Electrolyte methodology Flashcards
Is urinary electrolytes a routine test?
No
_________ should be used for potassium detection. 
Serum
(Potassium is released during clotting or hemolysis) 
What should not be used for detecting sodium and potassium levels? 
Sodium heparin or NH4- heparin
Whole blood should be analyzed within _____ hours 
3
What is the preferred method for detecting chloride?
Coulometric Titiration
-very accurate
What is a good method for chloride detection in normal range (80-125mM)? 
Mercuric Thiocvante Spectroscopy 
What is the most common method for detecting Chloride?
ISE
-Direct and indirect methods
Limitation: Same as sodium and potassium
Chloride interferes with…
Other halides
-Chloride ions in serum are complex with mercury to form soluble HgCl2
-serum proteins are precipitated with tungstic acid 
-soluble fraction is titrated with mercuric nitrate in the presence of sdiphenylcarbazone as indicator
-Indicator turns violet blue with first excess of mercuric ion
-Bilirubin or hemoglobin may Obscure the endpoint
Schales and Schales titration
What is an important test for cystic fibrosis? It is generally administered to children
Sweat Chloride 
How is the Sweat chloride test done?
-induce sweating with pilocarbpine 
What is the normal range for sweat chloride and what is the range typically seen in cystic fibrosis?
Normal is 0-40 mmol/L
Cystic fibrosis >60 mmol/L 
Total CO2 exists as….
Dissolved CO2 __%
carbamino derivatives of plasma protein _____%
HCO3 ____%
3
33
64
What is the normal Total CO2 values for a healthy adult?
22-30 mmol/L (method dependent)
What are 4 lab methods for detecting bicarbonate? 
-manometric (Measures CO2 gas)
Spectrophotometric
-PCO2 electrode
-enzymatic spectrophotometer
What is the most common method for detecting bicarbonate to determine total CO2? 
Enzymatic-spectrophotometer
Lab test that converts all CO2 forms to bicarbonate by addition of alkali serum and NADH consumption measured as decreased in 340nm absorption 
Enzymatic spectrophotometric
When testing for a total CO2 why can you not use other anticoagulants?

Must use HEPARINIZED plasma
(disturb erythrocyte and plasma CO2) boy cannot be used due to him bound CO2 and carbamino-bound CO2
What is a major error associated with total CO2 measurement?
Handling of the sample
Exposure to air should be minimal and centrifugation at 37°C. Tightly Stoppered before analysis
Serum or plasma total CO2 is stable for _________ days at ______ Degrees Celsius
Several, 4
Urinary excretion of sodium potassium in a healthy person is dependent on what two things? 
-dietary intake
-State of water balance
Urinary analysis of sodium may help to determine….
The route of sodium loss
(otherwise additional data is required to make diagnosis, This is not a routine test)
Urinary potassium excretion could be helpful to assess…..
Whether potassium is lost via the kidney or G.I. tract
(Used for hypokalemia, little use in hyperkalemia)
What is important for the differential diagnosis of persistent metabolic alkalosis? 
Urinary chloride
1 Osmolal Solution defined…
1 Osmol/kg H2O ***
Osmolality =
Osmol/KgH20 = Ønc **
Ø: Osmotic coefficient
n: # of Particle into which each molecule in the solution
c: molarity in mol/kg H2O
(need to be able to calculate this!) 
Because not all electrolytes can be dissociated, many solutions are not match with ideal case. What coefficient is used to correct deviation?
Osmotic coefficient (0-1)
Osmolality of 1M NaCl = 1x2x1= 2 Osmol
(Because NaCl can be dissociated into Na and Cl)
Osmolality is a “___________” property: a characteristic to which the number of dissolved particles contribute (not mass nor kind)
Colligative
Causes of hypoosmoality?
- overhydration, hyponaturemia, increased ADH
Causes of hyperosmolality?
-renal failure, diabetes, excessive water loss
Increasing solutes —-> __________ freezing pt, vapor pressure (Dew point temp), _________ boiling point, and osmotic pressure.
Decrease, increases
What is the most commonly employed measurement for osmolality? 
Freezing point depression***
-Thermoresister accurately measures heat released from freezing liquid
What are the two methods used for osmolality measurement?
-freezing point depression* (common)
-Vapor pressure depression 
Method for determining osmolality that is less commonly used. How is it done?
Vapor pressure depression (Ethanol, methanol, isopropanol)
-Measures dewpoint (Equilibrium pressure) of Vapor with solution
How do you calculate osmolality? (Show me a rough estimate due to only measuring three)***
=2 [Na+] + [glucose] + [urea] (all mmol/L)
=2 [Na+] + [glucose]/18 + [urea]/2.8 (glucose and urea in mg/dl)
A positive osmolality gap suggests…
Volatile substances such as alcohols
Osmol gap =
Measured osmolality (mOsm/kg- Calculated osmolality (mOsm/Kg)
