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Intravenous Infusions and Related Tasks
Lesson 2: Obtain a Blood Sample
2-4
2-4. OBTAIN A BLOOD SPECIMEN WITH AN ASSEMBLED SYRINGE
An alternate method of drawing blood is to use an assembled needle and syringe.
a. Either a straight needle or a butterfly device may be used. The size of the syringe will be determined by the amount of blood required. The syringe volume should not exceed 20 cubic centimeters; the vacuum created during collection of a blood sample with a larger syringe may cause the vein to collapse. Smaller volume syringes should be used with pediatric patients or others with fragile veins.
b. After placing the constricting band and penetrating the vein with the needle as described above, slowly pull back on the plunger to withdraw the required amount of blood. Excessive vacuum will be created if the plunger is pulled back too forcefully, and the vein may collapse.
c. If the blood volume required is greater than the volume of the syringe, the filled syringe may be removed from the needle and a new one attached. The process described above will be continued until the required volume is obtained. Extreme care must be taken to assure the needle is stabilized during blood drawing and syringe exchange.
d. If you have used a needle and syringe to obtain the blood, you will need to transfer the specimen into the tubes. Insert the needle into the rubber stopper of the tube and the vacuum within the tube will draw the specimen in and fill the tube. Transfer must be done promptly to prevent clotting of the blood in the syringe. Label tubes as in the instructions above.
