What are the best intravenous (IV) fluids for patients with kidney stones?

Best IV Fluids for Kidney Stones

Balanced crystalloid solutions such as Ringer's Lactate or Plasmalyte are the recommended IV fluids for patients with kidney stones due to their lower risk of hyperchloremic metabolic acidosis and adverse renal events compared to 0.9% saline.

Rationale for IV Fluid Selection

• Balanced crystalloid solutions have an electrolyte composition closer to plasma, which helps maintain acid-base balance and reduces the risk of hyperchloremia 1
• 0.9% saline has a higher chloride content (154 mmol/L) compared to balanced solutions like Ringer's lactate (108 mmol/L) or Plasmalyte (98 mmol/L), which can lead to hyperchloremic metabolic acidosis when administered in large volumes 2
• A recent study showed that balanced solutions are associated with better acid-basic balance compared to 0.9% NaCl 2
• The KDIGO guidelines suggest using isotonic crystalloids rather than colloids for expansion of intravascular volume in patients at risk for acute kidney injury (AKI) 2

Volume Considerations

• Intravenous fluids should be administered to patients with kidney stones, but caution should be used in determining the amount to avoid fluid overload 2
• There is no evidence that forced hydration (high volume IV fluids) is superior to maintenance IV fluids for patients with kidney stones 3
• A study comparing forced IV hydration (2L over 2 hours) with minimal IV hydration (20 mL/hour) showed no difference in pain scores, narcotic requirements, or stone passage rates 3
• The Cochrane review found no reliable evidence to support the use of high-volume fluid therapy for people with acute ureteric colic 4

Specific Recommendations

• For most patients with kidney stones, administer balanced crystalloid solutions (Ringer's Lactate or Plasmalyte) at maintenance rates 1, 3
• Avoid 0.9% saline when large volumes are needed as it may lead to hyperchloremic metabolic acidosis 1
• In patients with kidney stones and risk of AKI, isotonic crystalloids are preferred over colloids 2
• Synthetic colloids (hydroxyethyl starch, gelatin) should be avoided due to reported risks of renal failure and hemostasis disorders 2

Clinical Algorithm

1. Initial Assessment:

   • Determine hydration status and presence of comorbidities 2
   • Check baseline kidney function 2

2. IV Fluid Selection:

   • First choice: Balanced crystalloids (Ringer's Lactate or Plasmalyte) 1
   • Alternative (if balanced solutions unavailable): 0.9% saline 2
   • Avoid colloids due to risk of renal dysfunction 2

3. Volume Administration:

   • Standard maintenance rate (typically 1-2 mL/kg/hr) is sufficient 3
   • No evidence supports forced hydration over maintenance fluids 4, 3

4. Monitoring:

   • Monitor urine output, vital signs, and electrolytes 2
   • Adjust fluid rate based on clinical response 1

Common Pitfalls to Avoid

• Administering excessive IV fluids can lead to fluid overload without improving outcomes 4, 3
• Using 0.9% saline for large volume resuscitation can cause hyperchloremic metabolic acidosis 2, 1
• Synthetic colloids should be avoided due to increased risk of renal dysfunction 2
• Discontinuing concomitant nephrotoxins (e.g., NSAIDs, aminoglycosides) is important when administering IV fluids to patients with kidney stones 2