The traditional method, often referred to as the "4-2-1" approach, was established by Holliday and Segar in the late 1950s: 4 mL/kg/hr for the first 10 kg of body weight, 2 mL/kg/hr for the next 10 kg, and 1 mL/kg/hr for each kilogram above 20, which comes to about 110 mL/hr for a 70-kg adult. This conventional approach advocates for compensating fluid losses, including the so-called third space losses - the movement of fluid from the bloodstream into intercellular spaces. Despite its widespread endorsement in numerous medical texts and a typical postoperative body weight increase of 3–6 kilograms, contemporary critical analysis questions the validity of third space loss during surgery or shock.
In the app: the Master Anesthesia app's Fluids calculator (Calculators, then Fluids) runs this arithmetic for you: enter the patient's weight and NPO hours and it returns the 4-2-1 maintenance rate, the fasting deficit with half replaced in the first hour and a quarter in each of the next two, and hourly totals with surgical losses added.
A pivotal study in 2003 by Brandstrup et al. challenged this traditional wisdom by demonstrating that liberal intravenous (IV) fluid administration during abdominal surgeries could significantly heighten the risk of postoperative complications, as opposed to a more conservative fluid management strategy. Further scrutiny of fluid resuscitation practices was provided by the Fluid Expansion as Supportive Therapy (FEAST) trial, which evaluated 3141 children aged between 60 days and 12 years suffering from severe fever and compromised blood flow. Participants were randomly assigned to either receive boluses of 5% albumin solution, 0.9% saline solution, or no bolus at all. The study revealed that fluid boluses notably increased the risk of death within 48 hours in children with impaired perfusion, highlighting the potential dangers of aggressive fluid resuscitation.
These findings emphasize the complexity of fluid management in clinical settings and point to a critical reassessment of the efficacy and safety of bolus-fluid resuscitation. The evolving landscape of surgery, including the advent of minimally invasive and robotic techniques, has also influenced fluid therapy approaches by reducing evaporative fluid losses and the extent of physical tissue manipulation.
