Sodium and water balance

Question 1

How does ADH work?

Answer 1

Causes water to be reabsorbed from the renal tubules
Increased ADH results in a small volume of concentrated urine
Decreased ASH results in a large volume of dilute urine

Question 2

How is urine conc measured?

Answer 2

Urine osmolality
Concentrated urine = high osmolality
Dilute urine = low osmolality

Question 3

What is mineralocorticoid activity?

Answer 3

The effects of steroids on sodium balance - refers to sodium reabsorption in renal tubules in exchange for potassium/hydrogen

Question 4

What steroids have mineralocorticoid activity?

Answer 4

Aldosterone

Cortisol

Question 5

What occurs with high levels of mineralocorticoids?

Answer 5

Sodium gain and vice versa

Question 6

What is the normal conc levels?

Answer 6

135-145 mmol/mol

Question 7

What is the equation for sodium?

Answer 7

Na+ = mmol Na+/ ILH2O

Question 8

What can cause hyponatraemia?

Answer 8

Low sodium

Water retention

Question 9

What can cause hypernatraemia?

Answer 9

High sodium

Water loss

Question 10

What is the relative concs of sodium in and out of the cell?

Answer 10

140mmol/mol in the interstitial fluid

4 mmol/mol in the intracellular compartment

Question 11

Where can water be lost from?

Answer 11

All body compartments. Loss/gain of water is from/to the whole body

Question 12

Where can sodium be lost and gained from?

Answer 12

Confined to the ECF - pump in the plasma membrane

Sodium loss or gain is solely from/to the ECF

Question 13

What does water follow?

Answer 13

Sodium - if you gain/lose sodium from the ECF then you will lose/gain water with it

Question 14

What will happen if the ECF volume is too high?

Answer 14

The kidneys will secrete more Na and therefore you will lose water

Question 15

What are the symptoms of low sodium?

Answer 15

Postural decrease in BP
Increased pulse
Dry mucous membranes
Sunken eyeballs
Decreased skin turgor
Decreased consciousness
Decreased urine output

Question 16

What are the symptoms of hypernatraemia?

Answer 16

Coughing
Tiredness
SOB
Pulmonary oedema
Heart failure
Ankle oedema
Ascites

Question 17

What causes increased sodium loss?

Answer 17

Adrenal glands
Gut - N+V, IBD fistula
Skin - burns, TEN
Reduced sodium intake

Question 18

What can cause a decreased water excretion?

Answer 18

SIADH

Question 19

What can cause an increased sodium level?

Answer 19

Some IV meds
Near-drowning
Malicious

Question 20

What can cause an increased water loss?

Answer 20

Diabetes insipidus

Decreased water intake - very young and old

Question 21

How can you give sodium to a patient?

Answer 21

Form of saline

Can give dioralyte in D+V

Question 22

Why do you not give pure water IV?

Answer 22

Red blood cells would lyse

Give 5% dextrose

Question 23

What compartments with dextrose enter?

Answer 23

Plasma
Interstitial fluid
Intracellular fluid compartment

Question 24

What compartments will saline enter?

Answer 24

Plasma

Interstitial fluid

Question 25

What constitutes a low and high sodium?

Answer 25

Less than 120 mmol/L | Over 160 mmol/L

Question 26

What are the symptoms of abnormal sodium levels?

Answer 26

``` Altered consciousness Confusion Nausea Vomiting Fitting ```

Question 27

What are the 2 stimuli for ADH release?

Answer 27

Osmotic | Non-osmotic (disease)

Question 28

What are examples of non-osmotic stimuli of ADH release?

Answer 28

Hypovolaemia Hypotension Pain N+V

Question 29

What forces act on the capillary for fluid balance?

Answer 29

Hydrostatic inside the capillary pushing fluid out | Oncotic on the outside pushing fluid into the capillary

Question 30

What does oedema signify?

Answer 30

An effective circulating volume depletion - an altered balance of starling forces at capillary level

Question 31

What is high in an oedematous patient?

Answer 31

Too much sodium and water

Question 32

How is oedema treated?

Answer 32

Loop diuretics - loss of sodium and water

Question 33

What electrolyte balance will addisons disease present with?

Answer 33

Low sodium and high potassium | Increased pigmentation

Question 34

Why does addisons disease result in low sodium and increased potassium?

Answer 34

Adrenal insuffience so lack of mineralocorticoud activity | Can't retain sodium in kidneys so lose sodium and water from ECF

Question 35

Why are patients pigmented in addisons?

Answer 35

Excess ACTH from pituitary which is degraded by proteases exposing MSH

Question 36

What controls sodium and water?

Answer 36

Mineralocorticoid activity retains sodium | ADH release and action retains water