z- Test #4 Lab Measurements

You need a heparinized plasma tube (green top tube) or serum must be separated from the cells; NO Hemolysis
Use ISE (ion-selective electrode) to measure the amount of electrolyte present
Serum preferred
NO hemolysis
seperated from cells
no contact with air because of CO2 and bicarbonate interferences
Coulometric or Amperometric Titration: based on titration, silver will bind to chloride and you measure how much silver you used to bind the chloride and you know how much chloride you had.
the process by which you collect sweat sample, you would do this in infants with CF or Cystic fibrosis
How would you collect chloride from a pt with peptic or gastric ulcer?
Chloride Shift
Increased bicarbonate from metabolic activity inside cells cause it to diffuse out and chloride to go inside the cell > lower plasma pH

o Cell pH > 7.4
o Plasma pH = 7.4
o Cl- enters cell
o HCO3- leaves cell
? Increase in HCO3- raises cell pH

Carbon Dioxide
1st : Are we measuring venous or arterial because they are totally different in each?
2nd: If you leave the tube open for one hour you will lose 6 mmol/L (that is 20% of CO2)
3rd: The measurement of CO2 is different some labs measure only bicarbonate and some measure total CO2
Acidification of serum
convert all forms of CO2 to the gas form and then measure with ISE
convert all forms of CO2 to bicarbonate and then measure the amount of HCO3 (ISE or enzymatic method)
Total CO2
33% bound to protein, 3% is gas, 64% HCO3 and H2CO3

We only measure HCO3 and H2CO3

Anion Gap
o Anion Gap = Na+ – (Cl- + CO2)
o Anion gap is a calculation of the difference between anions and cations in the blood
o Represents chemical anions other than those used in the formulas the might be present in the blood
? Sodium
? Potassium
? Chloride
? Bicarbonate
o Used to estimate acid-base and electrolyte disturbances
o In many types of metabolic acidosis, anion gap is increased (>20) due to deficit of bicarbonate ions and presence of organic acids, such as acetoacetic acid, lactate, salicylate, formate, and glycolate.
o Circumstances that cause increase in sodium relative to deficiency of anions such as bicarbonate will also increase anion gap.
o Process by which blood is exposed to an ambient gas phase in such a way that each gas partitions at equiliptium stage
o Blood gas measurement
Buffer Systems
1. Renal buffer
2. Pulmonary Buffer
3. Hb Buffer
4. H2PO4 – + H+ ? H3PO4
5. NH3 + H+ ? NH4+
6. Albumin
? Histines H+ Acceptor
= (oxygen content/oxygen capacity) X 100
%O2 saturation
= [HbO2]/[Hb] X100
%sO2 vs. pO2
o Sigmoidal curve
? “Shift to the Left”
? “Shift to the Right”

o pH
? Acidic right
? Basic left
o CO2, up pCO2 = acidic pH shift to right
o 2,3 Diphosphoglycerate up = shift to the right
? Made in glycolysis
o Hypertheria = shift right
o Hypothermia = shift left

= Down CO2
= Up CO2
Best anticoagulant for blood gases
? Liquid Heperin
? Don’t use things with acid
• EDTA, Citrate
Potassium IV
= Hyperkalemia
Na+ IV
= hyponatremia
Hydration IV
o Hyponatremia
o Hypochlocemia
o Down in plasma osmolality
conc of solutes
o Electrolytes
o cH2O
o Waste Products
o Vitamins
o Drugs
o Hormones
o Dissolved in kg of solvent “pure H2O”
Plasma or Serum osmolality
= [1.86 (Na+ mmol/L) + (glucose mg/dL)]/18 + (Urea nitrogen mg/dL)/2.8 + 9

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