What is the recommended first-line fluid for resuscitation and maintenance, specifically using .9% sodium chloride (normal saline)?

Normal Saline (0.9% Sodium Chloride) for Fluid Resuscitation and Maintenance

Isotonic crystalloids, particularly 0.9% sodium chloride (normal saline), are recommended as first-line fluid for resuscitation in patients at risk for acute kidney injury, though balanced crystalloid solutions are increasingly preferred in many clinical scenarios due to reduced risk of hyperchloremic acidosis. 1, 2

First-Line Fluid Selection

Crystalloids vs. Colloids

• Crystalloids are strongly recommended as the initial management for expansion of intravascular volume in patients at risk for AKI or with AKI 1
• The KDIGO guidelines specifically suggest using isotonic crystalloids rather than colloids (albumin or starches) for initial fluid resuscitation (Grade 2B recommendation) 1
• Multiple meta-analyses have shown increased risk of death in patients treated with colloids compared to crystalloids, particularly in trauma subgroups 1

Normal Saline vs. Balanced Crystalloids

• While 0.9% sodium chloride (normal saline) has traditionally been the most commonly used crystalloid, there is increasing evidence favoring balanced crystalloid solutions:
  • For patients with sepsis or septic shock, balanced crystalloids are probably recommended over 0.9% NaCl to reduce mortality and adverse renal events (Grade 2+ recommendation) 1
  • Normal saline contains 153 meq of chloride which can induce hyperchloremic metabolic acidosis when administered in large volumes 1
  • The European Society of Intensive Care Medicine provides conditional recommendations for using balanced crystalloids rather than isotonic saline in critically ill patients in general (low certainty of evidence) 3

Special Clinical Scenarios

• Traumatic brain injury: Isotonic saline is conditionally recommended over balanced crystalloids (very low certainty of evidence) 3
• Cirrhosis: Albumin is conditionally recommended over crystalloids (very low certainty of evidence) 3
• Trauma patients: Crystalloids are suggested for initial treatment of bleeding trauma patients (Grade 2C) 1

Volume and Administration Guidelines

• Initial resuscitation: In adults with sepsis or septic shock, administer up to 30 ml/kg of intravenous crystalloids in the initial phase, with adjustments based on clinical context and frequent reassessments 4
• Trauma resuscitation: A restrictive fluid strategy is suggested after blunt trauma (moderate certainty) and penetrating trauma (low certainty) 4
• Target parameters:
  • Mean arterial pressure of 65-70 mmHg 2
  • Urine output >0.5 mL/kg/hr 2
  • Monitoring for early signs of inadequate circulation: relative tachycardia, relative hypotension, oxygen extraction >50%, and PvO2 <32 mm Hg 1

Practical Considerations and Caveats

• Hyperchloremic acidosis risk: 0.9% sodium chloride should be limited to 1-1.5L maximum to prevent hyperchloremic acidosis 2
• Monitoring: Daily plasma electrolyte measurements, urinary electrolyte assessment, fluid balance tracking, and daily weight measurements are essential 2
• Common errors to avoid:
  • Excessive fluid administration leading to volume overload and worsened renal function 2
  • Relying solely on diuresis without considering other hemodynamic parameters 2
  • Overlooking the acid-base implications of fluid therapy choices 2

Emerging Evidence and Trends

Recent evidence suggests a trend toward balanced crystalloid solutions over normal saline, particularly in patients with or at risk for acute kidney injury. The 2022 guidelines indicate that balanced crystalloid solutions, such as lactated Ringer's, are increasingly preferred due to their physiological or near-physiological concentrations of electrolytes, which provide better acid-base balance 2.

For patients requiring large volumes of fluid, the risk of hyperchloremic metabolic acidosis with normal saline should be considered, and a transition to balanced solutions may be warranted after initial resuscitation with normal saline 1, 2.