What is the preferred fluid choice between Plasma-Lyte R (PLR) and 0.9% Normal Saline (0.9% NS) for hyperchloremic metabolic acidosis during prolonged surgery?

Plasma-Lyte R is Superior to 0.9% Normal Saline for Hyperchloremic Metabolic Acidosis During Prolonged Surgery

Buffered crystalloid solutions like Plasma-Lyte R are strongly recommended over 0.9% normal saline for managing hyperchloremic metabolic acidosis during prolonged surgery due to their more physiologic electrolyte composition and reduced risk of worsening acidosis. 1, 2

Mechanisms of Hyperchloremic Metabolic Acidosis

• Administration of large volumes of 0.9% saline causes hyperchloremic acidosis due to its supra-physiological chloride concentration (>154 mmol/L) 2
• This acidosis occurs through dilution of bicarbonate and direct chloride load, leading to decreased strong ion difference 1
• Hyperchloremic acidosis from 0.9% saline is associated with increased 30-day mortality in surgical patients 1

Evidence Supporting Balanced Solutions

• Multiple studies show that buffered solutions like Plasma-Lyte R maintain acid-base balance better than 0.9% saline during prolonged procedures 1, 3
• A randomized trial of trauma patients demonstrated that Plasma-Lyte A resulted in significantly greater improvement in base excess compared to 0.9% saline (7.5 ± 4.7 vs 4.4 ± 3.9 mmol/L) 3
• Patients receiving balanced crystalloids have lower serum chloride levels and higher arterial pH 24 hours post-surgery 3, 4

Clinical Implications of Fluid Choice

• Hyperchloremic acidosis increases risk of tissue injury and organ dysfunction during prolonged surgery 2
• 0.9% saline administration is associated with:
  • Renal vasoconstriction and increased risk of acute kidney injury 1, 5
  • Increased need for vasopressor therapy 1
  • Higher rates of major adverse kidney events 1, 5
  • Decreased gastric blood flow and impaired gastric motility 2

Recommendations for Specific Surgical Scenarios

• For prolonged abdominal surgery:

  • Balanced crystalloids are associated with fewer complications (OR 0.79; 95% CI 0.66-0.97) compared to 0.9% saline 5
  • Patients receiving balanced solutions have lower rates of postoperative infection, renal failure requiring dialysis, and electrolyte disturbances 5

• For neurosurgical procedures:

  • While 0.9% saline has traditionally been used to avoid cerebral edema, balanced isotonic solutions like Plasma-Lyte are now preferred as they avoid hyperchloremic metabolic acidosis 1
  • A randomized controlled trial showed balanced crystalloids maintain better metabolic status without adversely affecting brain relaxation compared to normal saline 4

• For kidney transplantation:

  • Strong recommendation for buffered crystalloid solutions over 0.9% saline (high-quality evidence) 1
  • Buffered solutions reduce the risk of delayed graft function compared to 0.9% saline 1

Practical Approach to Fluid Management

• For patients with existing hyperchloremic metabolic acidosis during prolonged surgery:

  • Switch from 0.9% saline to balanced crystalloids like Plasma-Lyte R 2
  • Monitor acid-base status, electrolytes, and renal function 1, 2
  • Maintain adequate urine output to help resolve hyperchloremic acidosis 2

• For prevention of hyperchloremic metabolic acidosis:

  • Use balanced crystalloids as the primary intraoperative fluid 6
  • Administer fluids based on objective measures of hypovolemia, titrated by bolus 6
  • Maintain near-zero fluid and electrolyte balance during the procedure 2

Caveats and Special Considerations

• While balanced solutions are generally preferred, individual assessment of electrolyte status remains important, particularly for potassium levels 6
• The volume of fluid administered may have a dose-response relationship with adverse outcomes, regardless of fluid type 1
• Some recent large RCTs found no difference in complications between 0.9% saline and buffered solutions, but these studies used relatively small fluid volumes 1