16/01/2026
Icu colleagues.
The sodium anion
🧊 Chloride (Cl⁻): The Unsung Backup Dancer That Keeps the Rhythm
Normal Range: 98–106 mEq/L
Low: Hypochloremia
High: Hyperchloremia
⚡ Charge & Type
Charge: Negative → Anion
Type: Major extracellular anion
💃 Dancing Partner
Main Partner: Sodium (Na⁺), sometimes Potassium (K⁺).
They stick together to keep plasma electrically neutral and osmotic pressure balanced.
If Cl⁻ loses its partner: the acid–base balance goes sideways — you’ll see shifts in bicarbonate and hydrogen ions that can swing a patient from alkalosis to acidosis before you can find your ABG kit.
🔬 Pathophysiology Deep Dive
Chloride isn’t flashy, but it’s everywhere. It rides with sodium and helps control extracellular fluid volume, osmotic pressure, and pH. It’s part of hydrochloric acid in the stomach, helps CO₂ move as chloride shift (Hamburger phenomenon), and balances every positive charge in the blood.
Low Cl⁻ (Hypochloremia):
• Causes: vomiting, NG suction, loop diuretics, metabolic alkalosis.
• Lose chloride → kidneys hold bicarbonate → alkalosis worsens.
• Cells get confused; neurons start firing weirdly; patient gets twitchy or weak.
High Cl⁻ (Hyperchloremia):
• Causes: aggressive normal saline resuscitation, renal tubular acidosis, dehydration, or diarrhea.
• Excess chloride displaces bicarbonate → metabolic acidosis.
• You’ll see Kussmaul respirations, low pH, and maybe vasodilation-related hypotension.
❤️ Cardiac, Neuro & Systemic Effects
• Cardiac: Chloride indirectly affects rhythm through acid–base shifts. Hyperchloremic acidosis = decreased contractility and hypotension.
• Neuro: Acid–base imbalances alter neuronal firing; alkalosis → confusion, acidosis → lethargy.
• Muscle: Hypochloremia can cause weakness from pH-driven calcium shifts.
• Renal: Chloride’s the kidney’s barometer. If it’s off, tubular transport’s off acid–base regulation fails.
• GI: Chloride helps make stomach acid; low levels reduce gastric acidity, altering digestion.
💀 What Happens Without Its Partner
Without sodium or potassium to neutralize its negative charge, Cl⁻ floats free and the body scrambles to compensate. Hydrogen and bicarbonate ions shift to balance the pH, often leading to metabolic disturbances. It’s like pulling the drummer out of the band — everyone else starts missing the beat.
🧠 Why We Care
Because chloride’s the quiet stabilizer that nobody charts until it’s screaming.
Too low, and alkalosis sneaks up. Too high, and perfusion drops while acid builds.
Every liter of 0.9 NS you hang has 154 mEq/L of chloride you can literally cause acidosis trying to fix dehydration.
If sodium is the headline act, chloride’s the rhythm section keeping the patient’s chemistry from falling apart.