Nephrology

Question 1

What are the ways to arrive at a contraction alkalosis? What will this look like on labs?

What is the physiology of a contraction alkalosis?

Answer 1

Ways to arrive at: Chloride loss, which can occur via diuresis, loss of HCl from stomach fluids, skin chloride leeching (CF), sometimes profuse secretory diarrhea

On labs, this looks like a rise in the serum bicarbonate and drop in serum chloride. Often this onsets slowly in a patient being diuresed.

Physiology: Without sufficient chloride, pendrin on the luminal surface of beta intercalacted cells cannot get rid of excess bicarbonate.

Question 2

Why does adding sodium chloride have a net metabolic acidosis effect?

Answer 2

1: Adding any liquid that does not already contain bicarbonate means that the lungs will fill it with carbonic acid. This shifts the acid-base equilibrium to the acidic side.

Question 3

Mechanisms by which vasopressin concentrates urine

Answer 3

1. Activation of NKCl and NKCC2 in the thick ascending limb of the loop of Henle, concentrating the renal medullary space.
2. Insertion of AQP-2 into the apical surface of cells in the collecting duct.

Question 4

LR vs NS osm and Na

Answer 4

LR is slightly hypo-osmolar (308) and hyponatremic (130 mEq)

NS is slightly hyper-osmolar (273) and hypernatremic (154mEq)

Question 5

If you give someone with SIADH normal fluids . . .

Answer 5

. . . their Na will still drop

You have to give them hyperosmolar fluids to increase the Osm, otherwise fluids are just an opportunity to retain more free water. This is often helpful in the Ddx of hyponatremia.

Question 6

The combination of ___ and ___ for antibiotics is nephrotoxic

Answer 6

The combination of vancomycin and beta lactams (especially Zosyn) for antibiotics is nephrotoxic