April 11, 2016 - SG3 - Hypernatremia

Question 1

Diabetes Insipidus (Central)

Answer 1

Usually acquired.

ADH is no longer being produced by the hypothalamus, and therefore it cannot act on the kidneys. Because of this, the patient will pee a lot and be constantly thirsty.

To determine if it is central DI, nephrogenic DI, or primary polydipsia, you need to perform a fluid restriction test and give DDAVP. For central DI, when you give DDAVP, the kidneys will correct themselves, and in nephrogenic DI it won’t.

Treatment includes MRI of the head and supplemental AVP/ADH.

Question 2

Diabetes Insipidus (Nephrogenic)

Answer 2

Usually congenital.

The receptors for AVP are missing in the kidney, so even though AVP is being produced, it cannot act.

To diagnose this, you need to do a water restriction test and even when you give DDAVP, the kidneys will not correct themselves.

Question 3

Hypernatremia and Water Intake

Answer 3

If a patient does not have access to water, they will become hypernatremic as they are dehydrated.

If a patient does have access to water and their thirst receptors work, they may become hyponatremic as they are dehydrated (over and over again).

Question 4

Calculating Water Defecit

Answer 4

= (Mass in Kg) x (Man 0.6 or Woman 0.5) x (1 - 140/[Na] )