B5.050 LG Diabetes Insipidus

Question 1

normal plasma osmolality

Answer 1

275-295 mOsmo.kg

Question 2

what determines extracellular fluid osmolarity

Answer 2

sodium is the main extracellular electrolyte

hyponatremia = low plasma osmolality

Question 3

what is the risk associated with hyponatremia and low ECF osmolarity

Answer 3

causes shift of water between the cell and the extravascular fluid with cell swelling
Na+ deficit in ECF shifts sodium from cell into ECF, water then shifts into cell causing swelling

Question 4

acute hyponatremia

Answer 4

due to sudden changes in plasma sodium
pathophysiology is excess of water
causes brain cell swelling and intracranial pressure raise
leads to confusion, drowsiness, vomiting, seizures and eventually coma

Question 5

chronic hyponatremia

Answer 5

slow, common in hospitalized patients due to IV fluids
pathophysiology is deficit in water excretion (low GFR) or excessive water reabsorption in renal tubules
subtle symptoms, deficit in cognition and concentration

Question 6

hyponatremia as a prognostic factor

Answer 6

negative prognostic factor for malignancy of a tumor

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Question 7

treatments for hyponatremia

Answer 7

IV fluids

salt tablets if necessary