Blood has to be tested in most of the blood-related disorders, metabolic disorders and various infections. There are two different ways of obtaining the blood depending upon the volume of blood required for the test.
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1. Capillary or Peripheral Blood
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2. Venous Blood.
Capillary Blood Collection:
Capillary blood is obtained by pricking the tip of finger, lobe of ear, from the toe, and in infants it is obtained from the heel.
However, the most convenient place to prick is finger. It is to be pricked from about half (1/2) cm from the nail. It is to be pricked about 3 mm deep. The area to be punctured should not be cold. If it is cold, warm it by massaging. Disinfect the site of puncture by using spirit or 95% alcohol.
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Wipe-off the first drop of blood, and use the next drop for testing. After obtaining sufficient amount of blood, let the patient apply slight pressure by using spirit with sterile swab.
This way of blood collection can be used when the amount of blood required is only few drops, like Hb, TLC, DLC, etc. For capillary puncture, sterile needle or sterile lancet should be used.
Generally, nowadays, disposable needles are used. If, reusable needles are used, it should be sterile one.
Venous Puncture:
When large quantity of blood is required, it is obtained from the vein. Generally, vein of arm is used. There are five veins passing through arm. These are Cephalic vein, Basilic vein, Accessory Cephalic vein, Median vein and anterior ulnar vein.
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Any prominent vein is used for the collection of blood. In some cases, vein from wrist part or leg can be used, but it should be prominent.
The Collection Process:
First of all assemble all the necessary equipment’s such as,
1. Needle
2. Syringe
3. Tourniquet
4. Disinfectant
5. Cotton-swab
6. Tray of water
7. Collection bottle
Needle:
Sterilized sharp needles of bore size of 18 to 20 gauges (medium, 1.2 to 0.9 mm) for adults and 23 gauges (0.5 mm) for children are needed.
The length should be medium, about 20 mm for adults, and short about 15 mm for children are used. Generally, disposable needles are recommended. If reusable needles are used, it should be sterilized properly.
Syringe:
Syringe of different capacities like 2 ml, 5 ml, 10 ml, 20 ml, are available. The size of syringe should be selected on the basis of amount of blood required for testing. Generally, disposable syringes are used if reusable syringes are used, it should be washed immediately and then sterilized before using.
Tourniquet:
It may be soft rubber tube or belt. It is applied to arm about three inches above the elbow. It helps to slow the blood flow and makes vein more prominent, so that the puncture site is selected.
Disinfectant:
To clean and disinfect the site of puncture, disinfectant is used. It may be spirit or alcohol.
Cotton Swab:
It is used to apply the disinfectant.
Water Bath or Water Tray:
Water tray should be used in case, if reusable syringes are used. If any small amount of blood is present inside the syringe after pouring in a container, the blood will be dried and clotted. This will be difficult in cleaning and in the movement of piston to reuse. Therefore, water tray is used for rinsing the syringe immediately.
Collection Bottle:
The bottle should be sterilized and with cap. If anticoagulant is required, it should be added within the bottle in proper amount before blood collection. The bottle should be labeled for patient’s identification.
Procedure:
1. First of all decide the amount of blood required and select the container according to the test to be done.
2. Now ensure the patient what is to be done.
3. Lay the arm of the patient on the table.
4. Apply the tourniquet and select the prominent vein of the patient.
5. With cotton swab, disinfect the puncture site.
6. The cotton swab should be previously soaked in the disinfectant.
7. Assemble needle and syringe, check that, it is sharp and unblocked, and it is moving smoothly. Passing air through the syringe can do this. But there should not be any air present in the syringe at the time of blood collection.
8. With the left hand, hold patients arm, so that skin over vein is tightened. Ask the patient to open and close the wrist.
9. Take the syringe in right hand, holding index finger against the base of the needle, keep the point of needle to upper side and push firmly and steadily without any hesitation into the center of vein.
10. The angle between skin and needle should not be more than 30 to 40°. The moment needle enters in vein, blood flows back into syringe.
11. With your left hand, slightly pull back the piston till required amount of blood is obtained in the syringe.
12. Now, remove the tourniquet, place cotton swab over the needle and wound. Withdraw the needle slowly, and ask the patient to place a cotton swab over the wound. This stops bleeding from wound.
13. Remove the needle from the syringe and gently expel the blood into appropriate container.
14. If anticoagulant is used, gently shake the bottle for proper mixing.
15. If reusable syringe is used immediately wash the needle with water using water tray.