Sodium pathology Flashcards
Define plasma toxicity
blood plasma conc which produce toxicity/clinically relevant side effects/symptoms
Give a full definition of hyponatraemia
electrolyte abnormality seen in isolation or as a complication of another illness eg heart failure, renal and liver failure or pneumonia
What is the sodium level of hyponatraemia?
sodium <135mEq/L
What does ADH regulate?
osmolality - number of osmoles of solute per litre of solution
The kidney reacts by retaining water and producing small amounts of concentrated urine
What are symptoms of hyponatraemia
nausea,malaise- mild reduction in serum sodium
decreased level of consciousness, headache, lethargy- intermediate
coma, seizure-severe
Define water intoxification
defined as hyperhydration- drinking too much water pushing electrolytes out of safe zone causing overhydration– drinking too much water w/o adequate electrolyte supplementation
Explain the symptoms a/w water intoxification
More water outside of cell thus water moves from area of high concentration to an area of lower water conc i.e inside the cell – swelling of cell esp in brain – increased ICP (cytopathic effect of oedema) -> headache, drowsiness, personality and behavior changes, confusion -> cerebral oedema-> seizure, brain damage
What does daily water limit depend on?
- proper functioning ADH axis
- total solute intake
What is the daily solute intake of a person?
10mOsm/kg/day
How much water can you safely drink in a day?
14 litres
What characterises volume depletion?
Loss of total body sodium – as sodium moves w water
What are the causes of volume depletion
Extrarenal : Gi bleed, Gi vomitting and diarrhea , skin burns, excessive sweating
Pituitary, Renal, Adrenal: Addison Disease, DM, loop and thiazide diuretics
What are the signs of volume depletion
Skin turgor, dry mucous membranes, orthostatic hypotension, tachycardia
Is the concentration of urine sodium high/ low in volume depletion? What does this suggest? What kind of condition is it also seen in ?
low- suggests low tissue perfusion
also seen in heart failure patients
What other effects are there in volume depletion?
low serum osmolalility
low sodium/solute excretion- due to body trying to conserve remaining fluid by reabsorption
Define SIADH
too much ADH released- causing hyponatraemia due to excess of water rather than a deficiency in Na
Causes of SIADH
MEN, PS meds- antipsychotics, narcotics ectasy neuro- tumours, meningitis, trauma Pulmonary disease- lung cancer, TB Stress- vomiting, post surgical, pain
Other Features of SIADH
low serum osmolalility high urine osmolalility urinary sodium >30 ; reflects intake normal GFR, adrenal and thyroid axis normal total solute excretion
Managment of hyponatraemia
compensated, asymptomatic -water restriction -treat underlying cause -increase solute intake Meds; loop duiretics+NACL and demeclocycline- in palliative cases
uncompensated, mild symptoms
saline 0.9%
nephrology consult
uncompensated, severe symptoms
3% saline bolus 150 ml over 20 mins
nephrology consult
Define hypernatemia
Na >145mEq/L
Describe pathophysiology of hypernatemia
Water excretion exceeds intake
Two step process:
Generation
-gain in sodium, loss in water
Maintenance: - inability to ingest water
Which type of patients is hypernatraemia commonly seen?
elderly/cognitively impaired patients
Define free water deficit
Rise in Na proportional to weight loss due to water
Na-140/140 (xkgx0.5)
