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·        Lecture 33& 34 : Specimen collection and processing -1

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1 ·        Lecture 33& 34 : Specimen collection and processing -1
ط      Blood specimen types ط     Venipuncture , procedure, precautions ط     Pediatric venipuncture ط     Skin puncture, arterial puncture                                                B3  39-50;  C4   40 -  2

2 Introduction Proper patient identification, correct equipment, adequate knowledge (physiological & environmental factors) Proper collection (sample type, timely), transport, processing, analysis, reporting Previous chain is critical in providing most accurate clinical picture (weakest link) Added investment of time & effort for patients care & management of specific group Pediatric, obese, elderly, ICU, women?

3 Blood Specimen Types: Blood is most common specimen (Whole, serum, plasma) Blood can be obtained from veins, arteries, capillaries 1. Arterial blood is commonly used for blood gases & pH 2. Venous blood content varies depending on metabolic activity of tissue (time / site) 3. Capillaries (veins & arteries)

4 Blood Specimen Types: 1. Arterial blood is commonly used for blood gases & pH O2 is the largest difference Reflects the respiratory & metabolic status Others are protein, glucose, ammonia Limited to some conditions Collected & performed by trained personnel

5 Blood Specimen Types: 2. Venous blood content varies depending on metabolic activity of tissue (time / site) Timing & site of collection are critical Obtained by venipuncture Institute standardize collection, location, patient positioning, tourniquets

6 Blood Specimen Types: 3. Capillaries (veins & arteries) Obtained by skin puncture Similar to venipuncture: high glucose, low K, total protein, Ca++ Also contain intracellular & tissue fluids Used if venous is not accessible: Burns, chemotherapy, difficult veins (obese, elderly), risk of collapse (infants) Warming of site causes increase blood flow => lead to vasodilation => result in arterialization of capillaries Excessive squeezing result in increase of K

7 Venipuncture 1. evacuated-tube (vacutainer) Sample is completely contained to reduce risk of outside contaminant reduce hazards on the collector 2. Syringe collection necessary when patient has fragile or damage veins 3. Butter-fly infusion more expensive but convenient when both vacutainer tubes & syringe collected at the same time used mostly on pediatric patients, difficult veins

8 Tourniquet Belt or rubber or tubing used to apply venous pressure NO prolonged pressure For convenient & comfortable collection

9 Needles Bore size referred as gauge Larger needles (18 gauge) used for blood donors Smaller needles (21-22) used in routine collection Smallest needles (23-25) used with butterfly infusion, could cause hemolysis 1. single-sample needle: collecting with a syringe 2. multiple-sample needle: allow tube change without blood leakage (vacutainers) plastic sleeves with stopper: differ is size depending on manufacturer

10 Tubes Colour-coded stopper indicating additive present preservatives, anticoagulants, accelerators, plain

11 Others 1. Alcohol pads: to sterile site of puncture iodine used for blood culturing 2. Gauze: can use folded cotton gauze 3. Tape or adhesive bandage avoid in under 3 years old

12 site of venipuncture antecubical fossa most common, arm (median cubical vein) other sites are acceptable: hand, ankle, foot avoid collecting from: hematomas, scarring, previous puncture, mastectomy side, IV fluid site

13 Procedure of venipuncture
From 1 to 20 on page 49

14 Pediatric venipuncture
Hazard include: cardiac arrest, hemorrhage, venous thrombosis, arterispams, tissue damage, infection Use butterfly (21-23 gauge), 3ml syringe (tube) Collect only form superficial veins, secure arm, no bandage for under 3 years

15 Precautions during venipuncture
Fainting, nausea, vomiting STOP immediately Head lowered, cold compression, ammonia, physician

16 Skin Puncture Blood is brought to the surface of the skin by applying pressure to the site (infants) Alcohol pads used to sterile Lancet with controlled depth (2.4mm) to avoid abscess, bruises, bone damage .. Microcollection Tubes (additives are powder, freeze dried) Silican separator gel (separate liquid from cell components) Heel warmer, no more than 42ºC

17 Site of skinpuncture Finger: palmer surface, 3-4rd ring finger Heel: middle of the large toe to heel

18 Procedure of skinpuncture
From 1 to 17 on page 53-54

19 ·        Lecture 35& 36 : Specimen collection and processing-2
ط     Anticoagulants : mechanisms and uses ط     Preservation and transport ط     Factors affecting specimen collection, Sources of error,                                            B3  50-58;  C4   40 -  2

20 Additives Table 3.3 No additives (red, dark-blue) for blood culturing, then Sodium-citrate (light-blue) for coagulation studies followed by Heparin (green) for electrolyte then EDTA (lavender) for hematology and oxalate / fluoride (gray) for glucose

21 Specimen Transport Upon receiving in the lab, information should be matched and read correctly and accepted Then sorted as to type of test and distributed to the lab unit As soon as collected & quick as possible if no metabolic inhibitors present Avoid common problems as hemolysis Primary & secondary leak-proof containers Ice to maintain integrity of analytes Remove serum within 1hr of centrifugation & centrifuge max 60 min after collection Maintained in upright position, to promote clot & reduce hemolysis Temp 23-25ºC preferred Personnel aware of handling requirement (cart, agitation, delay) Some require chilling to inhibit metabolism (tube) Certain tests require avoiding light (dark tube)

22 Storage Stability Serum / plasma should be separated from cell within 2hrs of collection Analysis within 5hrs of centrifugation Serum / plasma in gel separators can be stored at room temp 8-24hrs Normally Storage at 2-8ºC up to 24hrs is acceptable for most analytes Storage beyond 24hrs is by freezing – 20ºC (once) Do NOT repeat freezing and thawing more than once Some analytes need to be freezed immediately after separation

23 Factors affecting specimen Table 3.1
Timing: Best time is early morning (basal state) Time-intervals may be desired to observe metabolic process as glucose tolerance and serum iron and also in therapeutic drug monitoring Diet: physicians must not if diet restriction is require to phlebotomist Fasting Specimen: diet high in protein, glucose, saturated & unsaturated FA, caffeine, serotonins Exercise: Moderate exercise can affect certain values Stress: Emotions may falsely elevate white blood cells Pasture: Body diurnal rythms and pasture (sitting or laying) Hemolysis & Tourniquet ** For forensic collection (law & medicine) in the presence of officer

24 Sources of error in venipucture
Table 3.5 Table 3.6

25 Other body fluids 1. Cerebral Spinal Fluid: Obtained by lumber puncture For glucose, total & specific protein determination, pH, CO2, bicarbonate 2. Paracentess Fluid (pleural, pericardial, peritoneal): Collected by aspiration of site For specific gravity, protein, LDH determination Collect blood sample in conjunction 3. Amniotic Fluid: Obtained by aspiration of fetus amniotic sac For fetal lung maturity, congenital diseases, hemolytic anemia, neural tube defect, gestational age 4. Urine: A. Random (first void): for protein, glucose, specific gravity, osomlility, Dark-colored contained for some test (e.g. bilirubin) B. Timed (12-24hrs/befor or after a meal): Low electrolyte, catecholamine in morning then peak at noon Preservatives (acid/base/refrigeration) used in certain analytes and bact. growth






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