Hypernatraemia Flashcards
Define hypernatraemia
Serum sodium concentration >145mmol/L
What is the difference between dehydration vs hypovolaemia
Dehydration: water loss in the absence of salt i.e. sodium
Hypovolaemia: loss of water and salt together
What is the formula for plasma sodium calculation
Plasma Na = Total body Na + K / Total body water
Hypernatraemia should be considered a problem with what?
a) Total body water
b) Sodium homeostasis
a) Total body water
Define acute hypernatraemia
A rise in serum sodium to > 145 mmol/L that occurs within a 24 hour period
Define chronic hypernatraemia
A rise in serum sodium to > 145 mmol/L and sustained for > 48 hours.
Which patient groups are most at risk of hypernatraemia
Elderly patients
Children
Total body water can be regulated to alter the plasma sodium concentration.
What are the two predominant mechanisms?
ADH system: leads to free reabsorption of water in the kidneys
Thirst: osmoreceptors in the hypothalamus are stimulated by a rise in osmolality
Describe the mechanism of thirst
Osmoreceptors in the hypothalamus are stimulated by a rise in osmolality
What is the predominant cause of hypernatraemia
Unreplaced water losses
Name the three main mechanisms that lead to hypernatraemia
Unreplaced water losses (most common)
Sodium overload: excess salt ingestion
Water loss into cells: usually temporary event that occurs following extreme exercise or seizure
What is the most common cause of hypernatraemia due to excess water loss
Diabetes insipidus
What is the three common cause of hypernatraemia due to excess water loss
Dehydration
Osmotic diuresis e.g., DKA, HHS
Diabetes insipidus
Name some of the symptoms of hypernatraemia
Thirst
Dehydration
Lethargy
Weakness
Name some of the signs of hypernatraemia
Confusion
Agitation
Seizure
Coma
