MT 12 LAB

• • specimen. collection is the first step in most laboratory analysis. [actually patient identification]
  • accuracy and precision can be measured by the proper specimen collection and handling
  • test results are therefore said to be as good as sample collection and handling
• PATIENT ID procedures;

  1. Conscious Inpatients - verbally ask full name, verify using ID bracelet [adult: wrist; infanst: foot] involving the first and last name, hospital # / unit #, room / bed, and physician’s name
• Patient ID procedures:

  2. sleeping patients - must be awakened before blood collection, identified same as conscious patients.

  3. unconscious, mentally incompetent patiens - identified by asking the attending nurse or relative; ID bracelet
• Patient ID procedures:

  4. Infants and children - nurse or relative may identify the patient or by ID bracelet.

  5. Outpatient patient - verbally ask full name, DOB and counterchek with driver’s license or ID with photo. If patient has ID card or bracelet, same manner as hospitalized patients
• Characteristics of blood

  • it is in fluid form in vivo due to the naturally circulating anticoagulants, but in vitro it coagulates within 5-10 minutes
  • red in color due to hemoglobin
  • a pH average of 7.4 (<7.45 - metabolic acidosis condition, hyperventilation, compensate with oxygen >7.5 metabolic alkalosis compensate with bicarbonate else kidney injuries)
• Characteristics of blood

  • thick and viscous, 3.5 - 4.5 thicker than water
  • for adult males, they have approx. 5-6 L of blood and 4-5 L of blood foor adult females
  • men are recommended for donation, females must donate 2 wks before / after menstruation
• Composition of blood

  1. Liquid portion

  Plasma - liquid portion of the unclotted blood with the protein fibrinogen

  Serum - liquid portion of the clotted blood without the fibrinogen

  2. Solid portion - RBCs and WBCs

  3. Gaseous portion - involve an exchange between oxygen and CO2; important in arterial blood gas (ABG).

  in a plasma sample: the part with the WBC and platelets is BUFFYCOAT; if leukemic = high WBC
• WBCs

  bacterial = neutrophil

  parasitic / allergies - eosinophil

  chronic infection = basophil

  bacterial / viral / chronic - monocyte (macrophages if inside the tissue; TB patients = high monocyte count)

  viral infection: lymphocyte
• Skin puncture / capillary puncture

  • a fingerstick to obtain blood for routine laboratory analysis is usually preferred for children.
  • length of lancet: 1.75 mm
  • depth of incision <2.0 mm for children and <2.5 mm for adults.
  • the cut should be oriented across the fingerprints to generate a large drop of blood using single deliberate motion
• For newborn, the lateral side of the heel (skin puncture)
• Preferred sites for skin puncture:

  1. Lateral plantar heel surface
  2. Palmar surface of the non-dominant fingers (3rd and 4th fingers - most coomon)
  3. Plantar surface of the big toe
  4. Earlobes - least site
• Sites to avoid [SP]

  • inflammed and pallor areas
  • cold and cyanotic areas (lack of blood supply)
  • congested and edematous areas (water and tissue juice)
  • scarred and heavily calloused areas
• advantages of skin puncture

  • it is accessible to the operator
  • easy to manipulate
  • ideal for peripheral blood smears (for dengue patients, drop near the patient)
  • less painful due to lesser nerve endings
  • there is more free flow of blood due to thinner skin layer
  • less tissue juice contamination due to lesser tissues and muscle (earlobe).
• Disadvantages of skin puncture

  • less amount of blood can be obtained
  • additional and repeated test cannot be done
  • blood obtained has tendencies to hemolyze easily
• hemolysis ; red-colored plasm / serum due to ruptured red cells
• alcohol, gauze, bandages

  • CLSI (Clinical Laboratory Standard Institute) recommends using 70% isopropyl alcohol to clean capillary bed of the skin with a lancet or other sharp device. If allergic to both, use 2% chlorhexidine.
  • gauze or cotton balls are used to wipe away the first drop of blood to eliminate alcohol residue and excess tissue fluid.
  • Bandages are used to cover the site after collection.
• Lancets

  • sterile, disposable, sharp instruments used for capillary puncture. their blades / points must permanently retract to prevent sharp injuries
  • automatic lancet: cannot control the depth of incision
• Warming devices (for patients with low / decreased blood circulation - increase blood flow)

  • warming the sites increases blood flow up tot seven times and is especially important when performing heel sticks
  • water temperature must not exceed 42 degrees celsius or it could scald the patient
  • minimum time is 5 minutes; for new born: immerse the foot in the basin with warm water
• Microcollection tubes

  • special small plastic tubes often referred to as bullets
  • must have color-coded stoppers that correspond to color-coding of ETS tubes
  • min: 0.5 mL / 500 microliters
  • max: 1 mL / 1000 microliters
  • red top: can fill til the top
• Microhematocrit tubes

  • narrow-bore capillary tubes primarily used for manual hematocrit determinations
  • either coated with heparin for collecting directly. from a capillary puncture or plain to be used when filling with blood from an EDTA tube
  • 2 capillary tubes per patient to balance during centri
  • blue band: no anticoagulant (ex: if from EDTA TUBE)
  • red band: with anticoagulant (heparin in skin puncture)
• Sealants: are claylike substances used to seal one end of of microhematocrit tubes

  2 sealant: clay seal and paraffin wax

  • 4 - 6 mm long (clay seal)
  • paraffin wax after
• Indications for. capillary puncture (dialysis / cancer patients)

  • can be done if small amount of blood is required
  • there are no accessible veins
  • available veins are fragile or must be saved for other procedures such as chemotherapy
  • blood is to be obtained for POCT procedures such as glucose monitoring
  • Capillary blood is the preferred specimen for some tests such as newborn screening (detect 25 congenital different diseases)
• Skin puncture

  1. Identify patient properly

  2. Verify patient's condition (medication taken - for coag studies need to increase blood thinner, allergies, how they feel)

  3. Position the patient (if patient is in supine position, let them stay as is because it could cause hemodilution, if sat down, wait for 5 mins)

  4. Choose the best location for fingerstick namely the 3rd and 4th fingers of the non-dominant (not used in writing) hand

  5. Disinfect the site of collection in concentric fashion; up down and side to side

  6. Allow area to dry completely

  7. Prepare the materials needed

  8. Make a skin puncture using sterile lancet

  9. Wipe away first drop of blood

  10. Collect drops of blood into the capillary tube

  11. Fill 2.3 of the two tubes

  12. Invert capillary tubes to mix (4 times - red band; none - blue)

  13. Place cotton on a puncture site and instruct patient to apply pressure until bleeding stops (5-15 mins; otherwise: hematoma)

  14. Seal tubes with clay and paraffin wax

  15. Dispose contaminated materials to appropriate containers
• Venipuncture

  • a process by which blood is obtained from a patient’s vein.
  • venous blood is the deoxygenated blood with a dark red color
  • sites: antecubital fossa, veins of the wrist, dorsal aspect of the hands, veins of the ankle
  • methods: syringe and evacuated tube
• Antecubital fossa

  • median cubital vein is the best site for venipuncture because it is the largest and the best anchored vein
  • cephalic vein: second choice
  • basilic vein: third choice
  • Basilic veins should not be chosen unless no other vein is more prominent due to its closeness to the brachial artery
• sites to be avoided:

  • intravenous lines in both arms
  • burned or scarred areas
  • areas with hematoma
  • edematous arms
  • cast on arms
  • thrombosed veins
  • arms with arteriovenous (AV) shunt or fistula
• things to remember for venipuncture:

  • verify that any dietary restritctions have been met (fasting, if appropriate) and check for any sensitivty to latex.
  • apply the tourniquet 3 -4 inches above the site and instruct the patient to make a first. never leave the tourniquet longer than one minute.
• things to remember for venipuncture:

  • disinfect the patient’s skin with alcohol pad starting at the point where you expect to insert the needle and moving outward in even widening concentric circles.
  • angle for needle insertion is between 15-30 degrees with the bevel side up
  • always remove the tourniquet first before withdrawing the needle. For evacuating tube method, remove tehe tube first and then the adaptor with needle.
• Proper labeling

  • a properly labeled sample is essential so that the results of the test match the patient, the key elements in labeling are:
  • patient’s surname, first and middle
  • patient’s id number / birthday and age (both ^^ should match the requisition form)
  • date, time of collection and initials of the phlebotomist must be on the label of each. tube
• Needle specifications

  • gauge of the needle is INVERSELY PROPORTIONAL related to the size of the needle, the larger the. gauge number, the smaller the needle bore and length
  • 21 gauge needle: standard for venipuncture
  • 23 gauge needle: for children, small, and difficult veins
  • 16 gauge needle: for blood donation
  • needle length: 1 inch or 1.5 inches - 21 to 23 gauge
• Syringe system

  • used for patients with small and difficult veins
  • has components including a. plastic syringe, hypodermic needle, and transfer device.
• Evacuated tube system:

  3 basic components:

  1. Multisample needle: allows collection of multiple tubes during venipuncture, can be screwed into a tube holder, has a beveled point on each end
  2. tube holder / adapter: a plastic cylinder with a small opening for a needle at one end and a large opening for tubes at the other
  3. evacuated tubes - have a premeasured vaccum that automatically draw the volume of blood indicated on the label
• Butterfly system

  • a short needle with a plastic part resembling butterfly wings and a length of tubing with a Luer fitting for syringe use or a luer adapter for ETS use.
  • 23 gauge: most commonly used for phlebotomy
• Complications encountered in blood collection:

  • ecchymosis (bruise): most common encountered in obtaining a blood specimen; caused by leakage of a small amount of fluid around tissue
  • syncope (fainting) - second most common complication. before drawing blood, the collector should ask if he / she had prior episodes of fainting
  • hematoma - when leakage of a large amount of fluid around the puncture site causes the area to swell. most commonly occurs when needle goes through the vein, beven is partially in the vein, and failure to apply enough pressure
• Complications encountered in blood collection:

  • failure to draw blood - one reason is that the vein is missed because of improper needle positioning. other reasons: excessive pull of plunger, piercing the other pole of the vein, incorrect bevel positioning, and absence of vacuum
  • petechiae - small red spots indicating the small amounts of blood have escaped into the skin epithelium
• Complications in Blood collection

  • edema - swelling caused by an abnormal accumulation of fluid in the intracellular spaces
  • obesity - veins may be neither readily visible nor easy to palpate, can use of a blood pressure cuff in locating the vein. cff should not be inflated any higher than patient’s diastolic pressure and should not bbe left on the arm longer than 1 minute
• complications encountered in blood collection

  • hemoconcentration - increased conc of large molecules and analytes (potassium) in the blood as a result of shift in water balance, can cause by leaving tourniquet on the patient’s arm for too long
  • hemolysis - rupture of RBCs with the consequent escape of hemoglobin, canuse the plasma or serum to appear pink or red
  • other complications - IV therapy, burned, damaged, scarred, and occluded veins, seizure and tremors, vomiting and choking, allergies and mastectomy patients
• physiologic factors affecting test results:

  • posture - chaing from supine to a sitting or standing position -> shift of body water from inside the blood vessels to the interstitial spaces
  • diurnal rhythm - levels of certain hormones such as cortisol and adrenocorticotrophic hormone decreases in the afternoon. other test values, like iron and eosinophil levels increases in the afternoon
  • exercise - muscle activity elevates creatinine, protein, creatine kinase, AST and LDH, activated coagulation and fibrinolysis and increases platelet and WBC
• physiologic factors affecting test results:

  • stress - anxiety can cause a temporary increase in white blood cells
  • diet - if a patient has eaten recently (less then 2 hrs earlier), there will be temporary increase in glucose and lipid content in the blood. serum may appear cloudy and turbid.
  • smoking - patients who smoke before blood collecitn may have increased white blood cell counts and cortisol levels. long term smoking can lead to decrease pulmonary function -> increased hemoglobin levels
• Additives in collection tubes

  • antiglycolytic agent - inhibits the use of glucose by blood cells. ex: sodium fluoride and lithium iodoacetate
  • anticoagulant agent - prevents blood from clotting. the mechanisms by which clotting is prevented varies with the anticoagulant.

  EDTA, CITRATE, OXALATE remove calcium by forming insoluble salts, whereas heparin prevents the conversion of prothrombin to thrombin. If calcium is removed or thrombin is not formed, coagulation does not occur