Electrolyte methodology

Question 1

Is urinary electrolytes a routine test?

Answer 1

No

Question 2

_________ should be used for potassium detection. 

Answer 2

Serum

(Potassium is released during clotting or hemolysis) 

Question 3

What should not be used for detecting sodium and potassium levels? 

Answer 3

Sodium heparin or NH4- heparin

Question 4

Whole blood should be analyzed within _____ hours 

Answer 4

3

Question 5

What is the preferred method for detecting chloride?

Answer 5

Coulometric Titiration
-very accurate

Question 6

What is a good method for chloride detection in normal range (80-125mM)? 

Answer 6

Mercuric Thiocvante Spectroscopy 

Question 7

What is the most common method for detecting Chloride?

Answer 7

ISE
-Direct and indirect methods

Limitation: Same as sodium and potassium

Question 8

Chloride interferes with…

Answer 8

Other halides

Question 9

-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

Answer 9

Schales and Schales titration

Question 10

What is an important test for cystic fibrosis? It is generally administered to children

Answer 10

Sweat Chloride 

Question 11

How is the Sweat chloride test done?

Answer 11

-induce sweating with pilocarbpine 

Question 12

What is the normal range for sweat chloride and what is the range typically seen in cystic fibrosis?

Answer 12

Normal is 0-40 mmol/L
Cystic fibrosis >60 mmol/L 

Question 13

Total CO2 exists as….
Dissolved CO2 __%
carbamino derivatives of plasma protein _____%
HCO3 ____%

Answer 13

3
33
64

Question 14

What is the normal Total CO2 values for a healthy adult?

Answer 14

22-30 mmol/L (method dependent)

Question 15

What are 4 lab methods for detecting bicarbonate? 

Answer 15

-manometric (Measures CO2 gas)
Spectrophotometric
-PCO2 electrode
-enzymatic spectrophotometer

Question 16

What is the most common method for detecting bicarbonate to determine total CO2? 

Answer 16

Enzymatic-spectrophotometer

Question 17

Lab test that converts all CO2 forms to bicarbonate by addition of alkali serum and NADH consumption measured as decreased in 340nm absorption 

Answer 17

Enzymatic spectrophotometric

Question 18

When testing for a total CO2 why can you not use other anticoagulants?


Answer 18

Must use HEPARINIZED plasma

(disturb erythrocyte and plasma CO2) boy cannot be used due to him bound CO2 and carbamino-bound CO2

Question 19

What is a major error associated with total CO2 measurement?

Answer 19

Handling of the sample

Exposure to air should be minimal and centrifugation at 37°C. Tightly Stoppered before analysis

Question 20

Serum or plasma total CO2 is stable for _________ days at ______ Degrees Celsius

Answer 20

Several, 4

Question 21

Urinary excretion of sodium potassium in a healthy person is dependent on what two things? 

Answer 21

-dietary intake
-State of water balance

Question 22

Urinary analysis of sodium may help to determine….

Answer 22

The route of sodium loss

(otherwise additional data is required to make diagnosis, This is not a routine test)

Question 23

Urinary potassium excretion could be helpful to assess…..

Answer 23

Whether potassium is lost via the kidney or G.I. tract

(Used for hypokalemia, little use in hyperkalemia)

Question 24

What is important for the differential diagnosis of persistent metabolic alkalosis? 

Answer 24

Urinary chloride

Question 25

1 Osmolal Solution defined…

Answer 25

1 Osmol/kg H2O ***

Question 26

Osmolality =

Answer 26

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!) 

Question 27

Because not all electrolytes can be dissociated, many solutions are not match with ideal case. What coefficient is used to correct deviation?

Answer 27

Osmotic coefficient (0-1)

Osmolality of 1M NaCl = 1x2x1= 2 Osmol
(Because NaCl can be dissociated into Na and Cl)

Question 28

Osmolality is a “___________” property: a characteristic to which the number of dissolved particles contribute (not mass nor kind)

Answer 28

Colligative

Question 29

Causes of hypoosmoality?

Answer 29

• overhydration, hyponaturemia, increased ADH

Question 30

Causes of hyperosmolality?

Answer 30

-renal failure, diabetes, excessive water loss

Question 31

Increasing solutes —-> __________ freezing pt, vapor pressure (Dew point temp), _________ boiling point, and osmotic pressure.

Answer 31

Decrease, increases

Question 32

What is the most commonly employed measurement for osmolality? 

Answer 32

Freezing point depression***

-Thermoresister accurately measures heat released from freezing liquid

Question 33

What are the two methods used for osmolality measurement?

Answer 33

-freezing point depression* (common)
-Vapor pressure depression 

Question 34

Method for determining osmolality that is less commonly used. How is it done?

Answer 34

Vapor pressure depression (Ethanol, methanol, isopropanol)

-Measures dewpoint (Equilibrium pressure) of Vapor with solution

Question 35

How do you calculate osmolality? (Show me a rough estimate due to only measuring three)***

Answer 35

=2 [Na+] + [glucose] + [urea] (all mmol/L)

=2 [Na+] + [glucose]/18 + [urea]/2.8 (glucose and urea in mg/dl)

Question 36

A positive osmolality gap suggests…

Answer 36

Volatile substances such as alcohols

Question 37

Osmol gap =

Answer 37

Measured osmolality (mOsm/kg- Calculated osmolality (mOsm/Kg)