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Tuesday, March 29, 2011

COLLECTION OF BLOOD SPECIMEN FROM PATIENTS


COLLECTION OF BLOOD SPECIMEN FROM PATIENTS

         Capillary or venous blood is used for all estimation made on blood. Capillary blood is usually obtained from a finger or a thumb and the most convenient place is on the thumb about half a cm from the side of the nail; the tip of the finger can also be used
         Maximum number of hours allowed between the taking of blood and actual examination.
Haemoglobin and RBC – 24 hours
Fragility, sedimentation, corpuscles, packed cell volume – 24 hours
Platelet count and blood film should not be done with stored blood.
a)      AMMONIUM AND POTASSIUM OXALATE MIXTURE
         A general purpose anticoagulant for haemotological investigation
                  Ammonium oxalate                 -           1.2g
                  Potassium oxalate                   -           1.8g
                  Distilled water                                    -           to 100ml
       Dissolve the oxalate salts in the distilled water and make upto 100ml. Deliver 0.4ml of the solution with the help of a graduated pipette into small bottles or tubes in an oven at 800C to evaporate the water content from the oxalate solution close the bottle with screw caps or cork to tubes and label as Winthrop’s bottle or haemogram bottle ready for use with 4ml of blood. The tube now contains 8mg of mixed oxalate salt.
       Collect the required amount of blood into a dry sterile hypodermic syringe by vein puncture. Expel the blood into the oxalate tube or bottle after removing the needle. Invert gently 10-20 times to ensure mixing of the anticoagulant and blood.
        2mg of mixed oxalate salt is required for 1ml of blood (0.1ml of solution per ml of blood) i.e. 0.1ml oxalate salt contains 20mg of mixed salts.
        Oxalate blood may be used for total RBC and WBC count, haemotocrit or PCV and hemoglobin estimation. Plasma may be used for estimation of bilirubin and prothrombin time. Smears are suitable for examination only if prepared immediately because the smears undergo morphological changes. The anticoagulant should not be blood intended for chemistry.

b)     EDTA (sequestrene)
                  A general purpose anticoagulant
EDTA (ethylene Diamine Tetra acetic Acid/disodium salt)         -           10g
Distilled water                                                                              -      to 100ml
                  Dissolve the dry sodium salt in the distilled water and make upto 100ml mark. Deliver 0.08ml of the solution with graduated pipette into small bottles or tubes marked at 4ml level. Allow the water content of the solution to evaporate at room temperature. Fix cap and label as containers 4ml of the blood.
                  Sequestrene is an effective anticoagulant at a concentration of 1-2mg/ml of blood at which concentration it does not affect the packed cell volume. As it is nontoxic even smears may be used and made from blood so preserved sequestrene is synonymous with versene.        




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