Perfect topic, Pasindu. Here’s a **short, clean, ICU-ready hyponatremia algorithm** you can **memorize and apply at the bedside**.
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# π§ **HYPONATREMIA — SHORT & SWEET ALGORITHM**
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## πΉ STEP 1: CONFIRM TRUE HYPONATREMIA
**Na⁺ < 135 mmol/L**
→ **Check serum osmolality (tonicity)**
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## πΉ STEP 2: CLASSIFY BY TONICITY (MOST IMPORTANT FIRST)
### **A. Isotonic (Pseudo-hyponatremia)**
* Serum Osm: **275–295 mOsm/kg**
* Causes:
* Hyperlipidaemia
* Hyperproteinaemia
* **Management:**
π No treatment for Na⁺ (lab artifact)
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### **B. Hypertonic Hyponatremia**
* Serum Osm: **>295 mOsm/kg**
* Cause:
* Hyperglycaemia (most common)
* Mannitol
* **Mechanism:** Water shifts from ICF → ECF
* **Management:**
π Treat cause (e.g. insulin for DKA)
π Na⁺ corrects automatically
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### **C. Hypotonic Hyponatremia** ✅ *(TRUE hyponatremia)*
* Serum Osm: **<275 mOsm/kg**
* → Go to **volume status**
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## πΉ STEP 3: CLASSIFY BY VOLUME STATUS (KEY CLINICAL STEP)
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## π’ **EUVOLEMIC HYPONATREMIA**
**(Most common in ICU)**
### Causes
* **SIADH**
* Hypothyroidism
* Adrenal insufficiency
* Drugs (SSRIs, carbamazepine)
### Clues
* No oedema
* No dehydration
* Urine Na⁺ > 30 mmol/L
* Urine Osm > 100 mOsm/kg
### Management
* **Fluid restriction** (800–1000 mL/day)
* Treat cause
* Severe symptoms → **3% saline**
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## π΅ **HYPERVOLEMIC HYPONATREMIA**
*(Too much water AND sodium — water more)*
### Causes
* Heart failure
* Liver cirrhosis
* Nephrotic syndrome
### Clues
* Oedema, raised JVP
* Urine Na⁺ < 20 mmol/L
### Management
* **Fluid restriction**
* **Salt restriction**
* **Loop diuretics**
* Treat underlying disease
* Severe → cautious **3% saline + loop diuretic**
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## π΄ **HYPOVOLEMIC HYPONATREMIA**
*(Loss of sodium > water)*
### Causes
* GI losses (vomiting, diarrhea)
* Diuretics
* Adrenal insufficiency
* Third spacing
### Clues
* Hypotension
* Tachycardia
* Dry mucosa
* Urine Na⁺:
* <20 → extrarenal loss
* > 20 → renal loss
### Management
* **0.9% Normal Saline**
* Stop diuretics
* Correct underlying cause
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## πΉ STEP 4: ASSESS SEVERITY (GUIDES URGENCY)
| Sodium | Severity |
| ------- | -------- |
| 130–134 | Mild |
| 125–129 | Moderate |
| <125 | Severe |
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## πΉ STEP 5: CHECK SYMPTOMS (OVERRIDES EVERYTHING)
### π¨ **SEVERE SYMPTOMS**
* Seizures
* Confusion
* Coma
* Raised ICP
π **Immediate 3% hypertonic saline**
**Dose (ICU standard):**
* 100 mL 3% NaCl IV over 10 min
* Repeat up to **3 times** if needed
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## πΉ STEP 6: SAFE CORRECTION LIMITS (CRITICAL)
### ❗ DO NOT OVERCORRECT
| Situation | Max Na⁺ rise |
| -------------------------------------------------- | ------------------ |
| General | ≤ 10 mmol/L / 24 h |
| High risk (alcoholic, malnourished, liver disease) | ≤ 8 mmol/L / 24 h |
**Reason:** Prevent **osmotic demyelination syndrome (ODS)**
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## πΉ ONE-LOOK SUMMARY TABLE
| Type | Volume | Cause | Treatment |
| ------------------------ | ------ | ------------------ | --------------------- |
| Isotonic | Normal | Lab artifact | None |
| Hypertonic | Normal | Hyperglycaemia | Treat cause |
| Hypotonic + Euvolemic | Normal | SIADH | Fluid restrict |
| Hypotonic + Hypervolemic | High | HF, cirrhosis | Fluid + salt restrict |
| Hypotonic + Hypovolemic | Low | GI loss, diuretics | Normal saline |
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## π§ **MEMORIZATION TRICK**
### **“T → V → S”**
* **T**onicity
* **V**olume status
* **S**ymptoms (decide urgency)
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## π ICU PEARLS (VERY IMPORTANT)
* **Always correct volume first** — Na⁺ often fixes itself
* **Symptoms > number**
* **SIADH = fluid restriction, not saline**
* **Heart failure hyponatremia = water problem, not sodium problem**
* **Slow correction saves brains**
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If you want next:
* πΉ **Hyponatremia correction calculator**
* πΉ **ICU causes vs ward causes table**
* πΉ **Quick differentiation of SIADH vs cerebral salt wasting**
Just tell me π
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