In a model, a patient has 150 mg of urea in every 100 mL of blood before dialysis…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
In a model, a patient has mg of urea in every mL of blood before dialysis. The dialyser clears mL of blood each minute. The session lasts hours, and the body water is L.
- What is the volume of blood cleared in the session, divided by the body water?
- How much urea is left in every mL of blood at the end?
- By what per cent does the urea fall?
Need a reminder? The key ideaShow
Uraemia is urea in the blood. In haemodialysis, blood from an artery gets heparin. It runs through a coiled cellophane tube in a dialysing fluid that is like plasma without the nitrogenous wastes. It returns through a vein after anti-heparin. Wastes diffuse down their concentration gradient. In a model, the urea left is per cent, where the ratio is the volume of blood cleared divided by the body water. Renal calculi are stones of crystallised salts. Glomerulonephritis is the inflammation of the glomeruli.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Start: mg in mL. Clearance: mL/min. Time: h. Body water: L.
Plan. Find the ratio. Then use the decay law.
Step 1. The ratio. The volume cleared is mL L. The ratio is .
Step 2. Urea left. mg in mL. In whole mg, the urea left is mg.
Step 3. The fall. .
Answer: ; mg; .
Check. A ratio of leaves of the urea, which gives a fall of .
Watch out. This is a one pool model with values from physiology books. It is not in the NEET syllabus text.
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