HEMATOLOGIC SYSTEM

The structures of the hematologic or hematopoietic system include the blood, blood vessels, and blood-forming organs (bone marrow, spleen, liver, lymph nodes, and thymus gland). The major function of blood is to carry necessary materials (oxygen, nutrients) to cells and to remove carbon dioxide and metabolic waste products. The hematologic system also plays an important role in hormone transport, the inflammatory and immune responses, temperature regulation, fluid-electrolyte balance, and acid-base balance.

Bone Marrow

  1. Contained inside all bones, occupies interior of spongy bones and center of long bones; collectively one of the largest organs of the body (4%-5% of total body weight)
  2. Primary function is hematopoiesis (the formation of blood cells)
  3. Two kinds of bone marrow, red and yellow
    1. Red (functioning) marrow
      1. Carries out hematopoiesis; production site of erythroid, myeloid, and thrombocytic components of blood; one source of lymphocytes and macrophages
      2. Found in ribs, vertebral column, other flat bones
    2. Yellow marrow: red marrow that has changed to fat; found in long bones; does not contribute to hematopoiesis
  4. All blood cells start as stem cells in the bone marrow; these mature into the different, specific types of cells, collectively referred to as formed elements of blood or blood components: erythrocytes, leukocytes, and thrombocytes.


Blood

  1. Composed of plasma (55%) and cellular components (45%)
  2. Hematocrit
    1. Reflects portion of blood composed of red blood cells
    2. Centrifugation of blood results in separation into top layer of plasma, middle layer of leukocytes and platelets, and bottom layer of erythrocytes.
    3. Majority of formed elements is erythrocytes; volume of leukocytes and platelets is negligible.
  3. Distribution
    1. 1300 ml in pulmonary circulation
      1. 400 ml arterial
      2. 60 ml capillary
      3. 840 ml venous
    2. 3000 ml in systemic circulation
      1. 550 ml arterial
      2. 300 ml capillary
      3. 2150 ml venous


Plasma

  1. Liquid part of blood; yellow in color because of pigments
  2. Consists of serum (liquid portion of plasma) and fibrinogen
  3. Contains plasma proteins such as albumin, serum globulins, fibrinogen, prothrombin, plasminogen
    1. Albumin: largest of plasma proteins, involved in regulation of intravascular plasma volume and maintenance of osmotic pressure
    2. Serum globulins: alpha, beta, gamma
      1. Alpha: role in transport of steroids, lipids, bilirubin
      2. Beta: role in transport of iron and copper
      3. Gamma: role in immune response, function of antibodies
    3. Fibrinogen, prothrombin, plasminogen (see Coagulation)


Cellular Components
Cellular components or formed elements of blood are erythrocytes (red blood cells [RBCs]), which are responsible for oxygen transport; leukocytes (white blood cells [WBCs]), which play a major role in defense against microorganisms; and thrombocytes (platelets), which function in hemostasis.

  1. Erythrocytes
    1. Bioconcave disc shape, no nucleus, chiefly sacs of hemoglobin
    2. Cell membrane is highly diffusible to O2 and CO2
    3. RBCs are responsible for oxygen transport via hemoglobin (Hgb)
      1. Two portions: iron carried on heme portion; second portion is protein
      2. Normal blood contains 12-18 g Hgb/100 ml blood; higher (14-18 g) in men than in women (12-14 g)
    4. Production
      1. Start in bone marrow as stem cells, released as reticulocytes (immature cells), mature into erythrocytes
      2. Erythropoietin stimulates differentiation; produced by kidneys and stimulated by hypoxia
      3. Iron, vitamin B12, folic acid, pyridoxine (vitamin B6), and other factors required for erythropoiesis
    5. Hemolysis (destruction)
      1. Average life span 120 days
      2. Immature RBCs destroyed in either bone marrow or other reticuloendothelial organs (blood, connective tissue, spleen, liver, lungs, and lymph nodes)
      3. Mature cells removed chiefly by liver and spleen
      4. Bilirubin: byproduct of Hgb released when RBCs destroyed, excreted in bile
      5. Iron: freed from Hgb during bilirubin formation; transported to bone marrow via transferrin and reclaimed for new Hgb production
      6. Premature destruction: may be caused by RBC membrane abnormalities, Hgb abnormalities, extrinsic physical factors (such as the enzyme defects found in G6PD)
      7. Normal age RBCs may be destroyed by gross damage as in trauma or extravascular hemolysis (in spleen, liver, bone marrow)
  2. Leukocytes: granulocytes and mononuclear cells: involved in protection from bacteria and other foreign substances
    1. Granulocytes: eosinophils, basophils, and neutrophils
      1. Eosinophils: involved in phagocytosis and allergic reactions
      2. Basophils: involved in prevention of clotting in microcirculation and allergic reactions
      3. Eosinophils and basophils are reservoirs of histamine, serotonin, and heparin
      4. Neutrophils: involved in short-term phagocytosis
        1. mature neutrophils: polymorphonuclear leukocytes
        2. immature neutrophils: band cells (bacterial infection usually produces increased numbers of band cells)
    2. Mononuclear cells: monocytes and lymphocytes: large nucleated cells
      1. Monocytes: involved in long-term phagocytosis; play a role in immune response
        1. largest leukocyte
        2. produced by bone marrow: give rise to histiocytes (Kupffer cells of liver), macrophages, and other components of reticuloendothelial system
      2. Lymphocytes: immune cells; produce substances against foreign cells; produced primarily in lymph tissue (B cells) and thymus (T cells) (see also Immune Response)
  3. Thrombocytes (platelets)
    1. Fragments of megakaryocytes formed in bone marrow
    2. Production regulated by thrombopoietin
    3. Essential factor in coagulation via adhesion, aggregation, and plug formation
    4. Release substances involved in coagulation



Blood Groups

  1. Erythrocytes carry antigens, which determine the different blood groups.
  2. Blood-typing systems are based on the many possible antigens, but the most important are the antigens of the ABO and Rh blood groups because they are most likely to be involved in transfusion reactions.
    1. ABO typing
      1. Antigens of system are labelled A and B.
      2. Absence of both antigens results in type O blood.
      3. Presence of both antigens is type AB.
      4. Presence of either A or B results in type A and type B respectively.
      5. Nearly half the population is type O, the universal donor.
      6. Antibodies are automatically formed against the ABO antigens not on person's own RBCs; transfusion with mismatched or incompatible blood results in a transfusion reaction (Table 4.17).
    2. Rh typing
      1. Identifies presence or absence of Rh antigen (Rh positive or Rh negative).
      2. Anti-Rh antibodies not automatically formed in Rh-negative person, but if Rh-positive blood is given, antibody formation starts and a second exposure to Rh antigen will trigger a transfusion reaction.
      3. Important for Rh-negative woman carrying Rh-positive baby; first pregnancy not affected, but in a subsequent pregnancy with an Rh-positive baby, mother's antibodies attack baby's RBCs ( in Unit 6).


TABLE 4.17 Complications of Blood Transfusion

Type

Causes

Mechanism

Occurrence

Signs and Symptoms

Intervention

Hemolytic

ABO incompatibility; Rh incompatibility; use of dextrose solutions; wide temperature fluctuations

Antibodies in recipient plasma react with antigen in donor cells. Agglutinated cells block capillary blood flow to organs. Hemolysis (Hgb into plasma and urine).

Acute:
first 5 min after completion of transfusion
Delayed:
days to 2 weeks after

Headache, lumbar or sternal pain, nausea, vomiting, diarrhea, fever, chills, flushing, heat along vein, restlessness, anemia, jaundice, dyspnea, signs of shock, renal shutdown, DIC

Stop transfusion. Continue saline IV. Send blood unit and client blood sample to lab. Watch for hemoglobinuria. Treat or prevent shock, DIC, and renal shutdown.

Allergic

Transfer of an antigen or antibody from donor to recipient; allergic donors

Immune sensitivity to foreign serum protein

Within 30 min of start of transfusion

Urticaria, laryngeal edema, wheezing, dyspnea, bronchospasm, headache, anaphylaxis

Stop transfusion. Administer antihistamine and/or epinephrine. Treat life-threatening reactions.

Pyrogenic

Recipient possesses antibodies directed against WBCs; bacterial contamination; multitransfused clients; multiparous clients

Leukocyte agglutination
Bacterial organisms

Within 15-90 min after initiation of transfusion

Fever, chills, flushing, palpitations, tachycardia, occasional lumbar pain

Stop transfusion.
Treat temperature.
Transfuse with leukocyte-poor blood or washed RBCs.
Administer antibiotics prn.

Circulatory overload

Too rapid infusion in susceptible clients

Fluid volume overload

During and after transfusion

Dyspnea, tachycardia, orthopnea, increased blood pressure, cyanosis, anxiety

Slow infusion rate.
Use packed cells instead of whole blood.
Monitor CVP through a separate line.

Air embolism

Blood given under air pressure following severe blood loss

Bolus of air blocks pulmonary artery outflow

Anytime

Dyspnea, increased pulse, wheezing, chest pain, decreased blood pressure, apprehension

Clamp tubing.
Turn client on left side.

Thrombocytopenia

Use of large amounts of banked blood

Platelets deteriorate rapidly in stored blood

When large amounts of blood given over 24 hr

Abnormal bleeding

Assess for signs of bleeding.
Initiate bleeding precautions.
Use fresh blood.

Citrate intoxication

Large amounts of citrated blood in clients with decreased liver function

Citrate binds ionic calcium

After large amounts of banked blood

Neuromuscular irritability
Bleeding due to decreased calcium

Monitor/treat hypocalcemia. Avoid large amounts of citrated blood. Monitor liver function.

Hyperkalemia

Potassium levels increase in stored blood

Release of potassium into plasma with red cell lysis

In clients with renal insufficiency

Nausea, colic, diarrhea, muscle spasms, ECG changes (tall peaked T-wave, short Q-T segment)

Administer blood less than 5-7 days old in clients with impaired potassium excretion.




Blood Coagulation
Conversion of fluid blood into a solid clot to reduce blood loss when blood vessels are ruptured.

  1. Systems that initiate clotting
    1. Intrinsic system: initiated by contact activation following endothelial injury ("intrinsic" to vessel itself)
      1. Factor XII initiates as contact made between damaged vessel and plasma protein
      2. Factors VIII, IX, and XI activated
    2. Extrinsic system
      1. Initiated by tissue thromboplastins, released from injured vessels ("extrinsic" to vessel)
      2. Factor VII activated
  2. Common pathway: activated by either intrinsic or extrinsic pathways
    1. Platelet factor 3 (PF3) and calcium react with factors X and V.
    2. Prothrombin converted to thrombin via thromboplastin.
    3. Thrombin acts on fibrinogen, forming soluble fibrin.
    4. Soluble fibrin polymerized by factor XIII to produce a stable, insoluble fibrin clot.
  3. Clot resolution: takes place via fibrinolytic system by plasmin and proteolytic enzymes; clot dissolves as tissue repairs.



Spleen

  1. Largest lymphatic organ: functions as blood filtration system and reservoir
  2. Vascular, bean shaped; lies beneath the diaphragm, behind and to the left of the stomach; composed of a fibrous tissue capsule surrounding a network of fiber
  3. Contains two types of pulp
    1. Red pulp: located between the fibrous strands, composed of RBCs, WBCs, and macrophages
    2. White pulp: scattered throughout the red pulp, produces lymphocytes and sequesters lymphocytes, macrophages, and antigens
  4. 1%-2% of red cell mass or 200 ml blood/minute stored in spleen; blood comes via the splenic artery to the pulp for cleansing, then passes into splenic venules that are lined with phagocytic cells, and finally to the splenic vein to the liver.
  5. Important hematopoietic site in fetus; postnatally produces lymphocytes and monocytes
  6. Important in phagocytosis; removes misshapen erythrocytes, unwanted parts of erythrocytes
  7. Also involved in antibody production by plasma cells and iron metabolism (iron released from Hgb portion of destroyed erythrocytes returned to bone marrow)
  8. In the adult, functions of the spleen can be taken over by the reticuloendothelial system.


Liver
See also Gastrointestinal Tract.

  1. Involved in bile production (via erythrocyte destruction and bilirubin production) and erythropoiesis (during fetal life and when bone marrow production is insufficient).
  2. Kupffer cells of liver have reticuloendothelial function as histiocytes; phagocytic activity and iron storage.
  3. Liver also involved in synthesis of clotting factors, synthesis of antithrombins.



HEMATOLOGIC PLANNING AND IMPLEMENTING

Goals

  1. Optimal nutrition will be maintained.
  2. Client will be free from infection.
  3. Adequate cerebral and peripheral tissue perfusion will be maintained.
  4. Client will maintain optimal respiratory function.
  5. Client will maintain adequate protective mechanisms.
  6. Optimal skin integrity will be maintained.
  7. Client maintains optimal health of oral mucous membranes.
  8. Client will have increased strength and endurance.
  9. Client's pain will be relieved/controlled.
  10. Client's anxiety will be relieved/reduced.


Interventions


Blood Transfusion and Component Therapy

  1. Purpose: improve oxygen transport (RBCs); volume expansion (whole blood, plasma, albumin); provision of proteins (fresh frozen plasma, albumin, plasma protein fraction); provision of coagulation factors (cryoprecipitate, fresh frozen plasma, fresh whole blood); provision of platelets (platelet concentrate, fresh whole blood)
  2. Blood and blood products
    1. Whole blood; provides all components
      1. Large volume can cause difficulty: 12-24 hours for Hgb and hct to rise
      2. Complications: volume overload, transmission of hepatitis or AIDS, transfusion reaction, infusion of excess potassium and sodium, infusion of anticoagulant (citrate) used to keep stored blood from clotting, calcium binding and depletion (citrate) in massive transfusion therapy
    2. Red blood cells
      1. Provide twice the amount of Hgb as an equivalent amount of whole blood
      2. Indicated in cases of blood loss, pre- and post-op clients, and those with incipient congestive failure
      3. Complications: transfusion reaction (less common than with whole blood due to removal of plasma proteins)
    3. Fresh frozen plasma
      1. Contains all coagulation factors including V and VIII
      2. Can be stored frozen for 12 months; takes 20 minutes to thaw
      3. Hang immediately upon arrival to unit (loses its coagulation factors rapidly)
    4. Platelets
      1. Will raise recipient's platelet count by 10,000/mm3
      2. Pooled from 4-8 units of whole blood
      3. Single-donor platelet transfusions may be necessary for clients who have developed antibodies; compatibility testing may be necessary
    5. Factor VIII fractions (cryoprecipitate): contains Factors VIII, fibrinogen, and XIII
    6. Granulocytes
      1. Do not increase WBC; increase marginal pool (at tissue level) rather than circulating pool
      2. Premedication with steroids, antihistamines, and acetaminophen
      3. Respiratory distress with shortness of breath, cyanosis, and chest pain may occur; requires cessation of transfusion and immediate attention
      4. Shaking chills or rigors common, require brief cessation of therapy, administration of meperidine IV until rigors are diminished, and resumption of transfusion when symptoms relieved
    7. Volume expanders: albumin; percentage concentration varies (50-100 ml/unit); hyperosmolar solutions should not be used in dehydrated clients.
  3. Nursing care
    1. Assess client for history of previous blood transfusions and any adverse reactions.
    2. Ensure that the adult client has an 18- or 19-gauge IV catheter in place.
    3. Use 0.9% sodium chloride.
    4. At least two nurses should verify the ABO group, Rh type, client and blood numbers, and expiration date.
    5. Take baseline vital signs before initiating transfusion.
    6. Start transfusion slowly (2 ml/minute).
    7. Stay with the client during the first 15 minutes of the transfusion and take vital signs frequently.
    8. Maintain the prescribed transfusion rate.
      1. Whole blood: approximately 3-4 hours
      2. RBCs: approximately 2-4 hours
      3. Fresh frozen plasma: as quickly as possible
      4. Platelets: as quickly as possible
      5. Cryoprecipitate: rapid infusion
      6. Granulocytes: usually over 2 hours
      7. Volume expanders: volume-dependent rate
    9. Monitor for adverse reactions (see Table 4.17).
    10. Document the following
      1. Blood component unit number (apply sticker if available)
      2. Date infusion starts and ends
      3. Type of component and amount transfused
      4. Client reaction and vital signs
      5. Signature of transfusionis


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