Sodium and Water Balance

Question 1

What are the key organs that control sodium and water balance

Answer 1

endocrine i.e. they secrete hormones

Question 2

describe the relationship between water and sodium

Answer 2

Water follows sodium everywhere. they are inseparable.

Question 3

What can happen to the patient when there is a decrease in extracellular volume

Answer 3

Increased use 
decrease in blood pressure 
decreased urine output 
Decreased consciousness
Decreased skin turgor 
Dry mucous membranes 
Soft, sunken eyeballs

Question 4

What controls sodium

Answer 4

Mineralocorticoid activity

Question 5

What does mineralocorticoid activity refer to

Answer 5

sodium retention in exchange for potassium and / or hydrogen ions

Question 6

What are some steroid which have mineralocorticoid activity

Answer 6

Aldosterone

Cortisol

Question 7

What does too much mineralocorticoid activity mean

Answer 7

Sodium retention

Question 8

What does too little mineralocorticoid activity mean

Answer 8

sodium loss

Question 9

What does sodium loss mean

Answer 9

Water loss (water always follows sodium)

Question 10

Where is ADH released

Answer 10

Posterior pituitary

Question 11

What does ADH act on

Answer 11

Renal tubules

Question 12

What does ADH cause

Answer 12

Water reabsorption

Antidiuretic effect

Question 13

Describe the relationship between ADH and urine

Answer 13

Increased ADH results in concentrated urine

Decreased ADH results in dilute urine

Question 14

What is the relationship between urine and ADH also known as

Answer 14

Urine osmolality

Question 15

What does concentrated urine mean in terms of urine osmolality

Answer 15

It will be high

Question 16

What does dilute urine mean in terms of urine osmolality

Answer 16

It will be low

Question 17

If the sodium concentration is low, what 2 things can this mean

Answer 17

Too much water or too little sodium

Question 18

IF the sodium concentration is high, what 2 things can this mean

Answer 18

Too little water or too much sodium

Question 19

What 2 things can cause too much water

Answer 19

Decreased excretion e.g. SIAD or

Increased intake e.g. compulsive water drinking

Question 20

What are some causes of having too little sodium

Answer 20

Increased sodium loss e.g. Kidneys (Addison’s), gut or skin

Decreased sodium intake (rare cause)

Question 21

How can we have too little water

Answer 21

Increased water loss - diabetes insidious (problem with ADH secretion or action)
Decreased water intake (e.g. very young or elderly patients

Question 22

Describe a typical presentation of a patient with Addison’s disease

Answer 22

malaise 
weight loss 
crave salty foods 
dizzy 
Postural hypotension
tanned / hyper pigmentation in mouth and hand creased 
Low sodium

Question 23

What happens in Addison’s disease

Answer 23

Adrenal insufficiency 
Cant make enough steroids 
not enoug mineralocorticoid activity 
can't retain enough sodium in the kidneys 
loses sodium from ECF 
Decreased ECF volume = dehydration

Question 24

Why does excess pigmentation occur in Addison’s

Answer 24

excess ACTH from pituitary. ACTH molecule contains a sequence for MSH within it. ACTH is degraded by proteases eventually exposing MSH

Question 25

What is the typical presentation of a patient with too much water

Answer 25

Often already in hospital with another illness Routine biochemistry shows decreased Na Volume status usually unremarkable Patient usually has no symptoms specifically due to low sodium Investigations for cause of sodium loss Patient presumed to have too much water innappropriate ADH secretion

Question 26

What is SIAD

Answer 26

Syndrome of inappropriate antidiuresis

Question 27

What are the 2 kinds of stimuli for ADH release

Answer 27

osmotic (in health) | or non osmotic (in disease)

Question 28

What are some examples of non-osmotic stimuli

Answer 28

Hypovolaemia / hypotension Pain nausea/ vomiting

Question 29

What causes water retention

Answer 29

ADH secreted in response to a non-osmotic stimulus

Question 30

Describe the typical presentation of a patient with diabetes insipidus

Answer 30

Urine output is excessive Fluid requirement is large sodium levels are high and need correcting

Question 31

Where is the most common place for problem resulting in diabetes insipidus

Answer 31

The pituitary or pituitary stalk

Question 32

What happens if there is a problem with the pituitary or pituitary stalk

Answer 32

Patient can't secrete ADH from posterior pituitary therefore none can work on the kidneys to cause water to be reabsorbed and therefore lots of water in los in the urine Patient's sodium is high

Question 33

How can we treat diabetes insipidus

Answer 33

Give exogenous ADH to replace it | Desmopressin

Question 34

How can we describe volume status

Answer 34

hypovolaemic Euvolaemic Hypervolaemic

Question 35

What does hypovolaemia imply

Answer 35

Water deficit | Present when Na is low, then there must be an even bigger sodium deficit

Question 36

What happens if there is hypovolaemia in hyponatraemia

Answer 36

Too little sodium

Question 37

What is hypervolaemia most often seen as

Answer 37

oedema

Question 38

What symptoms might a patient develop if they have seriously abnormal sodium

Answer 38

Altered consciousness Confusion Nausea

Question 39

What should be measured if we suspect adrenal insufficiency

Answer 39

Cortisol and ACTH

Question 40

What should be given immediately if we suspect adrenal insufficiency

Answer 40

Sodium replacement

Question 41

What do we do for a patient with too much water

Answer 41

Fluid restrict

Question 42

What do we do for a patient with too little sodium

Answer 42

give sodium

Question 43

What do we do for a patient with too little water

Answer 43

Give water

Question 44

What do we do for a patient with too much sodium

Answer 44

Get rid of excess sodium e.g. diuretics to induce natriuresis and then replace just the water

Question 45

What do we assess if a patient has too little sodium or water or too much sodium or water

Answer 45

volume status Na concentration Routine investigations e.g. cortisol and osmolality