[6] Hypernatraemia Flashcards
Is hypernatraemia common?
No, it is a relatively rare presentation
What is hypernatraemia defined as?
Serum sodium concentration over 145mmol/L
When are symptoms seen in hypernatraemia?
When serum sodium is >160mmol/L
What are the causes of hypernatraemia divided on the basis of?
Fluid volume status
What are the causes of hypovolaemic hypernatraemia?
- Diuretics
- Dehydration
- Acute tubular necrosis
- Hyperosmolar states
Which is the main diuretic that causes hypernatraemia?
Loop diuretics
Give 5 examples of things that can cause dehydration
- Fluid restriction
- Diarrhoea
- Vomiting
- Burns
- Excessive sweating
What are the causes of euvolaemic hypernatraemia?
Diabetes insipidus
What are the causes of hypervolaemic hypernatraemia?
- Excessive hypertonic saline administration
- Steroid excess
Give two examples of causes of steroid excess
- Conn’s syndrome
- Cushing’s syndrome
What is true of the symptoms of hypernatraemia?
Hypernatraemia is generall asymptomatic
What can mild cases of hypernatraemia result in?
Excessive thirst
What are the symptoms of more severe cases of hypernatraemia?
- Weakness
- Lethargy
- Irritability
- Confusion
What can happen in cases where sodiun concentration is >200?
Neurological deficits can appear, including;
- Ataxia
- Tremor
- Coma
- Seizures
What investigations are done in hypernatraemia?
- Metabolic panel of bloods
- Blood gas
- Urine osmolality
- Further investigations depending on underlying cause
What is looked at in the metabolic panel of bloods in hypernatraemia?
Serum sodium, glucose, potassium, chloride, urea, and creatinine
What further investigations may be done in hypernatraemia depending on suspected underlying cause?
- ADH levels
- CT head
As a general rule, what do sodium levels of 150-170mmol/L usually indicate as a cause?
Volume depletion
As a general rule, what do sodium levels of >170mmol/L usually indicate as a cause?
Diabetes insipidus
As a general rule, what do sodium levels of >190mmol/L usually indicate as a cause?
Exogenous sodium gain
What causes of hypernatraemia is hypertonic urine seen with?
Extra-renal fluid
What causes of hypernatraemia is isotonic urine seen with?
- Diuretic use
- Osmotic diuresis
- Salt wasting
What causes of hypernatraemia is hypotonic urine associated with?
Polyuria from diabetes insipidus
What laboratory signs may accompany hypernatraemia?
- Increased PCV
- Increased albumin
- Increased urea
What is the aim of the management of hypernatraemia?
To replace any fluid deficit, and correct serum sodium at a suitable rate
What does the means by which hypernatraemia is managed depend on?
The underlying cause
Why is it important not to correct serum sodium too rapidly in hypernatraemia?
Due to the risk of cerebral oedema
How fast should you aim to lower serum sodium in hypernatraemia?
By 10mmol/L/day
How is any fluid deficit replaced in hypernatraemia?
Enteric water replacement is preferred when possible, including administration via a nasogastric tube if possible. If enteric intake not possible, IV
What is the IV fluid of choice in hypernatraemia?
- 5% dextrose
- 0.9% saline if evidence of volume depletion
- 0.45% saline or Hartmann’s solution
What should rates and fluid composition of IV fluid be adjusted depending on in fluid replacement in hypernatraemia?
- Sodium levels
- Fluid status
