What is the ideal intravenous (IV) fluid for adult patients undergoing endoscopy and colonoscopy?

Ideal IV Fluid for Endoscopy and Colonoscopy

Balanced crystalloid solutions (lactated Ringer's or Plasmalyte) are the preferred intravenous fluids for adult patients undergoing endoscopy and colonoscopy, as they avoid the hyperchloremic acidosis and potential renal complications associated with normal saline while providing physiologically appropriate electrolyte composition. 1, 2

Primary Recommendation: Balanced Crystalloids

Use lactated Ringer's solution or Plasmalyte as first-line IV fluids for endoscopic procedures. 1, 2 These balanced crystalloids offer several advantages:

• Electrolyte composition closely mimics plasma, with sodium-to-chloride ratios that are more physiologic than normal saline 1, 2
• Prevents hyperchloremic metabolic acidosis that occurs with large volumes of 0.9% saline, which can impair renal function 1
• Reduces risk of acute kidney injury compared to normal saline in large randomized trials involving over 30,000 patients 1
• Lower vasopressor requirements and decreased extravascular fluid accumulation compared to high-chloride solutions 1

Specific Fluid Characteristics

Lactated Ringer's Solution

• Contains sodium 130 mmol/L, potassium 4 mmol/L, chloride 108 mmol/L, calcium 0.9 mmol/L, and lactate 27.6 mmol/L 1, 2
• Osmolarity of 273-277 mOsm/L (slightly hypotonic) 1, 2
• The 4 mmol/L potassium content is NOT a contraindication for routine use, as studies show no clinically significant hyperkalemia risk 1, 2

Plasmalyte

• Contains sodium 140 mmol/L, potassium 5 mmol/L, chloride 98 mmol/L, magnesium 3 mmol/L, and acetate 27 mmol/L 3
• Osmolarity of 294 mOsm/L (near-isotonic) 3
• Does not contain glucose, so separate dextrose administration may be needed for prolonged procedures 3

When to Avoid Balanced Crystalloids

Critical Contraindication: Severe Head Trauma

Do NOT use lactated Ringer's in patients with severe traumatic brain injury or increased intracranial pressure. 2

• Lactated Ringer's is hypotonic (273-277 mOsm/L vs plasma 275-295 mOsm/L) and can worsen cerebral edema 2
• Use 0.9% normal saline instead for patients with known or suspected severe head trauma 2

Other Specific Contraindications

• Rhabdomyolysis or crush syndrome: Avoid lactated Ringer's due to potassium content in these specific scenarios 2
• Severe hyperkalemia (>6.5 mmol/L): Use potassium-free crystalloid until hyperkalemia resolves 2

Normal Saline: When It's Acceptable

Normal saline (0.9% NaCl) can be used for endoscopic procedures, but it is not the preferred choice 1, 4:

• Acceptable for short procedures with limited fluid volumes (≤1-1.5 L) 2
• Causes hyperchloremic metabolic acidosis with larger volumes, leading to electrolyte derangements and potentially decreased renal perfusion 1
• Higher incidence of acute kidney injury compared to balanced crystalloids in large trials 1

Practical Algorithm for Fluid Selection

1. Screen for contraindications:

   • Severe head trauma/TBI? → Use 0.9% saline 2
   • Rhabdomyolysis/crush syndrome? → Use 0.9% saline 2
   • Severe hyperkalemia (>6.5 mmol/L)? → Use potassium-free crystalloid 2

2. For routine endoscopy/colonoscopy patients without contraindications:

   • First choice: Lactated Ringer's or Plasmalyte 1, 2, 3
   • Typical volume: 1-2 liters for hydration and bowel preparation-related losses 1

3. Monitor fluid balance:

   • Target postoperative fluid balance of 0-2 L positive 1
   • Avoid volume overload, which can cause organ dysfunction and delayed recovery 1

Common Pitfalls to Avoid

• Do not avoid lactated Ringer's due to potassium content in routine cases: The 4-5 mmol/L potassium does not cause hyperkalemia, even in renal transplant recipients 1, 2
• Do not use excessive volumes of normal saline: This causes hyperchloremic acidosis and increases AKI risk 1
• Do not assume all crystalloids are equivalent: Balanced solutions have demonstrable advantages over normal saline in large randomized trials 1
• Remember lactated Ringer's is hypotonic: While safe for most patients, this matters critically in head trauma 2

Evidence Quality Note

The recommendation for balanced crystalloids over normal saline is supported by high-quality evidence from the SMART trial (15,802 patients) and SALT trial (974 patients), both showing reduced major adverse kidney events and lower mortality with balanced crystalloids 1. A more recent trial in elective colorectal and orthopedic surgery (8,616 patients) showed no clinically meaningful difference between the two solutions 4, but the preponderance of evidence and physiologic rationale favor balanced crystalloids as first-line therapy 1, 2.