Aplastic anemia

Aplastic anemias

Aplastic or hypoplastic, anemias result from injury to or destruction of stem cells in bone marrow or the bone marrow matrix, causing pancytopenia (anemia, leukopenia, and thrombocytopenia) and bone marrow hypoplasia. Although commonly used interchangeably with other terms for bone marrow failure, aplastic anemia properly refers to pancytopenia resulting from the decreased functional capacity of a hypoplastic, fatty bone marrow.
These disorders generally produce fatal bleeding or infection, especially when they're idiopathic or caused by chloramphenicol (Chloromycetin) use or infectious hepatitis. The death rate for severe aplastic anemia is 80% to 90%.

Causes
Possible causes of aplastic anemia are:
Ø radiation (about half of such anemias)
Ø drugs (antibiotics, anticonvulsants), or toxic agents (such as benzene or chloramphenicol [Chloromycetin])
Ø autioimmune reactions (unconfirmed), severe disease (especially hepatitis), or preleukemic and neoplastic infiltration of bone marrow
Ø congenital (idiopathic anemias): two identified forms of aplastic anemia are congenital — hypoplastic or Blackfan-Diamond anemia (develops between ages 2 and 3 months); and Fanconi syndrome (develops between birth and 10 years of age).



Pathophysiology

Aplastic anemia usually develops when damaged or destroyed stem cells inhibit blood cell production. Less commonly, they develop when damaged bone marrow microvasculature creates an unfavorable environment for cell growth and maturation.



Signs and symptoms

Signs and symptoms of aplastic anemia vary with the severity of pancytopenia, but develop insidiously in many cases. They may include:
Ø progressive weakness and fatigue, shortness of breath, headache, pallor, and ultimately tachycardia and heart failure due to hypoxia and increased venous return
Ø ecchymosis, petechiae, and hemorrhage, especially from the mucous membranes (nose, gums, rectum, vagina) or into the retina or central nervous system due to thrombocytopenia
Ø infection (fever, oral and rectal ulcers, sore throat) without characteristic inflammation due to neutropenia (neutrophil deficiency).

Complications

A possible complication of aplastic anemia is:
life-threatening hemorrhage from the mucous membranes.


Diagnosis

The following test results help diagnose aplastic anemia:
Ø 1 million/µl or fewer RBC of normal color and size (normochromic and normocytic).
Ø RBCs may be macrocytic (larger than normal) and anisocytotic (excessive variation in size), with:
Ø very low absolute reticulocyte count
Ø elevated serum iron (unless bleeding occurs), normal or slightly reduced total iron-binding capacity, presence of hemosiderin (a derivative of hemoglobin), and microscopically visible tissue iron storage
Ø decreased platelet, neutrophil, and lymphocyte counts
Ø abnormal coagulation test results (bleeding time) reflecting decreased platelet count
Ø “dry tap” (no cells) from bone marrow aspiration at several sites
Ø biopsy showing severely hypocellular or aplastic marrow, with varied amounts of fat, fibrous tissue, or gelatinous replacement; absence of tagged iron (because iron is deposited in the liver rather than bone marrow) and megakaryocytes (platelet precursors); and depression of RBCs and precursors (erythroid elements).



Treatment

Effective treatment must eliminate an identifiable cause and provide vigorous supportive measures, including:
Ø packed RBC or platelet transfusion; experimental histocompatibility locus antigen-matched leukocyte transfusions
Ø bone marrow transplantation (treatment of choice for anemia due to severe aplasia and for patients who need constant RBC transfusions)
Ø for patients with leukopenia, special measures to prevent infection (avoidance of exposure to communicable diseases, diligent handwashing, etc.)
Ø specific antibiotics for infection (not given prophylactically because they encourage resistant strains of organisms)
Ø respiratory support with oxygen in addition to blood transfusions (for patients with low hemoglobin levels)
Ø corticosteroids to stimulate erythropoiesis; marrow-stimulating agents, such as androgens (controversial); antilymphocyte globulin (experimental); immunosuppressive agents (if the patient doesn't respond to other therapy); and colony-stimulating factors to encourage growth of specific cellular components.

Nursing Intervention
Ø Administer BT as ordered
Ø Administer medication as ordered
Ø Monitor and minimize risk of infection
Ø Monitor and prevent bleeding: use of electric razor, avoid IM inection, observe signs of bleeding
Ø Manage fatigue
Ø Teach client to prevent cause if possible











Sources: Brunner and Suddarth's textbook of Medical-Surgical Nursing, Frizzell- handbook of pathophysiology, Saunder's Manual of Nursing Care, Lippincott's Critical Care Challenges