Fluids/electrolytes - Amir Sam 250821 Flashcards
what are the two main stimuli for ADH secretions?
serum osmolality (osmoreceptors) and reduced blood volume/pressure (mediated by baroreceptors in carotids, atria, aorta)
what is the first step in the clinical assessment of a patient with hyponatremia?
clinical assessment of volume status
what are the clinical signs of hypovolaemia?
LOW URINE SODIUM <20 tachycardia postural hypotension dry mucous membranes reduced skin turgor confusion/drowsiness reduced urine output
what is the most important clinical sign (after assessing volume status) of hypovolaemia
low urine sodium
clinic what are the causes of hyponatremia in hypovolaemic patients
renal causes - diuretics
extra-renal diarrhoea vomiting
what are the causes of hyponatraemia in a euvolaemic patient
hypothyroidism
adrenal insufficiency
syndrome of inappropriate ADH (cns pathology, lung pathology, drugs, tumours, surgery)
clinical assessment of hyponatraemic euvolaemic
thyroid function tests, short synacthen test, low plasma and high urine osmolality
diagnosis of siadh made if no hypovolaemia, no hypothyroidism, no adrenal insufficiency, reduced plasma osmolality AND increased urine osmolality (>100)
how would you manage a hypovolaemic hyponatraemic patient
volume replacement with 0.9% saline
how would you manage a hypervolaemic patient with hyponatraemia
fluid restriction treat the underlying cause
what is the most important point to remember while correcting hyponatraemia
serum NA must not be corrected ?8-10 mmol/L in the first 24 hours, due to risk of central pontine myelionlysis
- quadriplegia, dysarthria, dysphagia, seizures, coma, death
Drugs used to treat SIADH
if water restriction is insufficient
demeclocycline
- reduces responsiveness of collecting tubule cells to ADH (monitor
tolvaptan - V2 receptor antagonist
hyponatraemia is mostly due to?
increased extracellular water
MAIN CAUSES OF HYPERNATRAEMIA
unreplaced water loss
patient cannot control water intake
what investigations would you order in suspected diabetes insupidus
serum glucose, potassiu,. calcium, plasma and urine osmolality, water deprivation test
how would you treat hypernatraemia
fluid replacement 5% dextrose, treat the underlying cause
if they are also hypovolaemic then need 0.9% saline as while
