Hyponatremia Assistant

Step 1 · Patient & severity

Required first

Age (years)

Weight (kg)

Sex

Sodium

Current Na⁺ (mmol/L)

Previous Na⁺ (mmol/L)

Time course

Acute/unclear duration is treated as higher‑risk by convention; chronicity changes correction‑limit caution, not the emergency protocol itself.

Na⁺ rise already given, last 24 h

Na⁺ rise already given, last 48 h

Symptoms & signs

Classification below follows the Society for Endocrinology 2022 severity definitions — based on symptoms, not on the sodium value alone.

Persistent vomiting Seizures Cardiorespiratory arrest Confusion / disorientation Headache Nausea without vomiting Fever

Non‑specific for severity grading, but a non‑osmotic ADH stimulus — feeds the infection‑related SIADH differential below

Dysuria / urinary symptoms

Feeds the urinary‑tract‑infection differential below

Falls / unsteady gait

Non‑specific — does not by itself set guideline severity grade

Glasgow Coma Scale (3–15)

GCS ≤ 8 is itself the "coma / markedly reduced consciousness" severe‑symptom criterion — no separate checkbox needed.

Step 2–3 · Laboratory & tonicity

Lab unit system

Affects glucose, urea/BUN and creatinine fields and the formulas that use them.

Potassium (mmol/L)

Chloride (mmol/L)

Bicarbonate (mmol/L)

Glucose (mmol/L)

Urea (mmol/L)

Creatinine (µmol/L)

Albumin (g/L) — optional

Measured serum osmolality (mOsm/kg) — optional, enables osmolar gap

Endocrine labs

Used to auto‑check the adrenal/thyroid exclusion in the SIADH criteria, and feed the corresponding differential entries.

Morning cortisol (nmol/L)

From µg/dL: ×27.6

ACTH (pmol/L) — optional

TSH (mIU/L)

Free T4 (pmol/L) — optional

Uric acid & FEUA

Separates SIADH from diuretic‑induced or volume‑depleted hyponatraemia — most useful exactly when the patient is already on a diuretic and urine Na⁺ can't be trusted alone.

Serum uric acid (µmol/L)

Urine uric acid (µmol/L)

Urine creatinine (µmol/L)

Other labs

Recorded for the documentation summary — not used by the algorithms above.

Mg (mmol/L)

Ca (mmol/L)

Phosphate (mmol/L)

More (CBC, CRP, ABG/VBG)

Hgb (g/L)

WBC (×10⁹/L)

Platelets (×10⁹/L)

CRP (mg/L)

pCO₂ (kPa)

Urine studies

Urine osmolality (mOsm/kg)

Urine sodium (mmol/L)

Urine potassium (mmol/L) — optional

Urinalysis — infection screen

Dipstick/microscopy is available immediately; culture takes 24–72 h to confirm. Both are recorded here since infection‑related SIADH can be flagged before culture returns.

Leukocyte esterase

Nitrites

Bacteria on microscopy

Urine culture status

A positive dipstick (leukocyte esterase/nitrites) or >20 bacteria/HPF supports a presumptive UTI while culture is pending — culture result, once back, is the confirmatory standard.

Step 4 · Volume status

Tick what's present. Classification is a transparent rule‑based read of the signs you select — not a numeric probability, since no guideline assigns one.

Orthostatic hypotension Tachycardia Dry mucous membranes Reduced skin turgor / delayed capillary refill Recent vomiting, diarrhea or GI losses Burns / third spacing Peripheral edema Ascites Pulmonary edema Raised jugular venous pressure Known heart failure Known liver cirrhosis Known nephrotic syndrome Known chronic kidney disease

Step 6 · Clinical history

Check everything present — used by the differential engine below.

Recent surgery (post‑op hyponatraemia) Pain / nausea (non‑osmotic ADH release) Pulmonary disease (pneumonia, TB, COPD, abscess) Known malignancy CNS disease (stroke, SAH, meningitis, viral/herpetic encephalitis, brain injury) Hypothyroidism / known thyroid disease Adrenal disease / steroid-dependent / pituitary disease Alcohol use disorder / beer potomania Very low protein/solute intake ("tea and toast") Polydipsia / high fluid intake Heart failure Liver cirrhosis Nephrotic syndrome Chronic kidney disease Strenuous exercise (marathon, military training) Pregnancy Diuretic use (thiazide / loop)

Step 7–8 · Differential & SIADH

Step 9 · Treatment

Complete Triage (and ideally Workup) first — treatment guidance is generated from those answers so it stays tied to this patient, not a generic default.

Step 10 · Correction safety tracker

Log each Na⁺ reading as it comes back. The tracker computes the rolling 24 h and 48 h rise and warns if guideline limits are exceeded.

Time since first reading (h)

Na⁺ (mmol/L)

ODS risk factors

Alcohol use disorder Malnutrition Hypokalemia Advanced liver disease Na⁺ ≤ 105 mmol/L Known/likely chronic hyponatremia (>48 h)

Step 11 · Monitoring schedule

Generated automatically once severity is classified in Triage.

Step 5 · Drug search

Search drug name or class

Start typing to search ~30 drugs associated with hyponatraemia.

Calculators

Free water excess

Estimates the water excess to remove (via restriction) to reach a target sodium in chronic, non‑emergency hyponatremia. Not the same calculation as "free water deficit" used in hypernatremia — and not a substitute for the emergency bolus protocol in Treatment.

Weight (kg)

Current Na⁺

Target Na⁺

Body water fraction

Clinical summary

Compiles everything entered above into one note — a direct readout of your inputs and the calculations already shown, nothing added. Review before pasting into a record.

Pearls & pitfalls

1Biochemical severity ≠ clinical severity. Treat the symptoms, not the number — profound hyponatraemia can be asymptomatic, and moderate hyponatraemia can present with severe symptoms.

Society for Endocrinology 2022

2Rule out pseudohyponatraemia before treating: severe hyperlipidaemia or hyperproteinaemia gives a falsely low sodium with a normal measured osmolality.

Spasovski et al. 2014

3Isotonic (0.9%) saline can paradoxically worsen SIADH‑related hyponatraemia — if urine is more concentrated than the saline, the infused sodium is excreted and the free water retained ("desalination").

Spasovski et al. 2014

4Don't use the Adrögue–Madias formula to plan acute hypertonic saline dosing in severe/moderately‑severe symptomatic hyponatraemia — it ignores ongoing losses and carries a higher overcorrection risk in that setting.

Society for Endocrinology 2022

5Post‑operative hyponatraemia is iatrogenic until proven otherwise — hypotonic IV fluids plus surgery‑related non‑osmotic ADH release is a classic, preventable combination.

Spasovski et al. 2014

6Once volume resuscitation begins in hypovolaemic hyponatraemia, ADH suppresses quickly and a brisk water diuresis can autocorrect sodium faster than expected — recheck sooner than the default schedule.

Spasovski et al. 2014

7Urine osmolality <100 mOsm/kg essentially excludes SIADH — don't diagnose it on clinical grounds alone without checking this.

Spasovski et al. 2014

8In a patient already on a diuretic, urine sodium can't reliably separate SIADH from volume depletion — FEUA is the better discriminator in that specific situation.

Fenske et al., JCEM 2008

9Always consider primary polydipsia in a psychiatric patient with hyponatraemia, especially with a low urine osmolality — it's easy to default to SIADH and miss this.

Spasovski et al. 2014

10Vaptans are not indicated in severe/moderately‑severe symptomatic hyponatraemia. Where used at all, reserve them for non‑emergency euvolaemic SIADH.

Society for Endocrinology 2022

Sources

Every recommendation in this app traces to one of the sources below. Where the spec asked for something no guideline actually quantifies (e.g. a numeric "confidence score" per differential diagnosis), the app shows a transparent rule‑based read‑out instead of an invented number — flagged inline wherever that applies.

Spasovski G, et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia (ECPG)

European Journal of Endocrinology 2014;170:G1–G47. Joint guideline of the European Society of Intensive Care Medicine, European Society of Endocrinology and European Renal Association–European Dialysis and Transplant Association. doi:10.1530/EJE-13-1020

Ball S, Barth J, Levy M. Emergency management of severe and moderately severe symptomatic hyponatraemia in adult patients

Society for Endocrinology Clinical Committee, 2022 update of the 2016 guidance (Endocrine Connections 2016;5:G4–G6). Source for the bolus protocol, correction limits, monitoring intervals and the diagnostic algorithm figure used in Workup.

Verbalis JG, et al. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations

American Journal of Medicine 2013;126:S1–S42. US expert‑panel counterpart to the European guideline; cited where it adds nuance (e.g. correction‑limit ranges for normal vs high ODS‑risk patients).

Hillier TA, Abbott RD, Barrett EJ. Hyponatremia: evaluating the correction factor for hyperglycemia

American Journal of Medicine 1999;106:399–403. Source of the 2.4 mmol/L per 5.6 mmol/L (100 mg/dL) glucose correction factor used in the corrected‑sodium calculation, in place of the older Katz 1.6 factor.

Session

Data stays in this browser tab only, in memory, and is cleared on reload — nothing is sent anywhere or stored on a server.

This tool assists clinical decision-making but does not replace physician judgment. Final diagnosis and treatment remain the responsibility of the treating clinician.

Step 1 · Patient & severity

Sodium

Symptoms & signs

Step 2–3 · Laboratory & tonicity

Endocrine labs

Uric acid & FEUA

Other labs

Urine studies

Urinalysis — infection screen

Step 4 · Volume status

Step 6 · Clinical history

Step 7–8 · Differential & SIADH

Step 9 · Treatment

Step 10 · Correction safety tracker

ODS risk factors

Step 11 · Monitoring schedule

Step 5 · Drug search

Current medications

Calculators

Free water excess

Clinical summary

Pearls & pitfalls

Sources

Session