4.3 Collection Compliance & Patient History Assessment
Key Takeaways
- Venipuncture must never be performed on the arm ipsilateral to a mastectomy due to disrupted lymphatic drainage, lymphedema risk, and heightened infection vulnerability.
- Selecting edematous, scarred, burned, or hematoma-covered skin distorts laboratory results due to tissue fluid dilution and hemolysis.
- Phlebotomists must never draw blood proximal to (above) an active IV line; the opposite arm or a site distal to the IV after a mandatory nurse shutoff period must be used.
- Applying a tourniquet for longer than 1 minute causes hemoconcentration, falsely elevating potassium, total protein, iron, lipids, and cellular blood counts.
- Strict adherence to fasting protocols (8–12 hours) and awareness of diurnal variations (e.g., morning peak cortisol and iron levels) are critical to pre-analytical sample integrity.
4.3 Collection Compliance & Patient History Assessment
Pre-analytical variables represent up to 70% of all diagnostic laboratory errors. A primary responsibility of the phlebotomist is evaluating the patient's physical condition to identify anatomical sites that must be avoided. Performing venipuncture on compromised sites can endanger patient health and produce inaccurate laboratory test results.
| Contraindicated Site | Clinical Concern / Risk | Required Action / Alternative |
|---|---|---|
| Mastectomy Side (Same Arm) | Lymphostasis, lymphedema, severe infection risk | Use opposite arm; seek physician clearance if bilateral |
| Edematous Tissue | Interstitial fluid dilutes blood sample analytes | Select non-edematous site; avoid swollen extremities |
| Hematoma Area | Sample contamination with hemolyzed, stagnant blood | Draw distal to (below) hematoma or select alternate arm |
| Extensive Scarring / Burns | Impaired circulation, difficult vein palpation, infection | Select undamaged anatomical area |
| Dialysis AV Fistula / Graft | Destruction of surgical access graft, severe hemorrhage | NEVER draw from or apply tourniquet to shunt arm |
Mastectomy & Lymphostasis
When a patient undergoes a radical or total mastectomy, surgical removal of axillary lymph nodes disrupts normal lymphatic drainage. Performing venipuncture or applying a blood pressure cuff/tourniquet on the arm on the same side (ipsilateral arm) can trigger severe lymphedema (chronic, painful swelling caused by fluid accumulation) and increases vulnerability to life-threatening bacterial infections. If a patient has had a single mastectomy, the phlebotomist must use the opposite arm. If the patient has had bilateral mastectomies, the phlebotomist must consult the attending physician to obtain written clearance for an alternative collection protocol.
Edema, Scarring, and Hematomas
- Edema: Accumulation of fluid in the interstitial tissue spaces distorts vein locations and dilutes blood specimens with tissue fluid, causing falsely decreased analyte concentrations (e.g., falsely low hemoglobin or total protein).
- Hematomas: A hematoma forms when blood leaks into surrounding tissues. Drawing blood through a hematoma yields a sample contaminated with hemolyzed, hemoconcentrated blood, causing erroneous potassium and enzyme elevations while causing significant pain to the patient.
- Dialysis Arteriovenous (AV) Fistulas/Grafts: An AV fistula or synthetic graft is a surgically created connection between an artery and a vein used exclusively for hemodialysis. Phlebotomists must never draw blood or apply a tourniquet to an arm with an AV fistula or shunt. Accidental puncture can destroy the vascular graft or cause fatal blood loss.
4.3 Collection Compliance & Patient History Assessment
Collecting blood specimens from a patient receiving intravenous (IV) fluids or blood products requires extreme caution. Intravenous fluids (such as 0.9% normal saline, 5% dextrose in water, or total parenteral nutrition) dilute blood specimens and alter chemical concentrations.
[ Patient with Active IV Line ]
|
+------------------------+------------------------+
| |
[ PREFERRED: Draw Opposite Arm ] [ ALTERNATIVE: Draw Distal to IV ]
- Complete absence of IV fluid - MUST be BELOW (distal to) IV site
contamination risk. - Nurse MUST turn off IV for 2-15 min
- Standard venipuncture protocol. - Discard first 5 mL waste tube
- NEVER draw proximal to (above) IV
Rule 1: Always Prefer the Opposite Arm
If a patient has an active IV line in one arm, the phlebotomist's first choice must always be to collect the blood specimen from the opposite arm. Drawing from the non-IV arm completely eliminates the risk of fluid contamination.
Rule 2: Protocol for Drawing Below (Distal to) an IV Line
If both arms have IV infusions, or if the opposite arm is inaccessible due to contraindications, blood may be drawn distal to (below) the IV site under strict clinical controls:
- Nurse Intervention: The phlebotomist must request that a nurse turn off the IV infusion for a minimum of 2 to 15 minutes prior to the draw (to allow infused fluids to disperse from the capillary bed).
- Select Distal Site: Select a vein located significantly below (distal to) the IV needle insertion site.
- Discard Waste Tube: Collect and discard a 5 mL waste tube of blood before filling required diagnostic tubes to clear any residual diluted blood or anticoagulant contamination from the vein segment.
- Document on Requisition: Note on the laboratory requisition form that the specimen was drawn distal to an active IV line and specify which fluid was infusing.
Never Draw Proximal to (Above) an IV Line: Drawing blood above an active IV site causes the specimen to be heavily contaminated with infusing IV fluid. For example, drawing proximal to an IV infusing 5% dextrose will result in catastrophic, falsely elevated blood glucose readings (exceeding 1,000 mg/dL), leading to erroneous clinical management.
4.3 Collection Compliance & Patient History Assessment
Pre-analytical variables encompass all physiological, environmental, and technical factors that occur prior to laboratory analysis. Phlebotomists must control these variables to guarantee valid diagnostic data.
Tourniquet Application & Hemoconcentration
A tourniquet is applied to restrict venous return and distend veins, making them easier to palpate. However, prolonged tourniquet application causes hemoconcentration—a localized process where plasma filter out of the capillary walls into surrounding tissues, concentrating cells and large-molecule analytes within the blood vessel.
- Maximum Application Time: A tourniquet must never remain applied for longer than 1 minute (60 seconds).
- Effects of > 1 Minute Application: Falsely elevates potassium, total protein, iron, calcium, cholesterol, and red blood cell (RBC) counts. If tourniquet time exceeds 1 minute during vein selection, release it immediately and wait at least 2 full minutes before re-applying.
- Pumping Fists Warning: Patients must never be instructed to vigorously pump their fist. Vigorous fist pumping causes rapid muscle contraction that releases intracellular potassium, resulting in falsely elevated serum potassium readings (pseudohyperkalemia).
Fasting Status & Lipemia
Certain laboratory tests require strict patient fasting for 8 to 12 hours prior to collection (typically overnight):
- Fasting Tests: Lipid panels, fasting blood glucose (FBG), triglycerides, and gastrin.
- Ingestion Interference: Eating food causes temporary elevations in glucose and triglycerides. Non-fasting specimens often appear lipemic (cloudy or milky serum/plasma due to high chylomicron concentrations), which interferes with automated spectrophotometric testing instruments.
Posture & Diurnal Variation
- Posture (Positioning): Shifting from a supine (lying down) to an upright sitting position causes fluid to shift from blood vessels into tissue spaces, concentrating proteins, enzymes, and cell counts by 5% to 15%.
- Diurnal Variation: Concentrations of certain blood constituents fluctuate predictably throughout a 24-hour cycle. For example, cortisol levels peak early in the morning (6:00 AM – 8:00 AM) and drop significantly by evening. Serum iron and ACTH also exhibit marked diurnal fluctuations, making precise collection timing essential.
A phlebotomist is preparing to collect a blood sample from a patient who had a left-sided radical mastectomy three years ago. How should the phlebotomist proceed with site selection?
A patient has an active IV line infusing normal saline in the right antecubital fossa, and the left arm is wrapped in a full cast. If blood must be drawn from the right arm, what is the mandatory protocol?
A phlebotomist leaves a tourniquet applied for 2.5 minutes while searching for a suitable vein in an elderly patient. Which laboratory result error is most likely to occur as a direct result of this delay?