Collection of blood Sample - physiology practical

Physiology practical for first year Medical and paramedical students

1. COLLECTION OF BLOOD SAMPLE PHYSIOLOGY PRACTICAL BY DR. RAVI DUTT

2. OBJECTIVES TYPES OF BLOOD SAMPLES ASEPSIS AND ASEPTIC TECHNIQUE UNIVERSAL PRECAUTIONS METHODS OF TAKING BLOOD SAMPLES PRECAUTIONS TAKEN DURING BLOOD SAMPLING ANTICAOGULANTS USED FOR BLOOD SAMPLING

3. TYPES OF BLOOD SAMPLE 3 TYPES OF BLOOD SAMPLES CAPILLARY BLOOD SAMPLE : When only small quantity of blood is required for doing investigations. VENOUS BLOOD SAMPLE: When large quantity of blood is required ARTERIAL BLOOD SAMPLE: Needed for special tests like blood pH, Blood gas analysis

4. ASEPSIS ASEPSIS: Refers to the condition of being free from septic or infectious pathogens like bacteria, virus etc. Aseptic technique  means using practices and procedures to prevent contamination from pathogens. This includes: Sterilization of equipments Sterilization of skin Prevention of contamination

5. UNIVERSAL PREACAUTIONS Universal precautions were introduced by the Centers for Disease Control (CDC) in 1985, mostly in response to the human immunodeficiency virus (HIV) epidemic. Universal precautions are a standard set of guidelines to prevent the transmission of bloodborne pathogens from exposure to blood and other potentially infectious materials  standard precautions: Hand hygiene, gloves, face shields, PPE, needle and sharp objects disposal in puncture resistant containers

6. COLLECTION OF BLOOD SAMPLE Capillary Blood: also called peripheral blood When only few drops of blood are needed – for eg. Hb estimation, cell counts, bleeding and clotting time, blood smear examination Site of skin puncture: In adults- Tip of middle or ring finger lobe of the ear In infants Side of heel or big toe

7. APPARATUS LANCET/ PRICKING NEEDLE STERIZED GAUZE/COTTON , 70% ALCOHOL/SPIRIT GLASS SLIDES/PIPETTES AS REQUIRED

8. PROCEDURE Aseptic precautions Clean the finger/puncture site with spirit swab and allow it to dry(why dry?) Sterilization effective only when spirit /alcohol has dried Thin film of alcohol cause blood to spread and satisfactory round drop of blood not formed Alcohol may cause hemolysis of blood Prick the finger sharply and quickly to a depth of 3-4 mm, blood should flow slowly, spontaneously and freely(without squeezing)

9. PROCEDURE CONT. Wipe away the first drop with dry sterile gauze(why?) Because first drop may be contaminated with tissue fluid Allow afresh drop of blood of sufficient size(3-4 mm) to well up from wound and use it for performing the test. After the sample collection, Clean the area of the prick with fresh swab and keep the swab pressed on the wound till bleeding stops. Finally dispose off the material used for sample collection as per Bio-medical waste management protocol.

10. PRECAUTIONS Site of prick should be clean, free from infection, skin disease or edema Site should be cleaned with sterile gauze soaked in spirit Lancet/needle should be sterile. Puncture should be deep enough to give free flowing blood but not too deep(which takes a lot of time to stop bleeding) Do not press or squeeze the finger to increase the blood flow.

11. VENOUS BLOOD SAMPLING Apparatus: Disposable gloves Sterile disposable syringe Test tubes/ vialss Sterile gauze/swab, Methylated spirit/70% alcohol Tourniquet

12. PROCEDURE Site :- antecubital veins Compress the upper arm to make veins prominent Apply the tourniquet about 2-3 cms above the elbow to obstruct the venous return. Subject may open and close the fist to make veins engorged with blood. Clean the skin over selected veins with alcohol soaked gauze and allow it to dry.(why?) Puncture the skin at an angle of 15-20° to the skin and advance the needle gently along the vein and pucture it from side. Withdraw blood slowly(not faster) and Collect the required amount of blood sample .

13. When the blood sample is collected, release the tourniquet and press a fresh swab over the skin puncture and withdraw the needle by keeping the swab in position. Ask the subject to flex the arm and keep it so as to maintain the pressure on puncture site till bleeding stops. Expel the blood gently in to different vials as per test requirement and gently shake the test tube so that anticoagulant mixes well without frothing.

14. PRECAUTIONS All aseptic precautions must be observed and disposable gloves, syringe and needles should be used. Site should be cleaned with sterile gauze soaked in spirit and allowed to dry. Tourniquet must be removed before taking out the needle to prevent hematoma formation. Blood sample should be transferred to the test tube without delay to prevent clotting. Subject should keep the swab in position till the bleeding stops.

15. Arterial blood sample Needed to perform special test like arterial blood gas analysis and blood pH estimation. Site: Radial or Femoral artery

16. ANTICOAGUALNTS (FOR IN VITRO USE) EDTA( Ethylenediamine Tetraacetic acid): used for most hematological studies except coagulation studies Trisodium Citrate : used for ESR estimation(by westergren’s methods) and for coagulation studies Double oxalate Mixture : mixture of ammonium oxalte and potassium oxalate in ratio of 3:2. Used where cell volume should remain unaffected like PCV and ESR estimation. Sodium Fluoride : for plasma glucose estimation(as fluoride inhibits glycolytic enzymes) Heparin : Used for Blood gas analysis, pH estimation and osmotic fragility test

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