Acute Hyponatraemia Protocol

⚠ Clinical Intelligence Engine: This tool does NOT blindly calculate an infusion rate for every sodium value. It first classifies severity, determines whether active IV correction is clinically indicated at all, and gates the output accordingly. Mild hyponatraemia will NOT receive an infusion protocol.

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 Catastrophe

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 Traps

⚠ Common Hazard Warning (Indian ER Context)
Empirically starting an IV drip of 3% Hypertonic Saline without meticulously calculating Total Body Water or strictly defining the patient's volume status is a dangerous practice that commonly leads to ODS. 3% Saline is a highly potent drug. Continuous infusions must be strictly monitored in an ICU/HDU setting with 2 to 4 hourly ABG/VBG electrolytes.

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 & Traps	Primary Action
Hypovolaemic	Dry mucosa, flat JVP, tachycardia. Trap: Once volume is restored with NS, ADH shuts off, kidneys dump free water, Na⁺ skyrockets past the safe limit.	NS to restore volume. Monitor closely for auto-correction. Consider prophylactic DDAVP clamping.
Euvolaemic	Normal exam. Think SIADH, hypothyroidism, adrenal insufficiency. Trap: 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 Traps ⚠ The Potassium Trap

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.

⚠ The Normal Saline Trap 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.

Proactive DDAVP Clamping Strategy

Modern best practice advocates proactive DDAVP clamping rather than reactive rescue. Give DDAVP 1 to 2 mcg IV at the start of therapy, then administer HTS at a calculated rate. This converts the patient into a "closed system" that behaves as the Adrogue-Madias formula predicts. Especially important for hypovolaemic patients at highest risk of auto-correction overshoot.

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. Do not hesitate to re-lower - ODS risk from overcorrection far outweighs transient re-lowering risk.

Abbreviations: Na⁺ (Sodium) · K⁺ (Potassium) · ODS (Osmotic Demyelination Syndrome) · TBW (Total Body Water) · SIADH (Syndrome of Inappropriate ADH) · D5W (5% Dextrose) · DDAVP (Desmopressin) · HTS (Hypertonic Saline) · NS (Normal Saline)

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 Therapeutic Pathways & Algorithms

Specialties Internal Medicine, Nephrology, Critical Care

Status New Pathway

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