Hematology & Transfusion Medicine study guide previews.

During transfusion, patients don’t just receive blood - they receive citrate, a preservative that can rapidly lower ionized calcium. This reduces biologically active calcium, even if total calcium looks normal. Ionized calcium is what matters clinically, not total calcium. Citrate is normally metabolized quickly by the liver (and to a lesser extent, kidneys and muscle). Low calcium leading to decreased contractility + decreased blood pressure.

Cryoprecipitate (“cryo”) is a plasma-derived blood product used in emergency and critical care to support clot strength, primarily by replacing fibrinogen. It is most often used when bleeding persists despite initial resuscitation, particularly when fibrinogen is suspected or known to be low. Think of cryo as the product for weak or unstable clots, not platelet plug failure or vitamin K-dependent factor deficiency. Factor XIII (important for clot cross-linking and durability).

Vitamin K-dependent clotting factors (II, VII, IX, X). Each cryo unit comes from one unit of fresh frozen plasma. When plasma is thawed, the cold-insoluble proteins are separated leading to that’s cryoprecipitate. Typically 5 units of cryoprecipitate are combined into 1 pool. This is the most common adult standard in the U.S. This is dramatically less than plasma volume needed for similar fibrinogen replacement. Fibrinogen include Is converted by thrombin into fibrin, the structural backbone of a stable clot and Is commonly the first coagulation factor depleted in major hemorrhage.

In bleeding patients, clot strength can be poor despite “normal” routine labs. Cryo is commonly considered when include There is active or refractory bleeding, Bleeding appears disproportionate to INR or platelet count, and Fibrinogen levels are low or rapidly declining.

Fresh Frozen Plasma introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

It’s primarily used for urgent reversal of anticoagulation and treatment of life-threatening bleeding. Unlike plasma, PCC delivers clotting factors fast, in a small volume, and without blood-type matching.

Packed Red Blood Cells introduces the clinical pattern, physiology, and bedside decisions that matter for emergency and critical care practice.

Platelet dysfunction (qualitative defects such as uremia, cardiopulmonary bypass, or antiplatelet medications, where benefit may be variable). The goal is to improve primary hemostasis by supporting platelet plug formation. One adult dose (≈ one apheresis unit or pooled equivalent) may increase the platelet count by ~30,000-60,000/µL in a typical adult. In critical illness, active bleeding, or inflammatory states, increments may be blunted. (e.g., chemotherapy, bone marrow failure) include Platelet transfusion is commonly considered when platelet counts are very low, to reduce the risk of spontaneous bleeding.

Clinically significant bleeding (medical or surgical) include Platelet transfusion is commonly considered when thrombocytopenia is thought to be contributing to impaired hemostasis. Critical-site bleeding (e.g., intracranial, spinal, ocular) include Clinicians often aim for more robust platelet support and Practice is conservative, and evidence quality is limited. Higher-risk procedures or those involving non-compressible or critical structures often prompt a more conservative transfusion approach, even in the absence of definitive evidence.

Life-threatening bleeding in an anticoagulated patient is a time-critical emergency. Reversal is about clinical bleeding, not just lab normalization. Match the reversal strategy to the anticoagulant mechanism. Anticoagulants impair hemostasis in different ways, so reversal is not one-size-fits-all. INR correction alone does not guarantee bleeding control.

The underlying physiology includes HbS polymerizes under stress (hypoxia, acidosis, dehydration), RBCs become rigid leading to vaso-occlusion, Endothelial activation + inflammation amplify the process, and Chronic hemolysis leading to nitric oxide depletion leading to vasculopathy. In the ED/ICU, think include “Is this occlusion, hemolysis, infection, or all three?”. Microvascular occlusion leading to ischemia leading to pain. Critical care considerations include Pain can mask evolving ACS or infection. Definition include New pulmonary infiltrate + respiratory symptoms.

DIC-like physiology / liver failure bleeding (interpret cautiously). Peri-procedural “do we need products?” decisions (select cases). Conceptual benefit includes it can reduce “INR-chasing” and support targeted product selection (plasma/PCC vs platelets vs cryo/fibrinogen vs TXA), when used with clinical context. TEG/ROTEM approximates these phases in real time using a moving pin/cup system and measures resistance as clot firmness changes. Figure 1: schematic tracing + labels (accurate conceptually). ROTEM includes cT (Clotting Time)Meaning: time until initial fibrin formation starts.

If prolonged includes consider impaired initiation (factor deficiency/anticoagulants/hemodilution), especially if bleeding is significant. ROTEM includes cFT (Clot Formation Time) and α angleMeaning: how quickly the clot strengthens once it starts. If slow / low alpha includes often suggests low fibrinogen or impaired fibrin polymerization (can also be platelet-related-context matters). ROTEM includes mCF (Maximum Clot Firmness)Meaning: overall clot “strength,” largely driven by platelets + fibrinogen interaction. If low includes think platelet number/function and/or fibrinogen contribution.