Lab Tech Midterm Review

1. Blood and blood components—general functions of components

Blood

• 5L circulates (1/13 of body weight)
• 3L plasma and 2L cells
• for 500 RBCs there are 30 platelets
• Fill a tube w/blood and centrifuge, all the RBC's would be down at the bottom, red in color
• Stuff on top is clear to straw colored—plasma
• Things big enough to fall to bottom (45%)—RBC, WBC (right on top of the RBC's), platelets (line on top of the pellet)
• RBC's are the heaviest (do to iron)—1000x's more RBC's than WBC's
• WBC's are the biggest
• % of RBC in blood--hematocrit
• Plasma—55%
• 91% water
• 7% proteins
• 1% small molecules—E, testosterone,
• 1% electrolytes

Proteins

• 60%5 albumin—osmotic regulator, controls blood volume, carrier of things that are usually not soluble
• 36% globulins
• a --carrier of things that are usually not soluble ex: cholesterol
• b --carrier of things that are usually not soluble
• g --antibodies (immunoglobulins)
• electrophoresis (gel)—gel w/ current running through it to separate molecules by weight
• 4% fibrinogen—forms clots
• serum proteins
• 63% albumin
• 37% globulins
• has no fibrinogen

2. Specificity and sensitivity of tests—what terms mean and why we must be concerned w/them

• Know test terminology, test purpose, actual test process and procedure, and normal test values or results

1. The clinical value of a test is related to its sensitivity, its specificity, and the incidence of the disease in the population tested. Sensitivity and specificity do not change when different populations of ill and well pts are tested
2. specificity--% of positive results in persons w/a given ds (When positive result is obtained in all pts who have the ds, the specificity of the test is 100%)
3. sensitivity--% of negative results among people who do not have the ds (when a negative result is obtained in all people who do not have the ds, the test has a sensitivity of 100%)
4. predicted values of a positive and negative test define the % of positive and negative results that are true positives or negatives—the higher prevalence of a specific ds (the % of persons who have this ds) w/in the population, the > is the predictive vale of a positive test result

2. Universal Precautions and other safety measures—the procedures and why we must follow them

• Designed to protect healthcare workers and pts from exposure to blood-borne pathogens
• Mandated by OSHA

1. wear personal protective equipment—aprons, gowns, gloves, goggles, face shields, masks, and CPR devices
2. wear gloves if skin is cut, abraded or chapped; when collecting or handling specimens or body fluids, cleaning or decontaminating; if contact w/mucous membranes, nonintact skin, GI or GU, active bleeding wounds, venipuncture, vascular access procedures, or other invasive procedures
3. gowns, aprons, scrubs, or lab coats must cover all exposed skin areas when splashing of bodily fluids is possible
4. mouth-to-mouth emergency resuscitation equipment—saliva is infectious
5. prevent injuries that can be caused by needles, scalpels, and other sharps—dispose of in puncture resistant containers—never recap, bend, break, or remove needles form disposable systems
6. remove torn or punctured gloves promptly—thoroughly wash immediately
7. place and transport specimens in leak-proof receptacle properly sealed—label biohazard—warning labels and tags should be visible
8. eating, drinking, applying cosmetics or lip balm and handling contact lenses are not permitted
9. healthcare workers should always take car of themselves first—presume all pts have HIV and Hep B
10. blood-borne pathogens—organisms that can be transmitted from one person to another by exposure to the infected person's blood—the major pathogens include Hep B, Hep C, HIV, and syphilis
11. Body substances—any fluids or solids that come out of or off of the human body—ex: saliva, sputum, urine, feces, wound drainage, etc.
12. exposure incident—the contact of blood or other body substances w/an employee's mucous membranes (eyes, mouth), nonintact skin (skin w/cuts, abrasion, dermatitis, or other); or contact by piercing or puncturing mucous membranes or skin w/a contaminated item
13. regulated (infectious) waste—items caked or saturated w/blood or other potentially infectious materials; contaminated sharps; pathologic and microbiologic waste
14. other potentially infectious materials (OPIM)—body substances specifically designated by the CDC or OSHA that may transmit blood-borne pathogens include semen, vaginal secretions, CSF, synovial fluid, pleural fluid, amniotic fluid, saliva in dental procedures, blood tainted

2. Fingersticks—procedure and safety aspects

1. select site—ball of 3^rd or 4^th finger, anterolateral side
2. clean w/alcohol pad
3. dry 30s
4. open package of spring loaded lancet
5. place at site and press release—no deeper than 2mm
6. wipe away first drop of blood—this contains lymph and interstitial fluid
7. apply pressure above site to obtain drop of blood—don't squeeze too hard or get interstitial fluid
8. touch drop to clean glass slide
9. apply pressure to site w/clean cotton ball until stop bleeding
10. apply band aide

2. Color-coded blood collection tubes—use of each and contents of each

• Red top- no additives to the tube and the blood clots as soon as it hits the tube wall.à Once spun in the centrifuge the bottom is the cells, and then above that is the serum
• Used for glucose test, ion concentration, or hormone tests
• Used for anything that is a serum test, such as serum glucose etc.
• Not for use in cell tests
• Blue Top- Used for buffered sodium citrate that is used as an anticoagulant
• The negative charges trap a calcium in a reaction called chelation
• Green Top- Contains sodium heparin because it inhibits thrombin which then can’t convert fibrinogen to fibrin.
• Purple Top- Contains potassium EDTA (Ethylene Diamine Tetra-acetate). Has 1/10 ml of liquid. Also traps calcium ions.
• EDTA is used as a preservative and also a standard for the electronic machines that count and separate blood cells.
• To test clotting time, you only need the plasma not the serum.

6. Coagulation

Blood Clotting

• Fibrin is the actual clot.
• Clotting is the coagulation cascade
• Platelets activate when they hit something that is not smooth healthy endothelium.
• Platelets also activate if the endothelium is injured swollen or broken.
• Activated platelets are sticky and sticks to what it bumps into, and with other platelets and they then become activated.
• We bleed all of the time spontaneously and the platelets plug the hole.
• Platelet count is 300,000/ul of blood, below 20,000 person is at risk of bleeding into the brain.
• The platelet aggregation starts the clotting cascade, because it forms on top of the platelet plug. The clot takes longer to form and is stronger.
• Clotting Factors which are enzymes
• Factor XII- activated by activated platelets and after activation changes its name to factor XIIa, which activates factor XIa.

Coagulation Cascade

• The endothelial wall or a glass tube can activate platelets; more platelets then collect on top of the other platelets, which then forms a plug and draws more platelets to form a more permanent clot.

1. Platelets come in contact with surfaces such as glass, collagen fibers or other activated platelets
2. Factor XII + Activated Platelets in platelet plugà Factor XIIa
3. Factor XIIa + Factor XIà Factor XIa
4. Factor XIa + Factor VIII + Calciumà Factor IXa
5. Factor IXa + Factor Xà Factor Xa

-or- (Tissue Factor VII + Factor Xà Factor Xa)

6. Factor II (prothrombin) + Factor Xa + Factor V & Calciumà Thrombin
7. Thrombin + Factor I (Fibrinogen)à Fibrin Monomer
8. Fibrin Monomer + cross connectionà Fibrin polymer insoluble clot.

• Anti coagulants-
• Heparin in green top tube. Can be given by an I.V. and starts working immeadiately due to it directly inhibiting thrombin.
• Asprin- anti coagulant destroys platelets
• EDTA/Citrates (chelates Ca2+)—purple top
• Warfarin- may be taken orally and may take one of these pills, sometimes refered to as a blood thinner.
• Takes two or three days to take effect and knocks out the production of the clotting factors
• Advantages of cascade scheme
• May sites for regulation
• Amplification of response by enzyme action at each site
• Plasma Proteins
• 60% albumin- Controls osmosis
• 36% Globulins- alpha, beta, and gamma globulinsà produced by electrophoresisà the large band is albumin, the next band is alpha etc.
• Alpha & Beta- carriers of atoms and other molecules that are not soluble in bloodà cholesterol.
• Gamma globulins- collective antibodies
• 4% Fibrinogen- needed to form clots
• Serum Proteins- liquid part of the blot that has already clotted
• 63% Albumin
• 37% Globulin
• Has no fibrinogen and is soluble due to it already being clotted
• Tests
• Prothrombin time (PT): prolonged—measures the function of second-stage clotting factors
• Partial thromboplastin time (PTT) or activated PTT: prolonged—determines the overall ability of the blood to clot, looks for coagulation disorders (intrinsic thromboplastin system and extrinsic coagulation mechanism pathway)—APTT heparin therapy monitor and detect circulating anticoagulants

7. Venipuncture

Veins

• basilic
• cephalic
• median cubital
• intermediate antebrachial

Complications of venipuncture

• Veins may roll
• Needle could be through the veinà Bring back slowly
• Needle is not deep enoughà Push needle gently in more
• Vasovagal "Fear" responseà The blood vessels dilate and drops the blood pressure while at the same time the Vagus nerve slows the heart rate and the patient passes out.

Treated by lying the patient down and elevating the legs of the patient and trying t cool them.

Procedure

1. gather equipment and supplies
2. assemble needle in holder
3. inspect arm, find suitable vein
4. clean skin over vein
5. apply tourniquet (max. 45sec)
6. enter vein, seat tube
7. remove tourniquet (1/2 full tube)
8. unseat tube (full)
9. w/draw needle, compress and raise arm
10. apply band-aide

3 important aspects to emphasize and master

1. accomplishing and maintaining steriltiyof venipuncture site
2. never leaving touniquet in place longer than 45s
3. stabilizing needle in vein during manipulation of tube on needle assembly

7. WCB

• Refer to hand on blood cells
• Normal range—3-10´ 10³/m L (3-10´ 10⁹/L)
• 1000x more RBCs
• Neutrophils—70% (40-70)
• Lymphocytes—25-28% (20-40)
• Monocytes—3-5% (~10)
• Eosinophils—1%
• Basophils--<1%
• Granulocytes
• Neutrophils
• Produced in the bone marrow during hematopoiesis
• Peripheral blood circulation for 7-10h
• Migrate to tissues
• 3 day life span
• first cell to respond in inflammation
• active phgaocytic cells
• contain lytic enzymes and bactericidal substances
• eosinophils
• motile
• phagocytic cells
• migrate from blood into the tissue spaces
• parasitic organisms allergic ds
• basophils
• phagocytic
• fxn by releasing pharmacologically active substances (heparin, histamines and serotonin)
• tissue basophils are called mast cells
• allergic responses
• Mononuclear Cells
• Monocytes
• Circulating in the blood 8h, enlarge
• Go to tissues and differentiate into macrophages
• Lymphocytes
• T cells—cell mediated immunity
• B cells—humeral immunity
• Differential WBC
• Blood smear and microscope
• Scan slide counting WBCs up to 100

7. CBC

• Test components
• HCT
• HGB
• RBC count
• RBC indices
• WBC count
• PLT
• Hematocrit (HCT)
• Determines RBC mass
• % of RBC in whole blood
• important for determination of anemia or polycythemia
• normal range 36-53%
• procedure
• fill capillary tube ¾ of the way
• centrifuge tube and height of packed cells is measured
• measurement is recorded as a % of of the totoal amount of blood in the capillary tube
• can be done on the automated hematology instruments, in which case a 7mL anticoagulated venous blood sample is obtained
• Hemoglobin (HGB)
• Normal range 12-18 g/dL
• Procedure
• Venous blood EDTA sample of 7mL
• Tube must be filled at least ¾
• Spectrophotmetric determination of cyanmethemmoglobin (hemoglobin-cyanide)
• Absorption at 540nm (green light)
• RBC count
• Normal range 4-6´ 10⁶ /m L (4-6´ 10¹² /L)
• Hemocytometer
• Uses changes in electrical impedance and laser light scattering
• Then determines HGB, MCV, HCT, MCH, MCHC
• RBC indices—used in differentiating anemias, determine volume and amount of hemoglobin
• MCV—mean cell volume
• HCT (%)´ 10/RBC (million/m L)
• Units fL
• Normal range is 80-100 fL (femto liters) = cubic microns
• Normocytic—normal size
• Micorcytic—smaller
• Macrocytic—larger
• MCH—mean cell hemoglobin
• HGB(g/L)/RBC/L
• Normal range is 27-33´ 10^-12g (27-33 picograms)
• MCHC—mean cell hemoglobin concentration
• HGB (g/dL)/HCT (as decimal)
• Normal range 32-36g/dL
• Platelet count
• Normal range 2-4´ 10⁵/m L (2-4´ 10¹¹/L)
• Hemocytometer