skip to main content

CVVH Convection Mechanism — FRCA Final MCQ

Instant feedback + full explanation. One question, done properly.

ModerateIntensive Care MedicineCVVH Convection MechanismFRCA Final

A patient in ICU requires CRRT. Continuous venovenous haemofiltration (CVVH) uses which mechanism to clear solute?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — Convection (solvent drag) across a semi-permeable membrane

CVVH uses convection (solvent drag) as the primary solute clearance mechanism. A transmembrane pressure gradient drives plasma water and dissolved solutes across a semi-permeable membrane (haemofilter), producing an ultrafiltrate. Replacement fluid is then infused to maintain circulating volume. In contrast, CVVHD (haemodiafiltration) uses diffusion (dialysate flows countercurrent to blood) and CVVHDF combines both convection and diffusion. Convection is more effective at clearing middle molecules (MW 500-50000 Da) than diffusion, making CVVH potentially better for inflammatory mediator removal in sepsis.

Reference: KDIGO – 2012 – AKI guidelines; ICS – 2023 – CRRT standards