Fluid Balance Management

Introduction to Fluid Balance

The American College of Cardiology defines fluid balance as the difference between all fluid inputs and all outputs, with positive balance occurring when intake exceeds output, and negative balance when output exceeds intake 1, 2, 3

Patients with positive fluid balance (>2.5L excess) have a 59% increased risk of complications and 3.4-day longer hospital stays compared to those maintained at near-zero balance, according to Clinical Nutrition 1, 2
Positive fluid balance is associated with specific complications, including pulmonary complications, renal dysfunction, gastrointestinal complications, abdominal compartment syndrome, cardiovascular effects, and poor wound healing 1, 2, 4, 5
The American College of Cardiology recommends avoiding fluid overload, as it can lead to increased morbidity and mortality 3

The goal is to maintain near-zero or even fluid balance (0-5% body weight change), avoiding both extremes, as recommended by Clinical Nutrition 1, 2
In the perioperative context, targeting a mildly positive balance of 1-2 liters by end of surgery and then transitioning to minimizing IV fluids postoperatively can protect kidney function, according to Praxis Medical Insights 4, 5
In critically ill patients, aiming for daily negative fluid balance to remove accumulated fluid after initial resuscitation and hemodynamic stabilization can improve outcomes, as suggested by Critical Care Medicine 7

Essential monitoring includes daily weights, accurate intake and output records, supine and standing vital signs, daily electrolytes, BUN, and creatinine, and clinical assessment of volume status and perfusion, as recommended by the Journal of the American College of Cardiology 3, 4

Administering large volumes of 0.9% saline can cause hyperchloremic acidosis, renal vasoconstriction, and impaired GI motility, and should be avoided in favor of buffered crystalloids, according to Clinical Nutrition and Praxis Medical Insights 1, 2, 4, 5
Fluid overload >2.5 kg perioperative weight gain should be avoided, as it dramatically increases complications, but stringently restrictive regimens also increase AKI risk, as noted by Praxis Medical Insights 4, 5