PAEA Surgery End Of Rotation (EOR) Practice Exam

What is the 421 rule for adult fluid replacement?

1. 4 mL/kg for the first 10 kg/hr, 1 mL/kg for each additional kg/hr

2. 4 mL/kg for the first 10 kg/hr, 2 mL/kg for each additional kg/hr

3. 4 mL/kg for the first 10 kg/hr, 2 mL/kg for the second 10 kg/hr

4. 5 mL/kg for the first 10 kg/hr, 2 mL/kg for each additional kg/hr

The correct answer is: 4 mL/kg for the first 10 kg/hr, 2 mL/kg for the second 10 kg/hr

The 421 rule for adult fluid replacement is structured to appropriately calculate fluid needs based on a patient's weight. Specifically, it states that for the first 10 kg of a person's body weight, you should account for 4 mL per kg of body weight. Following that, for the second 10 kg, you would use 2 mL per kg. This gradual increase in fluid requirement reflects the fact that as body weight increases, the metabolic and physiologic demands do not scale linearly. This method becomes beneficial in clinical settings where accurate fluid resuscitation is critical, especially in trauma or surgical patients who require close monitoring and adjustment of their fluid intake. The first 10 kg is typically where the majority of metabolic activity occurs, and the following weights represent more of an incremental requirement that balances the needs effectively. Options that suggest alternative rates of fluid administration significantly deviate from this systematic approach. For instance, a choice that uses 1 mL/kg for additional weight would underrepresent fluid needs, particularly as larger patients tend to have significant metabolic demands. The idea behind the 421 rule allows for efficient and safe fluid resuscitation while accommodating patients of varying sizes.