Preanalytical Considerations Chapter 9 Objectives List and describe

Preanalytical Considerations Chapter 9

Objectives List and describe the physiological variables that influence lab tests and identify the tests affected by each one List problem areas to avoid in site selection and identify causes for concern Identify and describe vascular access sites Identify and explain patient complications associated with blood collection Identify and explain procedural error risks and specimen quality concerns

Preanalytical Phase Preanalytical phase begins when a test is ordered and ends when testing begins Numerous factors associated with this phase can lead to errors that can affect specimen quality and jeopardize the patient’s health

Basal State Resting metabolic state of the body early in the morning after fasting for a minimum of 12 hours Reduces effects of diet, exercise, and other controllable factors on test results Outpatients are not at basal state

Physiologic Variables VARIABLE AFFECT Age Altitude Dehydration Diet Diurnal variation Drug therapy Exercise Fever Gender Jaundice (aka Icterus) Position Pregnancy Smoking Stress Temperature and humidity RBC, WBC, creatinine clearance RBC Hemoconcentration, RBC, enzymes, Fe, Ca, Na Glucose, lipids, electrolytes TSH, cortisol, Fe Enzymes, hormones p. H, PCO 2, CK, LDH, glucose Hormones, cortisol RBC, Hgb, Hct Yellow color interferes Protein, K CBC, fibrinogen CBC, cortisol, glucose WBC Hemoconcentration

Site Selection Variables that Influence Specimen Composition Site Problems: • Burns, scars, and tattoos • Damaged veins Sclerosed Thrombosed • Edema • Hematoma = swelling or mass of blood that is caused by blood leaking from a blood vessel during or following venipuncture • Mastectomy • Obesity

Site Selection Variables that Influence Specimen Composition Vascular Access Devices and Sites • Arterial Line = catheter placed in an artery No tourniquet! • Arteriovenous Shunt or Fistula • Heparin or Saline Locks • Intravenous Sites or previous IV Sites

AV Fistula

Central Vascular Access Devices (indwelling line) = inserted into a main artery or vein • Central Venous Catheter = inserted into large vein and into the superior vena cava • Implanted Port = small chamber attached to indwelling line that is surgically implanted under the skin • PICC = inserted into peripheral venous system and threaded into central venous system (main veins leading to heart)

Central Venous Catheter

PICC Line

Patient Complications and Conditions Allergies to latex, antiseptic, and adhesive Excessive Bleeding Fainting (syncope) Nausea/vomiting Pain Petechiae = tiny, nonraised red spots on patient’s skin when a tourniquet is applied Seizures/Convulsion

Petechiae vs. Purpura

Procedural Error Risks Hematoma Formation Iatrogenic Anemia = blood loss as a result of blood removed for testing • Removing blood on a regular basis or in large quantities Inadvertent Arterial Puncture Infection Nerve Injury Reflux of Anticoagulant Vein Damage

Specimen Quality Concerns Poor quality specimen = poor quality results Hemoconcentration from venous stasis • Tourniquet application causes venous stasis (impedes blood flow) • In response to venostasis, plasma and other components will pass through the capillary walls into the tissue resulting in hemoconcentration (decrease in fluid content of the blood) • Important to keep tourniquet application to 1 minute or less