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    marrow, which include disorders such as ane-mia, leukemia, polycythemia, thrombocytosis,and thrombocytopenia. The CBC also evaluatesmedical conditions that secondarily affect theblood and bone marrow resulting in hemato-logic manifestations such as infection, inflam-mation, coagulopathies, neoplasms, and toxicsubstance exposure. In many instances, specificsymptomatology of a medical condition maynot be present and hematologic changes on theCBC may be the only finding present. These

    changes prompt investigation to then identifythe medical condition.

    To foster the understanding of the usefulness ofthe CBC, the function and life cycle of thevarious cells are introduced. Test indications,characteristics, abnormal findings, and applica-tions for the perianesthesia nurse are discussed.

    Screening

    Screening usually refers to testing patients

    who are asymptomatic and have no physicalsigns of disease. However, symptoms or physi-cal signs may be very insensitive indicators ofsome diseases. In the perianesthesia setting, theuse of the CBC as a screening tool constantlyundergoes revision. Factors such as the preva-lence of disease in a population, the medicalandfinancial impact of missing a problem, thecost per problem found, financial reimburse-

    ment, and societal judgments determine whenscreening tests are indicated. Medicare does notsupport 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 his-tory, a physical examination, laboratory tests,and an assessment of surgical risk to identifycoexisting diseases and complicating condi-tions. To decrease the risk of morbidity andmortality in the perianesthesia setting, the CBCis used to assist with the identification of pa-tients who are at risk for complications of inad-

    equate tissue perfusion during the procedureand those with a possible infectious or inflam-matory process.3,4

    General indications for a CBC that are consid-ered medically reasonable and are accepted byMedicare are as follows:

    The hemogram should be evaluated forany patient with signs, symptoms, orconditions associated with anemia or

    polycythemia. See Table 2 for specifi

    csigns, symptoms, and conditions. The platelet count should be evaluated

    for patients with findings or conditionsassociated with increased or decreasedplatelet production, destruction, or dys-function (Table 2). The platelet count isusually obtained as part of the hemo-gram.

    The WBC differential should be evalu-ated for any patient with signs, symp-toms, or conditions associated with in-

    fections, inflammatory processes, bonemarrow alterations, and immune disor-ders (Table 2). The WBC count has alsobeen recently identified as a possible riskstratification tool for mortality in acutecoronary syndromes.5

    A hemoglobin and hematocrit (H&H)alone may be appropriate if there is onlya need to assess the oxygen-carrying ca-

    Table 1. Complete Blood Count

    WBC 4,500 to 11,000/L

    Differential white cell count See Table 7

    RBC 4.0 to 6.2 million/L

    HctWomen 35% to 47%

    Men 8 to 64 yr 39% to 50%

    Men 65 to 74 yr 37% to 51%

    Hgb

    Women 12 to 16 g/dL

    Men 14 to 18 g/dL

    RBC indices

    Mean corpuscular volume 82 to 93 m3

    Mean corpuscular Hgb 26 to 34 pg

    Mean corpuscular Hgb concentration 31% to 38%

    Platelet count 150,000 to 400,000 L

    Data from Chernecky et al.1

    UNDERSTANDING THE CBC WITH DIFFERENTIAL 97

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    pacity of blood before surgery for pa-tients who do not have the previouslylisted signs, symptoms, or conditions(Table 2). The H&H may be helpful in

    the intraoperative and postoperativephase of care to assess and track forblood loss but can be misleading becauseof the intercompartmental fluid shiftsthat occur during surgery and because ofthe dilutional effects of crystalloid ther-apy.

    Specific perianesthesia indications for the CBCalso 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 pro-

    cedures include soft tissue and eye procedures;

    minor ortho; as well as ear, nose, and throat andurologic procedures, among others. Keep in

    mind that a minor procedure may turn into a

    moderately complex procedure as complica-

    tions are identified or develop. Major proce-

    dures are those that are often prolonged, often

    with high risk of large fluid shifts or signifi-

    cant blood loss. They often involve major body

    cavities. These include major abdominal, vascu-

    Table 2. Signs, Symptoms, and Conditions That May Warrant a CBC or Parts of a CBC

    Hemogram

    (Findings Related to Anemia)

    Hemogram

    (Findings Related to Polycythemia)

    Hemogram

    (Findings Related to Platelet Dysfunction) WBC With Differential

    PallorWeakness

    Fatigue

    Weight loss

    Bleeding

    Acute or suspected blood loss

    from injury

    Hematuria

    Hematemesis

    Hematochezia

    Positive fecal occult

    Neuropathy

    Malnutrition

    Tachycardia

    Known malignancy

    Systolic heart murmurCongestive heart failure

    Dyspnea

    Angina

    Postural dizziness

    Syncope

    Nailbed deformities

    Known malignancy

    Jaundice

    Hepatomegaly

    Splenomegaly

    Lymphadenopathy

    Ulcers of the lower extremities

    FeverChills

    Ruddy skin

    Conjunctival redness

    Cough

    Wheezing

    Cyanosis

    Clubbing of the fingers

    Orthopnea

    Heart murmur

    Headache

    Memory changes

    Sleep apnea

    Weakness

    Pruritus

    DizzinessExcessive sweating

    Massive obesity

    Gastrointestinal bleeding

    Paresthesias

    Myocardial infarction

    Stroke

    Thromboembolism

    Hepatomegaly

    Splenomegaly

    COPD

    Diastolic hypertension

    Congenital heart disease

    Transient ischemic attack

    Visual symptoms

    Gastrointestinal bleedGenitourinary tract bleed

    Bilateral epistaxis

    Thrombosis

    Ecchymosis

    Purpura

    Jaundice

    Petechiae

    Fever

    Heparin therapy

    Suspected DIC

    Shock

    Preeclampsia

    Massive transfusion

    Recent platelet transfusion

    Cardiopulmonary bypassRenal diseases

    Hypersplenism

    Neurologic abnormalities

    Viral or other infection

    Thrombosis

    Exposure to toxic agents

    Excessive alcohol ingestion

    Autoimmunue disorders

    (SLE, RA)

    Hepatomegaly

    Splenomegaly

    Lymphadenopathy

    FeverChills

    Sweats

    Shock

    Fatigue

    Malaise

    Tachycardia

    Tachypnea

    Heart murmur

    Seizures

    Altered consciousness

    Pain such as headache

    Abdominal pain

    Arthralgia

    Odynophagia

    DysuriaRedness/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

    SplenomegalyLymphadenopathy

    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_ID61&NCD_vrsn_num1.

    GEORGE-GAY AND PARKER98

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    lar, cardiothoracic, orthopedic, gynecologic/urologic, head and neck, and neurologic proce-dures. Levels of surgical complexity from level 1(minor) to level 5 (major) are described in Table3. The American Society of Anesthesiologists(ASA) physical status classification system is an-other tool that can be used to assess the pa-tients current health status and overall periop-erative risk (Table 4). Although imprecise, it is away to predict the patients anesthetic/surgicalrisks. The higher the ASA class, the greater therisks.

    For the patient who is asymptomatic and activewith a reliable benign history and undergoing aminor procedure, an H&H assessment may beall that is necessary or may not be indicated atall. For those patients undergoing major proce-dures, a CBC with platelets should be com-pleted. The CBC is indicated for elderly patients

    (65 years of age) as part of their preoperativeassessment because of the comorbidities associ-ated with this age group as it may uncoverclinical problems that were not picked up onphysical examination.6 Patients classified withan ASA score of 3 or greater should have a CBCbefore their surgical procedure. In addition tothe general indications for CBC in Table 2,situations requiring a CBC before a surgicalprocedure are listed in Table 5.

    Optimally efficient testing entails considerationof a combination of factors including the age,gender, and reliability of the patient; the surgi-cal procedure; and the type of anesthesia beingused. Older or less reliable patients may bemore likely to have an unsuspected abnormalitypicked up by a screening test. Major proce-dures are associated with significant physiologicstress. Existing medical conditions, which may

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