Clinical Chemistry 2 collection of specimens

Butterfly apparatus attached to a vacutainer is

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Unformatted text preview: as damage to erythrocyte (red blood cell) membranes Causes leakage of cellular constituents into the plasma Some say large bore causes hemolysis due to high pressure and some say small bore causes hemolysis Hemolyzed specimens are unacceptable for many clinical tests Serum Separators Serum Separators The old type vacutainers required very careful separation of plasma or serum from the cellular components of blood In order to completely remove contaminating cells several centrifugations steps were necessary The advent of the serum separator has eliminated these steps Devices may be either integrated gel­tube system or devices inserted into the collection tube just before centrifugation Gel is at the bottom of the tube During centrifugation – because of its viscosity and density – the gel floats to a position above the cells and below the serum Pediatric Venipuncture Pediatric Venipuncture • If the venipuncture must be performed on a child younger than 2 years of age • A tuberculin or 3 ml syringe with a 21 or 23 gauge needle or butterfly apparatus attached to a vacutainer is recommended • Only superficial veins should be used and those needed for IV infusion should be avoided • The child should be well secured to avoid injury This tube draws 3mL of venous blood and is ideal for pediatric venipunctures.. Pediatric patient Pediatric patient Special consideratin should be given to the small amount of blood of the pediatric patient This makes is necessary to keep a record of each lood withdrawel with the amount Date and time in the patient chart – the patient could devleop anemia Specimen collection by skin puncture Specimen collection by skin puncture Blood sample collection by skin puncture from sites such as the finger, heel, earlobe, big toe Used when venipuncture is nto pratical Burns Obesity Small or extemely damaged veins Intravenous fluid flowing into the only accessible veins Infants Neonates Adequate specimens may be collected for measurement of NA+, K+, and Cl­, glucose, bilirubin, Ca2+, blood gas analysis Skin puncture is composed of capillary, venous, and arterial blood as well as intracellular and tissue fluids The first drop of blood is usually discarded because it contains excessive tissue fluid from the puncture Collection Variables Collection Variables Diurnal Variation The first item that must be considered in evaluating the clinical significance of results is the time of day the sample was taken Some analytes demonstrate significant diurnal variation Glucose Iron Estriol Catecholamines Corticosteroids Triglycerides Variations for these substances may be as much as 30% to 50%. Unless there is specific contraindications – it is best to collect samples as soon as the patient wakens Posture Posture The posture of the patient at the time of collection can have a significant effect upon protein and protein bound substances in the serum Some serum components known to demonstrate postural variation Total protein, albumin, lipids, iron, calcium, enzymes Why posture? Why posture? When a patient goes from the supine to the standing position these serum constituents increase their concentration 5% to 15% This is probably caused to the movement of water out of the intravascular space upon standing Sources of error in venipuncture Sources of error in venipuncture Prolonged tourniquet applications. Failure to dry site after cleasning Wrong insertion depth of needle Many other variables including improper labeling Stasis Stasis Prolonged use of a tourniquet may elevate a number of laboratory results The application of a tourniquet for an extended period results in a stasis or pooling of blood above the constriction Tourniquets should always be avoided during the collection of samples for blood gas analysis or for lactic acid determination Prolonged use of a tourniquet will increase the serum concentrations of protein and protein­ bound substances 3 minutes is time enough for this to happen...
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This document was uploaded on 03/22/2014.

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