What is the best IV fluid for a patient with dehydration and Acute Kidney Injury (AKI)?

Best IV Fluid for Dehydration with AKI

Use isotonic crystalloids—specifically buffered/balanced crystalloid solutions (such as Plasmalyte or Ringer's lactate) rather than 0.9% normal saline—as the preferred IV fluid for patients with dehydration and AKI. 1, 2

Fluid Type Selection

Primary Recommendation: Buffered Crystalloids

• Buffered crystalloid solutions are strongly preferred over 0.9% saline because large volumes of normal saline cause hyperchloremic acidosis, renal vasoconstriction, and worsen kidney injury. 2
• The KDIGO guidelines recommend isotonic crystalloids rather than colloids (albumin or starches) as initial management for expansion of intravascular volume in patients at risk for AKI or with AKI. 1
• Balanced solutions reduce the risk of hyperchloremic acidosis and kidney injury compared to normal saline. 3

Specific Fluid Choices

• Plasmalyte is particularly appropriate as it contains acetate and gluconate (not lactate) as buffers, making it suitable even in patients with lactic acidosis. 2
• If buffered crystalloids are unavailable, isotonic saline (0.9%) may be used but is inferior to balanced solutions. 1, 2

Avoid These Fluids

• Do not use starch-containing colloid solutions—they are associated with harm in patients at risk of AKI or with established AKI. 1
• Avoid albumin in patients with traumatic brain injury (associated with harm in this specific population). 1

Fluid Administration Strategy

Initial Rate and Volume

• Start with 75-100 mL/h (approximately 1-1.5 mL/kg/h) of isotonic buffered crystalloid, guided by repeated hemodynamic assessment. 2
• Target urinary flow rates of >0.5 mL/kg/h, which helps reduce tubular toxicity and prevents dehydration that worsens AKI. 2, 4
• The goal is achieving euvolemia while avoiding fluid overload—both hypovolemia and volume overload are associated with increased mortality. 3

Hemodynamic Monitoring

• Use dynamic indices rather than static pressures to assess fluid responsiveness: passive leg-raising test, pulse pressure variation, and stroke volume variation are more reliable than central venous pressure (CVP). 2, 3
• Reassess fluid status every 6-12 hours, monitoring urine output, signs of fluid overload, and adjusting the rate based on clinical response. 2

Critical Clinical Considerations

When to Increase Fluid Rate

• If the patient remains hypovolemic with ongoing hypoperfusion despite initial fluid administration, increase the rate to achieve hemodynamic stability, but reassess frequently. 2
• In hemodynamically unstable patients, earlier vasopressor use may be more appropriate than aggressive fluid loading. 2

When to Restrict Fluids

• In patients with established AKI who are unresponsive to fluid administration, fluid restriction is the treatment of choice. 3
• Avoid potassium-containing solutions until current potassium levels are confirmed to be normal. 2

Monitoring Parameters

• Target urine output >0.5 mL/kg/hour. 2, 4
• Monitor for signs of fluid overload: pulmonary edema, peripheral edema, worsening oxygenation. 2
• Check renal function at 24-48 hours to assess response and degree of kidney injury. 4

Common Pitfalls to Avoid

• Do not use 0.9% saline as first-line therapy—it worsens acidosis and kidney injury compared to balanced solutions. 2
• Do not use diuretics to prevent or treat AKI (except for management of volume overload). 1
• Do not use low-dose dopamine, fenoldopam, or atrial natriuretic peptide—these have no benefit in preventing or treating AKI. 1
• Avoid excessive fluid administration beyond hemodynamic targets, as fluid overload worsens outcomes. 4, 3
• Oral hydration alone is insufficient—IV isotonic crystalloids are the evidence-based standard. 4