What is the best IV fluid for patients with Acute Kidney Injury (AKI)?

Best IV Fluid for Acute Kidney Injury

Use isotonic crystalloids (specifically balanced crystalloids like Lactated Ringer's or Plasmalyte) as first-line therapy for patients with AKI, avoiding colloids and 0.9% saline when possible. 1

Primary Recommendation

KDIGO guidelines explicitly recommend isotonic crystalloids rather than colloids (albumin or starches) for initial management and expansion of intravascular volume in patients at risk for AKI or with established AKI (Grade 2B). 1 This recommendation is based on evidence showing no mortality benefit from colloids, increased cost, and documented harm from synthetic colloids including increased renal replacement therapy requirements and bleeding complications. 1

Crystalloid Selection: Balanced vs. 0.9% Saline

While KDIGO guidelines recommend crystalloids broadly, emerging evidence strongly favors balanced crystalloids (Lactated Ringer's, Plasmalyte) over 0.9% saline due to reduced risk of hyperchloremic metabolic acidosis and potentially lower rates of AKI. 1, 2

• 0.9% saline contains supraphysiologic chloride (154 mmol/L) compared to balanced solutions (108-98 mmol/L), leading to hyperchloremic acidosis with large volume administration. 2
• Two large multicenter RCTs examining this question were ongoing as of 2020, with accumulating evidence of biochemical abnormalities and adverse clinical outcomes associated with 0.9% saline. 1
• Balanced solutions maintain acid-base balance better and have electrolyte composition closer to plasma. 2, 3

Colloids: Avoid in AKI

Synthetic colloids (hydroxyethyl starch, gelatin) are contraindicated in critically ill patients, especially those with sepsis, due to increased mortality and renal dysfunction. 1

• The 6S Trial demonstrated that HES 130/0.42 resulted in more deaths, increased need for renal replacement therapy, and severe bleeding compared to Ringer's acetate. 1
• Consensus has emerged that synthetic colloids are harmful in critically ill patients with sepsis. 1
• Albumin showed no benefit over crystalloids in the SAFE trial for general ICU patients, though specific subpopulations may differ. 1

Clinical Algorithm for Fluid Selection in AKI

Step 1: Assess hemodynamic status and volume responsiveness

• Use dynamic indices (passive leg raise, pulse pressure variation) rather than static measures (CVP) to guide fluid administration. 4
• Repeated assessment is critical as both physiological response and underlying AKI are dynamic over time. 1

Step 2: Choose appropriate crystalloid

• First-line: Balanced crystalloid (Lactated Ringer's or Plasmalyte) 2, 3
• Alternative: 0.9% saline only if balanced solutions unavailable 1
• Never: Hypotonic solutions or synthetic colloids 1

Step 3: Administer guided by clinical response

• Target adequate perfusion (MAP, urine output, lactate clearance) without fluid overload. 4
• Volume overload >10-15% body weight is associated with adverse outcomes. 1

Step 4: Transition to fluid restriction when appropriate

• In established AKI unresponsive to fluid administration, fluid restriction becomes the treatment of choice. 4
• Consider early vasopressor support rather than excessive fluid administration for persistent hypotension. 1

Critical Pitfalls to Avoid

Excessive 0.9% saline administration: Large volumes cause hyperchloremic metabolic acidosis, which may worsen renal perfusion and outcomes. 2, 5 This is particularly problematic when multiple liters are required.

Synthetic colloid use: Despite theoretical advantages as plasma expanders, synthetic colloids increase mortality and AKI in septic patients with no volume-sparing benefit demonstrated. 1

Fluid overload: Both inadequate resuscitation AND excessive fluid administration lead to poor outcomes. 1, 4 Venous congestion from volume overload has adverse effects on kidney function. 1

Ignoring clinical context: While balanced crystalloids are generally preferred, specific situations may require modified approaches (e.g., hypertonic saline for traumatic brain injury with herniation). 1 However, for routine AKI management, balanced crystalloids remain the standard. 2

Delayed vasopressor initiation: Continuing fluid boluses for hypotension when patient is no longer fluid-responsive delays appropriate vasopressor therapy and worsens outcomes. 1

Special Considerations

Contrast-induced AKI prevention: IV volume expansion with either isotonic sodium chloride or sodium bicarbonate solutions is recommended over no IV expansion (Grade 1A), though balanced crystalloids would be preferred based on newer evidence. 1

Resource-limited settings: Where balanced crystalloids are unavailable or cost-prohibitive, 0.9% saline remains acceptable, though risks of hyperchloremia should be monitored. 1