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Chapter 7
PREEXAMINATION & PREANALYTICAL COMPLICATIONS
Categories of Preanalytical Variables
• Diet
– The term “fasting” refers to no food or drinks (except water).
– The required time period necessary for fasting should be for 8 to12 hours.
– Before collecting a specimen, the healthcare worker should ask the patient if he/she had
anything to eat or drink.
– If the patient has eaten recently, but the physician still needs the test, the word “nonfasting” must be written on the requisition and/or directly on the specimen.
– If asked to explain fasting restrictions to a patient, the instructions should be thorough and
clear, with emphasis on the important points of the procedure.
• Obesity
– Obese patients generally have veins that are difficult to visualize and/or palpate.
– If the vein is not entered when first punctured, the health care worker must be careful not
to probe excessively with the needle.
– Longer needles are available for collections from obese patients.
Categories of Preanalytical Variables
• Damaged, Sclerosed, or Obstructed Veins
– Obstructed or occluded veins do not allow blood to flow through them.
– Sclerosed or hardened veins are a result of inflammation and disease; and patients’ veins
that have been repeatedly punctured often become scarred and feel hard when
palpated.
– Because blood is not easily collected from these sites, they should be avoided.
• Allergies
– Chlorhexidine has been used as an alternative to decontaminate skin for patients who are
allergic to iodine, alcohol, or other solutions.
– Latex-free tourniquets, gloves, and bandages must be used for patients who are allergic to
latex.
– Check for color-coded armbands or posted signs indicating specific patient allergies.
Categories of Preanalytical Variables Cont.
• Mastectomy
– Patients who have undergone a mastectomy (i.e., surgical removal of the breast) often
have resulting lymphedema on the side of the surgery.
– The fluid in the area may make the patient more prone to infections.
– The arm on the side of the mastectomy must be protected from cuts, scratches, burns, and
blood collection.
• Edema (an abnormal accumulation of fluid in the tissues)
– Swelling can be localized or diffused over a larger area of the body.
– Veins in these areas are difficult to palpate or locate, and the specimen may become
contaminated with tissue fluid.
• Thrombosis
– Thrombi are solid masses derived from blood constituents that reside in the blood vessels.
– A thrombus may partially or fully occlude (close) a vein or artery, and such occlusion will
make venipuncture more difficult.
Categories of Preanalytical Variables Cont
• Burned, Scarred, or Tattooed Areas
– Burned areas are very sensitive and susceptible to infection.
– Veins under scarred areas are difficult to palpate.
–Collecting specimens from these sites can be very painful.
– Tattoos contain dyes that may interfere with laboratory tests. Also, tattooed areas are
susceptible to infections and impaired circulation.
• Vomiting
– Have the patient take deep breaths and use a cold compress on his/her head.
– Follow the health care facility’s protocol.
– Inform the phlebotomy supervisor and patient’s physician about this complication.
Complications Associated with Test Requests and Identification
• Identification Discrepancies
– Improper identification is the most dangerous and costly error a health care worker can
make, because it can be life threatening.
– Identification should include a match between the patient’s identification, his/her verbal
confirmation, and the test requisition.
– Discrepancies must be resolved before the collection of any samples.
• Time of Collection
– Early morning specimens are most commonly requested in hospital settings because a
fasting specimen is preferred.
– If a health care worker is running late, the specimen might be collected after an inpatient
has eaten breakfast and would require a special notation about the “non-fasting” condition.
• Requisitions
– Checking the requisition to match the laboratory tests requested with the appropriate type
of collection tube is essential to minimize the amount of blood collected from each patient.
Complications Associated with the Specimen Collection Procedure
• Tourniquet Pressure and Fist Pumping
– Laboratory test results can be falsely elevated or decreased if the tourniquet pressure is too
tight or is long.
– The pressure from the tourniquet causes biological analytes to leak from the tissue cells into
the blood, or vice versa.– Some enzyme levels can be falsely elevated or decreased
because of tourniquet pressure that is too tight or prolonged.
– Pumping of the fist before venipuncture should be avoided, because it leads to an
increase in the plasma potassium, lactate, and phosphate concentrations.
• Failure to Draw Blood
– Not inserting the needle deep enough
– Inserting the needle all the way through the vein
– Holding the needle bevel against the vein wall
– Losing the vacuum in the tube
• Needle Positioning
– During needle insertion, the gloved index finger can be used to help locate the vein.
– The needle may need to be moved or withdrawn somewhat and redirected.
– The only acceptable redirections are backward and forward in a straight line.
• Defective Tube
– On occasion, a blood collection vacuum tube will have no vacuum because of a
manufacturer’s error, age of the tube, or tube leakage after a puncture.
• Defective Tube– Needles for evacuated tube systems have been known to unscrew from
the barrel during venipuncture.– If this happens, the tourniquet should be released
immediately, and the needle removed.
• Fainting (Syncope)
– Syncope is the sudden loss of consciousness caused by
- lack of oxygen to the brain & results in an inability to stay in an upright position
– Low blood glucose
– Rapid breathing
– Heart ailments or mental conditions
– Medications
• Ask ambulatory patients if they tend to faint or if they have ever previously fainted during
blood collections. If so, they should be moved from a seated position to a lying position.
– If a seated patient feels faint, the needle and tourniquet need to be removed, the
patient’s head should be lowered between his/her legs, and the patient should be made to
breathe deeply.
– The health care worker should stay with the patient at least 15 minutes until he/she recovers
or until a nurse or physician takes over. A wet towel can be gently applied to the forehead
or a glass of juice or water may help the patient feel better.
• Hematomas Can Occur When:
– The needle has gone completely through the vein.
– The bevel opening is partially in the vein.
– Not enough pressure is applied to the site after puncture.
• Hematomas– If a hematoma begins to form, the tourniquet and the needle should be
removed immediately, and pressure should be applied to the area for approximately two
minutes.– If the bleeding continues, a nurse should be notified.
• Petechiae
– Small red spots appearing on a patient’s skin– Indicates that minute amounts of blood
have escaped into outer skin layers
– May be a result of a blood clotting abnormality and should be a warning that the patient’s
puncture site may bleed excessively
• Excessive Bleeding
– Patients on anticoagulant therapy, and/or high dosages of arthritis medication or other
medication, may bleed for a longer period.
– Pressure must be applied to the venipuncture site until the bleeding stops.
• Neurological Complications
– If the health care worker accidentally inserts the needle all the way through the vein,
he/she may hit the nerve below the vein.
– The patient will most likely have a sharp electric tingling (and painful) sensation radiating
down the nerve.
– The tourniquet should be released immediately, the needle removed, and pressure held
over the blood collection site.
– An incident report on the occurrence should be completed and given to the supervisor.
• Seizure– Rare complication– Immediately release the tourniquet,remove the needle, move
the patient toa lying position if he/she has not fallenalready, attempt to hold pressure
overthe blood collection site, and call forhelp from the nursing station
• Seizure– No attempt should be made to placeanything in the patient’s mouth unlessthe
health care worker is experiencedand authorized to do so
• Seizure
– Rare complication
– Immediately release the tourniquet, remove the needle, move the patient to a lying
position if he/she has not fallen already, attempt to hold pressure over the blood collection
site, and call for help from the nursing station
– No attempt should be made to place anything in the patient’s mouth unless the health
care worker is experienced and authorized to do so.
• Hemoconcentration
– The increase in red blood cells, and other cells and solids in the blood is caused from loss of
fluid in the surrounding tissues around the venipuncture site.
• Hemoconcentration Due to Several Factors
– Prolonged (i.e., longer than a minute)tourniquet application
– Massaging, squeezing, or probing a site
– Long-term IV therapy
– Sclerosed or occluded veins
• Intravenous Therapy
– Patients on intravenous (IV) therapy for extended periods often have veins that are
palpable and visible but damaged or occluded (blocked).
– The arm with the IV line should not be used for venipuncture because the specimen will be
diluted with IV fluid.
–Sometimes the nurse or the physician can disconnect the IV fluid and collect blood from
the line that is already inserted.
– The first few milliliters of the specimen should be discarded to remove the IV fluid.
– A note should be made on the laboratory requisition that this step was performed.
• Hemolysis
– Results when RBCs are lysed, hemoglobin is released and serum or plasma, which is
normally straw colored, becomes tinged with pink or red
– Can be caused by:
•
improper phlebotomy techniques
•
Using a needle that is too small
•
Expelling the blood vigorously into a tube
•
Shaking or mixing tubes vigorously
•
•
Performing blood collection before the alcohol has dried at the collection site
Pulling a syringe plunger back too fast
• Hemolysis may also be the result of physiological abnormalities
– Hemolysis causes falsely increased results for many analytes
– Hemolysis also shows falsely decreased RBC count, hemoglobin, and hematocrit
• Collapsed Veins
– Veins collapse when blood is with drawn too quickly or forcefully during venipuncture.
– In geriatric patients
– A collapsed vein should not be probed with the needle.
• Turbid or Lipemic Serum
– Turbid serum appears “cloudy” or “milky”.
– Can be a result of bacterial contamination or high lipid levels in the blood.
– Documentation about the appearance of the serum or plasma may be useful to the
physician.
• Improper Collection Tube
– Learn which common laboratory tests require which collection tubes.
– Be familiar with how and where to seek information about test and tube requirements.