Module 3: Principles of Dialysis

53 cards

Principles of Dialysi


 
  
Created Sep 18, 2010
by
ameyer08

 

 
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1
Dialysis replaces 3 main kidney functions
 
Removing wastes from the blood Removes excess fluid from the blood Keeping electrolytes in...
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Solutions
 
a mixture of a solvent and a solute
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Solvent
 
Fluid
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Solute
 
any substance that can be dissolved into the solvent
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Dialysate
 
the solution that is used during dialysis Solvent: Water Solute: Electrolytes (potassium,...
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Electrolyte Levels in Dialysate
 
closely match the levels in the human blood. This reduced the loss of these electrolytes out...
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Controlling pts blood electrolyte levels
 
can be controlled by changing the dialysate. Adding an electrolyte to the dialysate at a level...
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Semipermeable Membrane
 
a type of thin, flexible filter- a barrier that allows only particles smaller than a certain...
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Dialysis semipermeable membrane
 
In dialysis, the semipermeable membrane's holes allow small molecules, such as water and urea,...
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Diffusion
 
the process by which atoms, molecules, and/or other particles move from an area where they...
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Energy for Diffusion
 
Energy for the movement comes from the molecules themselves, and does not depend on outside...
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Factors affecting diffusion: The nature of the solution
 
Concentration Gradients Molecular weight of the solutes Temperature
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Concentration Gradients
 
Solutes move through a semipermeable membrane from an area of greater concentration to an area...
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Molecular weight of the solution
 
Smaller molecules diffuse more easily and quickly than larger ones. Large blood components...
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Temperature
 
Molecules move faster at higher temperatures, so warmer fluids allow faster diffusion. Dialysate...
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Factors Affecting Diffusion: The Nature of the Membrane
 
Membrane permeability Surface area of the membrane Flow geometry
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Membrane permeability
 
A membrane with more pores allows faster diffusion. Larger pores allow larger molecules to...
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Surface area of the membrane
 
Surface area is the amount of membrane in direct contact with the blood and dialysate. Larger...
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Flow geometry
 
In dialysis, blood flows one way while dialysate flows the opposite way. This countercurrent...
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Osmosis
 
In diffusion, solutes move. In osmosis, the solvent moves across the membrane. Osmosis is...
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Osmotic Pressure Gradient
 
The difference in concentration  
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Hydraulic pressure
 
Osmotic pressure can be overcome by hydraulic pressure using a pump, gravity or other means....
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Reverse osmosis water treatment devices
 
Hydraulic pressure can reduce or overcome osmotic pressure. This principle is the basis for...
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Filtration
 
the movement of fluid through a filter as the result of hydraulic pressure. Fluid will always...
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Ultrafiltration (UF)
 
Water removal from blood due to a pressure gradient across a membrane. In dialysis, UF is used...
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Convection
 
transfer of heat and solutes by physical circulation or movement of the parts of a liquid or...
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Solvent drag
 
as a solvent crosses a semipermeable membrane, it drags along smaller solutes
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Fluid
 
a liquid or gas that changes shape at a steady rate when acted upon by a force
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Dynamics
 
addreses the motion and equilibrium of systems
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Fluid dynamics
 
describes how two fluids-blood and dialysate-are pumped through tubing. Several forces affect...
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Flow rate
 
amount of fluid that flows through the tubing in a given period of time
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Flow velocity
 
speed at which the fluid moves through a given length of tubing. Velocity is based on the...
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Pressure in any fluid system
 
the pressure in any fluid system is always related to the flow and the resistance; the greater...
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Fluid compartments
 
The human body is made mostly of fluids. Fluids are found in 3 compartments: Intracellular...
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Pressure gradients in fluid compartments
 
Differences in the level of sodium and electrolytes between compartments (gradients) cause...
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Dialysis and body compartments
 
During dialysis, only fluid from the intravascular compartment can be removed
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Extracorporeal Circuit
 
Outside the body Together, the tubing and dialyzer are called the extracorporeal circuit
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Fluid intake
 
Food Beverages Intravenous fluids
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Fluid Output
 
Respiration Stool Perspiration adn skin water loss Dialysate loss Residual urine Vomiting
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Fluid dynamics in dialysis
 
blood pump speeds the flow of blood from the pt. Blood passes through the needle-the first...
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Resistance in the blood pump
 
The tubing The tiny hollow fibers in the dialyzer The small opening of the venous blood return...
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Resistance in the blood pump creates:
 
positive pressure inside the lines and dialyzer fibers. As blood passes through these resistances,...
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Venous pressure
 
The pressure measured after blood leaves the dialyzer (venous pressure) is the lowest positve...
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Positive hydraulic pressure
 
The average pressure of blood entering and leaving the dialyzer fibers is the true amount of...
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Countercurrent flow.
 
dialysate flows through the dialyzer and around the hollow fibers in one direction. Blood flows...
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Transmembrane pressure (TMP)
 
The machine can control the pressure differential between the blood and dialysate compartment...
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Diffusion in dialysis
 
The hollow fibers in the dialyzer are the semipermeable membrane. Blood passes through the...
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Electrolyte balance in dialysis
 
is also maintained with diffusion. It is vital to pts health to keep the right level of electrolytes...
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Diffusion occurs continuously in the pts body
 
as clenased blood is returned to the pt, it slowly dilutes the rest of the blood. The drop...
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UF in dialysis
 
UF requires pressure to force fluid through the membrane. The dialysis machine can create a...
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Convection in dialysis
 
As water (a solvent) moves from the blood compartment to the dialysate compartment, molecules...
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Osmosis in dialysis
 
the pressure of UF pushes fluid out of the blood nad into the dialysate. But osmotic forces...
53
Example of FIltration and UF
 
Soak a sponge in water. Hold the sponge over a bucket of water and watch the sponge filter...


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