Blood Sampling PDF

# Blood Sampling Dr. Neven Makram Aziz ## Blood Blood is the vital fluid tissue that circulates inside blood vessels. It represents 8% of body weight (5.6 L). ### Functions of blood: - Transport - Defensive - Hemostatic (stoppage of bleeding) - Homeostatic ## Composition of blood |...

# Blood Sampling Dr. Neven Makram Aziz ## Blood Blood is the vital fluid tissue that circulates inside blood vessels. It represents 8% of body weight (5.6 L). ### Functions of blood: - Transport - Defensive - Hemostatic (stoppage of bleeding) - Homeostatic ## Composition of blood | | Percentage by Volume | | | |:----------|:----------------------:|:------------------------------------------|:---------------------------------------------------| | | | Plasma (percentage by weight) | | | **Plasma** | 55% | Water 91% | Albumins 58% | | | | Proteins 7% | Globulins 38% | | | | Other Solutes 2% | Fibrinogen 4% | | | | | Ions, Nutrients, Waste products, Gases, Regulatory Substances| | **Buffy Coat** | | | | | | | | | | | | Formed elements (number per cubic mm) | | | | | Platelets: 250-400 thousand | White blood cells: | | **Formed Elements** | 45% | White blood cells: 5-10 thousand | Neutrophils: 60%-70% | | | | Red blood cells: 4.2- 6.2 million | Lymphocytes: 20%-25% | | | | | Monocytes: 3%-8% | | | | | Eosinophils: 2%-4% | | | | | Basophils: 0.5%-1% | ## Plasma Proteins | Type | Concentration | Function | Site of formation | |:------------|:----------------------|:-----------------------------------------------------------------------------------------------|:-------------------------| | Albumin | 4 gm/100 ml plasma | - Osmotic pressure due to its highest concentration. | Liver | | | | - Transport of some substances. | | | Globulin (α, β, γ) | 2.5 gm/100 ml plasma | - Defensive function (γ globulins). | Reticuloendothelial system (R.E.S) in liver, spleen, lymph nodes and bone marrow. | | | | - Transport of some substances. | | | Fibrinogen | 0.4 gm/100 ml plasma | - Blood clotting. | Liver | | | | - Blood viscosity (Elongated shape). | | | Prothrombin | 10 mg/100 ml plasma | - Blood clotting. | Liver | ## Blood Corpuscles - **Red blood corpuscles (R.B.Cs):** 5 million per cubic mm. Their decrease is called *anemia* and their increase is called *polycythemia*. - **White blood corpuscles (W.B.Cs):** 4000-11000 per cubic mm. Their decrease is called *leucopenia* and their increase is called *leucocytosis*. - **Platelets:** 250000 to 500000 per cubic mm. Their decrease is called *thrombocytopenia* and their increase is called *thrombocytosis*. ## Blood Vessels ### Diagram: The diagram shows a network of blood vessels starting from the heart. The blood flow starts with a red colored *Artery* then passes through smaller vessels called *Arterioles* which further break down into smaller vessels called *Capillary Bed*. The capillary bed then merges into *Venules* which eventually combines into a blue colored *Vein*. | | Description | |:---------------------------------------|:-------------------------------------------------------------------------------------------------------------------------------------:| | **Arteries** | - Blood vessels that transport blood away from the heart. | | | - Usually positioned deeper within the body. | | | - Arteries have a thick walls and a narrow lumens. | | | - Arteries are eight times less distensible (change in volume/change in pressure) because of the stronger walls. | | **Veins** | - Blood vessels that transport blood to the heart for oxygenation. | | | - Usually positioned closer or beneath the surface of the skin. | | | - Veins have a thinner walls and a wider lumens so can store blood. | | | - Veins are the most distensible - a slight increase in the pressure allow veins to accommodate 0.5 to 1 liters of blood so we give blood and fluid intravenous injection. | ## Types of Blood Samples 1. **Venous sample (preferred method for clinical tests):** - **Method of Collection:** - Direct puncture of superficial vein by venipuncture (needle). - (In infants, venous blood may have to be taken from the femoral vein, or the frontal venous sinus). - **Common Use:** - Routine laboratory tests (for complete hematological and biochemical investigations). 2. **Arterial sample:** - **Method of Collection:** - Direct puncture of artery (Radial or Femoral) by a needle. - **Common Use:** - Arterial blood gases - Blood pH 3. **Capillary sample:** - **Method of Collection:** - Dermal puncture of fingertip or heel. - (In adults and older children, capillary blood is generally obtained from a skin puncture made on the tip of the middle or ring finger, or on the lobe of the ear. In infants and young children in whom the fingers are too small for a prick, the medial or lateral side of the pad of the big toe or heel is used). - **Common Use:** - For estimation of Hb, cell counts, bleeding time and coagulation time, blood films, micro chemical tests but these values are likely to be on the lower side since some tissue fluid is bound to dilute the blood even when it is free-flowing. - For detection of blood groups. - It is used for Infants and young children, Elderly patients with fragile veins and severely burned patients. - There is greater risk of contamination ## Types of Blood Samples not Suitable for Hematological Tests 1. **Clotted samples:** Even little clots in the anti-coagulated blood can negate the results. 2. **Hemolysed samples:** The red cells may be damaged and ruptured during collection or handling of blood. The released Hb tinges the plasma or serum red, rendering the sample unfit for tests. ## Getting a Sample of Whole Blood or Plasma (Plasma = Blood minus all the blood cells) 1. Draw blood from a vein as described below and transfer it from the syringe to a container containing a suitable anticoagulant. 2. Mix the contents well (without foaming). 3. A sample of whole blood is now ready for tests. If plasma is desired, centrifuge the anti-coagulated blood for 20–30 minutes at 2500 rpm (revolution per minute). 4. Collect the supernatant plasma with a pipette and transfer it to another container. (The packed RBCs will be left behind) ## Getting a Sample of Serum (Serum = Plasma minus fibrinogen and all the clotting factors) 1. Transfer the blood from the syringe to a container without any anticoagulant in it. 2. After the blood has clotted in an hour or two and the clot shrunk in size, the serum will be expressed. 3. Remove the supernatant serum with a pipette and transfer it to a centrifuge tube. 4. Centrifuge it to remove whatever red cells may be present. Clear serum can now be collected with another pipette. ## Diagram of Serum vs Plasma A diagram shows two test tubes next to each other with a yellow liquid in the left tube and a red liquid in the right. In the left test tube, a red block is at the bottom labeled as “Blood Clot”. An arrow pointing towards the yellow liquid in the left tube is labeled as "Serum". An arrow pointing towards the liquid in the right tube labeled as "Plasma". Near the top of the liquid in the right test tube, a thin white layer is shown as "WBC" and red portion of the tube is labeled as "RBC". - **Serum:** Yellow liquid in the test tube with a blood clot at the bottom. - **Plasma:** Red liquid in the tube with a white layer on the top and red layer (RBC) below.