Fluid Resuscitation Strategy: Crystalloids vs Colloids vs Normal Saline
Primary Recommendation
Use balanced crystalloids (such as lactated Ringer's solution) as the first-line fluid for resuscitation in most adult patients, reserving normal saline for specific indications like severe traumatic brain injury. 1, 2, 3
Crystalloids vs Colloids
General Critical Illness
Crystalloids should be used rather than colloids for volume expansion in critically ill patients because colloids offer no mortality benefit, are significantly more expensive, and current evidence does not justify their routine use. 1, 3
A Cochrane systematic review of 70 randomized controlled trials found no difference in mortality between critically ill patients who received colloids versus crystalloids for fluid resuscitation. 1
The SAFE study (6,997 ICU patients) showed that albumin administration was not associated with improved outcomes compared to crystalloids. 1
Colloids probably make little or no difference to mortality at end of follow-up (RR 0.98,95% CI 0.92 to 1.06) compared to crystalloids. 4
Specific Populations Where Colloids May Be Considered
In patients with cirrhosis, albumin may be preferred over crystalloids for managing ascites-related hypovolemia and supporting colloid osmotic pressure. 1, 3
Albumin may have a role in patients with major hypoalbuminemia requiring large volumes of fluid therapy, though evidence is insufficient for a firm recommendation. 1
In sepsis or septic shock, albumin may be added to crystalloids when patients require large volumes of fluid, though this remains controversial. 1
Balanced Crystalloids vs Normal Saline
General Recommendation
- Balanced crystalloids (such as lactated Ringer's or Plasma-Lyte) should be used preferentially over 0.9% normal saline to reduce the risk of hyperchloremic metabolic acidosis, acute kidney injury, and potentially mortality. 1, 2, 3
Evidence Supporting Balanced Crystalloids
The SMART trial (15,802 critically ill patients) demonstrated that balanced crystalloids resulted in fewer major adverse kidney events compared to normal saline (OR 0.91,95% CI 0.84 to 0.99). 1, 2
In sepsis patients specifically, balanced crystalloids were associated with lower in-hospital mortality (OR 0.80,95% CI 0.67-0.97) and fewer major renal events. 1
Normal saline contains 154 mmol/L each of sodium and chloride, creating a non-physiological hyperchloremic state that can cause renal vasoconstriction and impaired kidney function. 2, 5
If normal saline must be used, limit administration to a maximum of 1-1.5 liters to minimize hyperchloremic effects. 2, 5
Critical Exception: Traumatic Brain Injury
In patients with severe traumatic brain injury or increased intracranial pressure, use normal saline (0.9% NaCl) rather than balanced crystalloids. 2, 6, 3
Lactated Ringer's solution has an osmolarity of 273-277 mOsm/L, making it slightly hypotonic compared to plasma (275-295 mOsm/L), which can worsen cerebral edema. 2, 6
Normal saline has an osmolarity of 308 mOsm/L and is truly isotonic, making it the preferred crystalloid for brain-injured patients. 2, 6
A meta-analysis showed higher mortality in TBI patients receiving balanced crystalloids compared to normal saline (RR 1.25,95% CI 1.02-1.54). 7
Clinical Decision Algorithm
Step 1: Assess for Contraindications to Balanced Crystalloids
Does the patient have severe traumatic brain injury or increased intracranial pressure?
Does the patient have rhabdomyolysis or crush syndrome?
- If YES → Use normal saline (avoid potassium-containing solutions) 2
- If NO → Proceed to Step 2
Step 2: Select Appropriate Crystalloid
For most critically ill patients: Use balanced crystalloids (lactated Ringer's or Plasma-Lyte) as first-line fluid. 1, 2, 3
For trauma patients (without severe TBI): Use balanced crystalloids to reduce mortality and adverse renal events. 1, 2
For sepsis/septic shock: Use balanced crystalloids to reduce mortality and major renal events. 1, 3
For burn patients: Use lactated Ringer's as the preferred balanced solution, administering 20 mL/kg within the first hour for burns ≥20% total body surface area. 2
For perioperative patients: Use balanced crystalloids to improve outcomes and avoid hyperchloremic acidosis. 2
Step 3: Consider Colloid Addition in Specific Scenarios
Cirrhosis with ascites: Consider albumin for volume support after paracentesis. 1, 3
Severe hypoalbuminemia with large volume requirements: Albumin may be added to crystalloids, though evidence is limited. 1
Septic shock requiring large volumes: Albumin may be added to crystalloids per Surviving Sepsis Campaign suggestions, though this remains controversial. 1
Monitoring and Pitfalls
Key Monitoring Parameters
Monitor serum chloride levels when administering normal saline; chloride >110 mEq/L indicates hyperchloremia and warrants switching to balanced crystalloids. 5
Assess acid-base status through arterial or venous blood gases to detect hyperchloremic metabolic acidosis. 5
Monitor renal function (creatinine, urine output) and watch for signs of acute kidney injury. 5
Track fluid balance to avoid volume overload, which can worsen outcomes regardless of fluid type. 1
Common Pitfalls to Avoid
Do not assume the potassium content in balanced crystalloids (4-5 mEq/L) is contraindicated in renal impairment unless severe hyperkalemia (>6.5 mmol/L) exists. 2
Do not use lactated Ringer's in patients with severe traumatic brain injury despite its benefits in other populations—the hypotonic nature can worsen cerebral edema. 2, 6
Do not continue normal saline beyond 1-1.5 liters when balanced crystalloids are available, as this increases risk of hyperchloremic acidosis and kidney injury. 2, 5
Do not use colloids routinely as first-line therapy given their higher cost and lack of mortality benefit compared to crystalloids. 1, 3
Do not use synthetic colloids (hydroxyethyl starch, dextrans) in critically ill patients due to associations with increased need for renal replacement therapy and potential renal toxicity. 1, 4
Special Clinical Scenarios
Acute Kidney Injury
Use balanced crystalloids rather than normal saline to reduce major adverse kidney events and avoid worsening hyperchloremic acidosis. 1, 2, 5
The potassium content in balanced solutions should not preclude their use unless severe hyperkalemia exists. 2
Hemorrhagic Shock/Trauma
Initiate crystalloid resuscitation (balanced crystalloids preferred) to restore end-organ perfusion. 1, 2
Consider restrictive fluid resuscitation strategies, as aggressive fluid administration may exacerbate blood loss and disrupt coagulation. 1
Diabetic Ketoacidosis
Use balanced crystalloids to avoid worsening acidosis with normal saline's hyperchloremic effect. 2
Monitor sodium closely during resuscitation, ensuring osmolality changes do not exceed 3 mOsm/kg/h. 5