Chem Path: Sodium and fluid balance Flashcards
What are the 2 receptors ADH acts on and what it does
Acts on V1 to reabsorb water and acts on V2 to vasoconstrict
What are the 2 stimuli for ADH relsease
Increased serum osmolality and reduced BP
What is the first thing you assess in a hypoNa patient?
Volume status - hyper, eu or hypo volaemic?
What is the most reliable clinical sign of hypovolaemia?
Low urine sodium (<20)
What are the causes of hypoNa and hypovolaemia?
Renal problems losing salt and water
D and V
Diuretics
What are the causes of euvolaemic hypoNa
Hypothyroid, Adrenal insufficiency, SIADH
What are the causes of hypervolaemic hypoNa?
Cardiac failure, cirrhosis and nephrotic syndrome
How is Cushings diagnosed?
24 hour cortisol. Then do dexamethasone suppression test. If cortisol is suppressed, it is a pituitary problem, if it isnt, its an adrenal problem
Why should you not bring Na up rapidly?
Can cause osmotic demyelination syndrome - dysphagia, quadriplegia, dysarthria, seizures, coma and death
How do you treat that?
Dextrose and DDAVP
How do you treat severe hypoNa
Hypertonic 3% saline, but do not give if no reduced GCS or if not in seizures
What is the extent to hoe much you can raise Na?
8-10mmol/L
What drugs do you use to treat SIADH
Demeclocycline and tolvaptan
What can cause hyperNa
Renal losses, GI loss, sweat loss and DI
How do you treat hyperNa
5% dextrose for water deficit. If hypovolaemic, also give normal saline 0.9% for EC fluid defecit, then 5% dextrose
What are the effect of DM on Na
Hyperglyaemia can draw out water from the cells, thereby causing hypoNa
Osmotic diuresis can lead to loss of water and hyperNa
Summarise: Hypovolaemic hypoNa causes
Urine Na > 30 - Aldosterone defeciency,
Urine Na < 30 - D&V, pancreatitis
Summarise: Euvolaemic hypoNa causes
Urine Na > 30 - SIADH, Glucocorticoid def
Urine Na < 30 - Hypothyroid, water overload
Summarise: Hypervolaemic hypoNa causes
Urine Na > 30 - renal failure
Urine Na < 30 - HF, cirrhosis, nephrotic syndrome
What are the clinical features of DI
Polydipsia, polyuria, hyperNa, lethargy, thirst, irritability, confusion, coma, fits, euvolaemia
What will the ADH be in cranial DI
Low or none
How do you diagnose?
Water deprivation test. Urine will only concentrate after giving desmopressin
