Sodium and Water balance physiology

Question 1

What is water balance controlled by?

Answer 1

ADH

Question 2

What does high ADH lead to in terms of urine?

Answer 2

small volume of concentrated urine

Question 3

What does low ADH lead to in terms of urine?

Answer 3

large volume of diluted urine

Question 4

What is sodium balance controlled by?

Answer 4

mineralocorticoid activity

Question 5

Which hormones possess mineralocorticoid activtiy?

Answer 5

aldosterone

cortisol

Question 6

What does high mineralocorticoid activtiy indicate in terms of sodium?

Answer 6

sodium gain

Question 7

What does low mineralocorticoid activtiy indicate in terms of sodium?

Answer 7

sodium loss

Question 8

What is mineralcorticoid activtiy?

Answer 8

Na absorption in the renal tubules in exchange for K/H

Question 9

What is the normal sodium levels?

Answer 9

135-145mmol/L

Question 10

What can low sodium be due to?

Answer 10

low Na

high H20

Question 11

What can high sodium be due to?

Answer 11

high Na

low H20

Question 12

What are dangerous numbers for sodium levels?

Answer 12

<120 or >160

Question 13

What are the signs of sodium that is too high or low?

Answer 13

nausea
altered conciousness
confusion
vomiting
fitting

Question 14

Where is sodium found?

Answer 14

ECF

Question 15

What follows sodium by osmosis?

Answer 15

water

Question 16

What can cause a decreased Na?

Answer 16

SIADH or compulsive water drinking = increasing H20 levels

Sodium loss through skin, kidneys or adrenals

Question 17

What can cause an increased Na?

Answer 17

H20 loss from diabetes insipious or just low water intake

increased Na from near drowing, some medication, children being force fed salt

Question 18

What is the management for decreased Na?

Answer 18

give 0.9% saline

Question 19

What is the management for increased Na?

Answer 19

remove sodium

Question 20

What is the management for increased H20?

Answer 20

fluid restrict

Question 21

What is the management for decreased H20?

Answer 21

give water in the form of 0.5% dextrose

Question 22

What is the benefit of giving 0.5% dextrose?

Answer 22

goes all the way into the ICF, through plasma and ECF

has the same concentration as blood

Question 23

What is oedema due to?

Answer 23

an altered balance of starlings forces at capillary level between oncotic forces bringing water in and hydrostatic forces pushing it out

Question 24

Where does water get retained in oedema?

Answer 24

in the ICF

Question 25

What does SIADH mean?

Answer 25

syndrome of innapropriate ADH release

can lead to hypovoleamia, hypotension, pain, nausea and vomiting

Question 26

What is pseudohyponatraemia?

Answer 26

extremely low Na levels caused by increased amount of proteins and lipids
the Na:H20 ratio is normal and it will be an incidental finding

Question 27

What is diabetes insipidus due to?

Answer 27

distruption of the pituitary or pituitary stalk meaning ADH cannot be secreted
lots of pure water lost in the urine

Question 28

How is diabetes insipidus treated?

Answer 28

desmopressin - exogenous ADH

desmospray, desmopressin oral tables, desmopressin injections

Question 29

How is diabetes insipidus investigated?

Answer 29

nil by mouth for 8-12 hours
Urine/serum osmol ratio <2 = DI
if improves after desmopressin = cranial DI