Understanding the Complete Blood Count With Differential CONTINUING EDUCATION

CONTINUING EDUCATION
Understanding the Complete Blood Count
With Differential
Beverly George-Gay, MSN, RN, CCRN
Katherine Parker, MEd, RN
The complete blood count (CBC) with differential is one of the most
common laboratory tests performed today. It gives information
about the production of all blood cells and identifies the patient’s
oxygen-carrying capacity through the evaluation of red blood cell
(RBC) indices, hemoglobin, and hematocrit. It also provides information about the immune system through the evaluation of the white
blood cell (WBC) count with differential. These tests are helpful in
diagnosing anemia, certain cancers, infection, acute hemorrhagic
states, allergies, and immunodeficiencies as well as monitoring for
side effects of certain drugs that cause blood dyscrasias. Nurses in the
perianesthesia arena are frequently challenged to obtain and evaluate all or parts of the CBC as a part of the patient’s preoperative,
intraoperative, and postoperative assessments. An enhanced understanding of this laboratory test is essential to providing quality care.
© 2003 by American Society of PeriAnesthesia Nurses.
Objectives—Based on the content of this article, the reader should be able to (1) discuss the
physiology of blood cell production; (2) describe the usefulness of the complete blood count (CBC);
(3) identify and differentiate the roles of the different types of leukocytes; (4) describe the characteristics of red blood cell (RBC) structure and function; (5) discuss the indications for CBC as part of
the perianesthesia evaluation; and (6) explore the nursing indications related to CBC findings in the
perianesthesia setting.
Beverly George-Gay, MSN, RN, CCRN, is the Nurse Educator
for Critical Care for the Department of Education and
Katherine Parker, MEd, RN, is a Nurse Educator for the
Department of Education at the Virginia Commonwealth
University Health System, Richmond, VA.
Address correspondence to Beverly George-Gay, MSN, RN,
CCRN, 11824 Club Ridge Dr, Chester, VA 23836; e-mail
address: [email protected].
© 2003 by American Society of PeriAnesthesia Nurses.
1089-9472/03/1802-0007$35.00/0
doi:10.1053/jpan.2003.50013
96
THE COMPONENTS OF the complete blood
count (CBC) include a hemogram and differential white blood cell (WBC) count. The hemogram includes the enumeration of WBCs, red
blood cells (RBCs), and platelets; it also provides determinations of hemoglobin, hematocrit, and RBC indices (Table 1). The WBC count
with differential enumerates the different WBC
types. Together, the components of the CBC
evaluate primary diseases of the blood and bone
Journal of PeriAnesthesia Nursing, Vol 18, No 2 (April), 2003: pp 96-117
UNDERSTANDING THE CBC WITH DIFFERENTIAL
Table 1. Complete Blood Count
WBC
Differential white cell count
RBC
Hct
Women
Men 8 to 64 yr
Men 65 to 74 yr
Hgb
Women
Men
RBC indices
Mean corpuscular volume
Mean corpuscular Hgb
Mean corpuscular Hgb concentration
Platelet count
4,500 to 11,000/␮L
See Table 7
4.0 to 6.2 million/␮L
35% to 47%
39% to 50%
37% to 51%
12 to 16 g/dL
14 to 18 g/dL
82 to 93 ␮m3
26 to 34 pg
31% to 38%
150,000 to 400,000 ␮L
Data from Chernecky et al.1
marrow, which include disorders such as anemia, leukemia, polycythemia, thrombocytosis,
and thrombocytopenia. The CBC also evaluates
medical conditions that secondarily affect the
blood and bone marrow resulting in hematologic manifestations such as infection, inflammation, coagulopathies, neoplasms, and toxic
substance exposure. In many instances, specific
symptomatology of a medical condition may
not be present and hematologic changes on the
CBC may be the only finding present. These
changes prompt investigation to then identify
the medical condition.
To foster the understanding of the usefulness of
the CBC, the function and life cycle of the
various cells are introduced. Test indications,
characteristics, abnormal findings, and applications for the perianesthesia nurse are discussed.
Screening
“Screening” usually refers to testing patients
who are asymptomatic and have no physical
signs of disease. However, symptoms or physical signs may be very insensitive indicators of
some diseases. In the perianesthesia setting, the
use of the CBC as a screening tool constantly
undergoes revision. Factors such as the prevalence of disease in a population, the medical
and financial impact of missing a “problem,” the
cost per problem found, financial reimburse-
97
ment, and societal judgments determine when
screening tests are indicated. Medicare does not
support the use of the CBC as a screening tool;
to be cost effective, the CBC should only be
ordered when indicated.2
Indications
Preoperative evaluation should include a history, a physical examination, laboratory tests,
and an assessment of surgical risk to identify
coexisting diseases and complicating conditions. To decrease the risk of morbidity and
mortality in the perianesthesia setting, the CBC
is used to assist with the identification of patients who are at risk for complications of inadequate tissue perfusion during the procedure
and those with a possible infectious or inflammatory process.3,4
General indications for a CBC that are considered medically reasonable and are accepted by
Medicare are as follows:
● The hemogram should be evaluated for
any patient with signs, symptoms, or
conditions associated with anemia or
polycythemia. See Table 2 for specific
signs, symptoms, and conditions.
● The platelet count should be evaluated
for patients with findings or conditions
associated with increased or decreased
platelet production, destruction, or dysfunction (Table 2). The platelet count is
usually obtained as part of the hemogram.
● The WBC differential should be evaluated for any patient with signs, symptoms, or conditions associated with infections, inflammatory processes, bone
marrow alterations, and immune disorders (Table 2). The WBC count has also
been recently identified as a possible risk
stratification tool for mortality in acute
coronary syndromes.5
● A hemoglobin and hematocrit (H&H)
alone may be appropriate if there is only
a need to assess the oxygen-carrying ca-
GEORGE-GAY AND PARKER
98
Table 2. Signs, Symptoms, and Conditions That May Warrant a CBC or Parts of a CBC
Hemogram
Hemogram
Hemogram
(Findings Related to Anemia)
(Findings Related to Polycythemia)
(Findings Related to Platelet Dysfunction)
Fever
Chills
Ruddy skin
Conjunctival redness
Cough
Wheezing
Cyanosis
Clubbing of the fingers
Orthopnea
Heart murmur
Headache
Memory changes
Sleep apnea
Weakness
Pruritus
Dizziness
Excessive sweating
Massive obesity
Gastrointestinal bleeding
Paresthesias
Myocardial infarction
Stroke
Thromboembolism
Hepatomegaly
Splenomegaly
COPD
Diastolic hypertension
Congenital heart disease
Transient ischemic attack
Visual symptoms
Gastrointestinal bleed
Genitourinary tract bleed
Bilateral epistaxis
Thrombosis
Ecchymosis
Purpura
Jaundice
Petechiae
Fever
Heparin therapy
Suspected DIC
Shock
Preeclampsia
Massive transfusion
Recent platelet transfusion
Cardiopulmonary bypass
Renal diseases
Hypersplenism
Neurologic abnormalities
Viral or other infection
Thrombosis
Exposure to toxic agents
Excessive alcohol ingestion
Autoimmunue disorders
(SLE, RA)
Hepatomegaly
Splenomegaly
Lymphadenopathy
Pallor
Weakness
Fatigue
Weight loss
Bleeding
Acute or suspected blood loss
from injury
Hematuria
Hematemesis
Hematochezia
Positive fecal occult
Neuropathy
Malnutrition
Tachycardia
Known malignancy
Systolic heart murmur
Congestive heart failure
Dyspnea
Angina
Postural dizziness
Syncope
Nailbed deformities
Known malignancy
Jaundice
Hepatomegaly
Splenomegaly
Lymphadenopathy
Ulcers of the lower extremities
WBC With Differential
Fever
Chills
Sweats
Shock
Fatigue
Malaise
Tachycardia
Tachypnea
Heart murmur
Seizures
Altered consciousness
Pain such as headache
Abdominal pain
Arthralgia
Odynophagia
Dysuria
Redness/swelling of skin soft
tissue or joint
Ulcers of skin or mucous
membrane
Gangrene
Bleeding
Thrombosis
Pulmonary infiltrate
Jaundice
Diarrhea
Vomiting
Opportunistic infections as
oral candidiasis
Hepatomegaly
Splenomegaly
Lymphadenopathy
Abbreviations: COPD, chronic obstructive pulmonary disease; DIC, disseminated intravascular coagulation; SLE, systemic lupus erythematosus; RA,
rheumatoid arthritis.
Data from Centers for Medicare and Medicaid Services (CMS). Available at www.cms.hhs.gov/ncd/searchdisplay.asp?NSD_ID⫽61&NCD_vrsn_num⫽1.
pacity of blood before surgery for patients who do not have the previously
listed signs, symptoms, or conditions
(Table 2). The H&H may be helpful in
the intraoperative and postoperative
phase of care to assess and track for
blood loss but can be misleading because
of the intercompartmental fluid shifts
that occur during surgery and because of
the dilutional effects of crystalloid therapy.
Specific perianesthesia indications for the CBC
also take into account the level of surgical com-
plexity for a given procedure. In general, minor
procedures are those with very low risk of large
fluid shifts or significant blood loss. Minor procedures include soft tissue and eye procedures;
minor ortho; as well as ear, nose, and throat and
urologic procedures, among others. Keep in
mind that a “minor” procedure may turn into a
“moderately complex” procedure as complications are identified or develop. Major procedures are those that are often prolonged, often
with high risk of large fluid shifts or significant blood loss. They often involve major body
cavities. These include major abdominal, vascu-
UNDERSTANDING THE CBC WITH DIFFERENTIAL
99
Table 3. Levels of Surgical Complexity
Level 1
● Minimal risk to the patient independent of anesthesia
● Minimally invasive procedures with little or no blood loss
● Often performed in an office setting with the operating room principally for anesthesia and monitoring
● Includes breast biopsy, removal of minor skin or subcutaneous lesions, myringotomy tubes, hysteroscopy, cystoscopy, fiberoptic
bronchoscopy
Level 2
● Minimal to moderately invasive procedure
● Blood loss less than 500 mL
● Mild risk to patient independent of anesthesia
● Includes diagnostic laparoscopy, dilatation and curettage, fallopian tubal ligation, arthroscopy, inguinal hernia repair, laparoscopic lysis of
adhesions, tonsillectomy/adenoidectomy, umbilical hernia repair, septoplasty/rhinoplasty, percutaneous lung biopsy, extensive superficial
procedures
Level 3
● Moderate to significantly invasive procedure
● Blood loss potential 500 to 1,500 mL
● Moderate risk to patient independent of anesthesia
● Includes hysterectomy, myomectomy, cholecystectomy, laminectomy, hip/knee replacement, major laparoscopic procedures,
resection/reconstructive surgery of the digestive tract; excludes open thoracic or intracranial procedures
Level 4
● Highly invasive procedure
● Blood loss greater than 1,500 mL
● Major risk to patient independent of anesthesia
● Includes major orthopedic-spinal reconstruction, major reconstruction of the gastrointestinal tract, major vascular repair without postoperative
ICU stay
Level 5
● Highly invasive procedure
● Blood loss greater than 1,500 mL
● Critical risk to patient independent of anesthesia
● Usual postoperative ICU stay with invasive monitoring
● Includes cardiothoracic procedure; intracranial procedure; major procedure on the oropharynx; major vascular, skeletal, neurologic repair
lar, cardiothoracic, orthopedic, gynecologic/
urologic, head and neck, and neurologic procedures. Levels of surgical complexity from level 1
(minor) to level 5 (major) are described in Table
3. The American Society of Anesthesiologists’
(ASA) physical status classification system is another tool that can be used to assess the patient’s current health status and overall perioperative risk (Table 4). Although imprecise, it is a
way to predict the patient’s anesthetic/surgical
risks. The higher the ASA class, the greater the
risks.
For the patient who is asymptomatic and active
with a reliable benign history and undergoing a
minor procedure, an H&H assessment may be
all that is necessary or may not be indicated at
all. For those patients undergoing major procedures, a CBC with platelets should be completed. The CBC is indicated for elderly patients
(⬎65 years of age) as part of their preoperative
assessment because of the comorbidities associated with this age group as it may uncover
clinical problems that were not picked up on
physical examination.6 Patients classified with
an ASA score of 3 or greater should have a CBC
before their surgical procedure. In addition to
the general indications for CBC in Table 2,
situations requiring a CBC before a surgical
procedure are listed in Table 5.
Optimally efficient testing entails consideration
of a combination of factors including the age,
gender, and reliability of the patient; the surgical procedure; and the type of anesthesia being
used. Older or less reliable patients may be
more likely to have an unsuspected abnormality
picked up by a “screening” test. Major procedures are associated with significant physiologic
stress. Existing medical conditions, which may
GEORGE-GAY AND PARKER
100
Table 4. ASA Classification
Class
Description
Examples
1
2
A normal healthy patient with no systemic illness
A patient with well-controlled systemic illness, but
without functional restrictions
A patient with significant degree of systemic effects that
limits activities
Healthy with good exercise tolerance
Well-controlled hypertension, diabetes, without systemic effects; no
evidence of COPD, anemia, or obesity
Controlled heart failure, stable angina, or history of myocardial
infarction; diabetes with systemic sequela; uncontrolled
hypertension; morbid obesity
Unstable angina, symptomatic heart failure, renal failure requiring
dialysis
3
4
5
6
E
A patient with severe systemic illness associated with
significant dysfunction and a constant potential threat
to life
A patient in critical condition, who is at substantial risk
of death within 24 hours with or without operative
procedure
A patient declared brain dead undergoing organ removal
for donor purposes
This symbol is added to any of the above classes to
designate an emergency
Multiple organ dysfunctions, hemodynamically unstable sepsis,
poorly controlled coagulopathy
Data from www.asahq.org, www.nurse-anesthesia.com/generalanesthesia.htm, and www.vh.org/adult/provider/anesthesia/proceduralsedation/
asapatientclassification.html. Accessed December 2002.
be of little concern during a brief and minor
procedure, may cause problems during and after a long and complex surgery. Preoperative
evaluation should reflect this need for an increased level of preparedness and monitoring.
Timing of the CBC
A CBC completed within 2 months of a procedure is acceptable unless a change is suspected
as a consequence of disease, medication, or
treatment. Repeat testing is indicated for abnormal results or for patients with normal results
who have conditions in which there is a conTable 5. Situations Requiring Preoperative CBC
Evaluation
● Abnormal bleeding (⫹ platelets)
● Heavy ETOH use (⫹ platelets)
● Potentially toxic medications (eg, which cause bone marrow
depression)
● Infection (⫹ differential)
● ASA score of ⱖ3
● Vascular surgery
● Anticipate prosthetic device or hardware placement
● Anticipate ⬎500 mL blood loss, invasive monitoring, or ICU (⫹
platelets)
● Level 4 or 5 surgery
Abbreviation: ETOH, alcohol.
tinued risk for the development of hematologic
abnormalities.
Blood
The average adult has approximately 5.5 L of
blood, consisting of plasma and cells. Plasma
makes up 55% of the blood components and
consists of proteins, water, and some waste
products. Cells, of which there are 3 main
types, make up the other 45%. They consist of
(1) WBCs (leukocytes), of which there are several subtypes; (2) RBCs (erythrocytes); and (3)
platelets (thrombocytes).
All blood cells are produced in the bone marrow from a mother cell called the pluripotential
(multipotential) stem cell (PSC). This PSC undergoes stages of differentiation until it becomes committed to either the erythrocyte,
thrombocyte, or one of the leukocyte subtypes
(Fig 1). Under normal conditions, only mature
blood cells should be found circulating in the
blood. Alterations in the production and function of these blood cells provide information
about the patient’s diagnosis, prognosis, re-
UNDERSTANDING THE CBC WITH DIFFERENTIAL
Fig 1.
101
Blood cell differentiation. Reprinted with permission from Garrett.16
sponse to therapies, and their recovery. The
laboratory procedure that gives us this information is the CBC.
Obtaining the Blood Sample
The blood sample is obtained via venipuncture
and is collected in a lavender top tube, which is
the nationally accepted color standard. The
blood sample will remain useable for analysis at
room temperature for up to 10 hours, after
which time the sample deteriorates and is not to
be considered reliable. The blood sample can
also be kept refrigerated and remain useable for
as long as 18 hours. The sample should never be
frozen. The patient should ideally be at rest for
10 to 15 minutes before obtaining the sample.
Automated electronic devices perform enumeration of the blood cells. Blood cell counts are
reported per microliter. Morphology is determined by stained smears.
The WBC Count With Differential
The WBC count with differential determines
the total number of WBCs (also called leukocytes) with a percentage of each type. The
major function of the WBC is to defend the
body against organisms and injury. WBCs are
the main players in infectious/inflammatory and
immune responses. To appreciate the role of
the WBC, a brief review of inflammation/infection and immunity is provided.
Inflammation and Infection
The inflammatory process is triggered by cell
injury, which can be caused by a variety of
conditions such as trauma, burns, ischemia, surgery, snakebite, caustic chemicals, and extremes in heat and cold, as well as infectious
microorganisms. It is important to remember
that although all infections are accompanied by
inflammation, not all inflammation is accompa-
GEORGE-GAY AND PARKER
102
nied by infection. In the perianesthesia setting,
surgical incisions would be the most common
trigger of inflammation.
Any damage to the vascular endothelium or the
mast cell will trigger an inflammatory response,
which is orchestrated by inflammatory cytokines. Cytokines are hormonelike protein mediators responsible for the cell-to-cell communication that regulates local and systemic
physiologic and pathologic interactions. The
cells of the vascular endothelium have been
recently identified as a major player in the
inflammatory process.
The mast cell (cellular bag of granules) is another important activator of the inflammatory
response. Mast cells are found in connective
tissues intimately surrounding blood vessels and
in mucosal surfaces. Once endothelial or mast
cells are injured or damaged, they release inflammatory cytokines, which orchestrate the
manifestations of inflammation.
Manifestations of inflammation include a short
period of vasoconstriction to limit bleeding followed by vasodilation. Vasodilation increases
blood flow to the area, bringing nutrients and
large amounts of WBCs. Vasodilation also results in hyperemia (redness and warmth). Another manifestation is increased capillary permeability, which allows for the immigration of
WBCs from the blood vessel to the interstitial
spaces where they can phagocytize unwanted
organisms and debris. The WBCs also release
cytokines to call more WBCs to the area and
to perpetuate the inflammatory response. Increased capillary permeability also allows for
the exudation of plasma and plasma proteins
resulting in edema. The edema may cause pressure on the nearby nerves resulting in pain.
Immunity
In the immune process, specific types of WBCs
respond to specific microorganisms. Immunity
can be classified as either cell mediated or humoral. Cell-mediated immunity involves specific types of WBCs called T lymphocytes or T
cells. These T cells will attack host cells within
tissue that have been infected by microorganisms, as well as cancer cells. Cell-mediated immunity provides primary defense against viruses, fungi, slow-growing bacteria, and tumors.
Humoral immunity or antibody-mediated immunity involves the production of antibodies
by B cells and mainly occurs in body fluid such
as plasma and lymph. Humoral immunity provides primary defense against bacteria. Cell-mediated immunity is initiated frequently first, but
both cell-mediated and humoral immunity can
be initiated simultaneously. Both types of immunity require specific types of WBCs to be effective.
White Blood Cells
Although the medical term for the WBC is leukocyte, the term WBC will be used in this article
for the sake of simplicity. WBCs can be divided
into 2 main groups: phagocytes and immunocytes. Phagocytes are WBCs that have the capability to attach to, engulf, and release enzymes
to kill and degrade unwanted microorganisms
and debris. The WBCs that are phagocytic include neutrophils, eosinophils, basophils, and
monocytes. Immunocytes include the lymphocytes, WBCs that drive the immune response.
A more common manner in which WBCs are
divided is by the presence of granules in the
cytoplasm. Those WBCs that contain granules
in their cytoplasm are neutrophils, eosinophils,
and basophils. WBCs that do not contain granules in their cytoplasm include monocytes and
lymphocytes (Fig 2). For the purpose of this
discussion, WBCs will be divided into granulocytes and nongranulocytes.
Granulocytes
Granulocytes get their name from the granules
present in their cytoplasm. These granules contain biochemical mediators that serve inflammatory and immune functions. Granulocytes also
contain enzymes in their cytoplasm capable of
destroying microorganisms and catabolizing debris ingested during phagocytosis. They take
about one week to develop in the bone mar-
UNDERSTANDING THE CBC WITH DIFFERENTIAL
Fig 2.
103
Granulocytes and nongranulocytes. Reprinted with permission from Catalano.8
row. They circulate for only about 6 to 12 hours
in the blood stream and 2 to 3 days after entering the tissue.
Neutrophils
Neutrophils are a type of granulocyte and are
mature cells that account for more than half of
all the WBC subtypes in circulation. They are
also called segmented neutrophils (segs) or
polymorphonuclear neutrophils (PMNs) or
polys because the nucleus of these cells consists
of 3 to 5 lobes connected by thin strands.
Highly motile, these cells are the first to arrive
(usually within 90 minutes) in response to acute
inflammation or infection; they migrate out of
the capillaries and into the inflamed tissue site
in a process called diapedesis or emigration.
The neutrophils ingest microorganisms and debris and then die, forming purulent exudate,
which is removed by the lymphatics or through
the epithelium.
When there is an increased demand for neutrophils, as in response to acute infection, immature neutrophils may be released from the bone
marrow. These immature cells have unseg-
mented nuclei that resemble bands or rods.
Thus, immature neutrophils are called bands or
stabs. They are normally found only in very low
percentages in circulating blood.
Eosinophils
Eosinophils function principally to ingest and
kill multicellular parasites. They are also effective in detoxifying antigen-antibody complexes
that form during allergic reactions. People with
chronic allergic conditions such as atopic rhinitis and extrinsic asthma typically have elevated
circulating eosinophil counts. Eosinophils are
believed to play a role in downregulating hypersensitivity responses by neutralizing histamine,
inhibiting mast cell degranulation, and inactivating
slow-reacting subtances (SRS) of anaphylaxsis.
Basophils
Basophils are associated with systemic allergic
reactions. Similar to mast cells, basophils have
granules that contain proinflammatory chemicals such as histamine, serotonin, bradykinin,
and heparin. They release their granules in response to stimulation by immune cells. Basophils circulate in the blood stream, whereas
GEORGE-GAY AND PARKER
104
mast cells are found in connective tissue. The
average basophil has a life span of days, but the
mast cell can live weeks to months.
Nongranulocytes
Nongranulocytes, as mentioned earlier, are
WBCs that do not have granules in their cytoplasm. Inclusive in this group are monocytes
and lymphocytes.
Monocyte/Macrophage
Monocytes are the largest of the WBCs and are
young cells found freely circulating in blood or
en route to a tissue location. Once the young
monocyte leaves the blood stream and enters
tissue, it transforms into a mature macrophage.
Macrophages live within tissue spaces in widespread locations. These cells have different
names related to the particular tissue in which
they are found, ie, the Kupffer cells are macrophages that live in the liver. Because of the
complex connection of these cells to the blood
stream and the tissue, monocytes and macrophages are described as one system, called the
mononuclear phagocyte system. Table 6 identifies specific macrophages and the particular
tissue in which they are found.
Macrophages arrive on the scene in about 5
hours after injury and become the predominant
leukocyte within 48 hours. Because macrophages lie within the tissue spaces, they are
usually the first cell to engulf and process the
antigen and present it to the immune cells
(lymphocytes) in a manner that will stimulate a
specific immune response to that particular antigen. In other words, the macrophage, in a
special process, can destroy the organism while
keeping its cell surface markers to give to the
lymphocytes so that they can always identify
that particular organism and mount a specific
defense against it.
Lymphocytes
Lymphocytes are also nongranulocytes and are
responsible for immune responses to specific
organisms. They are the most numerous circulating WBC after neutrophils. There are 2 major
Table 6. Mononuclear Phagocyte System
Macrophage
Kupffer cells
Alveolar macrophage
Histocytes
Pleural and peritoneal macrophages
Microglial cells
Osteoclasts
Mesangial
Langerhans
Dendritic cells
Tissue
Liver
Lung
Connective tissue
Serous cavities
Nervous system
Bones
Kidneys
Skin
Lymphoid tissue
classes of lymphocyte: the T lymphocyte (T
cell) and the B lymphocyte (B cell). Both T and
B cells can be sorted into subtypes based on
characteristic surface molecules on them called
cluster of differentiation (CD). Cluster of differentiation surface molecules assist in defining
the function of the different lymphocyte subtypes.
T cells. The T cell matures in the thymus and
is responsible for cell-mediated immunity as
previously described. The T cell can also stimulate the B cell, triggering humoral/antibody-mediated immunity (also previously described). The T cell has several subtypes that
can be divided into regulator or effector cells.
Regulator T cells are so called because of their
regulatory functions of turning on or off the
immune response. There are 2 types of regulator T cells: the helper T cell and the suppressor
T cell. The helper T cell is considered the
master switch of the immune system. These
cells are surveyors, and when a specific antigen
is presented to them, they release mediators
that influence and stimulate the production of
other immune cells including B cells. Helper T
cells have CD4 surface molecules on them.
Suppressor T cells suppress the immune response once the infection is controlled.
Effector cells are T cells that have a direct
action. The 2 types of effector cells are the
cytotoxic T cell and the memory T cell. The
cytotoxic T cell carries the CD8 molecule on
its surface. It attaches to identified infected
UNDERSTANDING THE CBC WITH DIFFERENTIAL
cells and cancer cells and releases enzymes to
destroy these cells. Cytotoxic T cells are particularly effective at destroying virally infected cells, foreign cells, and mutant cells.7
Memory T cells are produced after invasion
by a specific organism. They provide longlasting immunity against that particular organism and then wait to rapidly respond to a
second attack by the same organism. Their
average survival rate is about 5 years.
B cells. The B cell matures in the bone marrow and is responsible for humoral, also known
as antibody-mediated, immunity. When an antigen (foreign body) is presented to the B cell,
either by a macrophage or helper T cell, the B
cell becomes activated to produce plasma cells.
The plasma cell then releases antibodies specific for that specific antigen.
Natural killer cells. There is a third class of
lymphocyte that does not have T- or B-cell
markers called natural killer (NK) cells. NK
cells are nonspecific and can therefore respond to a variety of antigens. They are very
effective against tumor cells and virally infected host cells.
Evaluating the WBC Count With
Differential
The white count differential is expressed in
cubic millimeters and in percentages. See Table
7 for normal values of the differential.
Elevated Counts/Levels
An elevation in the total WBC count (WBC
⬎11,000/␮L) is called leukocytosis. Leukocytosis most commonly identifies infection, tissue
inflammation, or tissue necrosis associated with
disorders such as acute myocardial infarction,
burns, gangrene, leukemia, radiation exposure,
extremes in heat or cold, or lymphoma.8 A
WBC count of greater than 10,000 has been
associated with increased mortality rates in patients with acute coronary syndromes and is
now being used by some as a predictor of
adverse outcomes in these patients.5,9 The role
of inflammation in the pathogenesis of ischemic
105
Table 7. Normal White Blood Cell Counts
Cell Type
Absolute (␮L)
Differential (%)
Total WBC
Granulocytes
Neutrophils
Segmented
Bands
Eosinophils
Basophils
Nongranulocytes
Monocytes
Lymphocytes (Immunocytes)
T cells
B cells
Natural killer
4,500-11,000
100
3,000-7,000
2,800-5,600
150-600
50-400
25-100
60-70
54-68
3-5
1-5
0-0.75
100-800
1,000-4,000
800-3,200
100-600
50-400
3-7
25-33
80*
10-15*
5-10*
*Percent of total lymphocyte count.
stroke is also currently being studied. Patients
with elevated WBC counts during the stroke
event have been found to have a greater relative
risk of subsequent ischemic stroke than did
those with lower WBC counts.10 Thus, an elevated WBC count is being looked at as a predictor of ischemic stroke. Severely elevated total
WBC counts (⬎100,000), as seen in leukemia,
promotes circulatory sludging and increased
blood viscosity. Venous thromboembolism
(VTE) prophylaxis is required in these situations.11
Leukocytosis may also occur in response to
physical and emotional stressors such as overexertion, seizures, anxiety, anesthesia, and epinephrine administration. With stress leukocytosis, however, the WBC will return to normal
within an hour. Certain medications such as
corticosteroids, lithium, and ␤-agonists may also
cause leukocytosis.
In the preoperative setting, an elevation in the
WBC count frequently causes postponement or
cancellation of a surgical procedure for further
evaluation. If the total WBC count is elevated,
the differential and the patient should be evaluated and the surgeon and anesthesia provider
notified. The patient’s medication record and
recent history should also be closely reviewed
to discriminate among stress leukocytosis, drug
administration, recent ischemia, myocardial in-
GEORGE-GAY AND PARKER
106
farction, or infection as possible causes. An
evaluation of the differential will allow for further discrimination.
Neutrophilia
Neutrophilia is an increase in the total neutrophil count (including both segs and bands).
Because neutrophils account for greater than
96% of all granulocytes, neutrophilia may also
be referred to as granulocytosis. It is the most
common cause of elevated WBC count.
Neutrophilia is most commonly caused by an
acute bacterial infection. Neutrophil counts will
rise 4 to 6 hours after an invasion by microorganisms. If findings do not suggest infection, a
myeloproliferative disorder may be the cause.
Myeloproliferative disorders include polycythemia vera and chronic myelocytic leukemia,
which increases stem cell proliferation in the
bone marrow. Elevations in neutrophil counts
are also associated with obesity and cigarette
smoking. Additionally, neutrophil counts can
increase after the stress of surgery, but in this
case, counts will quickly return to normal if no
infection is present.12
An elevation in segmented neutrophils is considered a “shift to the right.” During tissue
breakdown from injuries such as burns, arthritis, myocardial infarction, hemorrhage, or electric shock, neutrophils are called in to clean up
the damaged or dead cells. In this case, reserve
mature neutrophils are called in, thereby increasing the neutrophil count without calling in
the immature cells. A severely elevated neutrophil count will be seen in certain pathologic
conditions causing the neutrophils to become
hypermature. Hypermature segmented neutrophils are those in which nuclear segmentation is
impaired, and there is an increased number of
segments (⬎5). This is seen in liver disease,
Down’s syndrome, and megaloblastic and pernicious anemia.
An elevation in bands is referred to as a “shift to
the left,” which means that there is an increased
number of immature neutrophils released from
the bone marrow and circulating in the blood.
This occurs in response to overwhelming infection when the numbers of mature neutrophil
reserves have been depleted. Clinically, the
term shift to the left specifies an acute bacterial
infection has depleted the normal reserves of
mature neutrophils, and the bone marrow has
had to resort to releasing immature ones.
Generally, a shift to the right can be considered
a result of tissue damage or necrosis, whereas a
shift to the left can be considered a result of an
overwhelming infection. As mentioned earlier,
however, an increased neutrophil count is the
most common cause of an elevated WBC count.
Although not common, the other types of
WBCs can also give rise to an elevation in WBC
count.
Eosinophilia
Eosinophilia identifies an increase in the eosinophil count. This count has been found to
increase with parasitic infections such as toxoplasmosis and with infections by gastrointestinal parasites. Elevations have also been noted
with bronchoallergic reactions such as asthma,
allergic rhinitis, and hay fever. Eosinophilia has
also been noted with skin rashes.
Basophilia
Basophila is the most uncommon cause of an
elevated WBC count. Increased basophil counts
have been found in patients with hypersensitivities compared with the general population.
These patients should have a thorough allergy
history obtained before any surgical procedure.
Monocytosis
Monocytosis, or increased monocyte counts,
occur late during the acute phase of infection
and with chronic infections such as tuberculosis and subacute bacterial endocarditis (SBE).
The patient with an elevated monocyte count
should be evaluated for further evidence of
these possible conditions before surgical procedures. Monocytosis also occurs with Hodgkin’s
disease, multiple myeloma, some leukemias,
and systemic lupus erythematosus.
UNDERSTANDING THE CBC WITH DIFFERENTIAL
Lymphocytosis
Lymphocytosis occurs in acute viral infections
such as mononucleosis, cytomegalovirus, measles, mumps, and rubella. Elevated lymphocyte
counts will also be noted in patients during
chronic infections and early in human immunodeficiency virus (HIV) disease. Severely elevated
levels would be seen with chronic lymphocytic
leukemia (CLL).13
Decreased Counts/Levels
A decrease in the total WBC count (⬍4,500/
␮L) is called leukopenia. Leukopenia results from decreased production of total
WBCs in the bone marrow or increased
destruction of WBCs. Total counts will usually fall with radiation therapy and chemotherapy as the bone marrow is depressed.
WBC counts fall to the lowest points 7 to 14
days after induction of most chemotherapeutic agents and will then begin to increase as the bone marrow normalizes. Patients receiving chemotherapy should have
their WBC counts closely monitored. If leukopenia is present, the patient should be
closely evaluated and the surgeon and anesthesia provider notified. Blood cultures, sinus and chest x-rays, and urine and stool
cultures may also be necessary. As with an
elevated WBC count, an evaluation of the
differential will allow for further discrimination.
Neutropenia
Neutropenia is clinically defined as a neutrophil
count of less than 2,000/␮L. Again, keep in
mind that the majority of all granulocytes (neutrophils, eosinophils, and basophils) are neutrophils, which account for greater than 96% of all
granulocytes. Because of this, the terms granulocytopenia (decreased granulocyte count) and
neutropenia (decreased neutrophil count) are
used interchangeably in the clinical setting.
Neutropenia can occur with severe prolonged
infections that exhaust the bone marrow supplies, where the production cannot keep up
with the demand. It can also be because of
increased destruction of WBCs that can occur
107
with increased splenetic pooling and destruction as seen in hypersplenism or splenomegaly.
Additionally, a variety of drugs can cause neutropenia such as certain antimicrobials, nonsteroidal anti-inflammatory drugs, and some
analgesics. Other drugs include certain tricyclic
antidepressants, anticonvulsants, antithyroids,
cimetidine, and antidysrhythmic agents. Patients with counts of less than 2,000/␮L may be
unable to mount an adequate defense when
challenged by infection. These patients should
be protected from cross contamination and
should not undergo surgical procedures when
at all possible.
Severe neutropenia is defined as a neutrophil
count of less than 500/␮L. This is also referred
to as agranulocytosis because a count this low
is almost equivalent to not having any granulocytes at all. Neutrophil counts below 500/␮L
predispose the patient to serious bacterial infection and opportunistic infections of the skin,
mouth, pharynx, and lungs. As counts fall below 100, the chance of gram-negative and grampositive sepsis and fungal infections increases
dramatically.
Other Reductions
Reductions in eosinophil (eosinopenia) and basophil (basopenia) counts are uncommon because so few of these cells normally circulate in
the blood. Monocytopenia is a rare occurrence
but has been seen with glucocorticoid therapy,
hairy-cell leukemia, and aplastic anemia. Lymphopenia, a decreased lymphocyte count, occurs normally as a person ages. Lymphopenia is
most significant with HIV and acquired immunodeficiency syndrome (AIDS). A CD4 count
(remember the helper T lymphocyte has the
CD4 marker on its surface) of less than 200 is
one indicator of conversion from HIV to AIDS.
Nursing Implications
The perianesthesia nurse should keep in mind
that the WBC count is a part of a larger picture.
One must look at the whole patient and put all
information into proper perspective.14 Trends
can help to identify truly abnormal findings.
GEORGE-GAY AND PARKER
108
The surgeon and anesthesia provider should be
notified for elevations in WBC count of greater
than 11,000, or decreases less than 4,500. Recognize that minor alterations may be a reflection of age. One must determine whether the
patient has enough neutrophils to combat and
protect from infection when counts are low.
Leukocytosis commonly signals infection,
whereas leukopenia indicates bone marrow depression that may result from viral infections or
toxic reactions. Be alert to signs and symptoms
of infection, especially in patients with invasive
lines, indwelling urinary catheters, surgical
drains, and incision sites. General signs of infection include fatigue, fever, a change in level of
consciousness (LOC), dehydration, pharyngitis,
or hypotension. More frequent temperature
monitoring may be indicated.
Neutropenic precautions should be considered
for severely immunocompromised patients and
those with severe neutropenia. Neutropenic
precautions include the following:
● Meticulous care of all intravenous lines
and indwelling catheters
● Avoiding raw and uncooked foods, in-
●
●
●
●
●
cluding fresh fruits and vegetables because of microorganism contamination
from soil
Avoiding crowds
Avoiding children who have just been
vaccinated
Avoiding indiscriminate use of antipyretics
Avoiding steroid use, because they impede mediator functions blocking inflammation; thus, the patient will not
show the true signs of inflammation or
infection
Reporting a temperature greater than
38°C (100°F), chills, sore throat, diaphoresis, or dysuria
Be suspect of the potential for septicemia in
patients with a neutrophil count of less than
500/␮L. Moving forward with any surgical pro-
cedure in patients with counts of less than
2,000/␮L should be considered only for emergent situations. Also note that patients with
WBC counts greater than 100,000 are at an
increased risk for thrombosis because of increased blood viscosity. Ensure adequate fluid
intake and VTE prophylaxis. See Table 8 for
recommendations regarding VTE prophylaxis in
the surgical patient. Patients with recent ischemic stroke or myocardial infarction, and a concomitant elevation in WBC count may be at
increased risk for mortality or morbidity.
Erythrocyte (RBC) Studies
The main function of the RBC is to carry oxygen
(O2), which it picks up in the lungs, to the cells
of the body, and to transport carbon dioxide
from the cell to the lungs for excretion. Essentially, RBCs are containers for hemoglobin
(Hgb). Hgb is the oxygen-carrying protein of the
RBC, which accounts for approximately 90% of
the cells’ dry weight. Information about the
RBC is obtained with a CBC but can also be
obtained separately with a hemogram.
RBCs are produced at a rate of 2 million cells
per second, or 35 trillion cells per day. The
average life span is approximately 120 days. The
mature RBC is a biconcave disk. This unique
shape allows for a greater surface area for oxygen to combine with Hgb. RBCs have no nucleus, and therefore cannot divide. Like the
WBC, the RBC is derived from the PSC in the
bone marrow (Fig 1). The production of RBCs
by the bone marrow is stimulated by low oxygen levels in peritubular cells of the kidney in a
process called erythropoiesis. During erythropoiesis, renal erythropoietic factor (an enzyme)
is secreted in response to peritubular cell hypoxia. This factor interacts with a plasma protein to form erythropoietin, a hormone that
circulates to the bone marrow to stimulate stem
cells to produce more RBCs. RBCs are released
from the bone marrow as reticulocytes and
then become mature RBCs in one day.
Vitamin B12, folic acid, and iron are also needed
for RBC metabolism. Vitamin B12 and folic acid
UNDERSTANDING THE CBC WITH DIFFERENTIAL
109
Table 8. Venous Thromboemolism Prophylaxis
Type of Surgical Procedure
General surgery
Minor procedure without additional risk factors
in patients less than 40 years of age
Minor procedure with additional risk factors in
patients less than 40 years of age
Minor procedure in patients 40 to 60 years of age
without additional risk factors
Major surgery in patients without additional risk
factors ⬎40 years of age
Nonmajor surgery with additional risk factors in
patients ⬎60 yr
Major surgery in patients ⬎40 yrs or with
additional risk factors
Major surgery in patients ⬎40 with multiple risk
factors
Gynecologic surgery
Major surgery for benign disease without
additional risk factors
Extensive surgery for malignancy
Urologic surgery
Transurethral surgery or other low-risk procedure
Major open urologic procedure
Highest risk patients
Orthopedic surgery
Elective total hip replacement
Elective knee replacement
Hip fracture surgery
Neurosurgery, trauma, & acute spinal cord injury
Intracranial neurosurgery
Trauma
Acute SCI
Medical conditions
Acute myocardial infarction
Ischemic stroke
General medical conditions with risk factors
Recommended Prophylaxis
Low risk
Early ambulation
Moderate risk
LDUH every 12 hours starting 1 to 2 hours before surgery
LMWH first dose generally before surgery
ES or IPC device to start immediately before procedure and continue until fully
ambulatory
High risk
LDUH every 8 hours, LMWH, or IPC device
Very high risk
LDUH, LMWH, combined with mechanical method (ES or IPC device)
LDUH twice a day, alternatively, LMWH or IPC device started just before surgery
and continued at least several days postoperatively
LDUH three times a day
For additional protection use LDUH plus ES or IPC device
Prompt mobilization
LDUH, ES, IPC device, or LMWH
LDUH or LMWH and ES with IPC device
LMWH started 12 hours before surgery, may be started 12 hours postoperatively;
ES or IPC device should be added
LDUH, aspirin, dextran, and IPC alone are not recommended
LMWH or adjusted dose warfarin to maintain an INR of 2 to 3
IPC is effective if used optimally; LDUH not recommended
LMWH or adjusted dose warfarin
IPC with or without ES
LDUH or LMWH postoperatively are alternatives with a concern about
intracranial hemorrhage
For high-risk patients the combination of mechanical and pharmacologic
prophylaxis may be more effective
LMWH started as soon as possible if no contraindications (risk of bleeding); if
contraindicated start ES and/or IPC
IVC filter is recommended if proximal DVT is seen and anticoagulation is
contraindicated; IVC filter is not recommended for primary prophylaxis
LMWH started as soon as possible; LDUH, ES, and IPC not recommended when
used alone. ES and IPC may benefit when used in combination with LMWH or
LDUH, or if anticoagulants are contraindicated.
For most patients, prophylaxis with LDUH or therapeutic doses of IV heparin are
recommended.
LDUH, LMWH or the heparinoid, danaparoid; if anticoagulation is
contraindicated, use ES or IPC device
LDUH or LMWH
NOTE. Risk factors include previous VTE, increasing age, major surgery, cancer, obesity, major trauma, lower extremity or hip fracture, pregnancy,
history of myocardial infarction, stroke, heart failure, hormone replacement therapy, prolonged immobilization, burns, paralysis, hypercoagulable
states, indwelling femoral vein catheter, inflammatory bowel disease.
Abbreviations: LDUH, low-dose unfractioned heparin; LMWH, low molecular weight heparin; ES, elastic stocking; IPC, intermittent pneumatic
compression; IFC, inferior vena cava; DVT, deep vein thrombosis; SCI, spinal cord injury.
Data from Geerts WH, Heit JA, Clagett GP, et al: Prevention of venous thromboembolism, Sixth ACCP Consensus Conference on Antithrombotic
Therapy. Chest 119:132s-175s, 2001, and Hirsh J: Managing venous thromboembolism: Methodology for achieving positive outcomes. CME-Today
(Cardiopulmonary and Critical Care) 1:11-15, 2002.
GEORGE-GAY AND PARKER
110
Table 10. Hemoglobin
are needed for cell growth, DNA synthesis, and
for reproduction. Iron is needed for Hgb synthesis.
Several tests are done to determine the adequacy of the RBC structure and function, the
RBC count, Hgb concentration, hematocrit
(Hct), and RBC indices.
Erythrocyte (RBC) Count
The RBC count is the part of the CBC that
determines the number of RBCs found in a
cubic centimeter of blood. It is also expressed
in International Units, which is the number of
RBCs per liter of blood. Electronic automated
devices perform the test. Although the total
RBC count does give information about the
oxygen-carrying capacity of blood, Hgb and Hct
provide more precise information. See Table 9
for normal values.
Hemoglobin
As previously mentioned, Hgb’s primary function is to carry oxygen to the cells and remove
carbon dioxide from the cells. Hgb is a complex
protein made up of heme and globin. It is
produced in the immature RBC. Synthesis stops
once the cell matures in circulation. There are
approximately 300 million molecules of Hgb in
one RBC. Hgb is measured in grams per deciliter. See Table 10 for normal values.
Adult male
Adult female
Conventional Units
SI Units
13.5-18 g/dL
12-16 g/dL
135-180 g/L
120-160 g/L
is considered fully saturated when it contains 4
oxygen molecules. Hgb saturated with oxygen
is called oxyhemoglobin. One should note that
oxygen saturation is a measure of the amount
of oxygen combined with Hgb in the blood and
should not be confused with the partial pressure of oxygen (PO2), which is the amount of
oxygen dissolved in plasma. Hgb also functions
as a buffer for extracellular fluid and is capable
of accepting hydrogen (H⫹) ions to prevent the
buildup of H⫹ ions in the blood.
Hematocrit
Hct represents the percentage of the total volume of RBCs relative to the total volume of
whole blood in a sample. “Hematocrit” means
“to separate blood.” With today’s method of
automated cell counting, Hct is calculated
rather than centrifuged. See Table 11 for normal
values. The surgeon and anesthesia provider
must be notified for values of less than 20% or
greater than 60%. Swelling of the RBC secondary to hyperglycemia or hypernatremia may
produce an elevated Hct. Excessively elevated
WBC counts may also alter the Hct.
The heme portion contains iron atoms and the
red pigment, porphyrin. The heme portion is
responsible for the red color of blood. When
the RBC is saturated with oxygen, the red color
is brightest. The globin portion is made up of 4
amino acid chains. One heme molecule attaches to each of the 4 amino acid chains.
Therefore, each Hgb molecule has 4 heme sites
that can bind with 4 oxygen molecules. A Hgb
Hgb and Hct levels parallel, in that Hct levels are
3 times the Hgb level. To estimate values, you
would divide the Hct by 3 to estimate the Hgb,
and multiply the Hgb by 3 to estimate the Hct.
This relationship is altered if RBCs are abnormal
in size or shape or if the synthesis of Hgb is
defective.
Table 9. RBC Count
Table 11. Hematocrit
Adult male
Adult female
Conventional Units
SI Units
4.6-6.2 million/␮L
4.2-5.4 million/␮L
4.6-6.2 ⫻ 1012/L
4.2-5.4 ⫻ 1012/L
The RBC count, Hct, and Hgb are closely related. Alterations in one are usually associated
Adult male
Adult female
Conventional Units
SI Units
40%-54%
38%-47%
0.40-0.54
0.38-0.47
UNDERSTANDING THE CBC WITH DIFFERENTIAL
with alterations in the other. As such, increases
and decreases in each are discussed together.
Increased Levels
An increase in the number of RBCs can be
described as either erythrocytosis or polycythemia. In the clinical setting, the terms are frequently used as synonyms. The term erythrocytosis, however, more accurately defines an
elevated RBC count, whereas the term polycythemia more accurately refers to a specific
group of disorders. These disorders can be described as either primary polycythemia or secondary polycythemia.
Primary polycythemia (vera) is an increase in
the number of RBCs secondary to a relatively
rare myeloproliferative disease of the bone marrow involving the excessive production of red
cell precursors. Secondary polycythemia describes an increase in RBCs as a physiologic
compensatory mechanism (via erythropoietin)
for decreases in oxygen delivery as seen in
cardiopulmonary diseases such as congestive
heart failure (CHF), cardiovascular malformation, and chronic obstructive pulmonary disease, as well as in those living in high altitudes.
Dehydration also causes a relative increase in
RBC, Hgb, and Hct because of a decrease in
plasma volume. This is clinically referred to as
hemoconcentration and may be seen frequently
in the perianesthesia setting. Other causes include excessive exercise, anxiety, pain, and certain drugs such as gentamycin and methyldopa
(Aldomet), as well as with renal and liver tumors.
Decreased Levels
Decreased levels of RBCs, Hgb, and Hct are
associated with hemodilution and anemia. Hemodilution occurs as plasma volume increases
from fluid therapy. Anemia is a reduction in the
total number of circulating RBCs or a decrease
in the quality or quantity of Hgb or in the
volume of packed cells (Hct). Nutritional anemias or anemias caused by chronic diseases are
caused by iron, folate, and vitamin B12 deficien-
111
cies. Acute anemias are caused by blood loss
due to hemorrhage, or by RBCs being destroyed
faster than the normal bone marrow can replace them. Extreme RBC destruction occurs in
conditions such as hemolytic or type II hypersensitivity blood transfusion reactions (hemolysis of RBCs because of ABO incompatibility).
Other conditions causing anemia are those that
alter erythropoiesis such as renal failure, chemotherapeutic agents (by suppressing the bone
marrow), and leukemia. Hemoglobinopathies
(such as sickle cell anemia) and the thalassemias
are also causes of anemia. Age also plays a role
in anemia because there is a tendency for lower
values in people over the age of 50. Lastly,
during pregnancy there is a relative anemia as
the normal number of RBCs becomes diluted
from the increase in body fluid that occurs
during pregnancy.
Although all types of anemia will be seen in the
perianesthesia setting, the most common cause
of decreased RBC, Hgb, and Hct levels overall is
blood loss or hemorrhagic anemia. Red cell
transfusion is almost always indicated for a Hgb
less than 6 g/dL and rarely indicated for Hgb
greater than 10 g/dL. Once the Hgb level falls
below 11 g/dL in an otherwise healthy adult,
the kidney will begin to secrete increasing
amounts of erythropoietin in a matter of hours.
Unfortunately, it will take 3 to 6 days before a
rise in circulating RBCs will be noted. However,
the decision to transfuse should never be dictated by a single Hgb trigger.15
Other RBC Values
Reticulocyte Count
The reticulocyte is an immature RBC found in
the bone marrow (Fig 1). There is a small percentage of reticulocytes released into the blood
stream that accounts for approximately 0.5% to
1.5% of the total RBC count. An increased count
indicates the bone marrow is attempting to
replace sudden RBC loss from hemorrhage or
destruction. A decreased count would indicate
bone marrow hypofunction. This count is normally increased in pregnancy.
GEORGE-GAY AND PARKER
112
Table 12. RBC Indices
Adult
MCV
MCH
MCHC
Conventional Units
SI Units
82-93 ␮m3
26-34 pg
31-38%
82-93 fL
1.61-2.11 fmol
19.2-23.58 mm/L
RBC Indices
RBC indices are calculated mean values that are
used to define the size, weight, and Hgb content of the RBC. They are mainly used to classify
anemias. RBC indices consist of mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). See Table 12 for
normal values.
Mean corpuscular volume. MCV describes
the RBC by size or volume. This measure uses
the size of the RBC to identify possible causes
of anemia as well as other disorders. The MCV
classifies RBCs as microcytic, normocytic, and
macrocytic. Microcytic cells are small or undersized. They are seen with iron deficiency
anemia and thalassemia. In hemorrhagic or
hemolytic anemias, the decrease in oxygencarrying capacity is caused by a decrease in
the number of RBCs; the cells that remain are
normal in size, thus the RBCs are normocytic.
RBCs that are macrocytic are large or oversized. These RBCs are seen in patients with
pernicious or folate deficiency anemia. MCV
is a calculated value obtained by dividing the
Hct by the RBC count.
Mean corpuscular hemoglobin. This value
is the index that measures the average weight of
Hgb in the RBC. An alteration in MCH tends to
track along with the MCV. For example, a smallsized cell will have less Hgb within it compared
with a large-sized cell, therefore its weight
would be lower. Decreases are related to microcytic anemias, and elevations are related to macrocytic anemias. Therefore, the MCH adds little
information independent of the MCV.
Mean corpuscular hemoglobin concentration. This index is a measure of the average
concentration of Hgb in the RBC per unit
volume. RBCs that contain less Hgb are hypochromic and are a pale color. Normal-colored
cells with normal amounts of Hgb are called
normochromic, and hyperchromic cells have
an increased concentration of Hgb and are
bright red in color.16
Nursing Implications
Polycythemic patients need to be monitored for
signs and symptoms of thrombus formation.
Patients should be monitored closely for complaints of leg pain, changes in color, temperature, and capillary refill in addition to initiating
VTE prophylaxis (Table 8) and ensuring adequate fluid administration. Sudden restlessness,
anxiety, and dyspnea may herald a pulmonary
embolus. Changes in a patient’s level of consciousness or neurologic examination can warn
of diminished cerebral blood flow and warn of
the potential for stroke.
Anemic patients are at additional risk anytime
they must undergo surgical procedures. Be sure
to request a type and crossmatch to ensure that
patient-compatible blood will be available in the
blood bank. Be alert to signs of blood loss,
including but not limited to hypotension, tachycardia, restlessness, hypoxia, chest pain, fatigue, and occult blood positive stools and gastric specimens. In the preanesthesia setting, the
decision to transfuse the patient with Hgb between 6 and 10 g/dL should be based on individual risk, such as type and extent of the
surgery, the ability to control the bleeding, and
the rate of uncontrolled bleeding. For elective
procedures, Hgb of 10 g/dL or greater is recommended. Preoperative Hgb below 10 g/dL is an
indication to postpone an elective case. If blood
transfusion is required, expect the Hgb to rise
by 1 g and the Hct by 3% for each unit of packed
RBCs transfused.
Patient care activities may need to be delivered
in such a way as to reduce the patient’s fatigue,
metabolic demand, and physical stress. Contin-
UNDERSTANDING THE CBC WITH DIFFERENTIAL
uous pulse oximetry is required to monitor for
hypoxia. Be prepared to provide supplementary
oxygen and to promote adequate lung expansion through optimal patient positioning. Also
use pulmonary hygiene strategies and teach patients to perform turn, cough, and deep breath
exercises.
Closely monitor intake and output in patients
with Hgb counts below 7 to 8 g/dL. Blood flow
to the kidneys is diminished in these states, and
the patient is at risk for oliguria. Secure and
maintain intravenous access for these patients.
Additionally, provide passive or active warming
measures because patients will complain of
cold and be pale in color.
RBC indices assist in classifying anemias. In
general, be sure to fully assess a patient’s nutritional status and consult a dietitian for further
workup and intervention as appropriate.
Wound healing can be grossly affected by nutritional anemias, and patients may require iron,
zinc, and vitamin C supplements to promote
surgical wound healing. Patients will also require teaching and need encouragement to include iron-rich foods such as liver, red meat,
raisins, peas, apricots, kidney beans, and fortified cereals and breads in their diets.
113
Platelets play a vital role in hemostasis; they,
along with the coagulation factors, are responsible for hemostasis in small and medium-size
arteries and veins. Platelets aggregate or stick
together to form the initial plug where there is
damaged endothelium. Clotting factors are then
triggered to form fibrin strands throughout the
plug to firmly hold the plug together. For the
capillaries, platelets plug and stop bleeding by
themselves, thereby sealing the multitude of
minute ruptures that occur on a daily basis. A
platelet plug forms within 3 to 5 minutes.
The platelet count only provides the number of
circulating plates; it does not describe how
adequately they function. The most indicative
test of platelet function is the “bleeding time.”
Increases in the platelet count or thrombocytosis are usually asymptomatic until counts reach
greater than 1,000,000 ␮/L, where increased
viscosity and inappropriate clotting may occur.
A transient thrombocytosis with platelet counts
of 450,000 to 600,000 ␮/L can be seen as a
physiologic response to physical stress, exercise, trauma, infection, and ovulation. Counts
greater than 600,000 ␮/L may be associated
with myeloproliferative disorders of the stem
cells in the bone marrow.
Increased RBC indices indicate an increased
number of circulating immature RBCs in the
peripheral circulation, increasing the patient’s
likelihood of jaundice, stomatitis, and glossitis.
Attention to mouth care will be essential. The
use of soft bristle toothbrushes and cool, alkaline mouthwash is recommended. The patient
should be informed to avoid sour, tart, and
spicy foods, as well as foods that are extremely
cool or hot in temperature. Jaundiced patients
will require comfort measures and medications
to reduce the discomfort associated with itching.
Thrombocytopenia or decreased platelet count
is defined as a count of less than 150,000 ␮/L.
Causes include depressed production by the
bone marrow or increased consumption or destruction as seen with idiopathic thrombocytopenia. Bleeding usually does not occur until
counts fall below 50,000 ␮/L if platelets are
functioning normally. Small hemorrhagic areas
under the skin called purpura may occur at this
level.
Platelets (Thrombocytes)
Patients with known thrombocytopenia are at
risk for bleeding, especially when counts fall
below 50,000 ␮/L. Counts under 20,000 ␮/L
significantly increase the risk for mortality secondary to hemorrhagic stroke or gastrointestinal hemorrhage.16 In these instances, consider
Platelets are the smallest of the cells found in
blood. They are nonnucleated, flattened diskshaped structures that can be round or oval.
They have a lifespan of 9 to 12 days.
Nursing Implications
GEORGE-GAY AND PARKER
114
advocating for the postponement of surgical
procedures and prepare for possible platelet transfusion. Platelet transfusion is recommended prophylatically for the surgical patient
with a platelet count of less than 50,000 ␮/L
who is undergoing a major procedure. Platelet
transfusion may also be indicated if there is
known platelet dysfunction and microvascular
bleeding despite adequate counts.16 For each
concentrate of platelets transfused, expect the
platelet count to increase by 5,000 to 10,000
␮/L. Keep in mind that one aspirin will coat the
platelet, preventing it from aggregating for the
life of that platelet. A preoperative aspirin may
be more important than platelet count in explaining a bleeding disorder.
Remember that thrombocytosis commonly occurs after hemorrhage and surgical procedures.
Counts soon return to normal limits once the
patient recovers from the primary insult. The
need for VTE prophylaxis (Table 8) for patients
with increased platelet counts also exists. Patient teaching should include precautions to
minimize the risk for infection and bleeding in
postsurgical recovery period.
Summary
It is clear that the needs of patients in the
perianesthesia setting are driven by the context
of their respective surgical treatment plans.
These needs become complex when integrated
with the magnitude of premorbid conditions
and drug profiles that exist for each individual
patient. Knowledge of a patient’s premorbid
state and medications should heighten the clinicians’ awareness and analysis of specific CBC
and differential results.
References
1. Chernecky C, Berger BJ (eds): Laboratory Tests and Diagnostic Procedures (ed 3). Philadelphia, PA, Saunders, 2001, pp
372-376
2. Centers for Medicare and Medicaid Services (CMS): National Coverage Determinations for Blood Counts. Available at
www.cms.hhs.gov/ncd/searchdisplay.asp?NCD_ID⫽61&NCD_
vrsn_num⫽1. Accessed December 2002.
3. Goodnough LT, Brecher ME, Katner MH, et al: Transfusion
medicine: Blood transfusion. N Engl J Med 340:438-447, 1999
4. Medicare Part B Model Local Medical Review Policy, Subject: Blood counts. Avera Health Lab News. 4:2-4, 2000. Available
at www.averalabnet.com/newsletters/NewsJanFeb00.htm. Accessed December 2002
5. Cannon CP, McCabe CH, Wilcox RG, et al: Association of
white blood cell count with increased mortality in acute myocardial infarction and unstable angina pectoris. Am J Cardiol
87:636-639, 2001
6. Baylor College of Medicine: Geriatric assessment, medical
assessment, laboratory work-up. Available at www.geri-ed.
com/modules/Asses/assess/medical_assessment.htm. Accessed
December 2002
7. Banasik JL: Inflammation and Immunity, in Copstead LC,
Banasik JL (eds): Pathophysiology Biological and Behavioral Perspectives (ed 2). Philadelphia, PA, Saunders, 2000, pp 184-218
8. Catalano P: White blood cell count with differential, in
George-Gay B, Chernecky C (eds): Clinical Medical-Surgical
Nursing. Philadelphia, PA, Saunders, 2002, pp 282-290
9. Sadovsky R: WBC predicts increased mortality in acute
MI. Am Fam Physician 64:1261, 2001
10. Koch-Kubetin S: WBC Count Predicts Stroke. OB GYN
News. 25:24, 2000
11. Tresler KM: Hematology screen, in Clinical Laboratory
Diagnostic Tests Significance in Nursing Implications (ed 3).
Norwalk, CT, Appleton Lange, 1995
12. Abramson N, Melton B: Leukocytosis: Basics of clinical
assessment. Am Fam Physician 62:2053-2060, 2000
13. Gawlikowski J: White cells at war. Am J Nurs 92:44-51,
1992
14. The ABCs of CBC: A common blood test. Mayo Clinic
Health Letter, August 2001, pp 4-5
15. American Society of Anesthesiologists: Practice Guidelines for Blood Component Therapy. Available at www.asahq.
org/practice/blood/blood_component.html. Accessed December
2002
16. Garrett K: Red blood cell counts, in George-Gay B,
Chernecky C (eds): Clinical Medical-Surgical Nursing. Philadelphia, PA, Saunders, 2002, pp 274-282
UNDERSTANDING THE CBC WITH DIFFERENTIAL
115
Understanding the Complete Blood Count With Differential
1.4 Contact Hours
Directions: The multiple-choice examination below is designed to test your understanding of the
Complete Blood Count With Differential according the objectives listed. To earn contact hours from the
American Society of PeriAnesthesia Nurses (ASPAN) Continuing Education Provider Program: (1) read the
article; (2) complete the posttest by indicating the answers on the test grid provided; (3) tear out the page
(or photocopy) and submit postmarked before February 28, 2005, with check payable to ASPAN (ASPAN
member, $12.00 per test; nonmember, $15.00 per test); and (4) return to ASPAN, 10 Melrose Ave, Suite
110, Cherry Hill, NJ 08003-3696. Notification of contact hours awarded will be sent to you in 4 to 6 weeks.
Posttest Questions
1. In the process of erythropoiesis, iron is needed for
a. hemoglobin synthesis.
b. DNA synthesis.
c. reproduction.
d. renal excretion.
2. When monitoring a patient who is not bleeding, the nurse would expect to find an increase
in Hct of 3% after a transfusion of one unit of packed RBCs.
a. True
b. False
3. The amount of blood combined with Hgb is a measurement of
a. partial pressure of oxygen (PaO2).
b. arterial-venous oxygen difference.
c. oxyhemoglobin.
d. oxygen saturation (SaO2).
4. In an adult patient with normal Hgb, the nurse will estimate the Hgb to be 10 g/dL if the Hct
was reported to be 30%.
a. True
b. False
5. Secondary physiologic polycythemia is caused by all of the following except
a. congestive heart failure.
b. renal failure.
c. high altitudes.
d. chronic obstructive pulmonary disease.
6. Pernicious anemia is caused by
a. alcoholism.
b. chronic blood loss.
c. vitamin B12 deficiency.
d. iron deficiency.
7. An elevated reticulocyte count would be expected in
a. a recovering trauma patient who lost significant amounts of blood.
b. a patient with a chronic inflammatory disease.
GEORGE-GAY AND PARKER
116
c. a patient in renal failure.
d. a patient with bone marrow hypofunction.
8. All of the following are included in the CBC except
a. erythrocyte sedimentation rate.
b. neutrophil count.
c. platelet count.
d. bands.
9. A CBC is indicated for patients greater than age 65.
a. True
b. False
10. “Shift to the right” means that
a. there is an elevation in bands.
b. the patient probably has an acute viral infection.
c. an acute hypersensitivity reaction is occurring.
d. hypermature segmented neutrophils are present.
11. Neutropenic precautions involves all of the following except
a. reverse isolation.
b. staying away from children recently vaccinated.
c. reporting temperatures of greater than 38°C.
d. avoiding indiscriminate use of acetaminophen.
12. The major cell of the immune response is the
a. cytotoxic T cell.
b. B cell.
c. plasma cell.
d. helper T cell.
13. Nutritional anemias as recognized in the RBC indices can assist in identifying patients
a. at risk for allergic reactions.
b. in need of postoperative blood transfusion.
c. at risk for poor wound healing.
d. none of the above.
14. Once Hgb levels fall below 11 g in an otherwise healthy adult, the kidney will begin to
secrete erythropoietin in a matter of hours. A rise in circulating red blood cells will be noted
within
a. 6 to 8 days.
b. 3 to 5 days.
c. 24 hours.
d. 48 hours.
15. Venous thromboembolism prophylaxis is required for patients with total WBC counts
greater than 100,000.
a. True
b. False
UNDERSTANDING THE CBC WITH DIFFERENTIAL
ANSWERS
System W010405. Please circle the correct answer
1.
a.
2.
a.
b.
b.
c.
d.
6.
a.
7.
a.
b.
b.
c.
c.
d.
d.
11.
a.
12.
a.
b.
b.
c.
c.
d.
d.
3.
117
a.
b.
c.
d.
a.
b.
c.
d.
a.
b.
c.
d.
8.
13.
4.
a.
b.
5.
9.
a.
b.
10.
14.
a.
b.
c.
d.
15.
a.
b.
c.
d.
a.
b.
c.
d.
a.
b.
Please Print
Name
Nursing License No/State
Address
City
State
Zip
Social Security
ASPAN Member #
EVALUATION: Understanding the Complete Blood Count With Differential
(SD, strongly disagree; D, disagree; ?, uncertain; A, agree; SA, strongly agree)
1. To what degree did the content meet the
objectives?
a. Objective #1 was met.
b. Objective #2 was met.
c. Objective #3 was met.
d. Objective #4 was met.
e. Objective #5 was met.
f. Objective #6 was met.
2. The program content was pertinent,
comprehensive, and useful to me.
3. The program content was relevant to my
nursing practice.
4. Self-study/home study was an appropriate
format for the content.
5. Identify the amount of time required to read the
article and take the test.
25 min 50 min 75 min 100 min 125 min
SD
D
?
A
SA
1
2
3
4
5
1
1
1
1
1
1
1
2
2
2
2
2
2
2
3
3
3
3
3
3
3
4
4
4
4
4
4
4
5
5
5
5
5
5
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
Test answers must be submitted before April 30, 2005, to receive contact hours.