Hypernatraemia Flashcards
major cause of hypernatraemia
Na+ concentration due to water loss
disease states which can cause hypernatraemia
haemorrhage
vomiting
diarrhoea
burns
diuretics states
sequestration
renal disease
excess sweat due to fever
hyperventilation
diabetes insipidus
reduced water intake
increased sodium intake
function of vasopressin/ADH
stimulates aquaporin channels to migrate to cell surface in collecting duct
more water is reabsorbed
urine is more concentrated
happens when you are thirsty/volume deplete
pathophysiology of SIADH
ADH secretion is excessive
it is not suppressed by already have enough water in body (reduced tonicity)
too much water is reabsorbed
Na+ gets diluted in body = hyponatraemia
causes of SIADH
neurological - stroke, encephalitis, meningitis, head injury, stroke
malignancy
drugs
pathophysiology of diabetes insipidus
ADH is insufficient or inactive
water loss in urine is not controlled
not enough is reabsorbed
Na+ gets concentrated = hypernatraemia
no ADH able to respond so continued fluid loss
what psychiatric drug can cause diabetes insipidus and what type
nephrogenic
lithium carbonate
used for bipolar disorder
what investigations should be done for hypo/hypernatraemia
electrolytes
FBC
infection screen
CXR
serum cortisol
CT/MRI brain
plasma osmolality
urine osmolality
urine sodium concentration
what disease would a low serum cortisol suggest
addison’s
treatment of hyponatraemia
water restriction
treat underlying cause or stop offending drug
allow time
why are Na+ supplements not used for hyponatraemia
it just makes patients more thirsty
hypernatraemia treatment
give water
e.g. as 5% dextrose IV
treat underlying cause or stop offending drug
allow time
cranial diabetes insipidus treatment
synthetic ADH
cranial diabetes insipidus treatment
synthetic ADH (desmopressin)
nephrogenic diabetes insipidus treatment
supraphysiological ADH
diuretics
NSAIDs
what can occur if you correct hyponatraemia too rapidly
central pontine myelinolysis
what is the recommended rate of correction of hyponatraemia
4-10mmol/l/day if asymptomatic
8-12mmol/l/day if symptomatic
signs of volume depletion/dehydration
postural hypotension
tachycardia
absence of JVP @ 45 degrees
reduced skin turgor
dry mucosae
supine hypotension
oliguria
organ failure
symptoms of volume depletion/dehydration
thirst
dizziness
dysphagia
weakness
confusion
aggression
coma
signs of volume excess/overhydration
hypertension
tachycardia
raised JVP @ 45 degrees
gallop rhythm
oedema
organ failure
symptoms of volume excess/overhydration
nausea
localised discomfort
dyspnoea
confusion
aggression
coma
what does a visible JVP at 45 degrees suggest
huge pressure in the right atrium
causes of visible JVP
heart failure
excess fluid
stenosis
what do you do if you can’t see the JVP at 45 degrees
press on liver
how do you check for oedema
press down for 30s
oedema will displace
fat will not
