What IV fluids should be infused in an adult patient?

IV Fluid Selection in Adult Patients

For adult patients requiring IV fluids, use isotonic balanced crystalloids (such as lactated Ringer's or Plasma-Lyte) as first-line therapy, avoiding hydroxyethyl starch colloids entirely and reserving 0.9% saline for specific situations where balanced solutions are contraindicated. 1, 2, 3

Type of Crystalloid Solution

Balanced vs. Unbalanced Crystalloids

• Balanced crystalloids (lactated Ringer's, Plasma-Lyte) are superior to 0.9% saline because they reduce the risk of hyperchloremic metabolic acidosis and decrease the incidence of acute kidney injury. 2, 4

• In patients with sepsis-induced hypotension, lactated Ringer's solution compared with 0.9% saline resulted in improved survival (adjusted hazard ratio 0.71,95% CI 0.51-0.99) and more hospital-free days (mean difference 1.6 days). 3

• The physiologic advantage stems from balanced solutions having electrolyte compositions closer to plasma, preventing the chloride load that occurs with large volumes of 0.9% saline. 4, 5

Colloids: Avoid in Most Situations

• Hydroxyethyl starch (HES) is contraindicated in sepsis or septic shock due to increased mortality (relative risk 1.17) and increased need for renal replacement therapy (relative risk 1.35). 1, 6

• Gelatin-based colloids should not be used in sepsis or septic shock, as they offer no mortality benefit over crystalloids and carry similar risks. 1

• The FDA label for hetastarch explicitly warns against use in critically ill patients, particularly those with sepsis, due to increased mortality and renal injury. 6

Clinical Scenarios and Fluid Selection

Sepsis and Septic Shock

• Administer at least 30 mL/kg of isotonic crystalloids within the first 3 hours of recognizing sepsis, using repeated boluses of 250-1000 mL with reassessment after each bolus. 2, 7

• Target mean arterial pressure ≥65 mmHg, with clinical endpoints including normalized heart rate, improved capillary refill, warm extremities, and urine output >0.5 mL/kg/h. 2, 7

• If hypotension persists after 30 mL/kg of crystalloids, initiate vasopressors (norepinephrine as first-line) rather than administering additional large fluid volumes. 7

Diabetic Ketoacidosis (DKA)

• Begin with isotonic saline (0.9% NaCl) at 15-20 mL/kg/h during the first hour (1-1.5 L in average adults) for initial volume expansion and restoration of renal perfusion. 1

• After the first hour, switch to 0.45% NaCl at 4-14 mL/kg/h if corrected serum sodium is normal or elevated; continue 0.9% NaCl if corrected sodium is low. 1

• Add 20-30 mEq/L potassium (2/3 KCl and 1/3 KPO4) to fluids once renal function is confirmed and potassium is not elevated. 1

• Note: DKA is one scenario where 0.9% saline remains appropriate for initial resuscitation due to the specific electrolyte derangements present. 1

Volume Depletion (Hypovolemia)

• For mild to moderate volume depletion, isotonic fluids should be administered orally, nasogastrically, subcutaneously, or intravenously depending on severity and patient ability to tolerate oral intake. 1

• In severe dehydration with serum osmolality >300 mOsm/kg (or calculated osmolarity >295 mmol/L) in patients unable to drink, intravenous isotonic fluids are required. 1

• Following excessive blood loss, assess using postural pulse change (≥30 beats per minute from lying to standing) or severe postural dizziness preventing standing ability. 1

Maintenance Fluid Therapy

• Calculate maintenance fluids at 30 mL/kg/day for stable adult patients who cannot take adequate oral fluids. 8

• Isotonic solutions (0.9% saline or balanced crystalloids) are preferred for maintenance as they distribute more evenly into extracellular spaces. 8

• Hypotonic solutions should be avoided in patients with or at risk for cerebral edema, as they distribute substantially into intracellular spaces and may exacerbate edema. 8, 4

Administration Technique and Monitoring

Bolus Administration Protocol

• Administer crystalloid boluses of 250-1000 mL rapidly (in less than 15 minutes), followed by immediate clinical reassessment. 2

• Reassess after each bolus by monitoring systolic/mean arterial pressure, heart rate, mental status, peripheral perfusion, and urine output. 2

• Use dynamic measures of fluid responsiveness (pulse pressure variation, stroke volume variation) rather than static measures like central venous pressure alone. 2

When to Stop Fluid Administration

• Discontinue fluid boluses when: no improvement in tissue perfusion occurs, signs of fluid overload appear (pulmonary edema, peripheral edema, elevated jugular venous pressure), or hemodynamic parameters stabilize. 2

• In trauma patients, minimize crystalloid volumes to avoid dilutional coagulopathy and worsening acidosis; consider using 500 mL bags rather than 1 L bags to reduce inadvertent over-resuscitation. 9

Special Populations and Considerations

Elderly Patients

• Exercise greater caution with fluid administration due to decreased physiologic reserve and increased risk of fluid overload. 8

• More conservative fluid strategies are appropriate, with closer monitoring for signs of volume overload. 1, 8

Cardiac or Renal Compromise

• Patients with heart failure or renal impairment require more cautious fluid administration with frequent reassessment. 8

• Consider smaller bolus volumes (250-500 mL) with more frequent reassessment in these populations. 8

Hemorrhagic Shock

• While crystalloids remain first-line, early consideration of blood product administration is critical when hemorrhage is the primary problem. 7

• Target hemoglobin >7-9 g/dL in the context of shock to optimize oxygen delivery. 7

Common Pitfalls to Avoid

• Never use hydroxyethyl starch in critically ill patients, especially those with sepsis, due to clear evidence of harm including increased mortality and renal failure. 1, 6

• Avoid administering excessive crystalloid volumes without reassessment, as both inadequate and excessive fluid administration lead to poor outcomes including increased infection risk and organ dysfunction. 10

• Do not rely solely on static hemodynamic measures (like CVP) to guide fluid therapy; incorporate dynamic assessments and clinical endpoints. 2

• Avoid hypotonic solutions in patients with actual or impending cerebral edema, as they worsen intracranial pressure. 8, 4

• Do not administer hetastarch-containing solutions through the same line as blood products due to risk of coagulation. 6

• Overestimating fluid needs in elderly patients or those with cardiac/renal dysfunction leads to harmful fluid overload. 8