Sodium pathology

Question 1

Define plasma toxicity

Answer 1

blood plasma conc which produce toxicity/clinically relevant side effects/symptoms

Question 2

Give a full definition of hyponatraemia

Answer 2

electrolyte abnormality seen in isolation or as a complication of another illness eg heart failure, renal and liver failure or pneumonia

Question 3

What is the sodium level of hyponatraemia?

Answer 3

sodium <135mEq/L

Question 4

What does ADH regulate?

Answer 4

osmolality - number of osmoles of solute per litre of solution
The kidney reacts by retaining water and producing small amounts of concentrated urine

Question 5

What are symptoms of hyponatraemia

Answer 5

nausea,malaise- mild reduction in serum sodium
decreased level of consciousness, headache, lethargy- intermediate
coma, seizure-severe

Question 6

Define water intoxification

Answer 6

defined as hyperhydration- drinking too much water pushing electrolytes out of safe zone causing overhydration– drinking too much water w/o adequate electrolyte supplementation

Question 7

Explain the symptoms a/w water intoxification

Answer 7

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

Question 8

What does daily water limit depend on?

Answer 8

• proper functioning ADH axis

- total solute intake

Question 9

What is the daily solute intake of a person?

Answer 9

10mOsm/kg/day

Question 10

How much water can you safely drink in a day?

Answer 10

14 litres

Question 11

What characterises volume depletion?

Answer 11

Loss of total body sodium – as sodium moves w water

Question 12

What are the causes of volume depletion

Answer 12

Extrarenal : Gi bleed, Gi vomitting and diarrhea , skin burns, excessive sweating
Pituitary, Renal, Adrenal: Addison Disease, DM, loop and thiazide diuretics

Question 13

What are the signs of volume depletion

Answer 13

Skin turgor, dry mucous membranes, orthostatic hypotension, tachycardia

Question 14

Is the concentration of urine sodium high/ low in volume depletion? What does this suggest? What kind of condition is it also seen in ?

Answer 14

low- suggests low tissue perfusion

also seen in heart failure patients

Question 15

What other effects are there in volume depletion?

Answer 15

low serum osmolalility

low sodium/solute excretion- due to body trying to conserve remaining fluid by reabsorption

Question 16

Define SIADH

Answer 16

too much ADH released- causing hyponatraemia due to excess of water rather than a deficiency in Na

Question 17

Causes of SIADH

Answer 17

MEN, PS 
meds- antipsychotics, narcotics
ectasy 
neuro- tumours, meningitis, trauma 
Pulmonary disease- lung cancer, TB 
Stress- vomiting, post surgical, pain

Question 18

Other Features of SIADH

Answer 18

low serum osmolalility 
high urine osmolalility 
urinary sodium >30 ; reflects intake
normal GFR, adrenal and thyroid axis
normal total solute excretion

Question 19

Managment of hyponatraemia

Answer 19

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

Question 20

Define hypernatemia

Answer 20

Na >145mEq/L

Question 21

Describe pathophysiology of hypernatemia

Answer 21

Water excretion exceeds intake

Two step process:
Generation
-gain in sodium, loss in water

Maintenance: - inability to ingest water

Question 22

Which type of patients is hypernatraemia commonly seen?

Answer 22

elderly/cognitively impaired patients

Question 23

Define free water deficit

Answer 23

Rise in Na proportional to weight loss due to water

Na-140/140 (xkgx0.5)