Hyponatraemia

Question 1

Hyponatraemia Homeostasis

Answer 1

Thirst, ADH, renin-angiotensin-aldosterone, renal handling of sodium

Question 2

Hyponatraemia Definition

Answer 2

Excess of water in relation to sodium

• Serum sodium of <136
• <120 is severe
• Can be falsely low with high serum lipids or proteins and hyperglycaemia

Question 3

Hyponatraemia Presentation

Answer 3

• Depends on severity also dictated by rate of fall
• Often asymptomatic if mild to moderate or chronic
• Whereas sudden fall my result in convulsions

Question 4

Hyponatraemia Symptoms

Answer 4

• Mild; anorexia, headache, nausea, vomiting, lethargy
• Moderate; personality change, muscle cramps, weakness, confusion, ataxia
• Severe; drowsiness

Question 5

Hyponatraemia Signs

Answer 5

• Neurological; decreased consciousness, cognitive impairment, focal or generalised seizures, brainstem herniation
• Signs of hypovolaemia
• Signs of hypervolaemia

Question 6

Hyponatraemia Aetiology

Answer 6

Hypovolaemic
-Urine Na <20; vomitting diarrhoea, skin loss
-Urine Na >20; adrenocortical deficiency, renal failure, diuretics
Euvolaemic
-Urine Na <40; acute water load, psycho polydipsia, diet
-Urine Na >40; SIADH, glucocorticoid deficiency, hypothyroidism, chronic water load
-Hypervolaemic
-Urine Na <20; CCF, cirrhosis, nephrotic syndrome, primary polydipsia
-Urine Na >20; renal failure or disease

Question 7

Hyponatraemia Ix

Answer 7

Serum Na+K, urine Na (paired), fluid status, TFTs, causes

Question 8

SIADH Presentation

Answer 8

Hyponatraemia, plasma hypo-osmolality, elevated urine osmolality, persistent urine Na>30, euvolaemia, normal thyroid and adrenal function

Question 9

Hyponatraemia Management

Answer 9

• If acute and symptomatic treat with hypertonic saline
• If euvolaemic; test urine for SIADH, if Na<20 reconsider hypo/hypervolaemia
• If hypovalaemic treat with 0.9% saline
• If hypervolaemic treat underlying cause