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SM Endocrine > Sodium and Water Balance > Flashcards

Sodium and Water Balance Flashcards

1
Q

What are the key organs that control sodium and water balance

A

endocrine i.e. they secrete hormones

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2
Q

describe the relationship between water and sodium

A

Water follows sodium everywhere. they are inseparable.

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3
Q

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

A 
Increased use 
decrease in blood pressure 
decreased urine output 
Decreased consciousness
Decreased skin turgor 
Dry mucous membranes 
Soft, sunken eyeballs
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4
Q

What controls sodium

A

Mineralocorticoid activity

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5
Q

What does mineralocorticoid activity refer to

A

sodium retention in exchange for potassium and / or hydrogen ions

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6
Q

What are some steroid which have mineralocorticoid activity

A

Aldosterone

Cortisol

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7
Q

What does too much mineralocorticoid activity mean

A

Sodium retention

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8
Q

What does too little mineralocorticoid activity mean

A

sodium loss

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9
Q

What does sodium loss mean

A

Water loss (water always follows sodium)

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10
Q

Where is ADH released

A

Posterior pituitary

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11
Q

What does ADH act on

A

Renal tubules

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12
Q

What does ADH cause

A

Water reabsorption

Antidiuretic effect

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13
Q

Describe the relationship between ADH and urine

A

Increased ADH results in concentrated urine

Decreased ADH results in dilute urine

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14
Q

What is the relationship between urine and ADH also known as

A

Urine osmolality

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15
Q

What does concentrated urine mean in terms of urine osmolality

A

It will be high

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16
Q

What does dilute urine mean in terms of urine osmolality

A

It will be low

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17
Q

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

A

Too much water or too little sodium

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18
Q

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

A

Too little water or too much sodium

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19
Q

What 2 things can cause too much water

A

Decreased excretion e.g. SIAD or

Increased intake e.g. compulsive water drinking

20
Q

What are some causes of having too little sodium

A

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

Decreased sodium intake (rare cause)

21
Q

How can we have too little water

A

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

22
Q

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

A 
malaise 
weight loss 
crave salty foods 
dizzy 
Postural hypotension
tanned / hyper pigmentation in mouth and hand creased 
Low sodium
23
Q

What happens in Addison’s disease

A 
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
24
Q

Why does excess pigmentation occur in Addison’s

A

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

25
Q

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

A

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

26
Q

What is SIAD

A

Syndrome of inappropriate antidiuresis

27
Q

What are the 2 kinds of stimuli for ADH release

A

osmotic (in health)

or non osmotic (in disease)

28
Q

What are some examples of non-osmotic stimuli

A

Hypovolaemia / hypotension
Pain
nausea/ vomiting

29
Q

What causes water retention

A

ADH secreted in response to a non-osmotic stimulus

30
Q

Describe the typical presentation of a patient with diabetes insipidus

A

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

31
Q

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

A

The pituitary or pituitary stalk

32
Q

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

A

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

33
Q

How can we treat diabetes insipidus

A

Give exogenous ADH to replace it

Desmopressin

34
Q

How can we describe volume status

A

hypovolaemic
Euvolaemic
Hypervolaemic

35
Q

What does hypovolaemia imply

A

Water deficit

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

36
Q

What happens if there is hypovolaemia in hyponatraemia

A

Too little sodium

37
Q

What is hypervolaemia most often seen as

A

oedema

38
Q

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

A

Altered consciousness
Confusion
Nausea

39
Q

What should be measured if we suspect adrenal insufficiency

A

Cortisol and ACTH

40
Q

What should be given immediately if we suspect adrenal insufficiency

A

Sodium replacement

41
Q

What do we do for a patient with too much water

A

Fluid restrict

42
Q

What do we do for a patient with too little sodium

A

give sodium

43
Q

What do we do for a patient with too little water

A

Give water

44
Q

What do we do for a patient with too much sodium

A

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

45
Q

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

A

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

SM Endocrine (27 decks)

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