Hyponatraemia

Question 1

Define Hyponatraemia.

Answer 1

Sodium level less than 135mmol/l

Question 2

How is Hyponatraemia classified?

Answer 2

Hyponatraemia with
1. Low serum osmolality <285mOsm/L
2. Normal serum osmolality 285-295mOsm/l
3. High serum osmolality >295mOsm/l

Question 3

What are the possible causes of Hyponatraemia?

Answer 3

1. Hyponatraemia with normal plasma osmolality; Hypelipidemia, hyperprotimemia,
   glycine absorption during TURP
2. Hyponatraemia with high plasma osmolality; hyperglycemia, mannitol administration.
3. Hyponatraemia with low plasma osmolality I.e

Question 4

Hyponatraemia with low total body sodium

Answer 4

Progressive loss of both Na and water with non psmotic ADH secretion which results in volume restoration at the expense of plasma osmolality.

Renal losses from thiazide
Gi loss

Question 5

Hyponatraemia with increased total body sodium

Answer 5

Edematous state such as cirrhosis, CCF, renal failure and nephritis syndrome.
Reduced free water clearance secondary to non osmotic ADH secretion coupled with sldecresed delivery of water to distal nephron.

Question 6

Hyponatraemia with normal total body sodium

Answer 6

Glucocorticoid deficiency, hypothyroidism, drugs and SIADH.

Question 7

Clinical features of Hyponatraemia

Answer 7

None specific : N&V, anorexia and weakness.
CNS sec to cerebral oedema: seizures, lethargy ,confusion, coma ,death

Question 8

Risk factors

Answer 8

Female
Premenopausal

Question 9

Treatment of choice

Answer 9

Isotonic saline if low total body sodium content.
H2O restriction if normal or high Na content.

Question 10

How is the correction rate calculated

Answer 10

Na def= TBW×desired NA-Present Na

Question 11

How fast should the Hyponatraemia be corrected?

Answer 11

Depends on how fast it developed and symptoms.
Asymptomatic 0.5mEq/l/hrs
Symptomatic 1mEq/l/hrs
Severely symptomatic 1.5mEq/l/h

Question 12

What are the daily targets for Na replacement

Answer 12

10-12mEq/l/day for symptomatic
4-5mEq/l/day asymptomatic

Question 13

What are the side effects of hypersonic saline?

Answer 13

It’s indicated for severe Hyponatraemia <110
May precipitate pulmonary 🫁 oedema, hypokalaemia, hypochloricemic metabolic acidosis,transient Hyponatraemia

Question 14

Anaesthetist considerations for Hyponatraemia?

Answer 14

Correct to 130mEq/l for GA, aim for >130 for elective procedures.

Low MAC
Postoperative agitation, confusion or somnolance.

Question 15

What is the algorithm for treatment of Hyponatraemia