Collection of Specimen 2024 PDF
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Summary
This document covers various blood sample collection methods, including venipuncture and capillary puncture, and discusses factors affecting results. It provides information on types of specimens, procedures, precautions, and associated complications. The document is useful for medical professionals in clinical chemistry and laboratory settings.
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Collection of Specimen Definition of Terms Antecubital Space located where the elbow ends Arterial Blood Gas (ABG) procedure that involves taking blood from an artery. Artery – blood vessel that carries richly oxygenated blood from the heart to the body tissues. ...
Collection of Specimen Definition of Terms Antecubital Space located where the elbow ends Arterial Blood Gas (ABG) procedure that involves taking blood from an artery. Artery – blood vessel that carries richly oxygenated blood from the heart to the body tissues. Capillaries – tiny blood vessels that connect the smallest arteries to the smallest veins. Definition of Terms Gauge Hematoma loss of blood from a vessel Hemoconcentration – increase in the concentration of formed elements in the blood caused by lack of fluid in the blood. Hemolysis – destruction or lysis of red blood cells Lumen – cavity or channel within the tubular organ, such as blood vessel. Phlebotomy – act of entering a vein with a needle for the purpose of obtaining venous blood. Definition of Terms Thrombosis – blood clot in a vessel. Tourniquet – device often a rubber band at least ½ inch wide, that reduces flow of blood in the veins and allows the veins become prominent. Vacuum Tube System/Vacutainer System – system used for blood collection; uses a special disposable needle, a holder, and blood collection tubes that have little or no air. Vein – blood vessels that carries deoxygenated blood from the tissues back to the heart Venipuncture – procedure where a needle is inserted into a vein to obtain a venous blood sample GENERAL PRECAUTIONS IN COLLECTION OF BLOOD SAMPLES: If a fasting specimen is required, confirm that the fasting order has been followed. Always read the request first to see whether the examination is complete or incomplete, to determine the amount of blood needed. Do not extract blood from patients while they are receiving intravenous medication because these solutions may influence the chemical analysis. GENERAL PRECAUTIONS IN COLLECTION OF BLOOD SAMPLES: Never draw out the syringe without removing first the tourniquet to avoid hematoma. Avoid prolonged application of tourniquet to avoid hemoconcentration. The blood specimen collected with anticoagulants must be well mixed to prevent coagulation. TYPES OF SPECIMENS ANALYZED IN CLINICAL CHEMISTRY LABORATORY: Blood Whole blood Plasma and formed elements (unclotted) Blood Serum Liquid portion of clotted blood Contains albumin and globulin Preferred specimen in clinical chemistry because of the following reasons: Certain substances like the lipemia clearing factor (LPL) are co precipitated during clotting Clearer than plasma There is no potential interference produced by anticoagulant Blood Plasma Liquid portion of unclotted blood Contains albumin, globulin and fibrinogen Advantages of plasma over serum: There is no delay necessary in obtaining plasma by centrifugation of the whole blood Usually a greater volume of plasma than serum is obtainable from a given volume of blood. Urine 24-hr sample Random sample Timed sample Other Body Fluids CSF (cerebrospinal fluid) Other specimens like ascitic fluid, peritoneal fluid, etc Timing of Collection Fasting- “nothing by mouth” - generally 6 -14 hours Random 24-Hour Postprandial CLASSIFICATION OF METHODS AS TO SAMPLE REQUIREMENTS: Macromethod Micromethod Ultramicromethod Nanoliter method FACTORS CONTRIBUTING TO THE VARIATION OF RESULTS: Exercise Transient or immediate effects (within the hour) Elevated lactate Elevated alanine Elevated fatty acids Long lasting effects Increased activity of: AST (SGOT) CPK (CK) LDH ALD (Izoenzyme A) Long term effects Elevated concentration of sex hormones Testosterone Luteinizing hormone Sex hormone binding globulin Elevated concentration of steroids Fasting Generally 6-14 hours Elevated blood glucose, potassium, and lipids like cholesterol and neutral fats are seen in patients not under NPO and the reverse is true with inorganic phosphorous Prolonged fasting has been associated with elevations in serum bilirubin, plasma triglycerides, glycerol, free fatty acids and a decrease in plasma glucose. Diet Any diet immediately increases potassium and triglycerides 2-4 hours after fatty meal – increases ALP activity High protein diet – increases urea, ammonia and urates with no significant increase in creatinine Increase turbidity or lactescence – triglycerides level exceeds 4.6 mmol/L (4.0 g/L) Posture or position Changes in position result to efflux of filterable substances from the intravascular space to the interstitial fluid spaces Non-filterable substances increase in concentration Tourniquet application One-minute application Prolonged application results to: Venous stasis Anaerobiasis Tobacco smoke Acute effects Increase in plasma NEFA concentration Increase in plasma cathecolamines and serum cortisol (due to nicotine) – affects the leukocyte peripheral count Increase in neutrophils Increase in monocytes Increase in eosinophils Chronic effects Increase in total WBC count Increase in blood hemoglobin values (carboxyhemoglobin) Increase in mean corpuscular Volume (MCV) Alcohol ingestion Increases plasma concentration of lactate, urate, acetate and acetaldehyde Increases gamma glutamyl transferase concentration Stress (anxiety) Affects hormone secretion Results in hyperventilation leading to a disturbance in acid-base balance in the blood Increases serum lactate Increases plasma free fatty acids Drugs - antacids GENERAL METHODS OF BLOOD SAMPLE COLLECTION: CAPILLARY PUNCTURE Formicromethod, ultramicromethod and nanoliter method The method of choice for: Pediatric infant Geriatrics Adults who are: CAPILLARY PUNCTURE/SKIN PUNCTURE/PRICK METHOD Sites of puncture: Palmar surfaces of fingertips Plantar heel surface in infants Plantar surface of the big toe Earlobes CAPILLARY PUNCTURE/SKIN PUNCTURE/PRICK METHOD Sites to be avoided: Edematous area (swollen with fluid) Cyanotic areas (purplish blue in color) Scarred area Traumatized area (black and blue) Heavily calloused area CAPILLARY PUNCTURE/SKIN PUNCTURE/PRICK METHOD Materials and Equipments: 70% isopropyl alcohol Absorbent cotton sponges/balls or swabs Sterile puncture instrument (lancet) Capillary tube ARTERIAL PUNCTURE/ANAEROBIC Generally used for the determination of blood oxygen, carbon dioxide tension and blood pH (Blood Gas Analysis). Special training is required for this procedure Tourniquet is not required After removing the needle, apply moderate pressure with 2 x 2 sterile gauze until bleeding ceases Insert needle (still attached to syringe) in stopper to prevent air from entering needle ARTERIAL PUNCTURE/ANAEROBIC Sites of puncture: Radial artery – most preferred site Femoral artery (fem tap) Brachial artery Scalp artery Umbilical artery ARTERIAL PUNCTURE/ANAEROBIC Materials needed: Syringe with gauge 21 needle with rubber cap Cotton (wet and dry) Alcohol or Iodine Heparin - preferred anticoagulant Warm towel (45ºC) – arterialization Iced water bath – preservative for transport VENIPUNCTURE Considered to be the most commonly used method of blood collection in Clinical Chemistry Sample obtained is called venous blood VENIPUNCTURE Sites of collection: Veins in the antecubital fossa Median cephalic vein – Cephalic vein – Basilic vein – Vein of the longitudinal sinus or sagittal sinus Femoral vein Wrist vein Jugular vein Saphenous vein Small saphenous vein Great saphenous vein Veins on the dorsal portion of the hand VENIPUNCTURE Materials needed: 70% alcohol Absorbent cotton or sterile swabs Tourniquet Syringe or Vacutainer set SYRINGE Used for blood collection only For single draw Parts: a. Bevel d. Adapter b. Shaft e. Barrel c. Hub f. Plunger Advantages of venipuncture Large amount of blood can be obtained Ideal for blood chemistry determinations It reduces the possibility of error in resulting from dilution with tissue juices. Disadvantages of venipuncture Requires more time and skill Requires more equipment More complications may arise hard to do on infants, children and obese individuals Procedure Assembling equipments Prepare the materials that will be needed in the procedure Positioning and identifying the patient Preparation of the needle and syringe Applying the tourniquet Procedure Selecting the vein Applying the antiseptic Inserting the needle Procedure Releasing the tourniquet Withdrawing the blood Withdrawing the needle Transferring the blood Checking the patient wound COMPLICATIONS OF VENIPUNCTURE Immediate Local Complications Localized hemoconcentration or Venous stasis Syncope or Fainting Due to sudden decrease of blood supply to the brain Remedy: Let the patient lie down COMPLICATIONS OF VENIPUNCTURE Failure of blood to enter the syringe due to: Excessive pull of the plunger which collapses the vein Going through the vein reaching the musculature Very small angle of entry wherein the needle reaches only the walls of the veins (transfixation of the vein) Delayed Local Complications: Thrombosis of veins Formation of blood clots inside the lumen of the vein due to trauma Thrombophlebitis Inflammation of the vein due to thrombus as manifested by an inflammatory reaction on the outer skin surface Hematomas Blue or black skin discoloration commonly due to repeated trauma or puncture of the veins General Delayed Complications: Serum Hepatitis AIDS COMMON DIFFICULTIES ENCOUNTERED DURING COLLECTION AND PROCESSING OF BLOOD Hemolysis This must be avoided because of the following reasons: Most constituents, such as SGOT, LDH, Acid Phosphatase and Potassium are present in large amount in erythrocytes Invalidates determination due to color changes May directly interfere in a chemical determination by inhibiting an enzyme such as lipase. Hemoglobin may interfere with the diazotization of bilirubin. Hemolysis can be prevented by: Proper collection of blood Venous stasis Moisture Excessive traction Small lumen needles Air leak Proper transfer of blood Expelling of blood through the needle Shaking Separation of blood Freezing Over centrifuge LIPEMIA OR LACTESCENSE This is caused by transient rise in chylomicrons following a meal containing fat It causes interference with large number of chemical analyses because of turbidity. It disturbs the following investigations particularly strongly: Amylase Bilirubin Protein SGOT SGPT CONCENTRATION CHANGES Thismay occur through dilution or evaporation. The sources of the errors are: Use of syringe and needles rinsed in saline solution Use of liquid form of anticoagulant Allowing the blood to stand in open container Centrifugation of blood specimens in open containers. COMPOSITION CHANGES Bacterial changes – such as formation of ammonia from urea Enzymatic changes Blood gas changes COMPOSITION CHANGES Extravascular interchange – this is due to movement of substance between the cells and plasma or serum, like K, water and chloride. Changes in lipid concentration – due to lipolysis Changes in phosphates – due to hydrolysis of organic phosphate esters. Order of Draw