Water and sodium balance

Question 1

Where sodium goes water follows

Answer 1

Where sodium goes water follows

Question 2

What hormone regulates water balance?

Answer 2

ADH

Question 3

Where is water found in the body?

Answer 3

All body compartments and can move freely between them.

Question 4

What does ADH do?

Answer 4

Increases water reabsorption in renal tubules

Question 5

What causes ADH release?

Answer 5

Increasing osmolality

Question 6

How is urine conc measured?

Answer 6

Osmolality

Question 7

What does a high osmolality indicate?

Answer 7

Conce urine

Question 8

What does a low osmolality indicate?

Answer 8

Dilute urine

Question 9

What are the extremes of urine osmolality range?

Answer 9

40 and 1200

Question 10

What hormone controls Na balance?

Answer 10

Aldosterone

Question 11

What is the physiological range of Na?

Answer 11

135-145 mmol/l

Question 12

What fluid compartment is Na mainly found in?

Answer 12

ECF

Question 13

How does aldosterone work?

Answer 13

Causes reabsorption of Na in renal tubules and lose K instead.

Question 14

How is aldosterone regulated?

Answer 14

RAAS

Question 15

Explain RAAS

Answer 15

Renin released from kidneys in response to drop in BP
Renin converts angiotensinogen to angiotensin I
ACE converts angiotensin I to angiotensin II
Angiotensin II causes release of aldosterone from adrenal glands

Question 16

What are the two major fluid compartments in the body and what are their volumes?

Answer 16

Extracellular fluid- 14L

Intracellular fluid- 28L

Question 17

What are the two components of the ECF and what are their volumes?

Answer 17

Plasma- 3.5L

Interstitial fluid- 10.5L

Question 18

What are the two pathologies of Na/water?

Answer 18

Hyponatraemia

Hypernatraemia

Question 19

What two things can cause hyponatremia?

Answer 19

Low Na

High fluids

Question 20

What two things can cause hypernatremia?

Answer 20

High Na

Low fluids

Question 21

When is hyponatraemia serious?

Answer 21

<120 mmol/L

Question 22

When is hypernatraemia serious?

Answer 22

> 160 mmol/L

Question 23

When might a normal range of sodium be serious?

Answer 23

If it changes fast

Question 24

What effect does decreasing Na have on fluid compartments?

Answer 24

Decrease ECF only. Large drop as only lost from here.

Question 25

What can cause Na decrease?

Answer 25

Reduced Na intake Na loss in vomiting/diarrhoea, burns, kidney damage Addison's disease

Question 26

How does low sodium present?

Answer 26

``` Tachycardia Dry membranes Sunken eyes Loss of consciousness Decreased urine output and BP ```

Question 27

How do you treat a low sodium?

Answer 27

Give sodium

Question 28

What effect does increasing fluid have on fluid compartments?

Answer 28

Small increase in all as it spreads throughout body.

Question 29

What can cause a fluid increase?

Answer 29

Increased fluid intake (compulsive drinking) | Decreased fluid loss- SIADH (V common)

Question 30

How do you treat a high fluid?

Answer 30

Fluid restrict

Question 31

How do you diagnose high fluid?

Answer 31

Someone with low sodium who doesn't look dehydrated

Question 32

What effects does increasing sodium have on fluid compartments?

Answer 32

Large increase in ECF as fluid gain restricted to here only.

Question 33

What can cause high sodium levels?

Answer 33

Increased Na intake Near drowning in salt water poisoning with salt

Question 34

How does high sodium present?

Answer 34

Coughing, SOB, tiredness, pulmonary oedema, pleural effusion, weak heart, ascites, oedema

Question 35

How do you treat high sodium?

Answer 35

Remove sodium with loop diuretics

Question 36

What effects does decreasing fluid have on fluid compartments?

Answer 36

Small decrease in whole body volume as lost from whole body

Question 37

What causes low fluid levels?

Answer 37

Increased fluid loss (DI) or decreased fluid intake

Question 38

How do you treat low fluid levels?

Answer 38

Give water- as 5% dextrose to maintain osmolality so don't damage RBC Collides- Plasma expanders

Question 39

What is pseudohyponatremia?

Answer 39

Increase in blood proteins and lipids reduces apparent blood volume and sodium when they're actually normal.

Question 40

When should you suspect pseudohyponatremia?

Answer 40

If have really low sodium but no clinical features.

Question 41

What is syndrome of inappropriate ADH?

Answer 41

Release of ADH in response to low blood volume when actually have enough fluid

Question 42

What regulates ADH release?

Answer 42

Blood osmolality | Hypovolemia/hypotension

Question 43

What happens in SIADH?

Answer 43

Fluid leaks out of vessels due to lack of albumin BP drops ADH released to restore volume Cycle continues

Question 44

How do you treat SIADH?

Answer 44

Loop diuretics to lose fluid and Na

Question 45

What happens to plasma osmolality during an abnormal water deprivation test?

Answer 45

Increases due to fluid loss

Question 46

Why is it better to undertreat than overtreat with desmopressin?

Answer 46

Because overtreatment can lead to very dangerous side effects

Question 47

How can glucose cause pseudohyponatremia?

Answer 47

By drawing water into extracellular compartments therefore diluting Na content

Question 48

How do you calculate normal urea production?

Answer 48

1ml/kg/hr

Question 49

What is classed as polyuria?

Answer 49

More than 50% greater than normal urine production

Question 50

How do you calculate osmolality?

Answer 50

2[Na+K]+Glucose+Urea

Question 51

What are some endocrine causes of hypertension?

Answer 51

Cushing's Conn's Phaeocytocratoma Acromegaly

Question 52

What is another cause of SIADH?

Answer 52

Patho too much ADH release | Ectopic ADH production- SCLC

Question 53

How does SIADH present?

Answer 53

Low Na and K Oedema High BP

Question 54

How do you treat SIADH?

Answer 54

Treat underlying cause Fluid restrict Loop diuretics