Skip to Main Content

++

Introduction

+

  • Continuous renal replacement therapies have come into increasing use in intensive care units (ICUs), and a variety of alternatives are available, ranging from fluid-removal approaches to continuous dialysis.

++

Definitions and Terms

+

  • ▪  Dialysis: Removal of waste products and fluid from the blood.
  • ▪  Ultrafiltration: Removal of excess fluid from the blood.
  • ▪  Convection: Movement of solutes and fluid across a semipermeable membrane across which there is a pressure gradient—effective for removal of fluid and certain molecules.
  • ▪  Diffusion: Movement of (typically small) solutes (like urea) along a concentration gradient from an area of high concentration (the blood) into an area of low concentration (the dialysate).
  • ▪  Continuous venovenous hemofiltration (CVVH): Convective dialysis which is very efficient at fluid and cytokine removal (Figure 50-1).
  • ▪  Continuous venovenous hemodialysis (CVVHD): Diffusive dialysis where the dialysate runs “countercurrent” to the blood (Figure 50-2).
  • ▪  Continuous venovenous hemodiafiltration (CVVHDF): Combination of convective and diffusive dialysis which is common in the ICU and very effective at fluid and solute removal (Figure 50-3).
  • ▪  Continuous arteriovenous hemodialysis: A largely archaic method of continuous dialysis in which arterial blood is processed prior to being reinfused into a vein.

++
Figure 50-1.
Graphic Jump Location

CVVH circuit showing the use of an outflow resistor to modify the pressure gradient across the membrane.

++
Figure 50-2.
Graphic Jump Location

CVVHD circuit showing countercurrent dialysis fluid flow relative to blood flow.

++
Figure 50-3.
Graphic Jump Location

CVVHDF circuit showing the combined use of a resistor and countercurrent dialysis to remove fluid and soluted.

++

Techniques

+

  • ▪  Prior to initiation of continuous venous dialysis, a special double lumen catheter is placed in a central vein.
  • ▪  Vascular cannulation is performed as per the chapter on central line placement (Chapter 34) with the exception that a larger specialty catheter is placed in the vein (Figures 50-4, 50-5, 50-6, and 50-7).
  • ▪  One lumen of the dialysis catheter is treated as the arterial lumen, for flow proceeding from patient into dialysis machine, whereas the second “venous” lumen is used to return blood to the patient (Figure 50-8).
  • ▪  Blood is routed through a dialysis machine and the selected dialytic method applied (Figure 50-9).
  • ▪  The effluent (equivalent of urine) is measured in the medical record (Figure 50-10).
  • ▪  Blood running through the system is often heated to prevent (Figure 50-11) patient cooling.

++
Figure 50-4.
Graphic Jump Location

Insertion of a large bore dilator over a wire in a Seldinger exchange.

++
Figure 50-5.
Graphic ...

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.

Ok

About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

AccessAnesthesiology Full Site: One-Year Subscription

Connect to the full suite of AccessAnesthesiology content and resources including procedural videos, interactive self-assessment, real-life cases, 20+ textbooks, and more

$995 USD
Buy Now

Pay Per View: Timed Access to all of AccessAnesthesiology

24 Hour Subscription $34.95

Buy Now

48 Hour Subscription $54.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.