What is the best choice of intravenous (IV) fluid for maintenance?

Choosing Intravenous Fluids for Maintenance Therapy

For maintenance intravenous fluid therapy in acute and critically ill patients, isotonic balanced crystalloid solutions with appropriate glucose and potassium should be used as the first-line choice to reduce the risk of hyponatremia and minimize length of stay. 1

Fluid Composition Recommendations

Tonicity

• Isotonic solutions should be used for maintenance fluid therapy in both acutely and critically ill patients to significantly reduce the risk of hyponatremia 1
• Isotonic solutions have sodium concentrations similar to plasma (135-144 mEq/L) 1
• Examples include PlasmaLyte (sodium 140 mEq/L, osmolarity 294 mOsm/L) and 0.9% sodium chloride (sodium 154 mEq/L, osmolarity 308 mOsm/L) 1

Balanced vs. Unbalanced Solutions

• Balanced solutions should be favored over 0.9% sodium chloride (normal saline) 1
• In critically ill patients, balanced solutions slightly reduce length of stay (evidence level B) 1
• In acutely ill patients, balanced solutions should be used to slightly reduce length of stay (evidence level A) 1
• Balanced solutions (e.g., lactated Ringer's, PlasmaLyte) have electrolyte compositions closer to extracellular fluid and cause fewer adverse effects on acid-base balance 2
• Excessive use of normal saline may lead to hyperchloremic metabolic acidosis, which can be avoided with balanced solutions 3, 2

Important Considerations for Specific Solutions

• Lactated Ringer's solution (sodium 130 mmol/L, potassium 4 mmol/L, chloride 108 mmol/L, calcium 0.9 mmol/L, and lactate 27.6 mmol/L) is physiologically more similar to plasma than 0.9% NaCl 4
• Lactate-buffered solutions should be avoided in patients with severe liver dysfunction to prevent lactic acidosis 1
• When using lactated Ringer's solution, remember it already contains 4 mmol/L of potassium 4

Additional Components

Glucose

• Glucose should be included in maintenance fluids in sufficient amounts to prevent hypoglycemia 1
• Blood glucose monitoring should be performed at least daily to guide glucose provision 1
• In critically ill children, excessive glucose should be avoided to prevent hyperglycemia 1
• Most clinical studies added dextrose (2.5%-5%) to intravenous solutions 1

Electrolytes

• Appropriate potassium should be added to maintenance fluids based on clinical status and regular monitoring to avoid hypokalemia 1
• There is insufficient evidence to recommend routine supplementation of magnesium, calcium, and phosphate in maintenance fluid therapy 1
• Similarly, routine supplementation of vitamins and trace elements is not recommended in the absence of deficiency 1

Volume Considerations

• To prevent fluid overload, the total daily amount of maintenance fluid should include all sources: IV fluids, blood products, IV medications, line flush solutions, and enteral intake 1
• Fluid overload and cumulative positive fluid balance should be avoided to prevent prolonged mechanical ventilation and extended length of stay 1
• In patients at risk of increased antidiuretic hormone (ADH) secretion, restriction of maintenance fluid volume should be considered to avoid decreased sodium levels 1
• Regular reassessment (at least daily) of fluid balance, clinical status, and electrolytes, especially sodium levels, is recommended 1

Common Pitfalls to Avoid

• Using hypotonic solutions for maintenance therapy, which significantly increases the risk of hyponatremia 1
• Failing to account for all sources of fluid when calculating total maintenance volume, leading to "fluid creep" and overload 1
• Not monitoring electrolytes regularly, especially in high-risk patients 1
• Using lactate-buffered solutions in patients with severe liver dysfunction 1
• Administering excessive chloride through large volumes of normal saline, which can lead to hyperchloremic metabolic acidosis 3, 5

Special Considerations

• In patients with heart failure, renal failure, or hepatic failure, maintenance fluid volume should be restricted to 50-60% of the calculated volume using the Holliday and Segar formula 1
• For patients at risk of increased ADH secretion, restricting maintenance fluid to 65-80% of the calculated volume should be considered 1
• When possible, enteral or oral routes should be used for maintenance fluid therapy if tolerated, to reduce complications associated with IV access 1