For adults undergoing major invasive surgical procedures where significant blood loss (greater than 500mL) and/or perioperative fluid shifts are anticipated, a zero-balance OR goal-directed therapy (GDT) approach is recommended.
Zero Balance
This approach only addresses fluid loss during the procedure. This is done typically by giving 1-3 ml/kg of crystalloid to replace sensible and insensible losses during the procedure.
Blood loss would be replaced by 1.5 ml of crystalloid per 1.0 ml of blood loss. Alternatively, 1.0 ml of colloid to 1.0 ml of blood loss is also an acceptable replacement. Preloading prior to general anesthesia or neuraxial blocks is avoided. Replacing 'third space' losses has no benefit. Modest excess of the above rules is warranted in patients exhibiting signs of hypovolemia (e.g. delayed capillary refill, tachycardia, poor color, oliguria, hypotension).
This approach also avoids excessively deep anesthesia ( bispectral index < 40).
Goal-Directed Fluid Therapy (GDFT)
This approach requires invasive monitoring of hemodynamics (eg. an arterial line). In this approach, intravascular fluids are replaced prior to using vasopressor therapy. Replacement amount is determined by the use of the arterial line pulse and VISUAL pressure variation (PPV), stroke volume variation (SSV), or systolic pressure variations (SPV). For higher risk surgeries (anticipated losses > 1000 ml)
AUTOMATED devices are employed to compute these values for you. Typically, boluses of 250 mL are given incrementally to improve intravascular hydration until PPV, SPV, or SSV are less than 10 percent. Fluid administration is avoided after those goals are reached to prevent overhydration.
