white blood cells, and platelets. Specimens are obtained through capillary skin punctures (finger, toe, heel), dried blood samples, arterial or venous sampling, or bone marrow aspiration. Specimens may be tested by automated or manual hematology instrumentation and evaluation.
Observe standard precautions (see Appendix A). Check for latex allergy. If allergy is present, do not use latex-containing products.
Obtain capillary blood from fingertips or earlobes (adults) or from the great toe or heel (infants). Avoid using the lateral aspect of the heel where the plantar artery is located.
Disinfect puncture site, dry the site, and puncture skin with sterile disposable lancet, perpendicular to the lines of the patient’s fingers, no deeper than 2 mm. If chlorhexidine is used, allow to dry thoroughly.
Wipe away the initial drop of blood. Collect subsequent drops in a microtube or prepare a smear directly from a drop of blood.
After collection, apply a small amount of pressure briefly to the puncture site to prevent painful extravasation of blood into the subcutaneous tissues.
Do not squeeze the site to obtain blood because this alters blood composition and invalidates test values.
Warming the extremity or placing it in a dependent position may facilitate specimen collection.
In this method, a lancet is used, and the resulting droplets of blood are collected by blotting them with filter paper directly.
Check the stability of equipment and integrity of supplies when doing a finger stick. If provided, check the humidity indicator patch on the filter paper card. If the humidity circle is pink, do not use this filter paper card. The humidity indicator must be blue to ensure specimen integrity.
After wiping the first drop of blood on the gauze pad, fill and saturate each of the circles in numerical order by blotting the blood droplet with the filter paper. Do not touch the patient’s skin to the filter paper; only the blood droplet should come in contact with the filter paper.
If an adult has a cold hand, run warm water over it for approximately 3 minutes. The best flow occurs when the arm is held downward, with the hand below heart level, making effective use of gravity. If there is a problem with proper blood flow, milk the finger with gentle pressure to stimulate blood flow or attempt a second finger stick; do not attempt more than two.
When the blood circles penetrate through to the other side of the filter paper, the circles are fully saturated.
Instruct patient about purpose and procedure of test.
Follow Chapter 1 guidelines for safe, effective, informed pretest care.
Apply small dressing or adhesive strip to site.
Evaluate puncture site for bleeding or oozing.
Apply compression or pressure to the site if it continues to bleed.
Evaluate patient’s medication history for anticoagulation, nonsteroidal anti-inflammatory drugs (NSAIDs), or acetylsalicylic acid (ASA)-type drug ingestion.
Follow Chapter 1 guidelines for safe, effective, informed posttest care.
Observe standard precautions (see Appendix A). If latex allergy is suspected, use latex-free supplies and equipment.
Position and tighten a tourniquet on the upper arm to produce venous distention (congestion). For elderly persons, a tourniquet is not always recommended because of possible rupture of capillaries. Large, distended, and highly visible veins increase the risk for hematoma.
Ask the patient to close the fist in the designated arm. Do not ask patient to pump the fist because this may increase plasma potassium levels by as much as 1 to 2 mEq/L (mmol/L). Select an accessible vein.
Cleanse the puncture site, working in a circular motion from the center outward, and dry it properly with sterile gauze. Chlorhexidine must dry thoroughly.
To anchor the vein, draw the skin taut over the vein and press the thumb below the puncture site. Hold the distal end of the vein during the puncture to decrease the possibility of rolling veins.
Puncture the vein according to accepted technique. Usually, for an adult, anything smaller than a 21-gauge needle might make blood withdrawal more difficult. A Vacutainer system syringe or butterfly system may be used.
Once the vein has been entered by the collecting needle, blood will fill the attached vacuum tubes automatically because of negative pressure within the collection tube.
Remove the tourniquet before removing the needle from the puncture site or bruising will occur.
Remove needle. Apply pressure and sterile dressing strip to site.
The preservative or anticoagulant added to the collection tube depends on the test ordered. In general, most hematology tests use EDTA anticoagulant. Even slightly clotted blood invalidates the test, and the sample must be redrawn.
Take action to prevent these venipuncture errors:
Improper patient identification
Failure to check patient compliance with dietary restrictions
Failure to calm patient before blood collection
Use of wrong equipment and supplies
Inappropriate method of blood collection
Failure to dry site completely after cleansing with alcohol
Inserting needle with bevel side down
Using too small a needle, causing hemolysis of specimen
Venipuncture in unacceptable area (e.g., above an intravenous [IV] line)
Prolonged tourniquet application
Wrong order of tube draw
Failure to mix blood immediately that is collected in additive-containing tubes
Pulling back on syringe plunger too forcefully
Failure to release tourniquet before needle withdrawal
Failure to apply pressure immediately to venipuncture site
Vigorous shaking of anticoagulated blood specimens
Forcing blood through a syringe needle into tube
Mislabeling of tubes
Failure to label specimens with infectious disease precautions as required
Failure to put date, time, and initials on requisition
Slow transport of specimens to laboratory
Instruct patient regarding sampling procedure. Assess for circulation or bleeding problems and allergy to latex. Verify with the patient any fasting requirements. Diagnostic blood tests may require certain dietary restrictions of fasting for 8 to 12 hours before test. Drugs taken by the patient should be documented because they may affect results.
Reassure patient that mild discomfort may be felt when the needle is inserted.
Place the arm in a fully extended position with palmar surface facing upward (for antecubital access).
If withdrawal of the sample is difficult, warm the extremity with warm towels or blankets. Allow the extremity to remain in a dependent position for several minutes before venipuncture. For young children, warming the draw site should be routine to distend small veins.
Be alert to provide assistance should the patient become lightheaded or faint.
Prescribed local anesthetic creams may be applied to the area before venipuncture; allow 60 seconds for light-skinned persons and 120 seconds for dark-skinned persons before performing the procedure.
If oozing or bleeding from the puncture site continues for more than a few minutes, elevate the area and apply a pressure dressing. Observe the patient closely. Check for anticoagulant or ASA-type ingestion. If venous bleeding is excessive and persists for longer than 10 minutes, notify the physician.
Be aware that the patient occasionally becomes dizzy, faint, or nauseated during the venipuncture. The phlebotomist must be constantly aware of the patient’s condition. If a patient feels faint, immediately remove the tourniquet and terminate the procedure. Place the patient in a supine position if possible. If the patient is sitting, lower the head between the legs and instruct the patient to breathe deeply. A cool, wet towel may be applied to the forehead and back of the neck, and, if necessary, ammonia inhalant may be applied briefly. Watch for signs of shock, such as increased heart rate and decreased blood pressure. If the patient remains unconscious, notify a physician immediately.
Prevent hematomas by using proper technique (not sticking the needle through the vein), releasing the tourniquet before the needle is withdrawn, applying sufficient pressure over the puncture site, and maintaining an extended extremity until bleeding stops. If a hematoma develops, apply a warm compress.
Assess the puncture site for signs and symptoms of infection, subcutaneous redness, pain, swelling, and tenderness.
In patients with leukemia, agranulocytosis, or lowered resistance, finger-stick and earlobe punctures are more likely to cause infection and bleeding than venipunctures. Should a capillary sample be necessary, the cleansing agent should remain in contact with the skin for at least 5 to 10 minutes. Chlorhexidine is a topical antimicrobial. It should be allowed to dry. It may then be wiped off with alcohol and the site dried with sterile gauze before puncture.
Never draw blood from the same extremity being used for IV medications, fluids, or transfusions. If no other site is available, make sure the venipuncture site is below the IV site. Avoid areas that are edematous, are paralyzed, are on the same side as a mastectomy, or have infections or skin conditions present. Venipuncture may cause infection or circulatory impairment or retarded healing.
Prolonged tourniquet application causes stasis and hemoconcentration and will alter test results. If a vein cannot be found within a minute, release the tourniquet temporarily to avoid tissue necrosis.
Strenuous activity immediately before a blood sample draw can alter results because body fluids shift from the vascular bed to the tissue spaces and produce circulatory blood hemoconcentration. It may take 20 to 30 minutes of rest and reduced stress to reestablish fluid equilibrium.
Assess for interfering factors, including cellulitis, phlebitis, venous obstruction, lymphangitis, or arteriovenous fistulas or shunts.
To avoid spurious test results due to infusion of solutions, do not draw above an IV catheter. Choose a site distal to the IV line site.
After two attempts, a physician or highly trained phlebotomist should be called.
Blood samples may be drawn off central lines. The lines first must be flushed with saline before the blood draw.
are normally collected directly from the radial, brachial, or femoral arteries. If the patient has an arterial line in place (most frequently in the radial artery), samples can be drawn from the line. Be sure to record the amounts of blood withdrawn because significant amounts can be removed if frequent samples are required.
Sites must have available collateral blood flow.
Sites must be easily accessible.
Sites must be relatively nonsensitive as periarterial tissues.
Assess patient for the following contraindications to an arterial stick or indwelling arterial line in a particular area:
Absence of a palpable radial artery pulse
Positive Allen’s test result, which shows only one artery supplying blood to the hand
Negative modified Allen’s test result, which indicates obstruction in the ulnar artery (i.e., compromised collateral circulation)
Cellulitis or infection at the potential site
Presence of arteriovenous fistula or shunt
Severe thrombocytopenia (platelet count 20,000/mm3)
Prolonged prothrombin time or partial thromboplastin time (>1.5 times the control is a relative contraindication)
A Doppler probe or finger pulse transducer may be used to assess circulation and perfusion in dark-skinned or uncooperative patients.
Before drawing an arterial blood sample, record the patient’s most recent hemoglobin concentration, mode and flow rate of oxygen, and temperature. If the patient has been recently suctioned or placed on a ventilator or if delivered oxygen concentrations have been changed, wait at least 15 minutes before drawing the sample. This waiting period allows circulating blood levels to return to baseline levels. Hyperthermia and hypothermia also influence oxygen release from hemoglobin at the tissue level.
Observe standard precautions and follow agency protocols for the procedure.
The patient assumes a sitting or supine position.
Perform a modified Allen’s test by encircling the wrist area and using pressure to obliterate the radial and ulnar pulses. Watch for the hand to blanch, and then release pressure only over the ulnar artery. If the result is positive, flushing of the hand is immediately noticed, indicating circulation to the hand is adequate. The radial artery can then be used for arterial puncture. If collateral circulation from the ulnar artery is inadequate (i.e., negative test result) and flushing of the hand is absent or slow, then another site must be chosen. An abnormal Allen’s test result may be caused by a thrombus, an arterial spasm, or a systemic problem such as shock or poor cardiac output.
Elevate the wrist area by placing a small pillow or rolled towel under the dorsal wrist area. With the patient’s palm facing upward, ask the patient to extend the fingers downward, which flexes the wrist and positions the radial artery closer to the surface.
Palpate for the artery, and maneuver the patient’s hand back and forth until a satisfactory pulse is felt.
Swab the area liberally with an antiseptic agent such as Chloraprep.
OPTIONAL: Inject the area with a small amount (<0.25 mL) of 1% plain Xylocaine, if necessary, to anesthetize site. Assess for allergy first. This allows for a second attempt without undue pain.
Prepare a 20- or 21-gauge needle on a preheparinized, self-filling syringe; puncture the artery; and collect a 3- to 5-mL sample. The arterial pressure pushes the plunger out as the syringe fills with blood. (Venous blood does not have enough pressure to fill the syringe without drawing back on the plunger.) Air bubbles in the blood sample must be expelled as quickly as possible because residual air alters ABG values. The syringe should then be capped and gently rotated to mix heparin with the blood.
When the draw is completed, withdraw the needle, and place a 4- × 4-inch absorbent bandage over the puncture site. Do not recap needles; if necessary, use the one-handed mechanical, recapping, or scoop technique or commercially available needles (e.g., B-D Safety-Glide [Franklin Lakes, NJ] or Sims Portex Pro-Vent [Keene, NH]). Maintain firm finger pressure over the site for a minimum of 5 minutes or until there is no active bleeding evident. After the bleeding stops, apply a firm pressure dressing but do not encircle the entire limb, which can restrict circulation. Leave this dressing in place for at least 24 hours. Instruct the patient to report any signs of bleeding from the site promptly and apply finger pressure if necessary.
Place the sample in an ice slurry and transport to the laboratory in a biohazard bag.
Label the sample with patient’s name, identification number, and date and time procured, and indicate the type and flow rate of O2 therapy or if the patient was on “room air.” Do not use blood for ABGs if the sample is more than 1 hour old.
In clinical settings such as the perioperative or intensive care environment, ABG studies usually include pH, PCO2, SO2, total CO2 content (TCO2), O2 content, PO2, base excess or deficit, HCO3, hemoglobin, hematocrit, and levels of chloride, sodium, and potassium.
Frequently monitor the puncture site and dressing for arterial bleeding for several hours. The patient should not use the extremity for any vigorous activity for at least 24 hours.
Monitor the patient’s vital signs and mental function to determine adequacy of tissue oxygenation and perfusion.
The arterial puncture site must have a pressure dressing applied and should be frequently assessed for bleeding for several hours. Instruct the patient to report any bleeding from the site and to apply direct pressure to the site if necessary.
For patients requiring frequent arterial monitoring, an indwelling arterial catheter (line) may be inserted. Follow agency protocols for obtaining arterial line blood samples. The procedure varies for neonate, pediatric, and adult patients (see Arterial Blood Gas Tests in Chapter 14).
Label all specimens appropriately and document pertinent information in the health care record.
Follow standard precautions. Check for latex allergy; if allergy is present, do not use latexcontaining products. Position the patient on the back or side according to site selected. The posterior iliac crest is the preferred site in all patients older than 12 to 18 months. Alternate sites include the anterior iliac crest, sternum, spinous vertebral processes T10 through L4, ribs, and tibia in children. The sternum is not generally used in children because the bone cavity is too shallow, the risk for mediastinal and cardiac perforation is too great, and the child may be uncooperative.
Clip hair if necessary, cleanse, and drape the site as for any minor surgical procedure.
Inject a local anesthetic (procaine or lidocaine). This may cause a burning sensation. At this time, a skin incision of 3 mm is often made.
Remember that the physician introduces a short, rigid, sharp-pointed needle with stylet through the periosteum into the marrow cavity.
Pass the needle-stylet combination through the incision, subcutaneous tissue, and bone cortex. The stylet is removed, and 1 to 3 mL of marrow fluid is aspirated. Alert the patient that when the stylet needle enters the marrow, he or she may experience a feeling of pressure. The patient may also feel moderate discomfort as aspiration is done, especially in the iliac crest. Use the Jamshidi needle for biopsy, although you can also use the Westerman-Jansen modification of the Vim-Silverman needle.
Remove the stylet and advance the biopsy needle with a twisting motion toward the anterosuperior iliac spine.
Rotate or “rock” the needle in several directions several times after adequate penetration of the base (3 cm) has been achieved. This “frees up” the specimen. Slowly withdraw the needle once this is done.
Push the biopsy specimen out backward from the needle. Use it to make touch preparations or immediately place in fixative. Make slide smears at the bedside.
Apply pressure to the puncture site until bleeding ceases. Dress the site.
Place specimens in biohazard bags, label properly, and route to the appropriate department.
TABLE 2.1 Normal Values for Bone Marrow*
A specific and diagnostic bone marrow picture provides clues to many diseases. The presence, absence, and ratio of cells are characteristic of the suspected disease.
Bone marrow examination may reveal the following abnormal cell patterns:
Multiple myeloma, plasma cell myeloma, macroglobulinemia
Chronic or acute leukemias
Anemia, including megaloblastic, macrocytic, and normocytic anemias
Toxic states that produce bone marrow depression or destruction
Neoplastic diseases in which the marrow is invaded by tumor cells (metastatic carcinoma, myeloproliferative and lymphoproliferative diseases); assists in diagnosis and staging
Agranulocytosis (a decrease in the production of white cells). This occurs when bone marrow activity is severely depressed, usually as a result of radiation therapy or chemotherapeutic drugs. Implications for the patient focus on the risk for death from overwhelming infection.
Some types of infectious diseases, especially histoplasmosis and tuberculosis
Deficiency of body iron stores, microcytic anemia
Lipid or glycogen storage disease
Myelodysplastic syndrome (MDS) is the name of a group of conditions that occur when bloodforming cells in the bone marrow are damaged.
Instruct the patient about the test procedure, purpose, benefits, and risks.
Ensure that a legal consent form is properly signed and witnessed. Bone marrow aspiration is usually contraindicated in the presence of hemophilia and other bleeding dyscrasias. However, risk versus benefit may dictate the choice made.
Reassure the patient that analgesics will be available if needed. Administer moderate sedation and analgesia, if ordered. Use an 02 sat monitor to evaluate breathing effectiveness.
Be aware that bone marrow biopsies or aspirations can be uncomfortable. Squeezing a pillow may be helpful as a distraction technique. Offer emotional support.
Observe standard precautions.
Sites used for bone marrow aspiration or biopsy affect pretest, intratest, and posttest care. Sites used include the posterosuperior iliac crest; anterior iliac crest (if the patient is very obese); sternum (not used as often with children because cavity is too shallow; danger of mediastinal and cardiac perforation is too great; and observation of procedure is associated with apprehension and lack of cooperation); vertebral spinous processes T10 through L4 and ribs; tibia (often in children); and ribs. Position according to the site selected, and assist in preparing the local anesthetic (i.e., procaine or lidocaine) for injection.
Explain to the patient the importance of remaining still during the procedure.
Monitor vital signs until stable and assess site for excess drainage or bleeding.
Recommend bed rest for 30 to 60 minutes; then normal activities can be resumed.
Monitor for signs and symptoms of shock (increased heart rate and decreased blood pressure).
Assess for signs and symptoms of infections (redness, swelling, pain and tenderness).
Administer analgesics or sedatives as necessary. Soreness over the puncture site for 3 to 4 days after the procedure is normal. Continued pain may indicate fracture.
Interpret test outcomes and monitor appropriately.
Follow Chapter 1 guidelines for safe, effective, informed posttest care.
Complications can include bleeding and sternal fractures. Osteomyelitis or injury to heart or great vessels is rare but can occur if the sternal site is used.
Manual and pressure dressings over the puncture site usually control excessive bleeding. Remove dressing in 24 hours. Redress site if necessary.
Fever, headache, unusual pain, or redness or pus at biopsy site may indicate infection (later event). Instruct patient to report unusual symptoms to physician immediately.
The patient must remain still throughout this invasive procedure.
TABLE 2.2 Normal Values for Hemogram
White blood cell count (WBC): leukocytes fight infection
Differential white blood cell count (Diff): specific patterns of WBC
Red blood cell count (RBC): red blood cells carry O2 from lungs to blood tissues and CO2 from tissue to lungs
Hematocrit (Hct): measures RBC mass
Hemoglobin (Hb): main component of RBCs and transports O2 and CO2
Red blood cell indices: calculated values of size and Hb content of RBCs; important in anemia evaluations
Mean corpuscular volume (MCV)
Mean corpuscular hemoglobin concentration (MCHC)
Mean corpuscular hemoglobin (MCH)
Stained red cell examination (film or peripheral blood smear)
Platelet count (often included in CBC): thrombocytes are necessary for clotting and control of bleeding
Red blood cell distribution width (RDW): indicates degree variability and abnormal cell size
Mean platelet volume (MPV): index of platelet production
Hct of less than 20% can lead to cardiac failure and death.
Hct of greater than 60% is associated with spontaneous clotting of blood.
Hb value of less than 5.0 g/dL (<50 g/L) leads to heart failure and death.
Hb value of greater than 20.0 g/dL (>200 g/L) results in hemoconcentration and clogging of capillaries.
A critical decrease in platelet value to less than 20 × 103/mm3 (<20 × 109/L) is associated with a tendency for spontaneous bleeding, prolonged bleeding time, petechiae, and ecchymosis.
Many physiologic variants affect outcomes: posture, exercise, age, altitude, pregnancy, and many drugs.
Physiologic variants affect Hct outcomes: age, sex, and physiologic hydremia of pregnancy.
Physiologic variations affect test outcomes: high altitude, excessive fluid intake, age, pregnancy, and many drugs.
High values may occur in newborns and infants.
Presence of leukemia or cold agglutinins may increase levels. MCHC is falsely elevated with a high blood concentration of heparin.
Hyperlipidemia and high heparin concentrations falsely elevate MCH values.
WBC counts greater than 50,000/mm3 falsely elevate Hb values and falsely elevate the MCH.
Hourly variation, age, exercise, pain, temperature, and anesthesia affect test results.
Physiologic conditions such as stress, excitement, exercise, and obstetric labor increase neutrophil levels. Steroid administration affects levels for up to 24 hours.
The eosinophil count is lowest in the morning and then rises from noon until after midnight. Do repeat tests at the same time every day. Stressful states such as burns, postoperative states, and obstetric labor decrease the count. Drugs such as steroids, epinephrine, and thyroxine affect eosinophil levels.
Physiologic factors include high altitudes, strenuous exercise, excitement, and premenstrual and postpartum effects.
A partially clotted blood specimen affects the test outcome.
Explain test procedure. Explain that slight discomfort may be felt when skin is punctured. Refer to venipuncture procedure for additional information.
Avoid stress if possible because altered physiologic status influences and changes normal hemogram values.
Select hemogram components ordered at regular intervals (e.g., daily, every other day). These should be drawn consistently at the same time of day for reasons of accurate comparison; natural body rhythms cause fluctuations in laboratory values at certain times of the day.
Dehydration or overhydration can dramatically alter values; for example, large volumes of IV fluids can “dilute” the blood, and values will appear as lower counts. The presence of either of these states should be communicated to the laboratory.
Fasting is not necessary. However, fat-laden meals may alter some test results because of lipidemia.
Some medications and other substances can alter results. Obtain a current medication history from the patient.
A high WBC count or diseases that cause RBCs to agglutinate may alter test results.
Apply manual pressure and dressings to the puncture site on removal of the needle.
Monitor the puncture site for oozing. Maintain pressure dressings on the site if necessary. Notify physician of unusual problems with bleeding. If a hematoma develops, apply a compress. If the hematoma is large, assess pulses distal to the phlebotomy site.
Resume normal activities and diet.
Bruising at the puncture site is not uncommon. Signs of inflammation are unusual and should be reported if the inflamed area appears larger, if red streaks develop, or if drainage occurs.
Evaluate the outcome and counsel the patient appropriately about anemia, polycythemia, risk for infection, and related blood disorders.
Monitor patients with serious platelet defects for signs and symptoms of gastrointestinal bleeding, hemolysis, hematuria, petechiae, vaginal bleeding, epistaxis, and bleeding from gums.
WBC <500/mm3 or <0.5 × 103/mm3 (or × 109/L) is extremely dangerous and is often fatal.
WBC <2.0 × 109/L represents a critical value.
WBC >30,000/mm3 or >30.0 × 103/mm3 (or × 109/L) is a critical value.
Obtain a venous anticoagulated EDTA (lavender-topped tube) whole blood sample of 5 mL or a finger-stick sample. Place specimen in a biohazard bag.
Record the time when specimen was obtained (e.g., 7:00 a.m.).
Blood is processed either manually or automatically, using an electronic counting instrument such as the Coulter counter or Abbott Cell-Dyne.
Leukocytosis: WBC >11,000/mm3 or > 11.0 × 103/mm3 (or >11 × 109/L)
It is usually caused by an increase of only one type of leukocyte, and it is given the name of the type of cell that shows the main increase:
Neutrophilic leukocytosis or neutrophilia
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