BLOOD COLLECTION, PRECAUTIONS TO PREVENT HEMOLYSIS AND STORAGE OF BLOOD SPECIMENS.

BLOOD COLLECTION, PRECAUTIONS TO PREVENT HEMOLYSIS AND STORAGE OF BLOOD SPECIMENS.-Dr Sowmya Srinivas

BLOOD COLLECTIONIn investigating physiological function and malfunction of blood, obtaining the specimen is the first step towards analytic procedures.It is important to use appropriate blood containers to avoid faults in specimen collection, storage and transport to the laboratory.Venous blood is generally used for most haematological examinations and for chemistry tests.

BIOHAZARD PRECAUTIONSSpecial care must be taken to avoid risk of infection during all aspects of laboratory practice.The safety procedures must be followed as far as possible when collecting blood. The operator should wear disposable plastic or thin rubber gloves.It is also desirable to wear a protective apron or gown, as well as glasses or goggles, if necessary.

Care must be taken to prevent injuries, especially when handling syringes, needles and lancets.Disposable sterilized syringes, needles and lancets should be used if at all possible, and they should never be re-used. Re-usable items must always be sterilized after use

The constituents of blood may be altered by several factors- Pre-collectionFood or water intake within 2 hrSmokingPhysical activity (including fast walking) within 20 minStressDrugs or dietary supplement administration within 8 h.

During collection

Different times (diurnal variance)Posture: lying, standing or sittingHaemoconcentration from prolonged tourniquet pressureExcessive negative pressure when drawing blood into syringeIncorrect type of tubeCapillary versus venous blood.

Handling of specimen

Insufficient or excess anticoagulantInadequate mixing of blood with anticoagulantError in patient and/or specimen identificationInadequate specimen storage conditionsDelay in transit to laboratory.

ITEMS IN PHLEBOTOMY TRAYDisposable Syringes and needlesTourniquetSpecimen containers plain and with various anticoagulantsRequest form70% isopropanol swabs or 0.5% chlorhexidineSterile gauze swabs or cellulose padsAdhesive dressingsRack to hold specimens upright during process of fillingA puncture-resistant disposal container should also be available.

DISPOSABLE SYRINGE AND NEEDLEThe needles should not be too fine, too large, or too long, those of 19 or 21G are suitable for most adults.23G are suitable for children and ideally should have a short shaft (about 15 mm).

SPECIMEN CONTAINERSThe common containers for haematology tests are available commercially with dipotassium, tripotassium, or disodium ethylenediaminetetra-acetic acid (EDTA) as an anticoagulant. And they are marked at a level to indicate the correct amount of blood to be added.Container with no additives are also used when serum is required.

EVACUATED TUBE SYSTEMSThese are now in common use.It consists of a glass or plastic tube/container (with or without anticoagulant) under defined vacuum, a needle, and a needle holder which secures the needle to the tube.

ADVANTAGESThe cap can be pierced, so that it is not necessary to remove it either to fill the tube, or subsequently to withdraw samples for analysis, thus minimizing the risk of aerosol discharge of the contents.The vacuum controls the amount of blood which enters the tube.Minimise the exposure to blood.

PHLEBOTOMY PROCEDUREBlood is best withdrawn from an antecubital vein or other visible veins in the forearm.It is recommended that the skin should be cleaned with 70% alcohol (e.g. isopropanol) or 0.5% chlorhexidine, and allowed to dry spontaneously.

The tourniquet should be applied just above the venepuncture site and released as soon as the blood begins to flow into the syringe or evacuated tube.After cleaning and drying the site and applying a tourniquet, ask the patient to make a fist a few times.If a syringe is used for blood collection, the piston of the syringe should be withdrawn slowly and no attempt made to withdraw blood faster than the vein is filling.Anticoagulated specimens must be mixed by inverting the containers several times.

HOW TO PREVENT HEMOLYSISBy using clean apparatusWithdrawing the blood slowly Not using too fine a needle, delivering the blood gently into the receiver and avoiding frothing during the withdrawal of the bloodSubsequent mixing with the anticoagulant.

SERUMThe difference between plasma and serum is that the latter lacks fibrinogen and some of the coagulation factors.Blood collected in order to obtain serum should be delivered into sterile plain (non-anticoagulant) tubes and allowed to clot undisturbed for about 1 h at room temperature.Then loosen the clot gently from the container wall.

The tubes are centrifuged for 10 min at about 1200 rpm. Pipette the supernatant serum into another tube and centrifuge again for 10 min at about 1200 rpm. Transfer the supernatant serum to tubes for tests or for storage. For most tests, serum should be kept at 4C until used, but if testing is delayed, serum can be stored at -20C for up to 3 months and at -40C or lower for long-term storage.

BLOOD COLLECTIONEuropean and American guidelines recommend that the volume of whole blood collected is between 450 and 500 mL 10%.Blood is collected into an anticoagulant comprised of citrate, phosphate and dextrose designed to prevent blood from clotting and maintain cellular function during storage.

The initial storage temperature of whole blood determines which components can be produced from it. Because platelet function rapidly deteriorates at 4C, whole blood must be processed on the day of blood collection or stored overnight at 22C for platelet production. However, for the production of red cells, whole blood can be stored at 4C for 48-72 hours prior to separation

STORAGE OF BLOOD SPECIMEN By using Anticoagulants like-EDTASodium citrateHeparinAcid-citrate dextrose(ACD), Citrate-phosphate dextrose (CPD) or Alsevers solution for long term preservation of red cells.

Routine blood storage is 42 days or 6 weeks for stored packed red blood cellsPlatelets may only be stored for 7 days, due largely to their greater potential for contamination, which is in turn due largely to a higher storage temperature.

Red cells Leucocyte depleted:Shelf-life - 42days with the appropriate additivesStorage temperature range - 26 C

Fresh Frozen Plasma:Shelf-life -12 monthsStorage temperature range - At 25 C or below

Cryodepleted Plasma Precipitate:Shelf-life -12 monthsStorage temperature range - At 25 C or below

Platelets:Shelf-life - 5 daysStorage temperature range - 2024 C

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