lesson 6 - pre-analytical considerations in phlebotomy

• pre-analytical testing phase includes procedures such as laboratory handling and identification which take place prior to any laboratory testing
• in pre-analytical testing phase, proper control measures are placed to avoid subsequent issues . It starts when the doctor's order is given and ends when the laboratory testing has officially commenced.
• laboratory test is used by physicians to diagnose and monitor the presence of a disease . The physicians compare the results to a reference range or reference interval.
• reference range or reference interval shows the high and low limits of result values compared to healthy individuals.
• the basal state is ideal in establishing reference range since it represents the condition of metabolism of the body early in the morning or after approximately 12 hours of fasting.
• basal state can be influenced by age, gender, and conditions of body
• the physiological variables that influence laboratory test results

  • age
  • altitude
  • dehydration
  • diet
  • diurnal variation
  • drug therapy
  • exercise/IM injection
  • fever
  • gender
  • jaundice
  • intramuscular injection
  • position
  • pregnancy
  • smoking
  • stress
  • temperature and humidity
• physiological variables - blood composition affected

  • age - RBC , WBC , CREATININE CLEARANCE
  • altitude - rbc
  • dehydration - hemoconcentration, rbc, enzymes, Fe, Ca, Na
  • diet - glucose, lipids, electrolytes
• physiological varirables - blood composition affected

  position - protein, potassium (K)

  pregnancy - rbc

  smoking - cholesterol, cortisol, glucose, growth hormones (GH), triglyceride, wbc

  stress - wbc, Fe, adrenocorticotropic hormone (ACTH), catecholamine, cortisol

  temperature and humidity - hemoconcentration
• problem areas to avoid and trouble shooting in the site infection

  1. burns, scars, tattoos
  2. damaged veins
  3. edema
  4. hematoma
  5. mastectomy
  6. obesity
• burns, scars, tattoos - may be difficult to examine and blood circulation may be impaired
• burns - may be painful to touch
• tattoos - may also be susceptible to infection due to the dyes used
• damaged veins - difficult to perform, produce inaccurate results. Could also be sclerosed or hardened or thrombosed or clotted
• edema - also known as as oedema, is an abnormal swelling caused by accumulation of fluid in the tissues . May be caused due to reactions from medications, pregnancy, infections, and other medical problems
• hematoma - a solid swelling of or mass of blood in the tissues caused by the leakage of blood from the vessels during venipuncture. Could also lead to contamination of blood sample
• mastectomy - surgical removal of breast tissue and lymph nodes
• obesity - a condition in which a person is overweight or has excess body fat
• obese patients - deep veins and difficult to locate . A solution is using a longer tourniquet or locating the cephalic or cubital vein
• Vascular access sites and devices (VADs) - are needed for blood sampling, infusing medication , central venous pressure readings, and blood transfusion of a patient.
• Vascular Access Sites and Devices used in phlebotomy

  1. arterial line
  2. arteriovenous shunt or fistula
  3. blood-sampling device
  4. heparin-saline lock
  5. intravenous (IV) sites
  6. central vascular access devices (CVADs)
• arterial line - to obtain samples, for arterial blood gas and blood pressure monitoring. Critically ill patients require this where a thin catheter is inserted into an artery
• arteriovenous shunt or fistula - a passageway v=created through surgery and is usually in the arms with the intention of connecting artery and a vein directly. This may be created for hemodialysis
• blood-sampling device - used to avoid the use of needle, sticks, prevent infections, and reduce wastage from line draws. This device collects blood from the arterial or central venous catheter where it is connected.
• heparin or saline lock - commonly called "hep=lock", is an IV catheter attached to a stopcock or cap with diaphragm. It provide access for administering medicine or drawing blood from the patient. It is threaded in the peripheral vein, which is in the lower arm above the wrist for up to 48 hours . It is usually flushed with heparin or saline (to prevent clogging) and capped for future use.
• Intravenous (IV) sites - a thin plastic tube catheter inserted into a vein in the forearm to inject a volume of fluids into the bloodstream
• central vascular access devices (CVADs) - also known as indwelling lines, are tubings inserted to the main vein or artery used for blood collection, monitoring the patient's pressures
• 3 types of CVADs

  1. central venous cathether
  2. implanted port
  3. peripherally inserted central catheter (PICC)
• central venous catheter - also known as catheter line inserted into the large vein (subclavian) and advanced into the superior vena cava
• implanted port - surgically implanted disk-shaped chamber attached to the indwelling line. Usually placed on the upper chest just below the collarbone.
• peripherally inserted central catheter - flexible tube inserted into the veins of extremities and the central veins
• Handling patient complications associated with blood collection

  • allergies to equipment and supplies
  • excessive bleeding
  • fainting
  • nausea and vomiting
  • pain
  • petechiae
  • seizures or convulsions
• Error Risks and Failure to Draw Blood

  1. hematoma formation
  2. iatrogenic anemia
  3. inadvertent arterial puncture
  4. infection
  5. nerve injury
  6. reflux of anticoagulant
  7. vein damage
  8. specimen quality
  9. troubleshooting failed venipuncture
  10. collapsed veins
  11. tube vacuum
• hematoma formation - a cold compress or ice pack may be offered to help address the swelling
• iatrogenic anemia - results from blood loss due to blood draw. It is important to ensure that only the amount of blood needed is drawn.
• inadvertent arterial puncture - happens when blood is filling up the tube rapidly and there is a rapid formation of hematoma on the site.
• nerve injury - happens when there is improper site selection , rapid needle insertion , excessive redirection of the needle and blind probing
• reflux of anticoagulant - presence of tube additives
• Factors affecting specimen quality:

  • Hemoconcentration
  • Hemolysis
  • Partially filled tube/ short draw
  • Specimen contamination
  • Wrong or expired collection tube
• hemoconcentration - a decrease in the fluid content or plasma volume