[6] Hypernatraemia

Question 1

Is hypernatraemia common?

Answer 1

No, it is a relatively rare presentation

Question 2

What is hypernatraemia defined as?

Answer 2

Serum sodium concentration over 145mmol/L

Question 3

When are symptoms seen in hypernatraemia?

Answer 3

When serum sodium is >160mmol/L

Question 4

What are the causes of hypernatraemia divided on the basis of?

Answer 4

Fluid volume status

Question 5

What are the causes of hypovolaemic hypernatraemia?

Answer 5

• Diuretics
• Dehydration
• Acute tubular necrosis
• Hyperosmolar states

Question 6

Which is the main diuretic that causes hypernatraemia?

Answer 6

Loop diuretics

Question 7

Give 5 examples of things that can cause dehydration

Answer 7

• Fluid restriction
• Diarrhoea
• Vomiting
• Burns
• Excessive sweating

Question 8

What are the causes of euvolaemic hypernatraemia?

Answer 8

Diabetes insipidus

Question 9

What are the causes of hypervolaemic hypernatraemia?

Answer 9

• Excessive hypertonic saline administration
• Steroid excess

Question 10

Give two examples of causes of steroid excess

Answer 10

• Conn’s syndrome
• Cushing’s syndrome

Question 11

What is true of the symptoms of hypernatraemia?

Answer 11

Hypernatraemia is generall asymptomatic

Question 12

What can mild cases of hypernatraemia result in?

Answer 12

Excessive thirst

Question 13

What are the symptoms of more severe cases of hypernatraemia?

Answer 13

• Weakness
• Lethargy
• Irritability
• Confusion

Question 14

What can happen in cases where sodiun concentration is >200?

Answer 14

Neurological deficits can appear, including;

• Ataxia
• Tremor
• Coma
• Seizures

Question 15

What investigations are done in hypernatraemia?

Answer 15

• Metabolic panel of bloods
• Blood gas
• Urine osmolality
• Further investigations depending on underlying cause

Question 16

What is looked at in the metabolic panel of bloods in hypernatraemia?

Answer 16

Serum sodium, glucose, potassium, chloride, urea, and creatinine

Question 17

What further investigations may be done in hypernatraemia depending on suspected underlying cause?

Answer 17

• ADH levels
• CT head

Question 18

As a general rule, what do sodium levels of 150-170mmol/L usually indicate as a cause?

Answer 18

Volume depletion

Question 19

As a general rule, what do sodium levels of >170mmol/L usually indicate as a cause?

Answer 19

Diabetes insipidus

Question 20

As a general rule, what do sodium levels of >190mmol/L usually indicate as a cause?

Answer 20

Exogenous sodium gain

Question 21

What causes of hypernatraemia is hypertonic urine seen with?

Answer 21

Extra-renal fluid

Question 22

What causes of hypernatraemia is isotonic urine seen with?

Answer 22

• Diuretic use
• Osmotic diuresis
• Salt wasting

Question 23

What causes of hypernatraemia is hypotonic urine associated with?

Answer 23

Polyuria from diabetes insipidus

Question 24

What laboratory signs may accompany hypernatraemia?

Answer 24

• Increased PCV
• Increased albumin
• Increased urea

Question 25

What is the aim of the management of hypernatraemia?

Answer 25

To replace any fluid deficit, and correct serum sodium at a suitable rate

Question 26

What does the means by which hypernatraemia is managed depend on?

Answer 26

The underlying cause

Question 27

Why is it important not to correct serum sodium too rapidly in hypernatraemia?

Answer 27

Due to the risk of cerebral oedema

Question 28

How fast should you aim to lower serum sodium in hypernatraemia?

Answer 28

By 10mmol/L/day

Question 29

How is any fluid deficit replaced in hypernatraemia?

Answer 29

Enteric water replacement is preferred when possible, including administration via a nasogastric tube if possible. If enteric intake not possible, IV

Question 30

What is the IV fluid of choice in hypernatraemia?

Answer 30

* 5% dextrose * 0.9% saline if evidence of volume depletion * 0.45% saline or Hartmann's solution

Question 31

What should rates and fluid composition of IV fluid be adjusted depending on in fluid replacement in hypernatraemia?

Answer 31

* Sodium levels * Fluid status