How do you check for gastric residual volume?

Use the same large 50-60ml syringe as you do for administering meds through the NGT, but start empty when you open the valve on the tube and pull back instead of pushing in. You should receive residuals in 50-60ml increments (minus some air) that you can empty bit by bit into a grad cylinder at bedside. When you meet resistance, the stomach is empty and you add it all up. Then, you gotta put it all back bit by bit, maybe with (crushed/liquid) meds mixed in if any are due. We used 400ml as a line to call the doctor c/f gastroparesis.