Sodium and Water Balance Flashcards
What does mineralocorticoid activity refer to?
Sodium retention in exchange for potassium and/or hydrogen ions
How do you assess ADH?
Urine osmolarity (high osmolarity = concentrated urine, low osmolarity = dilute urine)
Actions of Cortisol
Helping to regulate blood pressure.
Helping to regulate the immune system.
Helping to balance the effect of insulin in regulating the blood sugar level.
Helping the body to respond to stress.
Causes of too much sodium
- Some IV medications given as sodium salts
- Near-drowning in the sea
- Infants given high salt feeds
Typical presentation of Addison’s
A 24 year-old student presents with a six month history of malaise, tiredness, poor appetite and one stone weight loss. She has developed a craving for salty foods – crisps in particular. She has had a number of dizzy spells particularly while in warm places.
She is thin. She has low BP which falls further on standing. You have the impression that she is tanned, and you find increased pigmentation in her mouth and hand creases.
Her bloods show a low sodium [122] and a high potassium [5.8
Non-osmotic stimuli for ADH release
Hypovolaemia/hypotension
Pain
Nausea/vomitting
If the pituitary can’t make/release ADH then what can you give to replace it?
Desmopressin
How do you assess sodium/water balance?
Volume status
Hyponatremia?
Low sodium concentration in blood
AVP
Arginine vasopressin
ADH
What is hypervolaemia most commonly seen as?
Oedema
How do you usually assess sodium/water balance?
In the context of hyponatremia or hyperhatremia
What controls sodium and water?
Mineralocorticoid activity
ADH release and action
How do you assess disorders of water and sodium?
Volume status (VERY USEFUL)
[Na] - most common scenario
Rountine investigations e.g. cortisol, osmolarity
