HSBTE, 2nd Semester, DMLT, Collection and Preservation of Clinical Specimens for Biochemical Analysis of Blood.

BLOOD COLLECTION:

A laboratory technician who collects blood samples from the human body is called a phlebotomist. The phlebotomist should be well-trained to

• 1. Collect materials for specimen preparation

• 2. Fill laboratory request form properly

• 3. Collect medication information from patients carefully

• 4. Collect patient condition carefully

• 5. Interact with the patient pleasantly and confidently

• 6. Instruct patient carefully

• 7. Collect blood specimens properly and quickly

• Phlebotomist collects blood from the human body for the following purposes:

• 1. Investigation of microbiological infection

• 2. Investigation of hematological parameters and

• 3. Blood transfusion.

• 4. Investigation of blood gas.

Blood collection for biochemical analysis: A small volume of blood is required for biochemical investigation For this purpose blood is collected by skin puncture. Skin puncture provides capillary blood as a specimen. There are two types of skin puncture. Following venipuncture materials and equipment are used by the phlebotomist to collect blood from the vein of the patient: collection tube, needle, lancet, tourniquet, alcohol or iodine wipes or swabs, gauze, gloves, and disposable units.

Collection tube: It is also known as an evacuated collection tube. It is also used to store the blood collected through the venipuncture procedure. It is made up of glass or plastic.

Needle: A phlebotomist uses a needle to pierce into a vein to collect blood.

Tourniquet: It is a smooth wide band wrap arm and develops pressure to control blood flow inside the vein without damaging the vein.”

Swabs/wipes: The Venipuncture site should be cleaned and sanitized with an alcohol 70%v/v swab.

Gauze sponges: A Gauze sponge is applied to the venipuncture site after the withdrawal of blood from a vein Gloves: Gloves are the most important venipuncture material for the protection of both phlebotomists and patients. Gloves protect phlebotomists from any contamination from patient blood

1. Finger prick:

A finger prick is used to collect small amounts of blood from adults and grown-up children. The tip of the middle finger or ring finger on palmer side of the nonwriting hand is the most suitable site for a finger prick.

Procedure:

• · Arterialisation: Warm the fingertip by using a wet warm cloth or massage the fingertip to increase blood flow before the finger prick.

• · Clean the selected site by using a sterile cotton ball or gauze containing 70% ethanol or isopropyl alcohol.

• · Allow the cleaned site to dry.

• · Hold around the capillary puncture site without touching the capillary puncture site. This will prevent sudden movement of the capillary puncture site during pricking.

• · Make a sharp perpendicular incision using a sterile lancet.

• · Allow blood flow under gravitational force by putting your hand down.

• · Discard the first drop of blood.

• · Collect the next drop of blood as a blood specimen.

• · Place a cotton ball or gauze containing 70% ethanol or isopropyl alcohol on the fingertip for a few minutes.

Precautions:

• i. Don’t press the side of the finger, center of finger, or tip of the finger after incision to increase blood flow. It causes outflow of tissue fluid that is not part of blood plasma.

• ii. Incision should not be more than 2.5 mm to avoid nerve damage.

• iii. Don’t use the thumb and index finger as they have thick skin and more nerve supplies.

• iv. Don’t use the little finger as it has insufficient soft tissue depth.

• v. Don’t select swollen, damaged, scarred, infected, or rash fingers.

2. Hill prick:

A small amount of blood collection from infants is carried out using a hill prick for capillary puncture.

Procedure:

· Immobilize pediatric patients with the help of a parent or nurse (preferably a parent).

• · Carry out Arterialisation by covering the puncture site with a warm and moist towel for 3 to 5 minutes before the capillary puncture. Arterialization helps to collect adequate blood sample volume without applying pressure around the capillary puncture site.

• Clean the puncture site by using a sterile cotton ball or sterile gauze dipped in an aqueous solution of Isopropyl alcohol 70% v/v.

• · Allow air drying of the capillary puncture site.

• · Hold around the capillary puncture site without touching the capillary puncture site. This will prevent sudden movement of the capillary puncture site during pricking.

• · Incision or pricking should be made quickly and appropriately by using the lancet or incision device.

• · Wipe away the first drop of blood by using sterile cotton or sterile gauze.

• · Collect a second drop of blood

• · Avoid excessive pressure, massaging, and squeezing of the capillary puncture site during capillary blood collection. Excessive pressure causes hemolysis, blood contamination with interstitial and intracellular fluid

3. Arterial puncture:

Arterial puncture is carried out to collect blood samples for blood gas determination. The radial artery in the wrist or brachial artery in the elbow are selected for arterial puncture.

Procedure:

• i. Select a heparinized glass syringe with 18 or 20 gauze needles.

• ii. Perform arterial puncture and collect blood in a syringe.

• iii. Apply firm pressure on the puncture site for 5 minutes to stop bleeding.

• iv. Seal the nozzle of the syringe put it inside ice and transport it to the pathology laboratory.

4. Blood transfusion:

Blood is collected for blood transfusion by vein puncture technique. A phlebotomist conducts vein puncture to collect blood from the patient veins. The phlebotomist uses the following materials and equipment to collect blood from the vein of the patient: collection tube, needle, lancet, tourniquet, 70% v/v ethanol, or isopropyl alcohol. wipes or swabs, gauze, gloves, sterile wide-mouth bottle, and disposable syringe.

The following steps are followed for blood collection through vein puncture.

• a. Patient preparation: The patient should fulfill the following criteria before vein puncture.

  • · Patient should not consume any intoxicating substances and medicines.

  • · Patients should not undergo vigorous exercise just before the vein puncture procedure.

  • · There should be no allergy and anxiety in the patient.

  • · Patient should be comfortable and

  •  Lie down on his back with a straight arm resting on a pillow or

  •  In a sitting position with a straight arm and no bending at the elbow.

• b. Selection of the vein site: Veins located in the arm are suitable for vein puncture. Among them, the median cubital vein is the most suitable. The cephalic and Basilic veins are used if vein puncture is unsuccessful in the median cubital vein. For diabetes or CVS disease or any other reason superficial veins in the foot and ankle are also used for vein puncture.

• c. Cleansing the vein puncture site: Clean the vein puncture site by using 70% v/v ethanol. Allow to dry it.

• d. Vein puncture procedure: Follow the following steps to perform vein puncture:

  • i. Keep sterile venipuncture equipment readily available and within reach

  • ii. Select the proper size syringe and needle. Make sure free movement of the syringe plunger.

  • iii. Select the vein and sanitize the vein puncture site by using alcohol 70% v/v or betadine or chlorohexidine wipe. Allow the vein puncture site to dry in the air. Do not touch the vein puncture site after its sanitization.

  • iv. Clean and massage the surrounding area of the vein puncture site by using a circular motion with a narrow radius and moving outward. Do not touch the clean area during the massage.

  • v. Using your thumb, draw the skin taut. Insert the needle into the vein lumen at an angle of 15 to 30○. Do not use your index finger to pull the skin.

  • vi. Allow blood to enter the syringe. Remove the tourniquet after collecting the required amount of blood

  • vii. Remove the needle from the patient's vein swiftly. Allow the patient to open the fist. Put gauze at the vein puncture site and apply pressure to stop bleeding.

BLOOD PRESERVATION:

Collected blood is stored at a temperature of 2 to 6 degrees C in a glass bottle or plastic bag. Plastic bag is preferred because it is light in weight and compressible in nature. The expiry period of collected blood depends upon the anticoagulant used. Expiry period of collected blood containing

• i. ACD anticoagulant is 14 days.

• ii. CPD anticoagulant is 21 days

• iii. CPD-A-1 anticoagulant is 35 days

• iv. Heparin anticoagulant is 48 days.

Dr Pramila Singh.