Dehydration (Hypernatraemia)

Question 1

what is normal serum sodium concentration

Answer 1

135-145 mmol/L

Question 2

hypernatraemia blood results?

Answer 2

> 145 mmol/L

Question 3

what causes hypernatraemia

Answer 3

Hypernatraemia represents a deficit of water relative to sodium and can result from a number of causes, including free water losses, inadequate free water intake, and, more rarely, sodium overload. Unlike hyponatraemia, hypernatraemia is always associated with serum hyperosmolality.

Question 4

causes of hypernatraemia

Answer 4

free water losses (sweat, diarrhoea, renal) MOST COMMON CAUSE

inadequate water consumption (limited access/ impaired thirst pathway),

sodium overload (mineralocorticoid excess- aldosterone)

Question 5

presenting symptoms of hypernatraemia (history and exam)

Answer 5

CNS manifestations (dehydration causes brain shrinkage), diarrhoea or vomiting, impaired thirst, weight loss, postural hypotension, oliguria, decreased JVP

Question 6

investigations

Answer 6

UREA AND ELECTROLYTES, urine and serum osmolarity, urine electrolytes and desmopressin challenge test

Question 7

treatment

Answer 7

Oral or IV fluids

treat underlying cause (if its due to diarrhoea or due to mineralocorticoid excess, treat this as well)

Question 8

prognosis

Answer 8

mortality is high

prognosis of hypernatraemia is worse than any other electrolyte imbalance