D-dimer alone proves little — it rises in VTE, DIC, infection, surgery, pregnancy, and cancer. It’s most useful when normal to help rule out clot in a low-risk patient.
The platelet count is a number from the CBC; it says nothing about whether those platelets work.
Platelet count ≠ platelet function. A normal count with mucocutaneous bleeding (aspirin, uremia, von Willebrand disease) is a functional problem that the CBC will never show.
The pathway picture (just enough to localize)
Intrinsic → aPTT
XII · XI · IX · VIII
A long aPTT with a normal PT points here.
Extrinsic → PT
VII
A long PT with a normal aPTT points here (or early warfarin/vit K).
Common → both
X · V · II · fibrinogen
Both prolonged → common pathway, DIC, liver, or strong anticoagulation.
Approach to a prolonged screening test
Rule out the artifact first
Before chasing a coagulopathy, exclude a preanalytic cause: an underfilled citrate tube, a heparin-contaminated line draw, a clotted or hemolyzed sample. The most common “coagulopathy” on the wards is a bad tube.
Localize with the pattern
Isolated long PT → factor VII, early warfarin/vitamin K deficiency, early liver disease. Isolated long aPTT → hemophilia, vWD, heparin, lupus anticoagulant. Both long → common pathway, DIC, liver, vitamin K deficiency, or strong anticoagulation.
For a long aPTT, do a mixing study
Mix the patient’s plasma 1 : 1 with normal plasma and repeat the test. This single step splits the two big categories.
The normal plasma supplied the missing factor. Think factor deficiency (hemophilia, vWD). Confirm with factor assays.
Something is neutralizing the factor even in normal plasma. Think inhibitor — a factor antibody or a lupus anticoagulant.
Memorize this one line and you can reason through most consults: “Long aPTT? Mix it. Corrects = deficiency. Doesn’t correct = inhibitor.”
Pattern-recognition cards
DIC
Everything consumed. ↓ platelets, ↓ fibrinogen, ↑ PT/aPTT, ↑↑ D-dimer, schistocytes. Driven by sepsis, malignancy, trauma, obstetric catastrophe. Treat the cause; support if bleeding.
Liver disease
Failing synthesis of most factors → PT rises first. Factor VIII is often normal/high (made by endothelium) — that’s how you separate it from DIC.
Vitamin K deficiency / warfarin
Factors II, VII, IX, X need vitamin K. PT/INR prolongs first (factor VII). Causes: poor intake, antibiotics, malabsorption, warfarin. Corrects with vitamin K.
Heparin
Unfractionated heparin prolongs the aPTT. LMWH is monitored by anti-Xa, not aPTT. A suddenly long aPTT? Check for a heparin line draw.
Hemophilia A / B
X-linked deficiency of factor VIII (A) or IX (B). Isolated long aPTT, normal PT, corrects on mixing. Deep bleeds — joints, muscles.
von Willebrand disease
Most common inherited bleeding disorder. Mucocutaneous bleeding; vWF also carries factor VIII, so the aPTT can be mildly long. Confirm with vWF antigen + activity.
Lupus anticoagulant
The paradox: a long aPTT that doesn’t correct on mixing, yet the patient clots, not bleeds. Confirm with dRVVT + antiphospholipid antibodies.
Thrombocytopenia buckets
Three mechanisms: ↓ production (marrow), ↑ destruction (ITP, TTP, HIT, DIC), or sequestration (splenomegaly). The mechanism, not the number, drives action.
It prolongs a lab test (in-vitro phospholipid effect) but promotes clotting in the patient (in vivo). Long aPTT does not always mean a bleeding risk — context decides.
Specialized tests & specimen quality
When the special tests get sent
Mixing study — deficiency vs inhibitor. Factor assays — quantify a specific factor once localized. LA / antiphospholipid panel — dRVVT, anticardiolipin, β2-glycoprotein-I; needs persistence ≥ 12 weeks to call APS.
An acquired factor inhibitor is titrated in Bethesda units; thromboelastography (TEG/ROTEM) gives a whole-blood, real-time view in trauma and the OR. Specialist territory — recognize the names.
Specimen pitfalls that fake a coagulopathy
Rule: a surprising result in a patient who looks fine deserves a redraw before a work-up.
Try it — interpret the panel
Quick checkpoint
Apheresis: selectively remove or exchange one part of the blood.
A machine separates blood into its components, the problematic part is removed or swapped out, and the rest is returned. That one sentence covers everything below. This is the transfusion service’s procedural and consult arm.
Therapeutic apheresis
Treating the patientRemove a pathologic component from a sick patient — an antibody, a paraprotein, sickled red cells, or a dangerous excess of cells — and return the rest.
Donor apheresis
Collecting from a healthy donorCollect a single component from a healthy donor — platelets, plasma, double red cells, granulocytes, or stem cells — and return everything else. Same machine, opposite goal.
The core modalities — match the tool to the problem
Plasma exchange (TPE)
Removes a bad plasma factorRemoves the patient’s plasma — and whatever pathologic antibody, immune complex, or paraprotein it carries — and replaces it with albumin or donor plasma.
Problem solved: “a harmful molecule is circulating in the plasma.”
Red cell exchange (RCE)
Swaps red cellsRemoves the patient’s red cells and replaces them with donor red cells — rapidly lowering HbS% in sickle cell disease without causing hyperviscosity or iron overload.
Problem solved: “these red cells are dangerous and must be replaced.”
Cytapheresis
Removes excess cellsLeukapheresis for symptomatic hyperleukocytosis (leukostasis in acute leukemia); plateletpheresis for symptomatic extreme thrombocytosis.
Problem solved: “there are too many of one cell, right now.”
HPC / stem-cell collection
Collects progenitor cellsAfter mobilization (G-CSF ± plerixafor), collect CD34+ hematopoietic progenitor cells from the blood for transplant — autologous or allogeneic.
Problem solved: “we need stem cells for a transplant.”
The can’t-miss consult: TTP
Thrombotic thrombocytopenic purpura is a deficiency of ADAMTS13 (usually an autoantibody) → ultra-large von Willebrand multimers → platelet microthrombi everywhere. Recognize it as microangiopathic hemolytic anemia + thrombocytopenia with no better explanation — don’t wait for the full “pentad.”
Start urgent plasma exchange with plasma replacement — it removes the antibody and ultra-large multimers and replaces ADAMTS13. It is lifesaving and is ASFA Category I. Add steroids; caplacizumab/rituximab often follow.
Do not transfuse platelets in TTP unless there is life-threatening bleeding — you’re adding fuel to the microthrombi.
Both have low platelets and schistocytes. TTP: PT/aPTT and fibrinogen are normal. DIC consumes them, so PT/aPTT are prolonged and fibrinogen is low. That panel is how you tell them apart.
Indications a student should recognize
| Scenario | Modality | What it’s solving | ASFA-style role |
|---|---|---|---|
| TTP | Plasma exchange (plasma) | remove anti-ADAMTS13, replace enzyme | Category I |
| Sickle: stroke / acute chest | Red cell exchange | lower HbS% fast, no hyperviscosity | Category I |
| Guillain-Barré · myasthenic crisis | Plasma exchange (albumin) | remove pathogenic antibody | Category I |
| Anti-GBM (Goodpasture) | Plasma exchange | remove anti-GBM antibody | Category I |
| Hyperviscosity (Waldenström / myeloma) | Plasma exchange | remove excess paraprotein | Category I/II |
| Symptomatic hyperleukocytosis | Leukapheresis | relieve leukostasis | Category II/III |
ASFA categories (from the Journal of Clinical Apheresis guidelines) rank indications I–IV: I = first-line, II = second-line, III = individualized/uncertain, IV = ineffective or harmful. You don’t need the full list — just the concept and the Category I emergencies.
Replacement fluids & complications
Albumin vs plasma — what goes back in
In plasma exchange you remove a patient’s plasma, so you must replace the volume.
Albumin contains no clotting factors — repeated exchanges deplete fibrinogen and immunoglobulins, so the team watches for bleeding. TTP is the classic reason to replace with plasma instead.
Risks & line issues
Mid-procedure perioral and fingertip tingling is citrate-induced hypocalcemia — the most common apheresis complication. Slow the rate and give calcium.
What a transfusion medicine physician actually does on the apheresis service
- Decides whether apheresis is even indicated (and its ASFA category) when a team pages a consult.
- Chooses the modality, replacement fluid, number of procedures, and schedule.
- Sorts out vascular access and monitors calcium, counts, and fibrinogen between runs.
- Manages complications and hands the patient back to the primary team with a plan.
Try it — the consult page
Quick checkpoint
Case lab — reason one step at a time.
Each case reveals itself in stages. Read the scenario, decide what you would do next, then open the discussion. These cases cross pillars the way real consults do.
Quiz center.
Mixed review and per-pillar banks. Pick an answer for instant feedback — correct answer, why the distractors are wrong, and a teaching pearl. Scoring is in-session only.
Glossary & quick reference.
Beginner-friendly definitions. Terms with a blue edge are the must-know set — the vocabulary to be comfortable with by the end of the day.
Final recap — what to carry onto service.
If you remember nothing else from today, Chloe & Matt, remember these. They’re enough to be safe and genuinely useful on a transfusion or hematology service.
- Every safe transfusion begins with correct patient identification at the bedside — the deadliest reaction (ABO hemolysis) is a preventable clerical error.
- O is the universal red-cell donor; AB is the universal plasma donor — opposite answers for opposite products.
- Transfuse one unit of red cells, then reassess; default to a restrictive trigger around Hgb 7 g/dL.
- Platelets sit at room temperature → highest sepsis risk; avoid them in TTP and HIT unless there is life-threatening bleeding.
- FFP replaces many factors (DIC, liver, massive transfusion); cryoprecipitate is the fibrinogen product.
- Any reaction: stop the transfusion, keep saline running, recheck identification, call the blood bank.
- TACO = volume overload (hypertensive, diurese); TRALI = lung injury (normal pressures, within 6 h, support).
- Coagulation starts with three questions: bleeding vs clotting, inherited vs acquired, screening vs specialized.
- PT = extrinsic/common (warfarin, vitamin K, liver); aPTT = intrinsic/common (heparin, hemophilia, vWD, lupus anticoagulant).
- Long aPTT? Mix it. Corrects = deficiency; doesn’t correct = inhibitor.
- DIC consumes everything (low platelets & fibrinogen, high D-dimer, long PT/aPTT); liver keeps factor VIII normal.
- Platelet count ≠ function — normal count with mucosal bleeding suggests dysfunction (aspirin, uremia, vWD).
- Rule out the bad tube before chasing a coagulopathy.
- Apheresis removes or exchanges one component; replacement is albumin by default, plasma for TTP.
- TTP = microangiopathic hemolysis + thrombocytopenia with a normal coagulation panel → urgent plasma exchange, and don’t give platelets.
How to sound smart on rounds
- Before a second unit — has the first one been reassessed?
- This is TACO, not TRALI: he’s hypertensive and the timing fits volume.
- Isolated prolonged aPTT — I’d send a mixing study first.
- Low fibrinogen and platelets with a high D-dimer — that’s a consumptive picture; think DIC.
- MAHA with a normal coag panel — let’s rule out TTP and call transfusion medicine.
Good questions to ask on service
- What did the antibody screen find, and how does it change which units we can give?
- Would 4-factor PCC be faster than plasma to reverse this INR?
- What ASFA category is this apheresis indication, and what replacement fluid are we using?
- Does this immunocompromised patient need irradiated products?
- Is this thrombocytopenia from production, destruction, or sequestration?
You came in knowing anemia, bleeding, and thrombosis. You’re leaving able to act on them through the transfusion service. Nicely done, Chloe & Matt.