Hypernatraemia

Introduction
Identification
Severity assessment
Management based on severity
Relevant history
Investigations
Referral criteria
Discharge criteria
Treatment Algorithm

Introduction/ Description

HyperNa⁺ is diagnosed when the serum sodium >145 mmol/l

Identification/recognition/diagnosis of problem

• ↓Total body water
• Pure water (isolated free water loss): insensible losses (dermal/ respiratory), hypodipsia, Diabetes insipidus or drugs (e.g. Lithium, amphotericin B)
• Hypotonic fluid loss (water loss > Na⁺ loss): renal (loop diuretics, osmotic diuretics, post-obstructive diuresis), gastrointestinal (vomiting, nasogastric drainage, fistula, diarrhoea, lactulose), cutaneous (burns, excessive sweating), high glucose in uncontrolled diabetes mellitus
• ↑ Sodium
• Includes: acute renal failure, hypertonic feeds (formula too concentrated), Sodium Bicarbonate or hypertonic saline administration, sea water ingestion, or endocrine abnormalities (primary hyperaldosteronism, Cushing’s syndrome)
• Groups at highest risk for HyperNa⁺ are patients with altered mental status, intubated patients, infants and the elderly

Differential Diagnosis

• Cirrhosis
• Diabetes Mellitus, Type 1
• HypoCa²⁺
• HypoNa⁺

Severity assessment (Triage)

• A reduced level of consciousness (confusion vs coma) is a critical finding as brain shrinkage from a sudden increase in Na+ can cause SAH/ intracerebral bleeding.
• Assess fluid status for
• Hypovolaemia: tachycardia, decreased skin turgor, decreased cap refill, orthostatic hypotension and/ or decreased urine output
• Euvolaemia
• Hypervolaemia: ↑ JVP and/ or signs of fluid overload (oedema and S3)

Management based on severity

• What is the cause of the HyperNa⁺? – Find and treat the cause.
• What is the patient’s volume status – Management plan to correct the Na⁺
• How long did it take for HyperNa⁺ to develop? – How quickly can it be corrected?

Immediate action:

Non-drug treatment

• Stabilise using ABCs, perform blood glucose, apply oxygen if hypoxic and establish IV access.
• If depressed level of consciousness, intubate and ventilate as indicated.  Terminate seizures with benzodiazepines/ phenytoin (check glucose). 
• Find and treat the cause of the HyperNa⁺:
• Stop GIT fluid loss
• Control pyrexia
• Correct feeding preparation
• Correct Hyperglycaemia/ glycosuria
• Withhold lactulose/ diuretics
• Treat HyperCa²⁺/ HypoK⁺

Added tables/dose charts

What is the patient’s fluid status?
HYPOVOLAEMIA (Water loss > Sodium loss)	EUVOLAEMIA (Isolated loss of free water)	HYPERVOLAEMIA (Fluid overload, increased total Na+)
Normal Saline until Euvolaemic Then ½ N/S or 5% Dextrose water IV	If stable: give water po/ NGT If unstable or symptomatic: give ½ N/S or 5% DW IV	Diuretics. Serum Na+ lowered at rate of no more than 1 mmol/h
Water Deficit Calculation Water deficit (L) = This deficit needs to be replaced over 24-48hrs depending of rapidity of development of HyperNa+
How long did it take for the HyperNa+ to develop?
LONG: (Developed over > 12 hours, OR Unknown length of time) – Avoid rapid and extreme changes in serum sodium in patients with prolonged HyperNa+ as this may cause cerebral oedema. (Aim to lower Na+ by 0.5 mmol/L/hr (<10mmol/L/24 hr) SHORT: (Known to have developed over a period of hours) – can be corrected more rapidly. Aim to lower Na+ by 1mmol/L/hr

Relevant history

Includes thirst, muscle weakness, fatigue to malaise, confusion, coma and/ or seizures.  The severity of symptoms are determined by speed of rise in serum Na⁺

Investigations

• Serum sodium.  A venous blood gas can give an early indication of sodium levels
• Urine sodium and osmolality
• Renal function
• CXR to assess fluid overload
• CT head if level of consciousness out of keeping with Na⁺, altered mental state not attributable to Na⁺ or if there is a clinical suspicion of head injury

Referral criteria

All patients with severe symptoms, Na⁺ >160 or an unidentifiable cause for the HyperNa⁺ need to be discussed with a physician for investigation and/or management.  Others can be managed in overnight or short stay wards.  If Diabetes Insipidus is suspected, then obtain a consultation from endocrinologist (this need not occur in EC).

Discharge criteria/checklist

May be discharged with appropriate follow-up a Primary Care facility

If they are asymptomatic and Na⁺ <150 mmol/l and aetiology identified and addressed

Treatment algorithm for acute presentation of Hypernatraemia

References

Adrogue, Madias. Hypernatraemia. New England Journal of Medicine. 342 (20) p1493-1499.

Ramrakha, Moore. Oxford Handbook of Acute Medicine. Second edition 2005.  P576

Rossiter D, Blockman M (eds.). South African Medicines Formulary. 11th Ed. Cape Town: Health and Medical Publishing Group; 2014

Cameron P, Jelinek G, Kelly A, et al. Textbook of Adult Emergency Medicine. 4th Ed. Elsevier; 2015