hematology

Comprehensive Notes on Hematologic Function and Transfusion Therapy

Main Takeaway: This document provides a comprehensive overview of hematologic system components, blood cell formation, diagnostic evaluations, therapeutic approaches to hematologic disorders, and detailed information on blood transfusions, including administration, complications, and management. Nurses play a critical role in all aspects of transfusion therapy, especially monitoring for and managing complications.

1. Anatomic and Physiologic Overview of the Hematologic System

1.1. Components

• Blood: Fluid state, composed of plasma and cells.

• Sites of blood production: Bone marrow and Mononuclear Phagocyte System (MPS/RES).

1.2. Blood Characteristics

• Plasma:

• Approximately 55% of whole blood volume.

• 95% water.

• Contains proteins (albumin, globulin, fibrinogen), electrolytes, waste products, and nutrients.

• Albumin maintains osmotic pressure; fibrinogen is a clotting factor.

1.3. Bone Marrow

• Site of Hematopoiesis: Formation and maturation of blood cells.

• Adult production sites: Pelvis, ribs, vertebrae, and sternum.

• Marrow Composition: Red marrow (cellular components) separated by yellow marrow (fat).

• Stem Cells:

• Ability to self-replicate and differentiate.

• Myeloid stem cells produce erythrocytes, leukocytes, and platelets.

• Lymphoid stem cells produce T or B lymphocytes.

1.4. Cellular Components of Blood

• Erythrocytes (RBCs): Perfusion ("Delivery Truck").

• Leukocytes (WBCs): Protection.

• Thrombocytes (Platelets): Patching, hemostasis.

• Cellular components: Make up 45% of blood volume.

1.5. Continuous Hematopoiesis

• Primary site: Bone marrow.

• Secondary sites (embryonic development/certain conditions): Liver and spleen (extramedullary hematopoiesis, can lead to hepatosplenomegaly).

2. Erythrocytes (Red Blood Cells)

2.1. Structure and Function

• Shape: Biconcave disk, flexible, thin membrane – facilitates oxygen absorption and release.

• Hemoglobin (Hgb):

• Composed of iron and protein.

• Makes up 95% of cell mass.

• Principal function: Transport oxygen between lungs and tissues.

• Oxyhemoglobin in arterial blood, reduced hemoglobin in venous blood.

• Weak connection to oxygen; releases at lower oxygen concentrations in tissues.

• Carbon Dioxide Transport: Binds to hemoglobin (as $\text{CO}_2$) for transport back to lungs.

• No nucleus in mature red blood cells.

2.2. Hemoglobin Levels

• Males: 14 to 17.4 g/100 mL.

• Females: 12 to 16 g/100 mL (lower due to menstruation and less muscle mass).

2.3. Erythropoiesis (RBC Production)

• Process: Myeloid stem cells $\rightarrow$ erythroblasts $\rightarrow$ reticulocytes (lose nucleus) $\rightarrow$ mature erythrocytes.

• Erythropoietin:

• Hormone produced by kidneys (peritubular interstitial fibroblast-like cells in renal cortex).

• Stimulates erythrocyte production in response to low oxygen levels (hypoxia).

• Negative feedback loop.

• Requirements: Iron, vitamin B12, folate, pyridoxine, protein, intrinsic factor, and other chemical factors/cytokines.

2.4. Iron Stores and Metabolism

• Regulation: Based on stored iron and erythrocyte production rate.

• Daily Dietary Requirements: Varies by age, sex, health status (e.g., pregnant individuals require up to 30 mg daily).

• Storage/Transport: Stored as ferritin, transported by transferrin, incorporated into hemoglobin.

• Iron Deficiency: Rapid depletion of marrow iron stores, depressed hemoglobin synthesis, leads to smaller erythrocytes (microcytic anemia) and decreased oxygen carrying capacity.

• Can cause low-grade oxygen deficiencies, e.g., shortness of breath in pregnant women (hemodilution).

2.5. Vitamin B12 and Folate Metabolism

• Role: Required for DNA synthesis in RBC production.

• Folate:

• Absorbed in the proximal small intestine (duodenum).

• Limited body storage – exits quickly.

• Crucial during pregnancy to prevent megaloblastic anemia.

• Deficiency common in alcoholics due to accelerated gastric emptying.

• Vitamin B12:

• Combines with intrinsic factor (produced in stomach).

• Absorbed in the distal ileum.

• Deficiency (often due to lack of intrinsic factor, e.g., pernicious anemia) leads to megaloblasts (giant cells) and megaloblastic anemia.

• Can cause neurological damage (paresthesia, numbing, tingling) and takes years to show.

2.6. Red Blood Cell Destruction

• Lifespan: Average 80 to 120 days.

• Removal: Older, less flexible erythrocytes trapped in small blood vessels and spleen.

• Removed by reticuloendothelial cells.

• Hemoglobin Recycling: Most is recycled; some forms bilirubin, secreted in bile (can cause jaundice).

• Iron Recycling: Recycled to form new hemoglobin; small amounts lost daily.

3. Leukocytes (White Blood Cells)

3.1. Categories and Normal Count

• Categories: Granulocytes and Agranulocytes (lymphocytes, monocytes).

• Normal Count: 4,000 to 11,000 cells/mm$^3$ (4-11k).

• <4,000 cells/mm$^3$: immunocompromised (leukopenia).

• 11,000 cells/mm$^3$: infection/massive stress/injury (leukocytosis).

3.2. Granulocytes (Phagocytosis - "First Responders")

• Characteristics: Contain granules in cytoplasm.

• Eosinophils: Bright red granules (increase in allergic reactions, parasitic infections).

• Basophils: Deep blue/purplish granules (contain heparin/histamine, involved in inflammation/allergies).

• Neutrophils: Pink to violet granules (most abundant, 60-80%).

• Polymorphonuclear neutrophils (PMNs) or segmented neutrophils (segs).

• Function: Phagocytosis (engulf invaders, bad tissue, cancerous cells).

• Short lifespan (live 6 days, mature 10 days).

• Band cells: Less mature granulocytes, single-lobed nucleus, increased during infection (a "left shift" on CBC with differential indicates severe acute bacterial infection).

• Agranulocytosis: Absence of granulocytes.

3.3. Monocytes (Agranulocytes - "Long-term Defense & Cleanup")

• Characteristics: Single-lobed nucleus, granule-free cytoplasm.

• Normal Count: Approximately 5% of total leukocytes.

• Function: Transform into macrophages (largest leukocyte), active in spleen, liver, peritoneum, alveoli.

• Remove debris, phagocytize bacteria, clean up organs.

• Indicate chronic or resolving infections.

• Monitor: Spleen/liver for swelling, liver enzymes, pain.

3.4. Lymphocytes (Agranulocytes - "Long-term Security")

• Characteristics: Small cells, scanty cytoplasm.

• Sources: Bone marrow (lymphoid stem cells), thymus (T lymphocytes).

• Function: Principal cells of immune system, produce antibodies, identify foreign cells.

• T lymphocytes (T-cells): Cellular immunity, kill foreign cells, release lymphokines (commanders, produced in thymus, attacked by HIV).

• B lymphocytes (B-cells): Humoral immunity, differentiate into plasma cells, produce antibodies.

• Natural Killer (NK) cells: Potent killers of virus-infected and cancer cells, secrete cytokines.

3.5. Function of Leukocytes (Summary)

• Neutrophils/Monocytes: Protection against infection and tissue injury via phagocytosis.

• Lymphocytes: Develop cellular and humoral immunity.

• Eosinophils/Basophils: Hypersensitivity reactions, produce/neutralize histamine.

4. Platelets (Thrombocytes)

4.1. Characteristics

• Granular fragments of megakaryocytes, not true cells.

• Cannot reproduce or repair.

• Short lifespan: 8 to 11 days.

4.2. Regulation of Production

• Thrombopoietin (hormone) stimulates production and differentiation of megakaryocytes.

4.3. Function

• Control bleeding, form platelet plug at injury site (initial plug).

• Activate coagulation factors (clotting cascade).

• Platelet aggregation is a key step, leading to fibrin formation.

• Normal Count: 150,000-450,000 cells/mm$^3$.

• <150,000 cells/mm$^3$: Thrombocytopenia (risk of bleeding).

• 200,000 cells/mm$^3$: Risk for GI bleed.

5. Plasma and Plasma Proteins

5.1. Composition

• 90% water (dehydration is a big problem).

• Primarily plasma proteins, clotting factors, nutrients, enzymes, waste products, gases.

• Serum: Plasma without fibrinogen and several clotting factors.

5.2. Plasma Proteins

• Albumin:

• Maintains fluid balance (osmotic pressure).

• Transports substances.

• Low albumin can lead to water leakage into tissues (edema), ascites, third-spacing.

• Globulins: Alpha, beta, gamma (antibodies - immunoglobulins).

• Fibrinogen: Clotting factor.

6. Mononuclear Phagocyte System (MPS)

6.1. Composition

• Specialized tissue macrophages; monocytes differentiate into macrophages in tissues.

6.2. Functions

• Defend against foreign invaders.

• Remove old/damaged cells.

• Stimulate inflammatory process.

• Present antigens to immune system.

6.3. Tissue Histiocytes

• Kupffer cells: In liver (gobble up old fragments, waste).

• Peritoneal macrophages: In peritoneal cavity.

• Alveolar macrophages: In lungs.

6.4. Spleen

• Major site of macrophage activity.

• Sequesters reticulocytes.

• Immunologic functions (B-cell maturation).

• Splenectomy risk: Life-threatening infections for the rest of life (lack of baseline immunity), as B-cells don't mature effectively. Patients often on antibiotic prophylaxis and receive specific vaccinations (pneumonia, meningococcal, influenza).

7. Hemostasis (Stopping Bleeding)

7.1. Process

• Primary Hemostasis:

1. Vessel constriction (vasoconstriction) due to injury.

2. Platelet aggregation (initial plug formation).

• Secondary Hemostasis:

1. Activation of coagulation factors.

2. Formation of fibrin (rebar of concrete) to reinforce platelet plug and make it permanent.

• Prothrombin $\rightarrow$ thrombin $\rightarrow$ fibrinogen $\rightarrow$ fibrin.

7.2. Pathways of Activation

• Extrinsic Pathway: Initiated by tissue factor (thromboplastin) release from damaged tissue.

• Intrinsic Pathway: Initiated by contact activation (e.g., exposure to collagen in blood vessel walls).

7.3. Fibrinolytic System

• Plasmin: Enzyme that digests fibrin, dissolving the clot (fibrinolysis).

• Body produces plasmin when clot has done its job (healing).

8. Gerontological Considerations

8.1. Decreased Bone Marrow Response

• Results in leukopenia or anemia.

• Factors: Diminished production/response to growth factors, DNA damage in stem cells.

• Impact: Slower blood cell production and slower healing.

• Older patients require more aggressive interventions (e.g., B12, folate, D complex, Vitamin C with iron) for nutritional anemias.

8.2. Immunosenescence

• Age-related decrease in immune system response due to diminished production and function of blood cells.

9. Diagnostic Evaluation

9.1. Hematologic Diseases

• Reflect defects (quantitative or qualitative) in hematopoietic, hemostatic, or mononuclear phagocyte systems.

• Initial symptoms often minimal/insidious.

• Extensive lab tests and continuous monitoring (trends over time) are essential.

9.2. Hematologic Studies

• Complete Blood Count (CBC):

• Identifies total leukocytes, erythrocytes, platelets.

• Includes hemoglobin, hematocrit, and RBC indices.

• CBC with Differential: Further breaks down WBCs (eosinophils, basophils, neutrophils, monocytes, lymphocytes).

• Peripheral Blood Smear:

• Manual examination under microscope.

• Provides information on shape, size, and appearance (morphology) of blood cells (e.g., sickle cells, macrocytic/megaloblastic anemia).

• Coagulation Tests:

• Prothrombin Time (PT): Replaced by International Normalized Ratio (INR).

• Activated Partial Thromboplastin Time (aPTT).

• Evaluate clotting ability and anticoagulant effectiveness.

• Crucial: Require correct blood volume in test tube (e.g., blue top tube for coags must be filled to indicator line).

9.3. Bone Marrow Aspiration and Biopsy

• Purpose: Assess blood cell formation, quantity/quality; document infection/tumor (e.g., leukemia).

• Procedure:

• Aspirated/biopsied from iliac crest (posterior) or sternum in adults.

• Local anesthetic for surface, but bone itself cannot be numbed – described as sharp, brief, intense pain ("nail hammered into hip"). Pressure sensation.

• Patient must remain still.

• Specialized Tests: Cytogenetic analysis, immunophenotyping (identify malignant conditions).

• Risks: Infection and bleeding (especially with low platelet count or altered platelet function).

• Post-procedure Care: Pressure, sterile dressing for 48 hours, mild analgesics (avoid aspirin/NSAIDs), avoid rigorous activity.

• Kids: Done more frequently, can be a nightmare due to pain and difficulty with stillness; often requires sedation (ketamine/versed).

10. Therapeutic Approaches to Hematologic Disorders

10.1. Splenectomy

• Surgical removal of spleen: For excessive blood cell destruction, severe thrombocytopenia.

• Risks: Hemorrhage, increased clotting, damage to surrounding organs (e.g., pancreas).

• Long-term risks: Life-threatening infections (vaccinations for pneumonia, influenza, meningococci; antibiotic prophylaxis).

10.2. Therapeutic Apheresis

• Definition: Separation of blood components. Blood taken from patient, specific components removed, remaining blood returned.

• Types:

• Plateletpheresis: Removal of platelets.

• Leukapheresis: Removal of leukocytes.

• Plasmapheresis: Removal of plasma (can be done as plasma donation).

• Indications: Harvesting stem cells, removing dangerous substances (immune complexes, autoantibodies).

10.3. Hematopoietic Stem Cell Transplantation (HSCT)

• Overview: Potential cure or longer remission for hematologic disorders.

• Types:

• Allogeneic: Stem cells from a donor (must be compatible, often genetically related).

• Autologous: Patient's own stem cells are harvested and used (ideal if no damage/mutation in stem cells).

• Conditions Treated: Severe aplastic anemia, leukemia, thalassemia, multiple myeloma.

• Mechanism: Healthy stem cells proliferate and differentiate, taking over function of damaged cells.

10.4. Therapeutic Phlebotomy

• Definition: Controlled removal of a certain amount of blood (similar to blood donation).

• Indications:

• Elevated hematocrits (e.g., polycythemia vera - blood too thick, too much Hct/Hgb, excessive iron accumulation).

• Excessive iron absorption (hemochromatosis).

• Effects: Produces iron deficiency over time, reduces ability to produce erythrocytes.

• Note: Blood removed usually cannot be used for transfusion to others.

11. Blood Component Therapy

11.1. Overview

• Whole blood separated into erythrocytes, platelets, and plasma.

• Each component has different storage life and processing.

11.2. Packed Red Blood Cells (PRBCs)

• Concentrated hematocrit ($\approx 70\%$).

• Stored at 6°C, lasts up to 42 days with preservatives.

• Primary therapeutic goal: Increase oxygen carrying capacity.

11.3. Platelets

• Stored at room temperature (68-72°F).

• Lasts for 5 days.

• Used for bleeding (e.g., hemorrhagic stroke, liver laceration) to form clots.

11.4. Plasma

• Frozen immediately.

• Lasts for 1 year if frozen.

11.5. Blood Derivatives

• Albumin: Expands blood volume in hypovolemic shock or septic shock (pulls fluid into vascular cavity due to osmotic pressure).

• Immune Globulin (IgG): Replaces inadequate amounts, used in chronic lymphocytic leukemia, HSCT, autoimmune disorders (source must be healthy, non-inflamed donor).

• Factor VIII Concentrate: Treats hemophilia A and von Willebrand disease.

• Factor IX Concentrate: Treats hemophilia B and factor VII/X deficiencies.

• RhoGAM: Derived from blood products, given to Rh-negative mothers with Rh-positive children post-pregnancy.

12. Procuring Blood and Blood Products

12.1. Blood Donation

• Process: Examining/interviewing prospective donors, venipuncture, blood withdrawal.

• Minimal Requirements:

• Body weight: $\ge 50$ kg (110 lb).

• Interval: $\ge 8$ weeks between whole blood donations.

• Oral temperature: $\le 37.5$°C (99.6°F).

• BP: Systolic 80-180 mmHg, Diastolic 50-100 mmHg.

• Hemoglobin: $\ge 12.5$ g/dL (if $<11$ g/dL, cannot donate).

• Travel restrictions (e.g., outside US/Canada within 3 years, UK/Europe for CJD risk, Africa/South America for Zika/malaria exposure).

• Deferral for HIV+, certain medications, transfusions within 12 months.

• Arthur Ashe example: Contracted HIV from a tainted blood transfusion, leading to instrumental changes in blood screening.

12.2. Types of Donations

• Directed Donation: From friends/family for a specific patient. Not necessarily safer; many centers no longer accept.

• Standard Donation: 450 mL withdrawn in <15 minutes.

• Post-donation: Hold arm straight, apply pressure, rest for 15 min, increase fluid intake, avoid heavy lifting/smoking/alcohol.

• Autologous Donation: Patient's own blood collected for future transfusion (e.g., elective surgeries).

• Collected 4-6 weeks pre-op (1 unit/week), iron supplements prescribed.

• Advantages: Prevents viral infections, transfusion reactions, alloimmunization.

• Contraindications: Acute infection, severe chronic disease, Hgb <11 g/dL, unstable angina, acute CV/cerebrovascular disease.

• If not used, typically discarded or (with consent) enters general donor supply.

• Intraoperative Blood Salvage: Blood lost during surgery into a sterile cavity is suctioned, washed, filtered, and reinfused to patient (e.g., vascular, orthopedic, thoracic surgery, hemothorax in trauma).

• Cannot be stored due to bacterial contamination.

• Your own blood, so no reaction risk.

• Warmed and reinfused immediately.

• Hemodilution: 1-2 units of blood removed before/after anesthesia induction, replaced with colloid/crystalloid solution, then reinfused after surgery.

• Advantage: Fewer erythrocytes lost during surgery due to dilution.

• Not recommended for patients at risk for myocardial injury, cardiopulmonary bypass, or kidney ischemia.

12.3. Complications of Blood Donation

• Excessive bleeding at venipuncture site: Bleeding disorder, technique error (laceration, insufficient pressure).

• Fainting: Emotional factors, vasovagal reaction, prolonged fasting, blood volume loss. Observe for 30 minutes.

• Anginal chest pain: In patients with unsuspected coronary artery disease (contraindication).

• Seizures: Low incidence in donors with epilepsy.

12.4. Blood Processing

• Testing: Samples tested for antibodies to HIV, HBV, HCV, HTLV-I/II, syphilis (RPR), West Nile virus, Zika virus, CMV. Nucleic acid amplification testing (NAT) increases detection.

• Pathogen Reduction Technologies: Used to reduce/inactivate pathogens (e.g., irradiation).

• Blood Typing: Crucial for transfusion safety (ABO and Rh systems).

• Type O blood: Universal donor in emergencies.

• Rh antigen: Present in 85% of population (Rh-positive).

• Leukocyte Filtration (Leukoreduction): Reduces likelihood of reactions and refractoriness, used for long-term transfusion needs.

• Irradiated Blood Products: Prevent transfusion-associated graft-versus-host disease (shorter shelf life).

13. Transfusion Administration and Complications

13.1. Administration of Blood and Blood Components

• Nurse's Responsibility: Knowledge of administration techniques, awareness of complications, familiarity with agency policies.

• Settings: Acute care, outpatient (infusion centers, clinics, physician offices), sometimes home (limited to PRBCs and factor components).

• Verification: Two-nurse process for confirming every piece of information before initiation.

• Patient Education: Review signs/symptoms of reactions, reassurance about testing, address HIV fears (very low possibility).

• Administration Rate: Blood cannot be hung for more than 4 hours (cells degrade). Always run through a filter.

13.2. Transfusion Complications (Nursing Management: Prevention, Recognition, Control)

13.2.1. General Nursing Management

• Vital signs: Thorough set before, during (first 15 minutes at bedside), and after transfusion. Accurate oral temperature is critical.

• Immediate action if reaction suspected:

1. STOP TRANSFUSION IMMEDIATELY AND DISCONNECT.

2. Notify primary provider and blood bank.

3. Thorough patient assessment (VS, respiratory status, chills, diaphoresis, JVD, back pain, urticaria, change in mental status, changes in voice).

4. Send blood container, tubing, and associated setup back to blood bank for testing.

5. Maintain IV access with saline (e.g., 250mL slow infusion or 30-60mL flush).

13.2.2. Complications of Long-Term Transfusion Therapy

• Increased risk for infection transmission and sensitization to donor antigens.

• Iron Overload (#1 concern):

• One unit of PRBCs contains 250 mg of iron.

• Excess iron deposits in body tissues, causing organ damage (liver, kidney, spleen).

• Requires iron chelation therapy to remove excess iron.

13.2.3. Specific Transfusion Reactions

13.2.3.1. Febrile Nonhemolytic Reaction (FNHTR)

• Cause: Antibodies to donor leukocytes.

• Most common type of reaction.

• Frequency: More frequent in patients with previous transfusions and Rh-negative individuals with Rh-positive children.

• Symptoms: Chills followed by fever within 2 hours of transfusion.

• Management: Treat fever (antipyretics).

• Prevention: Leukocyte reduction filter for future transfusions.

13.2.3.2. Acute Hemolytic Reaction

• Most dangerous and potentially life-threatening.

• Cause: Donor blood incompatibility with recipient (ABO incompatibility is most severe, Rh is less severe).

• Mechanism: Rapid intravascular hemolysis.

• Symptoms (rapid onset): Rapid fever, chills, low back pain (kidney damage), nausea, chest tightness, dyspnea, anxiety, hemoglobinuria (peeing red blood cells/hemoglobin), hypotension, bronchospasm, vascular collapse (distributive shock).

• Prevention: Meticulous attention to blood component labeling and patient identification (two-nurse verification).

• Nursing Care: Nurse must remain at bedside for first 15 minutes. Frequent vital signs (e.g., every 5 minutes if concern).

13.2.3.3. Allergic Reaction (Anaphylactic/Histamine Reaction)

• Cause: Sensitivity to plasma protein within blood component (histocompatibility issue, not blood type).

• Symptoms: Urticaria (hives), itching, flushing.

• Severe symptoms: Bronchospasm, laryngeal edema, shock (rapid onset).

• Management:

• Mild: Antihistamines (diphenhydramine/Benadryl).

• Severe: IMMEDIATELY STOP TRANSFUSION, administer antihistamines, corticosteroids (e.g., Solu-Medrol/Solu-Cortef).

• Prophylaxis: Antihistamines/corticosteroids before transfusion.

• Prevention: Washed blood components for severe reactions.

• Best practice: Have Benadryl at bedside for immediate access.

13.2.3.4. Transfusion-Associated Circulatory Overload (TACO)

• Cause: Hypervolemia from too much blood infused too quickly (e.g., >250 mL/hr by gravity).

• Aggravated in: Older patients, those with pre-existing increased circulatory volume, or poor cardiac function.

• Symptoms: Dyspnea, orthopnea, tachycardia, increased BP, anxiety, JVD, crackles, hypoxemia, pulmonary edema (inducing heart failure).

• Management: Slow infusion rate, diuretics (e.g., Lasix), upright positioning, oxygen, morphine.

• Prevention: Control infusion rate (max 4 hours, aim for 2 hours if tolerated), monitor for BP shifts and heavier breathing.

13.2.3.5. Bacterial Contamination

• Incidence: Low, but high risk if occurs.

• Source: Often donor's skin organisms during procurement, or contaminated equipment (e.g., recalled filters).

• Symptoms: Fever, chills, hypotension (onset slower, more gradual than acute hemolytic). Leads to bacteremia/sepsis.

• Treatment: Discontinue transfusion, fluids, broad-spectrum antibiotics, corticosteroids, vasopressors.

• Prevention: Meticulous care in procurement/processing, rapid culturing of platelet units.

13.2.3.6. Transfusion-Related Acute Lung Injury (TRALI)

• Potentially fatal reaction: Occurs within 4-6 hours of transfusion (delayed onset).

• Most common cause of transfusion-related death.

• Mechanism: HLA or HNA antibodies in donor plasma react with recipient leukocytes, causing inflammatory response, cytokine release, and fluid shift into lungs.

• Symptoms: Acute shortness of breath, hypoxia, hypotension, fever, bilateral pulmonary edema (without cardiac cause).

• Diagnosis: Hypoxemia, bilateral pulmonary infiltrates, no cardiac cause for pulmonary edema.

• Prevention: Limiting frequency/amount of blood products, screening donors for antibodies.

• Nursing Care: Essential to report time transfusion started and ended to subsequent shifts, as monitoring continues for up to 6 hours post-transfusion.

13.2.3.7. Delayed Hemolytic Reaction

• Occurs: Within 14 days after transfusion (gradual reaction).

• Mechanism: Gradual extravascular hemolysis via mononuclear phagocyte system. Body slowly recognizes non-self.

• Symptoms: Fever, anemia, increased bilirubin, decreased haptoglobin, jaundice.

• Recognition/Prevention: Difficult due to low antibody levels.

• Management: Usually mild, requires no specific intervention beyond symptom management (e.g., for fever).

13.2.3.8. Transfusion-Transmitted Infection

• Risk: Reduced due to evidence-based donor screening and testing (0.00x% incidence).

• Pathogen reduction technologies: Minimize risk.

13.3. Pharmacologic Alternatives to Blood Transfusions

• Hematopoietic growth factors: Stimulate blood cell production (e.g., Epoetin Alfa/Procrit for kidney patients to stimulate erythropoietin pathway).

• Oxygen carrier substitutes: Research on hemoglobin-based oxygen carriers and perfluorocarbons (none currently approved for human use).

• Synthetic blood expanders: Dextran, Hetastarch (synthetic starches/protein derivatives), increase osmotic pressure to hold fluid in vascular cavity, used when blood is refused (e.g., Jehovah's Witnesses). Cannot give albumin as it's human-derived.

14. Hemodynamic Goals in Transfusion

• Maintain circulatory volume and stroke volume: By infusing fluids and blood products.

• Increase oxygen carrying capacity: By providing red blood cells (if hemoglobin is low).

• Prevent chronic hypoxia/low-grade injury: Which can lead to increased cardiac workload, decreased myocardial perfusion time, and organ damage.

15. General Concepts

• Homeostasis: Body's ability to maintain normal internal conditions.

• Negative Feedback Loop: Many bodily systems, including erythropoiesis, are regulated by negative feedback.

• Demographic Refusal of Blood: Jehovah's Witnesses.

• Allowed: Autologous transfusions (pre-donation of own blood for self); blood expanders (synthetic, not human-derived).

• Refused: Allogenic blood/blood products, and will not allow their own blood to be transfused into another person if unused.