Is there evidence to support targeting chloride rather than sodium when administering intravenous (IV) fluids like normal saline in dehydration?

Targeting Chloride vs Sodium in IV Fluid Therapy for Dehydration

There is no evidence supporting the targeting of chloride rather than sodium when administering IV fluids for dehydration; instead, current guidelines emphasize using balanced crystalloid solutions that contain physiologically appropriate ratios of both electrolytes to avoid hyperchloremic acidosis while maintaining adequate sodium replacement. 1

The Chloride Problem with Normal Saline

The concern about chloride stems from normal saline's non-physiological composition—it contains equal concentrations of sodium and chloride (154 mmol/L each), whereas plasma contains approximately 140 mmol/L sodium and only 98-106 mmol/L chloride. 1

• Excessive chloride administration from normal saline causes hyperchloremic metabolic acidosis, which has been associated with adverse outcomes including neurological morbidities and growth faltering, particularly in premature infants and children with high ongoing losses. 1
• Balanced crystalloid solutions are more physiological than 0.9% sodium chloride because they replace part of the chloride anions with organic anions (lactate or acetate) to align with plasma chloride levels. 1

Current Guideline Recommendations

For Severe Dehydration Requiring IV Therapy

• Isotonic fluids (lactated Ringer's or normal saline) should be administered for severe dehydration, shock, or altered mental status, with lactated Ringer's preferred as a balanced solution. 1
• Initial resuscitation should use isotonic saline at 15-20 mL/kg/hour during the first hour in the absence of cardiac compromise. 2

For Maintenance Fluid Therapy

• Isotonic balanced solutions are recommended over normal saline for maintenance IV fluid therapy in hospitalized children to prevent both hyponatremia and hyperchloremic acidosis. 1
• Balanced solutions (like Ringer's lactate) likely result in slightly reduced hospital stay (mean difference -0.35 days) and probably produce higher increases in blood pH and bicarbonate levels compared to normal saline. 3

Practical Approach: Sodium Remains the Primary Target

The clinical approach focuses on sodium concentration and tonicity, not chloride targeting:

Step 1: Assess Sodium Status

• Calculate corrected sodium in hyperglycemic patients: Corrected [Na+] = Measured [Na+] + 1.6 × ([Glucose in mg/dL - 100]/100). 4
• If corrected sodium is low, use isotonic saline (0.9% NaCl). 4
• If corrected sodium is normal or high, use half-normal saline (0.45% NaCl) in specific contexts like diabetic ketoacidosis. 4

Step 2: Choose Balanced Solutions When Possible

• For most dehydration scenarios, balanced crystalloids (Ringer's lactate, Plasma-Lyte) are preferred over normal saline to avoid chloride overload while providing adequate sodium. 1, 3
• Balanced solutions likely reduce the risk of hypokalaemia (RR 0.54) after IV correction compared to normal saline. 3

Step 3: Avoid Chloride Overload in High-Risk Populations

• In children requiring long-term parenteral nutrition with high electrolyte losses, replace part of sodium chloride with sodium lactate or sodium acetate to prevent hyperchloremic acidosis. 1
• Monitor serum chloride levels along with sodium, particularly in premature neonates and patients with short bowel syndrome. 1

Key Monitoring Parameters

Regular monitoring should include:

• Plasma sodium, potassium, chloride, and bicarbonate levels to detect electrolyte imbalances early. 1, 2
• Serum pH and base deficit to identify hyperchloremic acidosis from excessive chloride administration. 3
• Fluid balance, urine output, and hemodynamic parameters to assess adequacy of rehydration. 2

Common Pitfalls to Avoid

• Do not use hypotonic solutions (0.45% saline) in patients with hyponatremia or traumatic brain injury, as this risks cerebral edema. 4
• Avoid exclusive use of normal saline for prolonged periods when balanced solutions are available, as cumulative chloride load increases acidosis risk. 1
• Do not target chloride levels independently of sodium—there is no evidence supporting this approach, and sodium concentration determines fluid tonicity and osmotic effects. 1