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Unformatted text preview: no analytical or physiological significance Venous blood is used because of the ease of collection For a limited number of analytes, such as blood gases and lactic acid, significant differences arise between venous and arterial blood Most testing is performed on the liquid or serum fraction of blood that has been allowed to clot The assumpttion is made that the distributionn of constituents between the cellular and extracelluar components of the blood is equal One can extrapolate the concentration of an analyte in blood from that measured in serum is equal This assumption is usually valid for some analytes it is necessary to inhibit the blood clotting process using an anticoagulant Other analytes require the addition of a preservative for accurate results Venipunture devices
Venipunture devices The three most commonly used devices in venipuncture include:\ The evacuated system Syringe Butterfly infusion The evacuated system
The evacuated system Consists of A needle Tube holder Tube The needle screwed securely to the tube holder and evacuated tubes slides easily into the opening of the holder
To secure a tube it is pushed onto the needle up to the guideline on the tube holder.
Once the tube stopper is punctured completely by the needle the vacuum inside the tube draws blood Syringe
Syringe A syringe may be used particularly when a patient had very small fragile or damaged veins, tht might easily collapse due to the vacuum pressure of the tube
Syringes require a needle that locks onto the collection device
The phlebotomist creates a controlled vacuum by gently pulling the plunger back to draw blood into the container
The vacuum may be less forceful and better for veins easily damaged Butterfly infusion Butterfly infusion A butterfly holder has a needle attached to it A piece of plastic tubing connects the needle to an adapter that may be attached to a syringe of luer adapter Needles can be of different diameter and are distinguished by their color Routinely a 20 gauge needle may be used However, for patients with very poor or small veins a 21 gauge needle is recommended to decrease the amount of vacuum pressure on the vein There is conflicting data on sources of error in the use of certain needle sizes Particularly with regard to hemolysis Hemolysis is defined...
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This document was uploaded on 03/22/2014.
- Spring '14