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  • CONTINUING EDUCATION

    Understanding the Complete Blood CountWith Differential

    Beverly George-Gay, MSN, RN, CCRNKatherine Parker, MEd, RN

    The complete blood count (CBC) with differential is one of the mostcommon laboratory tests performed today. It gives informationabout the production of all blood cells and identifies the patientsoxygen-carrying capacity through the evaluation of red blood cell(RBC) indices, hemoglobin, and hematocrit. It also provides informa-tion about the immune system through the evaluation of the whiteblood cell (WBC) count with differential. These tests are helpful indiagnosing anemia, certain cancers, infection, acute hemorrhagicstates, allergies, and immunodeficiencies as well as monitoring forside effects of certain drugs that cause blood dyscrasias. Nurses in theperianesthesia arena are frequently challenged to obtain and evalu-ate all or parts of the CBC as a part of the patients preoperative,intraoperative, and postoperative assessments. An enhanced under-standing of this laboratory test is essential to providing quality care.

    2003 by American Society of PeriAnesthesia Nurses.

    ObjectivesBased on the content of this article, the reader should be able to (1) discuss thephysiology 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 charac-teristics of red blood cell (RBC) structure and function; (5) discuss the indications for CBC as part ofthe perianesthesia evaluation; and (6) explore the nursing indications related to CBC findings in theperianesthesia setting.

    THE COMPONENTS OF the complete bloodcount (CBC) include a hemogram and differen-tial white blood cell (WBC) count. The hemo-gram includes the enumeration of WBCs, redblood cells (RBCs), and platelets; it also pro-vides determinations of hemoglobin, hemato-crit, and RBC indices (Table 1). The WBC countwith differential enumerates the different WBCtypes. Together, the components of the CBCevaluate primary diseases of the blood and bone

    Beverly George-Gay, MSN, RN, CCRN, is the Nurse Educatorfor Critical Care for the Department of Education andKatherine Parker, MEd, RN, is a Nurse Educator for theDepartment of Education at the Virginia CommonwealthUniversity Health System, Richmond, VA.

    Address correspondence to Beverly George-Gay, MSN, RN,CCRN, 11824 Club Ridge Dr, Chester, VA 23836; e-mailaddress: bgay@mcvh-vcu.edu.

    2003 by American Society of PeriAnesthesia Nurses.1089-9472/03/1802-0007$35.00/0doi:10.1053/jpan.2003.50013

    Journal of PeriAnesthesia Nursing, Vol 18, No 2 (April), 2003: pp 96-11796

  • 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. Thesechanges 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 patientswho 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 medicaland financial 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 beordered 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 orpolycythemia. See Table 2 for specificsigns, symptoms, and conditions.

    The platelet count should be evaluatedfor 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/LDifferential white cell count See Table 7RBC 4.0 to 6.2 million/LHct

    Women 35% to 47%Men 8 to 64 yr 39% to 50%Men 65 to 74 yr 37% to 51%

    HgbWomen 12 to 16 g/dLMen 14 to 18 g/dL

    RBC indicesMean corpuscular volume 82 to 93 m3

    Mean corpuscular Hgb 26 to 34 pgMean 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

  • 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 inthe 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, minorprocedures are those with very low risk of largefluid 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 inmind that a minor procedure may turn into amoderately complex procedure as complica-tions are identified or develop. Major proce-dures are those that are often prolonged, oftenwith high risk of large fluid shifts or signifi-cant blood loss. They often involve major bodycavities. 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

    PallorWeaknessFatigueWeight lossBleedingAcute or suspected blood loss

    from injuryHematuriaHematemesisHematocheziaPositive fecal occultNeuropathyMalnutritionTachycardiaKnown malignancySystolic heart murmurCongestive heart failureDyspneaAnginaPostural dizzinessSyncopeNailbed deformitiesKnown malignancyJaundiceHepatomegalySplenomegalyLymphadenopathyUlcers of the lower extremities

    FeverChillsRuddy skinConjunctival rednessCoughWheezingCyanosisClubbing of the fingersOrthopneaHeart murmurHeadacheMemory changesSleep apneaWeaknessPruritusDizzinessExcessive sweatingMassive obesityGastrointestinal bleedingParesthesiasMyocardial infarctionStrokeThromboembolismHepatomegalySplenomegalyCOPDDiastolic hypertensionCongenital heart diseaseTransient ischemic attackVisual symptoms

    Gastrointestinal bleedGenitourinary tract bleedBilateral epistaxisThrombosisEcchymosisPurpuraJaundicePetechiaeFeverHeparin therapySuspected DICShockPreeclampsiaMassive transfusionRecent platelet transfusionCardiopulmonary bypassRenal diseasesHypersplenismNeurologic abnormalitiesViral or other infectionThrombosisExposure to toxic agentsExcessive alcohol ingestionAutoimmunue disorders

    (SLE, RA)HepatomegalySplenomegalyLymphadenopathy

    FeverChillsSweatsShockFatigueMalaiseTachycardiaTachypneaHeart murmurSeizuresAltered consciousnessPain such as headacheAbdominal painArthralgiaOdynophagiaDysuriaRedness/swelling of skin soft

    tissue or jointUlcers of skin or mucous

    membraneGangreneBleedingThrombosisPulmonary infiltrateJaundiceDiarrheaVomitingOpportunistic infections as

    oral candidiasisHepatomegalySplenomegalyLymphadenopathy

    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

  • 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 th

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