Lab Exam 2 Flashcards
What equipment is needed for a safe venipuncture?
Gloves, sterile needles, blood collection tubes, needle holder, tourniquet
Veins for venipuncture procedure
medial cubital, cephalic (lateral), basillic (medial)
Identify additives, their functions, their volume, and specimen considerations for the color coded tubes
LIght blue top:
- sodium citrate
- coagulation
- 2.7 ml
Red top:
- No additives, used for serum separation
- 5-10 ml
Green top:
- Heparin
- 4-8 ml
- electrolytes
Gray top:
- sodium fluoride
- 2-4 ml
- glucose
Lavender top:
- EDTA
- 3-5 ml
- used for CBC
What is the order for drawing proper specimen collection?
coagulation, heparin, complete blood count (CBC)
What areas should you avoid when performing venipuncture and why?
visible veins, previous IV sites, areas close to major arteries or nerves
Given a set of “out of control” values, calculate the dilution necessary to obtain a value within the analyte assay range and calculate the final result
Dilution factor = initial concentration / desired target concentration
What are the parts of a hemocytometer?
2 counting chambers
Identify the parts of the 3 dimensions of the counting chamber
- Length = 1 dimension
in mm - Area = 2 dimensions in
mm (L x W = mm2) - Volume = 3 dimensions
in mm
(L x W x H = mm3)
Serpentine pattern
Allows for continuity
Which border lines count when cells are touching them?
top or left. never bottom or right
Proper counting pattern for WBC
left, right, down, left
Proper counting pattern for RBC
left, right, down, left, middle
How to calculate a WBC and RBC count using the universal formula
cells/mm3 = (Average # of cells x depth factor x dilution factor) / area (mm2)
Normal ranges for Manual WBC count
Adult - 5.0-10.0 x 10^3 / mm^3
Children - 4.5-12.0 x 10^3/mm^3
Newborn - 9.0-30.0 x 10^3 / mm^3
Name the diluting fluid for WBC count
Ammonium oxalate with 100 dilution factor
Normal ranges for manual RBC count
Adult male :
4.5-6.0 x 10^12 / L
Adult female:
4.0-5.5 x 10^12/L
Newborn:
5.0-6.3 x 10^6/mm^3
Diluting fluid for RBC count
Isotonic saline with 200 dilution factor
Components of hemoglobin molecule
Heme (iron containing portion)
Globin (the protein portion)
What do hemoglobin variants contain?
Amino acid chains: alpha, beta, gamma, and delta
Alpha chain has 141 amino acids
Beta chain has 146 amino acids
Normal HbA and HbA2 Variants
HbA has 2 alpha and 2 beta chains
HbA2 has alpha chains that are paired with 2 delta polypeptide chains
Normal HbF Variant
2 alpha chains are paired with 2 gamma chains
Abnormal variants
Hb C & S because both of them have amino acid substituions in the beta chain
Hemoglobin derivatives
Carboxyhemoglobin (usually bc of smokers), methemoglobin (unable to bind with O2) sulfhemoglobin (from ingesting oxidizing drugs)
Cyanmethemoglobin method for hemoglobin measurement
mixing Drabkin’s reagent to a sample of blood forming cyanmethemoglobin. This oxidized blood is read in a
spectrophotometer
Cyanmethemoglobin Method Procedure
- Pipet 5mL of Drabkin’s
- Add 20uL of whole blood
- Cover the test tube with parafilm, invert and allow to stand at RT for 10 minutes
- Turn on the spec and set the λ to 540
- Set the blank curvette that only has Drabkin’s to read 0 abs 100%T.
- Read the absorbance of the prepared standards, then the patients and control
Cyanmethemoglobin Reaction
RBCs are lysed; the Fe2+ of the released HgB is oxidized to Fe3+ to form methemoglobin. This reacts with the cyanide of K+ cyanide to form cyanmethemoglobin, read by spec at 540λ
What does Drabkin’s reagent contain?
iron,potassium, cyanide and sodium bicarbonate (this is a corrosive reagent)
How to find concentration of Hb?
Conc = amount / vol g/dl
Hgb Concentration reference ranges
Adult males: 13-18 g/dL
Adult females: 11-16 g/dL
Infant :10-14 g/dL
Formula for Hct
Volume of RBC / Volume of blood
Reference ranges for Hct
Adult males: 40-54%
Adult females: 37-47%
Give 3 reasons for erroneous (wrong) hemoglobin values due to patient considerations
Hemodilution: if pt has IV
Dehydration: concentration changes
Hemolysis: shaking tube
Extruded
being released from the cell
What are some factors that can affect hemoglobin levels?
Age, altitude, gender, and diet
Preparation of a Standard curve
x axis - concentration of Hb (g/dL)
y axis - Aborsbance hgb values
straight line