Hyponatraema is a common finding, especially within our elderly population. However, its significance is is not a simple numbers game, and needs senior input. Prior to treatment the following need to be considered and balanced.
- Symptoms Severity – these are not exclusive to hyponatraemia and may be due to other disease processes (esp. if the low sodium is long-term)
- Sodium Level – the sodium concentration doesn’t always correlate to the clinical picture, and is dependant on speed of change, and co-morbidities
- Rate of Drop – the faster sodium levels drop the more symptomatic the patient often is (i.e. with long term hyponatraema the patient may be profoundly hyponatraemic but asymptomatic)
- Co-morbidities – Increasing sodium too quickly risks osmotic demyelination. How well will the patient cope with treatment?
Emergency treatment (hypertonic saline) is generally indicated in those with Severe/Moderately Severe Symptoms ONLY
1. Symptom Severity
- Severe: Cardiorespiratory arrest, Seizures, Reduced Conscious level, Vomiting (sodium typically <130mmol/l)
- Moderately Severe: Confusion, Headache, Nausea
- Mild/None
2. Sodium Level
- Profound: <125mmol/l
- Moderate: 129-125mmol/l
- Mild: 135-130mmol/l
3. Rate of Drop
Look at the patients previous blood results, if the hyponatraemia has been a long term issue, but the symptoms have just started, is there something else going on?
Emergency Treatment
- In general hypertonic saline treatment should be reserved for those with Severe/Moderately Severe symptoms ONLY + [Na] <130mmol/l
- Less severely symptomatic patients would generally be better treated in a more planned manner, either under medicine or GP management but senior input will be important in striking the right balance
- Aim to increase [Na] by 5mmol/l within 1 hour
- If symptoms do not improve with Step 1 you may consider progressing to Step 2
Step 1
*If no 3% NaCl avalible use 2.7% NaCl
- 150ml 2.7% Sodium Chloride, 20min – this must be done in Resus with close monitoring
- Recheck [Na] – use iStat for quick result (if using lab proceed to 3. as results will have approx. 1hr delay) – Stop if [Na] increased by ≥5mmol/l
- 150ml 2.7% Sodium Chloride, 20min – if [Na] not increased sufficiently this may be repeated twice more (but keep checking [Na])
- Stop Hypertonic Sodium Chloride – commence 0.9% NaCl start disease specific treatments and investigation, repeat U&E @ 6+12hr
Step 2 – consider if Step 1 has failed to increase [Na] by 5mmol/l
- 150ml 2.7% Sodium Chloride, 20min – this must be done in Resus with close monitoring, aiming to increase [Na] by 1mmol/l
- Indications to stop hypertonic saline
- Symptomatic improvement
- [Na] – Rise of 10mmol/l OR Reaches 130mmol/l (whichever happens first)
Urine Osmolality
If you get the chance – send a urine sample for osmolality as this can help the diagnostic process for medicine.
- <100mOsm/kg – Primary polydipsia, Inappropriate IV fluid
- >100mOsm/kg
- Urine [Na] <30mmol/l – Heart Failure, GI losses, Diuretics, Portal hypertension, Low Albumin, 3rd Space loss
- Urine [Na] >30mmol/l – Vomiting, SIADH, Addisons, Salt wasting, NSAID, AVP like drugs, (if on ACEi/ or diuretic consider the causes in [Na]<30mmol/l differentials)
