# 🧂 Sodium Disorders

### 🎯 Key Concept: Water vs Sodium Balance

Sodium disorders reflect water balance, not sodium balance

ADH controls water retention → affects serum sodium concentration

## 🌊 Sodium Disorder Overview

### 🌊 Hyponatremia

**Na+ \< 135 mEq/L** - Most common electrolyte disorder

- **Mechanism:** Excess water relative to sodium
- **Key Test:** Urine osmolality (ADH activity)
- **Emergency:** RIB therapy for severe symptomatic
- **Correction:** 4-8 mEq/L per 24 hours (standard risk)
- **Risk Factors:** Chronic, alcoholism, liver disease

**Common Causes:** SIADH, volume depletion, heart failure, medications

### 🔥 Hypernatremia

**Na+ \> 145 mEq/L** - Water deficit state

- **Mechanism:** Loss of free water or gain of sodium
- **Formula:** Water deficit = TBW × \[(Na/140) - 1\]
- **Correction:** ≤0.5 mEq/L per hour maximum
- **Volume Status:** Hypovolemic (most common)
- **Risk:** Cerebral edema with rapid correction

**Common Causes:** Diabetes insipidus, diarrhea, insensible losses, osmotic diuresis

## 🔄 Physiology Review

### ADH System: The Master Water Controller

#### 🧠 Central Control

- **Osmoreceptors:** Hypothalamic sensors
- **Threshold:** ~280-290 mOsm/kg
- **Response:** ADH release + thirst
- **Fine-tuning:** 1% osmolality change triggers response

#### 🫘 Kidney Response

- **Target:** Collecting duct principal cells
- **Mechanism:** Aquaporin-2 (AQP2) insertion
- **Result:** Water reabsorption
- **Range:** 50-1200 mOsm/kg urine concentration

#### ⚖️ Clinical Assessment

- **Urine Osmolality:** Reflects ADH activity
- **Serum Osmolality:** Confirms true hypo/hypernatremia
- **Volume Status:** Separate from ADH system
- **Medications:** Many affect ADH

## 🎯 Clinical Decision Framework

### Systematic Approach to Sodium Disorders

#### 1️⃣ Confirm the Value

- Rule out pseudohyponatremia
- Check serum osmolality
- Consider lab error

#### 2️⃣ Assess Symptoms

- Neurologic manifestations
- Acute vs chronic onset
- Severity assessment

#### 3️⃣ Volume Status

- Physical examination
- Hemodynamic assessment
- Urine sodium

#### 4️⃣ Urine Studies

- Urine osmolality (key test)
- Urine sodium
- Urine volume

#### 5️⃣ Medication Review

- Diuretics
- SSRIs, antiepileptics
- NSAIDs, ACE inhibitors

#### 6️⃣ Treatment Plan

- Address underlying cause
- Safe correction rate
- Monitor response

### 🌊 Comprehensive Hyponatremia Guide Available!

For in-depth coverage including 2024 RIB protocols, emerging therapies, and risk stratification

📚 For Educational Purposes Only

© 2025 Andrew Bland MD - All Rights Reserved


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