Phlebotomy Notes

Introduction to Phlebotomy

  • Collecting and Processing Blood Samples

Blood Components

  • Blood is a connective tissue.

  • Formed elements include:

    • Erythrocytes (red blood cells)

    • Leukocytes (white blood cells)

    • Thrombocytes (platelets)

  • AS-5 RED BLOOD CELLS: Adenine-Saline Added.

  • Key terms: Volunteer Donor, Properly Identify Intended Recipient.

  • Plasma is the extracellular matrix of blood.

Characteristics of Blood

  • Freshly oxygenated blood is bright red.

  • Deoxygenated blood is darker red.

  • Color depends on hemoglobin content.

  • Blood is viscous (5x more than water) and sticky.

  • Normal temperature is about 100.4^\circ F.

  • Normal pH is about 7.4.

  • Males have an average of 5-6 liters of blood.

  • Females have an average of 4-5 liters of blood.

Blood Plasma Composition

  • Composed primarily of water (92%).

  • Straw-colored.

  • 7% is made of plasma proteins.

Blood Plasma Proteins

  • Albumin: Most abundant, manufactured by the liver, maintains osmotic pressure and water balance.

  • Globulins: Involved with the immune system.

  • Fibrinogen: Involved with clotting.

Other Plasma Solutes (1% of Plasma)

  • Electrolytes (sodium, potassium, calcium).

  • Dissolved gases (oxygen, carbon dioxide, nitrogen).

  • Various nutrients (vitamins, lipids, glucose, amino acids).

  • Metabolic wastes.

Production of Formed Elements

  • Lifespan is very brief.

  • Body must form new blood cells and platelets quickly and continuously.

  • Plasma is replaced within 24 hours after blood donation.

  • It takes 4-6 weeks to replace blood cells.

Erythrocytes (Red Blood Cells)

  • Most common formed element.

  • Males: about 5.4 million erythrocytes per microliter of blood.

  • Females: about 4.8 million erythrocytes per microliter of blood.

  • Primary function: pick up inhaled oxygen from the lungs and transport it to the body’s tissues.

  • Also pick up some carbon dioxide waste at the tissues and transport it to the lungs for exhalation.

Hematocrit

  • Measures the percentage of erythrocytes in a blood sample.

    • Males: 42-52%.

    • Females: 37-47%.

  • Performed by spinning the blood sample in a centrifuge.

  • Heavier elements separate from the lighter, liquid plasma.

  • Erythrocytes settle at the bottom.

  • Volume of erythrocytes after centrifugation is also called packed cell volume (PCV).

  • Typically, about 45% of a sample is erythrocytes.

  • Plasma is 55% of total blood volume.

  • Buffy coat (leukocytes & platelets) is less than 1% of total blood volume.

  • Erythrocytes are 45% of total blood volume.

  • Buffy coat is leukocytes and platelets in a centrifuged sample.

Leukocytes (White Blood Cells)

  • Major component of the body’s defenses against disease.

  • Protect the body against invading microorganisms and body cells with mutated DNA, and they clean up debris.

  • Far less numerous than RBCs.

  • True cells- possess a nucleus and organelles.

  • Normal value 4,000- 11,000 per microliter of blood.

  • Life span ranges from few days to few hours.

Types of Leukocytes

  • Neutrophils: Engulf bacteria and cellular debris (37-77%).

  • Lymphocytes: Produce antibodies, regulate the immune response (10-44%).

  • Monocytes: Engulf cellular debris, antigen processing (2-10%).

  • Eosinophils: Parasitic infections, allergic response (1-7%).

  • Basophils: Hypersensitivity, release histamine (0-1.6%).

Platelets

  • Not actually a cell but rather a fragment of the cytoplasm of a cell called a megakaryocyte.

  • Typically, 150,000- 450,000 per microliter of blood.

  • Critical to hemostasis.

Phlebotomy and Venipuncture

  • Phlebotomy: The withdrawal of blood from a vein.

  • Venipuncture: The puncture of a vein with a needle for the purpose of drawing blood.

Capillary Puncture

  • Smaller blood samples can be obtained by piercing the surface of the skin and collecting blood from the capillaries there.

Test Requisition

  • A form that reflects the order for the laboratory tests.

Equipment for Drawing Blood

  • Venipuncture chair

  • Alcohol wipes, sterile gauze, adhesive band-aids.

  • Povidone-iodine or benzalkonium chloride may be used if alcohol can cause inaccurate results for certain tests.

  • Tourniquet

  • Personal protective equipment

Evacuated Systems

  • Most common is the Vacutainer system (manufactured by Becton Dickinson).

  • Use a double-pointed needle, plastic needle holder/adapter, collection tubes.

  • Collection tubes are sealed to create a slight vacuum-called evacuation tubes.

  • Easy to collect several specimens from one venipuncture (uses interchangeable collection tubes).

  • Calibrated by vacuum to collect the right amount of blood.

  • Some tubes are prepared with additives needed to correctly process the blood.

  • Low potential for exposure to contaminated blood.

Butterfly Systems

  • Winged infusion set

  • Small or fragile veins

  • Usually uses a smaller needle (23 gauge).

  • Collection tubes

  • Specimens must immediately be mixed with the appropriate additives in the correct collection tubes before they are transported to the laboratory for testing.

Common Blood Collection Tubes

  • Various colors indicate different additives.

  • Examples:

    • Red (None)

    • Red Marble Top or Gold (Clot activator and gel for serum separation)

    • Light Blue (Sodium Citrate)

    • Green (Sodium Heparin or Lithium Heparin)

    • Lavender (EDTA-ethylenediamine tetraacetic acid)

    • Gray (Potassium Oxalate/Sodium Fluoride or Sodium Fluoride)

    • Yellow (SPS-Sodium Polyanethol-sulfonate)

    • Yellow Marble Top or Orange (Thrombin)

    • Light Green (Lithium Heparin and gel for plasma separation)

    • Pink (EDTA)

    • Tan (Sodium Heparin [glass tubes] EDTA [plastic])

    • Royal Blue (Sodium Heparin EDTA None)

Blood Collection Tubes - Order of Draw

  • 1st: Blood Culture (Culture Media) - Must draw first: use sterile technique

  • 2nd: Coagulation Studies (Sodium Citrate) - Invert 3-4 times

  • 3rd: Chemistry (Clot activator, silicone-coated) - Invert 5 times

  • 4th: Chemistry (Gel for serum separator) - Invert 5 times

  • 5th: Chemistry (Clot activator) - Invert 8 times

  • 6th: Hematology (K2 EDTA) - Invert 8-10 times

  • 7th: Hemoglobin A1C (EDTA) - Invert 8 times

  • 8th: Blood Group Cross-matching (Sodium Fluoride) - Invert 8-10 times

    • Note that blood culture and blood glucose are likely not relevant for a bleeding patient.

Capillary Puncture Details

  • Smaller blood samples.

  • Collected in small calibrated glass tubes or on glass microscope slides.

  • Applied directly to reagent strips.

  • May also use special screening cards for tests such as phenylketonuria (PKU).

Lancets

  • Used for capillary puncture.

  • Automatic puncturing devices are more accurate and comfortable.

Capillary Tubes

  • May be used to collect capillary blood for certain tests.

Patient Interaction

  • Greet and Identify Patient.

  • Verify that the name that the patient gives is the same name on the requisition slip.

  • Most facilities verify date of birth or require photo ID for adults.

  • Fasting is the most common requirement for pretest preparation (ex: lipid profile, fasting blood glucose).

Chain of Custody

  • Procedure for ensuring that a specimen:

    • Is obtained from a specified individual.

    • Is correctly identified.

    • Is under the uninterrupted control of authorized personnel.

    • Has not been altered or replaced.

  • Used for drug, alcohol, paternity testing.

  • Patient must sign a consent for testing.

Interacting with the Patient

  • Remain professional.

  • Do not ask about medical conditions.

  • Do not offer opinions or advice regarding conditions.

Bruising/Hematoma

  • Explain that some bruising is possible but that it will fade in a few days.

  • Most bruising caused by a hematoma, which occurs when blood leaks out of the vein and collects under the skin.

  • Hematomas can be prevented by releasing the tourniquet before withdrawing the needle and applying proper pressure over the puncture site.

Patients at Risk for Uncontrolled Bleeding

  • Patients with a bleeding disorder such as hemophilia.

  • Patients who are taking blood-thinning medication.

  • Hold several gauze squares over the puncture site for at least 5 minutes to make sure bleeding has stopped completely.

Difficult Venipuncture

  • Allow yourself two tries to get the appropriate blood samples.

  • Some facilities have a venoscope, which is a piece of equipment that uses LED lights to illuminate the subcutaneous tissue and highlight the veins.

Fainting

  • Always position patients so that if fainting does occur, no injury will result.

  • If the patient does faint and the needle is still in the vein, release the tourniquet and withdraw the needle quickly and safely.

  • Apply pressure to the site.

  • Most people come around without intervention.

  • Do not leave the patient alone.

Most Common Sites for Venipuncture

  • Antecubital fossa (Median cubital vein, Cephalic vein, Basilic vein)

  • Important anatomical structures: Brachial artery, Median nerve, Ulnar artery, Radial artery.

Blood Cultures

  • Collected to test for the presence of bacteria in the blood.

  • When collecting these, it is important that no skin organisms contaminate the specimen.

  • Proper aseptic technique is essential.

  • If drawing additional specimens for other tests, ALWAYS draw the blood culture first to eliminate possibility of contaminating the culture with additives from other tubes.

Venipuncture Complications

  • Hematoma- collection of blood that forms under the skin.

  • Hold the needle still.

  • Hold pressure on the venipuncture site as soon as you remove the needle.

  • Have patient elevate the arm but not bend the elbow.

  • Nerve Injury: Inserting a needle into a nerve can cause nerve damage. Know and understand the anatomy of the antecubital fossa.

  • Infections: Rare, but they do occur and can be serious. Use only approved single-use venipuncture equipment. Cleanse the venipuncture site well before the procedure.

Hematologic Tests

  • Complete Blood Count includes:

    • Red blood cell count

    • White blood cell count

    • Platelet count

    • Hematocrit

    • Hemoglobin

  • Hematocrit- identifies how much of a specimen’s volume is made of erythrocytes after the specimen is spun in a centrifuge.

  • Plasma: Water, proteins, nutrients, hormones, etc.

  • Buffy coat: White blood cells, platelets

  • Hematocrit: Red blood cells

  • Normal Blood hematocrit:

    • 37%-47%

    • 42%-52%

  • Anemia: Depressed hematocrit %

  • Polycythemia: Elevated hematocrit %

Differential Count

  • The percentage of each type of leukocytes in the first 100 leukocytes of a specimen.

Normal Differential Count

Key:

  • Cell Type %

  • Neutrophils 50-70

  • Eosinophils 1-3

  • Basophils 0-1

  • Lymphocytes 25-35

  • Monocytes 4-6

Morphology

  • The study of the shape or form of objects.

  • Hereditary Spherocytosis and Sickle Cell Disease are examples of abnormal morphologies.

Coagulation Tests

  • These may be ordered to identify potential bleeding problems before surgical procedures.

  • Or to monitor therapeutic drug levels when a patient is receiving anticoagulant therapy (heparin, coumadin).

Erythrocyte Sedimentation Rate

  • The rate at which red blood cells settle in whole blood.

  • Measures the distance in millimeters that they fall in one hour.

  • Screen for the presence of any inflammatory process and does not diagnose any one condition.

Blood Chemistry Tests

  • Evaluates various components in the blood.

  • Examples: Glucose, Sodium, Potassium, Chloride, Carbon dioxide, Anion gap, BUN, Creatinine, GFR estimate, Calcium, Total bilirubin, Total protein, Albumin, Alkaline phosphatase, AST, ALT, Cholesterol, LDL cholesterol, HDL cholesterol, Triglycerides.

Hemoglobin A1C

  • Test that measures the health of diabetic patient.

  • Measures the amount of glycosylated hemoglobin in the blood.

  • Test results provide an idea of the average blood sugar for 2-3 months.

    • Normal: Below 5.7%

    • Prediabetes: 5.7 to 6.4%

    • Diabetes: 6.5% or higher