Land of Lilyplant - HYponatremia/ hypernatremia

Hyponatremia

Rule out pseudohyponatremia - true hyponatremia is when serum osmolality is low with low serum sodium, pseudohyponatremia is when serum osmolality is normal but low serum sodium

physiology : vasopression secretion causing increased water retention

When vasopressin levels are inappropriately high, the kidneys retain excess water, diluting the sodium in the bloodstream and causing hyponatremia

Classifications :

Hypovolemic

Euvolemic

Hypervolemic

Hypovolemic

Serum osmolarity

Urine osmolarity > 20 : likely renal cause - aldosterone insufficiency --> hyperkalemia, low BP etc

extra-renal cause : vomiting / diarrhoea / diuretic use

Cerebral wasting syndrome secondary to traumatic head injury

### difference between cerebral wasting with SIADH - cerebral wasting responds well to sodium chloride therapy

treatment: give normal saline to reduce vasopressin, which increase diuretic effect and reduce dilutory effect increasing sodium concentration. if hyponatremia more than 48 hours, need to slow down rate of normal saline infusion, to prevent ODS

Hypervolemic

heart failure, CKD, liver failure

characterised by low urine osmolarity despite given NS treatment

Treatment : for CHF, treatment that increase myocardial function will helps with hyponatremia

Euvolemic

most common :

SIADH - causes of SIADH

- CNS causes; subarachnoid hemorrhage

- Squamous cell carcinoma, pleural effusion

- SSRI

hypothyroid

malnutrition secondary to alcoholism

Acute hyponatremia

situations : marathon runner : increased vasopressin level with high consumption of water --> hyponatremia

post op - increased vassopressin --> if given hypotonic solution -> can cause acute hyponatremia

take MDMA - increased thirst -> hyponatremia

chronic hyponatremia

> 48 hours

hyponatremia

SYMPTOMATIC when < 125

Treatment

not for rapid correction - not more than 10mmol/ litre in 24 hour or 18 mmol/ litre in 48 hours， monitor sodium every

2-4 hour

damange BBB - causes osmotic demyelinatimng syndrome

Fluid restriction

Urine Sodium + K / serum sodium > 1 restrict fluid < 500

Urine sodium concentration + Urine k concentration / serum sodium = 1 - 500 - 700ml

<1 - 1 litre / day

amolirode treatment - 20mg BD - help to reduce urine concentrate

can give free water D5W, or DDVAp - safe treatment to prevent rapid reduced Na

Hypernatremia

serum Na > 145

relatively rare compared to hyponatremia
mortality up to 40-60
iatrogenic causes like hypertonic saline infusion

nephrogenic and non nephrogenic cause

burn, excessive esercise, excessive heat exposuire
diarhoea etc

Nephrogenic cause

high sugar level, increased urea, mannitol causing osmotic diuresis
problematic aquaporin 2, where is cant concenytrate urine in collecting tubules
nephrogenic DI also causes low potassium
long term lithium can cause nephrogenic DI
Amiloride

central diabetes insipidus

water deprivation test with vasopression administration to differentiate between nephrogenic and central DI

in Central DI - collecting tubule will respond to vasopressin and reabsorb water, reducing urine osmolarity

in nephrogenic DI - will not respond to vasopressin

Hyponatremia

Hypernatremia treatment

reduce sodium slowly - not more than 10mmol in less than 24 hour

unless

> 160, allow 1mmol / hour

desmopression - used to treat central diabetic insipidus

thiazide

amiloride

Hyponatremia

most common cause

polydypsia

body produces antidiuretic hormone - retention of water

thiazide diuretic - increased soidium secretion

heart failure and liver failure

SIADH - take cortisol and thyroid - if all ruled out

hypothyroid can cause low sodium

Addison disease - low cortisol, low sodium, high potassium