Approach to Abnormal Electrolyes

Question 1

If serum [Na] is normal, what can you infer about an abnormal [electrolyte] concentration?

Answer 1

that the abnormal [electrolye] concentration is due to an abrnoaml amount of solute.

Question 2

abnormal [Na+] is almost always due to an:

Answer 2

abnormal amount of solvent– usually because the person has reduced or increased body water.

If [Na+] normal…
 Abnormal [Electrolyte] assumed due to abnormal amount of
solute

Question 3

If [Na+] normal, Abnormal [Electrolyte] assumed due to abnormal amount of solute. what three main mechanism causes abnormal amounts of solute?

Answer 3

1. due to intake change,
2. due to loss
3. due to shift.
   - these mechanisms are mainly measured intravascularly. it’s difficult to sample shift in interstitial fluid levels (imagine truying to sample between cells or something), or intercellularly (microscopic).

Shift between body fluid compartments– intracellular vs extracellular (interstitial and intravascular (most sampled) compartments).
• In the intravascular compartment– cahnge in electrolyte compartment can be due to changes in intake, loss (through urine or GI secretions), or if there is movement to other compartments (ex/ to the interstitial compartment)

Question 4

Outlline the scheme appraoch to abnormal [electrolyte] (solute) concentration. What first mechanisms should you consider?

Answer 4

Recall that Abnormal solute can be due to intake. loss, or shift
- You should first consider “Loss through renal handling changes” as the first cause of abnormal solutes. You can also lose electrolytes through GI loss/vomit or diarrhea as well–>” other”

Question 5

diabetic ketoacidosis causes a __ change, resulting in abnormal solute concentration

Answer 5

SHIFT change (recall that solutes can be abnormal due to loss, gain, shift)

Question 6

dialysis causes a __ change, resulting in abnormal solute concentration

Answer 6

INTAKE. ex/ dialysis patients often have high potassium because it isn’t excreted as readily– when they eat foods with potassium (intake), there is a marked increase/abnormality in solutes

Question 7

Renal handling is typically based upon interpretation of the __ __ of the electrolyte in question
- Renal loss determined by __ and tubular function

• __ usually reabsorb electrolytes (except ___)

Answer 7

Renal handling is typically based upon interpretation of the fractional excretion of the electrolyte in question
- Renal loss determined by filtration and tubular function

• Tubules usually reabsorb electrolytes (except K+)

Question 8

outline the difference between the renal handling of creatining and Na+

Answer 8

creatinine has an FE of 100%, or close to. almost all creatinine from the muscles gets filtered by the kidneys and excreted. most does not get reabsorbed.

Na+ has a lot of reabsorption (ex/ in the loop of henle), so the FE% is a lot lower.

Question 9

Outline the fractional excretion equation

Answer 9

Amount of solute in urine /amount of createnine excreted

• Creatinine is almost 100% excretion, so it’s like a fraction.

If [electrolyte] is low, FE should be lower than normal. If not, kidney is to blame.
If [electrolyte] is high, FE should be higher than normal. If not, kidney is to blame.

Question 10

Note: Key points: