Electrolyte Disorders

Question 1

In ECF volume depletion, would you expect the sodium concentration in the urine to be high or low? Why?

Answer 1

The sodium concentration should be low, since the kidneys will be retaining sodium in response to decrease circulating volume through the RAAS system.

Question 2

In ECF volume depletion, what does a high sodium concentration in the urine mean?

Answer 2

This finding in the context of ECF volume depletion could suggest a renal origin or use of diuretics.

Question 3

Explain in basic terms the movement of water in response to solutes within the body.

Answer 3

Solutes that cannot permeate the plasma membrane contribute to the osmolality and induce transcellular shifts of water. Water will attempt to equilibrate the osmolality on both sides of the membrane.

Question 4

What is examined when assessing volume status?

Answer 4

• JVP
• Blood pressure
• Heart (auscultation)
• Lung (auscultation)
• Skin turgor
• Oedema (incl. ascites)
• Urine output
• HCT, serum protein
• Body weight

Question 5

What is resonium?

Answer 5

Potassium binder.

Question 6

What determines electrolyte excretion in urine and is there a normal range of values?

Answer 6

Excretion of electrolytes depends on intake, as well as current physiological state. Thus there are no normal values, rather, the values must be interpreted in the context of the patient’s current state.