Ch03: Blood Transfusion（输血）

Preparatory Mindset

Transfusion is a life-saving but dangerous therapy. The exam focuses on: indications for transfusion, the most common complication (febrile) vs the most severe (hemolytic), autologous transfusion types, component transfusion (成分输血), and the massive transfusion triad. The Chinese prep PDFs drill the exact answers (see Core Concepts).

Exam mindset: "最常见的早期输血并发症：发热反应"; "最严重的输血并发症：溶血反应"; "溶血反应典型症状：输入十几毫升血型不合后立即出现沿输血静脉红肿及疼痛"; "自体输血类型：回收式、预存式、稀释式". Know these verbatim.

Core Concepts

1. Indications for blood transfusion (MUST KNOW)

1. Massive blood loss (大量失血) — acute hemorrhage (>15-20% blood volume), hemorrhagic shock
2. Anemia or hypoproteinemia (贫血或低蛋白血症) — Hb < 70 g/L (or 80-100 with comorbidities), low albumin
3. Severe infection (严重感染) — when antibiotics fail / neutropenia (granulocyte transfusion historically)
4. Coagulation abnormalities (凝血异常) — platelet/FFP/cryoprecipitate for coagulopathy (DIC, liver disease, anticoagulants)

• General rule: blood products are given to increase oxygen-carrying capacity (RBCs), restore volume (colloids/crystalloids first), correct coagulopathy (FFP/platelets/cryo), or replace proteins (albumin)

2. Component transfusion (成分输血) — MUST KNOW

- Packed red blood cells (浓缩红细胞) — anemia, blood loss - Fresh frozen plasma (FFP) — coagulopathy, multiple factor deficiency, massive transfusion, TTP - Platelets (血小板) — thrombocytopenia < 20-50 ×10⁹/L or platelet dysfunction with bleeding - Cryoprecipitate (冷沉淀) — fibrinogen deficiency, von Willebrand disease, hemophilia A - Albumin (白蛋白) — hypoproteinemia, burns - Granulocytes — severe neutropenia with infection (rarely used)

• Definition: blood is separated into components; the patient receives only the missing component ("缺什么补什么")
• Components:
• Advantages of component therapy: better use of blood resources, targeted treatment, less circulatory overload, fewer reactions

3. Autologous transfusion (自体输血) — MUST KNOW (three types)

1. Recovery/salvage (回收式自体输血) — collect & reinfuse the patient's own shed blood (intraoperative cell salvage)
2. Preoperative deposit (预存式自体输血) — patient donates own blood weeks before elective surgery
3. Hemodilution (稀释式自体输血) — acute normovolemic hemodilution before surgery (withdraw blood, replace with crystalloid, reinfuse later)

• Advantages: safe (no immune reaction, no disease transmission), economical

4. Complications of transfusion (MUST KNOW)

- Management: STOP the transfusion immediately, keep the IV line, check the blood bag & patient samples (repeat cross-match, direct Coombs), maintain urine output (fluids, diuretics, alkalinize urine), treat DIC/renal failure; support BP

• Most common early complication: febrile non-hemolytic reaction (发热反应) — fever/chills 1-2 h after starting; often due to leukocyte antibodies or cytokines
• Most severe complication: acute hemolytic transfusion reaction (溶血反应) — ABO incompatibility; typically within minutes of starting (as little as 10-20 ml): pain along the transfused vein (redness & pain), fever, chills, back/flank pain, dyspnea, hypotension, hemoglobinuria (red/dark urine), DIC, acute renal failure
• Allergic reactions (过敏反应) — urticaria to anaphylaxis (IgA deficiency)
• Transfusion-related acute lung injury (TRALI) — acute hypoxemia + bilateral infiltrates within 6 h (antibodies to donor leukocytes); leading cause of transfusion death
• Transfusion-associated circulatory overload (TACO) — heart failure in volume overload (elderly, cardiac patients)
• Transfusion-transmitted infections — hepatitis B/C, HIV, syphilis, malaria (screening reduces risk)
• Metabolic complications (massive transfusion): citrate toxicity (hypocalcemia), hyperkalemia (old blood), hypothermia, coagulopathy/DIC (dilutional), 2,3-DPG depletion
• Delayed hemolytic reaction — 3-10 days (minor blood group antibodies)
• Immunosuppression — may increase infection/recurrence risk

5. Massive transfusion (大量输血)

• Definition: replacement of >1 blood volume in 24 h (or >4 units RBC in 1 h with ongoing loss)
• Problems: dilutional coagulopathy, thrombocytopenia, hypocalcemia (citrate), hyperkalemia, hypothermia, acidosis
• Management: balanced transfusion ratio (1:1:1 RBC:FFP:platelets) in trauma (damage control resuscitation), warm blood, monitor Ca²⁺/K⁺/ABG/coagulation, treat hypocalcemia/hyperkalemia

6. Blood groups & compatibility (MUST KNOW)

• ABO system: A (anti-B), B (anti-A), AB (no antibodies — universal recipient), O (anti-A & anti-B — universal donor)
• Rh system: D antigen; Rh-negative patient exposed to Rh-positive blood → anti-D antibodies → hemolytic disease of the newborn (HDN) in subsequent pregnancies (Rh-negative mother + Rh-positive fetus)
• Cross-match (交叉配血): major (donor cells + recipient serum) & minor (recipient cells + donor serum) — required before transfusion
• O-negative = universal donor (RBC); AB-positive = universal recipient (plasma)

High-Yield Points

• Indications: 大量失血、贫血/低蛋白、严重感染、凝血异常
• Most common complication: febrile reaction; most severe: hemolytic reaction (ABO)
• Hemolytic reaction: stop immediately; pain along vein, fever, back pain, hemoglobinuria, shock, DIC, renal failure
• Autologous transfusion: 回收式、预存式、稀释式
• Component therapy = "缺什么补什么"
• Massive transfusion ratio 1:1:1 (RBC:FFP:platelets); watch citrate hypocalcemia, hyperkalemia, hypothermia
• O- = universal donor; AB+ = universal recipient
• TRALI = leading cause of transfusion death (hypoxemia + bilateral infiltrates)
• Transfusion threshold: Hb < 70 g/L (restrictive); platelets < 20-50 ×10⁹/L

Topic Summary

Transfusion indications: massive loss, anemia/hypoproteinemia, severe infection, coagulopathy. Component therapy gives only what's missing (RBCs, FFP, platelets, cryo, albumin). Autologous transfusion has three types (salvage, preoperative deposit, hemodilution). Complications: febrile (most common), acute hemolytic (most severe — ABO, stop immediately), allergic, TRALI, TACO, infections, massive-transfusion metabolic issues (1:1:1 ratio). Know ABO/Rh compatibility and cross-match. The classic exam Q&A: "自体输血有简便安全有效优点，主要有回收式、预存式、稀释式三种形式; 输血最严重反应为溶血反应".