Electrolyte Imbalance

Question 1

for hyponatremia we have to assess first what ?

Answer 1

if the patient is hypovolumic

hypervolemic

or euvolemic

Question 2

Causes of hypovolumic hyponatremia

Answer 2

Urinary sodium < 20 mmol/l
extra renal cause

diarrhoea,
vomiting,
sweating
burns

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Urinary sodium > 20 mmol/l
renal loss

diuretics: thiazides, loop diuretics
Addison’s disease/ adrenal insufficiency
diuretic stage of renal failure

Question 3

Causes of hypervolemic hyponatremia ?

Answer 3

secondary hyperaldosteronism: heart failure, liver cirrhosis
nephrotic syndrome

Question 4

Causes of euvolemic hyponatremia ?

Answer 4

SIADH (urine osmolality > 500 mmol/kg)
- SAH , LUNG CANCER OR GASTROINTESTINAL CANCER , PNEUMONIA , MENINGITIS

medication stimulating vasopressin release is -SSRI ,, tricyclic antidepressants, anti-epileptics (carbamazepine, sodium valproate), angiotensin converting enzyme inhibitors, proton pump inhibitor

hypothyroidism

pseudohyponatremia - MULTIPLE MYELOMA , HIGH Glucose , hyperlipidemia

psychogenic polydipsia

Question 5

Symptoms of hyponatremia?

Answer 5

if developing acutely - cerebral edema
nausea
vomiting
seizures

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volume depletion - hypovolemic
= low urine output
orthostatic hypotension
poor skin turgor

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volume overload - hypervolemic
edema
ascites
rased jugular venous pressure

Question 6

investigations for hyponatremia ?

Answer 6

bedise -
ECG

BLOODS - FBC , UE
LIPID PROFILE !!
ALBUMIN
TSH
cortisol level

URINE DIPSTICK
URINE AND SERUM OSMOLARITY
urinary sodium

GLUCOSE - if more than 5.5
corrected sodium formula should be used to see if there is true hyponatremia

Question 7

what do you figure out from urine and serum osmolarity ?

Answer 7

serum osmolarity is high = hyperglycemia , mannitol, severe uraemi

serum osmolarity is normal =
hyperlipidemia , hyperproteinemia

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if serum osmolarity is low

1)assess volume status

2)if hypervolemic
urine sodium <20-
heart failure , cirrhosis , nephrotic syndrome
urine sodium >20 = HF treated with diuretics

2) if euvolemic
urine sodium >20
urine osmolarity high - SIADH,SAH, hypothyroidism

URINE OSMALIRTY IS LOW - primary polydipsia
urine osmolarity variable - prolonged exercise

2)IF HYPOVOLEMIC
urine sodium <20 - Vomiting, diarrhoea, pancreatitis/ileus, burns, sweating

urine osmolarity >20 - Diuretics, salt-wasting nephropathy, diuretic stage of renal failure, Addison’s disease

Question 8

Mx of hyponatremia ?

Answer 8

acute onset

Hypertonic saline of 3 percent 100-300ml
8-12mmol/l/day

<8mmol//day recommended to prevent myelinosis

serum sodium tested every 2 hours to guide therapy

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chronic onset >48hr

hypovolemic hyponatremia
=normal saline

hypervolemic or euvolemic
=fluid restriction of 1L a day
based on urine output set at 50ml less than daily urine volume.

we should target also the underlying cause of the hyponatremia

if fluid restriction fails we need to contact endocrinology - and might possibly need to start demeclocycline