Acute Hyponatraemia Protocol

A correction rate that will not cause osmotic demyelination, gated by severity · v1.1

How to use this tool: Enter the sodium, symptoms, volume status and chronicity. The tool first classifies severity and decides whether active intravenous correction is indicated at all, then gates the output accordingly. Mild hyponatraemia does not receive an infusion protocol. It is written for adults. It does not establish the cause, and it will run the sodium correctly while leaving the SIADH, the cirrhosis or the diuretic that produced it entirely untreated.

1. Patient Baseline

Age (yrs)

Biological Sex

Weight (kg)

Current Serum Na⁺ (mEq/L)

Serum K⁺ (mEq/L, optional)

Blood Glucose (mg/dL, for pseudo-hypoNa correction)

Serum Osmolality (mOsm/kg, optional)

Neurological Symptoms

2. Aetiology, Acuity & Risk Modifiers

Clinical Volume Status

Chronicity of Hyponatraemia

High Risk for ODS present? Check if any: Severe Malnutrition, Alcoholism, Advanced Liver Disease, Hypokalaemia, or Serum Na⁺ < 105 mEq/L. (Restricts max 24h correction to 6 mEq/L).

3. Infusate Selection

This selection applies only if active IV correction is clinically indicated. The engine will gate this decision.

Target IV Fluid

Kinetic Profile

Severity

Total Body Water

Litres

Total Na⁺ Deficit

mEq

(Theoretical deficit to 140. This is NOT the 24h correction target.)

Management Plan

Patient/Family Explanation

Osmotic Demyelination Syndrome (ODS): The Overcorrection Risk

ODS (formerly "central pontine myelinolysis") occurs when chronic hyponatraemia is corrected too rapidly. In chronic hyponatraemia, brain cells adapt by losing organic osmolytes. If extracellular Na rises too fast, water is pulled out of adapted neurons, causing demyelination. Symptoms appear 2 to 6 days after overcorrection: dysarthria, dysphagia, quadriparesis, "locked-in syndrome," and potentially death. ODS is irreversible. Prevention is the only strategy.

Golden Rule: In chronic hyponatraemia, do NOT raise sodium by more than 8 mEq/L in 24 hours (or 6 mEq/L in high-risk patients). If overcorrection occurs, actively re-lower sodium with D5W infusion or desmopressin (DDAVP 2 mcg IV q8h).

Algorithm Architecture & Clinical Cautions

Practice Advisory: The Empirical 3% Drip
An empirical drip of 3% Hypertonic Saline, started without the Total Body Water calculated and the volume status defined, is one of the commoner routes to ODS. 3% saline is a drug, not a fluid. Continuous infusions belong in an ICU or HDU, with ABG or VBG electrolytes every 2 to 4 hours.

1. Severity Classification & Management Tiers

Not every patient with Na⁺ < 135 needs IV correction. This tool gates its output based on severity and clinical context:

Na⁺ Range	Severity	Default Management
130 to 134	Mild	No IV correction. Fluid restriction (eu/hyper) or NS volume resuscitation (hypo). Investigate cause.
125 to 129	Moderate	Fluid restriction primary (eu/hyper). Active IV correction only if severely symptomatic or trending down.
120 to 124	Severe	Active correction indicated. ICU/HDU admission. Calculated infusion.
110 to 119	Profound	Urgent active correction. ICU mandatory. Consider DDAVP clamping.
< 110	Critical	Life-threatening emergency. ICU, bolus protocol if symptomatic, strict monitoring.

Acute vs Chronic: The 48-Hour Rule

Chronicity	ODS Risk	Correction Approach
Acute (<48h)	Very Low	More aggressive correction permitted (up to 10 mEq/L/24h). Brain has not adapted.
Chronic (>48h)	HIGH	Strict slow correction (8 mEq/L/24h max, 6 for high-risk). Brain has adapted by expelling osmolytes.
Unknown Duration	Treat as Chronic	If you cannot prove onset was <48h with prior normal labs, assume chronic.

The Absolute Limits of Correction

Scenario	Max 24h Rise	Notes
Standard Risk, Chronic/Unknown	8 mEq/L	European (2014) and API (2019) consensus
High Risk (SHAM), Chronic/Unknown	6 mEq/L	Sterns 2015
Documented Acute, Standard Risk	10 mEq/L	ODS risk very low
Documented Acute, High Risk	8 mEq/L	Still apply caution despite acuity

Volume Status: The Key Branching Point

Volume Status	Clinical Script & Cautions	Primary Action
Hypovolaemic	Dry mucosa, flat JVP, tachycardia. Caution: Once volume is restored with NS, ADH switches off, the kidneys dump free water, and the Na⁺ runs past the safe limit before anyone has re-checked it.	NS to restore volume. Monitor closely for auto-correction. Consider prophylactic DDAVP clamping.
Euvolaemic	Normal exam. Think SIADH, hypothyroidism, adrenal insufficiency. Caution: NS can paradoxically worsen SIADH. Always check TSH and morning cortisol first.	Fluid restriction (800-1000 mL/day). HTS only if severely symptomatic.
Hypervolaemic	Oedema, raised JVP, ascites. Total body Na⁺ is high but water is massively higher.	Fluid restriction + Loop Diuretics. NEVER give continuous saline.

Mnemonic: "SHAM" for High ODS Risk

Patients at highest risk for ODS require the strict 6 mEq/L/24hr limit. Remember SHAM:

S - Severe baseline hyponatraemia (< 105 mEq/L)
H - Hypokalaemia (concurrent)
A - Alcoholism / Advanced Liver Disease
M - Malnutrition (severe)

3% Hypertonic Saline: Practical Guide

3% NaCl contains 513 mEq/L of Na. It is used for symptomatic hyponatraemia (seizures, coma) to rapidly raise Na by 1 to 2 mEq/L per hour for the first 2 to 3 hours.

Fixed bolus (preferred for emergencies): 150 mL of 3% NaCl IV over 20 minutes. Recheck Na after 20 minutes. Repeat up to 2 more times if symptoms persist (maximum 3 boluses). Each 150 mL bolus raises Na by approximately 1.5 to 2 mEq/L in a 70 kg patient.

3% NaCl is not available in all Indian hospitals. Prepare by adding 30 mL of NaCl 23.4% to 470 mL NS. Label clearly. Administer via infusion pump with mandatory Na monitoring every 2 hours.

Key Clinical Cautions 1. The Potassium Effect

Correcting hypokalaemia simultaneously raises serum Na⁺. K⁺ enters cells and displaces Na⁺ outward. Every 1 mEq of K⁺ replaced has the same osmotic effect as 1 mEq of Na⁺ infused. K⁺ correction must be counted against the 24h Na⁺ correction limit.

2. The Normal Saline Caution in SIADH

In SIADH, kidneys maximally concentrate urine. If you infuse 1 litre of 0.9% NS (154 mEq Na⁺ in 1000 mL), the kidneys may excrete those 154 mEq in only 500 mL of concentrated urine, retaining 500 mL of electrolyte-free water. Net effect: you have worsened the hyponatraemia despite giving sodium.

3. Proactive DDAVP Clamping Strategy

Proactive DDAVP clamping is DDAVP at the start, not in reserve for a rescue. Give DDAVP 1 to 2 mcg IV at the start of therapy, then administer HTS at a calculated rate. The patient becomes a closed system. That is the assumption the Adrogue-Madias formula was built on, and the only state in which its prediction holds. The evidence for the proactive approach is observational rather than randomised. It matters most in the hypovolaemic patient, who is at the highest risk of auto-correction overshoot once the volume is restored.

4. Pseudohyponatraemia & Dilutional Hyponatraemia

Hypertonic hyponatraemia: Hyperglycaemia pulls water out of cells, diluting sodium. For every 100 mg/dL rise in glucose above 100, Na drops by 1.6 mEq/L. Corrected Na = Measured Na + 1.6 × ((Glucose - 100) / 100). If corrected Na is normal, treat the hyperglycaemia, not the sodium.

Isotonic hyponatraemia: Severe hyperlipidaemia or hyperproteinaemia (myeloma). Serum osmolality will be normal. Not true hyponatraemia.

SIADH: Diagnosis & Management

Diagnostic criteria: (1) Serum Na < 135, (2) Serum osmolality < 275, (3) Urine osmolality > 100, (4) Urine Na > 40, (5) Euvolaemic, (6) Normal thyroid and adrenal function. Common causes in India: CNS infections (TB meningitis, encephalitis), lung disease (TB, pneumonia, lung cancer), drugs (SSRIs, Carbamazepine, Cyclophosphamide).

Management: (1) Fluid restriction (800 to 1000 mL/day). (2) Salt tablets (NaCl 3g TDS with meals). (3) Tolvaptan 15 mg PO daily if fluid restriction fails (Indian brands: Tolva, Natrise). Start in hospital with Na monitoring every 6 hours. (4) Treat the underlying cause.

Adrogue-Madias Formula & Infusate Concentrations

ΔNa⁺ = (Infusate Na⁺ - Serum Na⁺) / (Total Body Water + 1)

Limitation: Assumes zero renal water handling. Systematically underestimates correction in hypovolaemic patients and may overestimate in SIADH.

IV Fluid	Na⁺ (mEq/L)	Typical Use
3% HTS	513	ICU bolus and infusion for symptomatic hyponatraemia
1.6% HTS	274	Peripheral line option
0.9% NS	154	Volume resuscitation in hypovolaemic hyponatraemia
Ringer's Lactate	130	Mild hypovolaemia

Overcorrection Rescue Protocol

Stop all sodium-containing IV fluids and K⁺ replacement immediately.
Give D5W at 6 mL/kg IV over 1 to 2 hours.
Give DDAVP 2 mcg IV every 8 hours.
Re-check serum Na⁺ every 1 to 2 hours until stabilised.
Goal: Re-lower Na⁺ back to within the originally intended limit. Re-lower without hesitating. The risk from overcorrection is far greater than the risk of putting the sodium transiently back down.

What This Tool Does Not Cover

It is written for adults, and its age field starts at 18. It classifies the sodium, sets a ceiling and calculates an infusion, and it does not establish the cause: the SIADH, the cirrhosis, the hypothyroidism or the thiazide that produced the number is left entirely to you. It does not manage exercise-associated hyponatraemia, beer potomania or psychogenic polydipsia as distinct entities. It does not decide who needs tolvaptan, or for how long. It does not cover hyponatraemia in pregnancy or in children. And it cannot watch the patient: every number it prints assumes the monitoring schedule is actually followed, and the commonest way this goes wrong is not a miscalculation but a sodium nobody re-checked at hour four.

Abbreviations: ABG (Arterial Blood Gas) · ADH (Antidiuretic Hormone) · API (Association of Physicians of India) · CNS (Central Nervous System) · D5W (5% Dextrose in Water) · DDAVP (Desmopressin) · ER (Emergency Room) · HDU (High Dependency Unit) · HTS (Hypertonic Saline) · ICU (Intensive Care Unit) · IV (Intravenous) · JVP (Jugular Venous Pressure) · K⁺ (Potassium) · Na⁺ (Sodium) · NaCl (Sodium Chloride) · NS (Normal Saline) · ODS (Osmotic Demyelination Syndrome) · PO (Per Os) · SBAR (Situation, Background, Assessment, Recommendation) · SHAM (Severe Hyponatraemia, Hypokalaemia, Alcoholism or Advanced Liver Disease, Malnutrition) · SIADH (Syndrome of Inappropriate Antidiuretic Hormone Secretion) · SPEP (Serum Protein Electrophoresis) · SSRI (Selective Serotonin Reuptake Inhibitor) · TB (Tuberculosis) · TBW (Total Body Water) · TDS (Three Times Daily) · TSH (Thyroid Stimulating Hormone) · VBG (Venous Blood Gas)

Algorithm References & Evidence Base

Verma A, et al. API Expert Consensus on Management of Hyponatraemia. JAPI. 2019.
Adrogué HJ, Madias NE. Hyponatremia. N Engl J Med. 2000;342(21):1581-1589.
Spasovski G, et al. Clinical practice guideline on hyponatraemia. Eur J Endocrinol. 2014;170(3):G1-47.
Sterns RH. Disorders of Plasma Sodium. N Engl J Med. 2015;372(1):55-65.
Perianayagam A, et al. DDAVP for overcorrection prevention. CJASN. 2008;3(2):331-336.
Sterns RH, et al. ODS following correction of hyponatremia. N Engl J Med. 1986;314(24):1535-1542.
Verbalis JG, Goldsmith SR, Greenberg A, et al. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013;126(10 Suppl 1):S1-S42.

How to Cite This Tool

AMA Style:
Umakanth S. Acute Hyponatraemia Protocol. MEDiscuss. Published 2026. Accessed .

Vancouver Style:
Umakanth S. Acute Hyponatraemia Protocol [Internet]. MEDiscuss.org; 2026 [cited ]. Available from:

Category Acute ResuscitationProtocol

Specialties Internal Medicine, Nephrology, Critical Care

Written and maintained by Dr Shashikiran Umakanth.
Last revised: 29 July 2026

Acute Hyponatraemia Protocol

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