sodium/ water states Flashcards
hypotonic hyponatraemia versus non-hypotonic hyponatraemia= plasma osmolality levels
hypotonic hyponatraemia= <275 (urine osmolality >100)
non-hypotonic hyponatraemia >275 (urine osmolality <100)
what are non-hypotonic causes of hyponatraemia 5
ethanol- beer potonmania hyperglycaemia pseudohypo-natraemia low sodium intake polydipsia =pure water gain
what is pseudohyponatraemia
paraproteinaemia causes it
2 ways of classifying hyponatraemia
- ECF- hypo, euv, hypervolaemia
2. urine osmolality <20 or >20
causes of hypervolaemia hyponatraemia with a urinary sodium <30 5
Increased interstitial salt
- liver failure
- cirrhosis
- hepato-renal syndrome
- CCF-cardiac
- nephrotic syndrome
mechanism behind hypervolaemic hyponatraemia with <20 urine sodium
due to the above diseases- blood pressure drops
- causes release of AVP which causes salt and water to be retained
- but more water retained than salt
- salt and water excess
causes of euvolaemic hyponatraemia with urine osmolality < serum
(aka trick question= non-hypotonic hyponatraemia) water intoxification -polydipsia -beer potomaina water overload
causes of euvolaemic hyponatraemia with urine osmolality >serum or urine sodium >30
7
- SIADH
- secondary adrenal insufficiency
- hypothyroidsim- myxoedema
- lung disease
- cancer-siadh small cell
- chest
- CNS
causes of hypovolaemic hyponatraemia with urine sodium <30 3 main ones
pre renal: sodium loss in excess of water GI loss 3rd space losses previous diuretic use -diarrhoea -sweat -vomiting -burns -fistula -cirrhosis -SBO -villous adenoma rectum
causes of hyponatraemia hypovolaemic with urine sodium >30 4
renal?: salt and water lost through kidney but more salt loss than water
- kidney failure
- addison’s-primary adrenal failure
- vomiting
- CSWS
treatment for each type of hyponatraemia
hypervolaemic: restrict salt and water
euvolaemic: restrict water
hypovolaemic: give salt and water
2 body compartments
- extracellular: intravascular and intercellular
- intracellular
what compartments should sodium and potassium be found in
sodium=extracellular (so plasma sodium good estimate)
potassium- intracellular (so plasma potassium bad estimate eg in DKA)
hyponatraemia complication of going down too low and the symptoms
=cerebral oedema
- nausea, vomiting, headache and confusion
- reduced consciouscness
- 6th nerve palsy
hyponatraemia complication of coming up too quickly
=central pontine myelinolysis (osmotic demyelination) affects brain stem
symptoms of central pontine myelinolysis
dysarthria mutism dysphagia lethargy mood change spasitc quadriparesis seizure coma death neuro (focal, cranial, bulbar signs)
when does central pontine myelinolysis appear
3-4 days after sodium corrects
how does hyperglycaemia cause hyponatraemia
glucose level high increases osmolality
-> so body pushes sodium down to maintain osmolality level
seen in DKA
classification of mild, moderate and profound hyponatraemia
mild: 130-135
moderate: 125-129
severe <125
moderately severe symptoms of hyponatraemia
nausea without vomiting, confusion headache
severe symptoms of hyponatraemia
vomiting
cardio-resp distress
abnormal and deep somnolence seizure
coma
difference between acute and chronic hyponatraemia and risks
acute: develops <48 hours- more at risk of cerebral oedema
chronic: develops >48 hours more at risk of pontine myelinolysis on repletion
guideline for use of hypertonic fluid for hyponatraemia
-300mls of sodium chloride 1.8% over 30 minutes=hypertonic
-needs urgent treatment
-monitor sodium aim for a 5mmol/l increase in na with no more than 10mmol/l rise in 1st 24 hrs
then 8mmol/l rise every 24 hrs after
-not for hypervolaemic
what should not be used for a hypovolaemic hyponatraemic patient treatment
hypertonic sodium chloride due to already volume depletion
mangement of hypovolaemic hyponatraemia
-fluid but no more than 10mmol/l in first 24 hours
-use an isotonic fluid for resuscitation eg normal saline 0.9% or Hartman or
plasmalyte
-check sodium 4 hourly at least
how is hypovolaemia diagnosed
clinical diagnosis tachycardia hypotension absent JVP postural hypotension