Doalysis

Question 1

Dialysis

Answer 1

filtering metabolic waste products from blood:
 separation of dissolved substances from a solution by allowing the solution to diffuse through a semipermeable membrane

Question 2

Hemodialysis

Answer 2

 Removing waste products such as creatinine and urea, as well as free water from the blood when the kidneys are in renal failure.

Question 3

Peritoneal Dialysis(PD)

Answer 3

A treatment for patients with severe chronic kidney disease. The process uses the patient’s peritoneum as a membrane across which fluids and dissolved substances (electrolytes, urea, glucose, albumin and other small molecules) are exchanged.

Question 4

Continuous Ambulatory Peritoneal Dialysis(CAPD).

Answer 4

Fluid is introduced through a tube in the abdomen and flushed out either every night while the patient sleeps or via regular exchanges throughout the day PD is used as an alternative to hemodialysis (especially in kidlets)

Question 5

The dialysis solution in the dialyzer (filter) helps _____ and contains ______

Answer 5

remove wastes/fluid from blood. Contains chemicals in concentrations similar to blood, a mixture of purified water and measured chemicals, which flows countercurrent on the outside.

Question 6

Substances that must remain in the bloodstream, such as glucose, sodium, calcium, and magnesium, are in

Answer 6

the dialysate in concentrations similar to blood.

Question 7

The composition of the dialysate determines

Answer 7

which solutes pass out of and which stay in the blood during dialysis.

Question 8

Dialyzer

Answer 8

an artificial kidney filter designed to provide controllable transfer of solutes and water across a semi permeable membrane separating flowing blood and dialysate streams.

Question 9

the tranfer processes for a dialyzer

Answer 9

diffusion (dialysis) and convection (ultrafiltration).

Question 10

three basic dialyzer designs

Answer 10

coil, parallel plate, and hollow fiber configurations.

Question 11

convection

Answer 11

transport of a constituent by bulk motion of a fluid

Question 12

diffusion

Answer 12

transport due to concentration gradients

Question 13

acute renal failure

Answer 13

sudden loss of kidney function due to illness injury or toxin

Question 14

chronic kidney disease

Answer 14

long slow process where kidney loses their function

Question 15

end stage renal disease

Answer 15

kidneys have completely and permanently shut down

Question 16

Renal failure is described as

Answer 16

a decrease in glomerular filtration rate (GFR).

Question 17

Biochemically, renal failure is

Answer 17

typically detected by an elevated serum creatinine level.

Question 18

CLASSIFICATIONS OF RENAL FAILURE

Answer 18

I. Acute Kidney Injury II. Chronic Kidney Disease

Question 19

ARF

Answer 19

 Rapid loss of kidney function (hypovolemia).  Causes include low blood volume  Exposure to harmful substances

Question 20

ARF diagnosed by

Answer 20

the basis of lab findings  elevated blood urea nitrogen (BUN)
 Elevated creatinine  inability of the kidneys to produce sufficient amounts of
urine.

Question 21

complications of ARF

Answer 21

Complications: metabolic acidosis, high potassium levels, uremia, changes in body fluid balance, and effects to other organ systems.

Question 22

ARF may be caused by

Answer 22

obstruction of the urinary tract

Question 23

Chronic kidney disease is identified by

Answer 23

significantly elevated creatinine.

Question 24

higher levels of creatinine indicate

Answer 24

a falling glomerular filtration rate and as a result a decreased capability of the kidneys to excrete waste products. Creatinine levels may have been normal in the early stages

Question 25

Problems frequently encountered in kidney malfunction include:

Answer 25

 abnormal fluid levels in the body  deranged acid levels  abnormal levels of potassium, calcium, and phosphate  anemia.  hematuria (blood loss in the urine)  proteinuria (protein loss in the urine)

Question 26

Long-term kidney problems have significant repercussions on

Answer 26

other diseases, such as cardiovascular disease

Question 27

Ultrafilters/Hemoconcentrators – removed total body water on the principle of

Answer 27

hydrostatic pressure gradients

Question 28

Dialysis – utilized to treat renal failure | removal of diffusable solutes based on the principle

Answer 28

of a concentration gradient and solute drag established by a dialysate solution

Question 29

dialysis uses a semi permeable membrane for

Answer 29

selected diffusion

Question 30

SOLVENT DRAG (CONVECTION)

Answer 30

The influence exerted by a flow of solvent through a membrane on the simultaneous movement of a solute through the membrane.

Question 31

COIL DIALYZER

Answer 31

 Blood compartment consisted of one or two long membrane tubes placed between support screens and wound around a plastic core.  Serious performance limitations, which gradually restricted its use as better designs evolved.  Coil design did not produce uniform dialysate flow distribution across the membrane.

Question 32

PARALLEL PLATE DIALYZER

Answer 32

reens, and then stacked in multiple layers ranging from 2 to 20 or more.  Allows multiple parallel blood and dialysate flow channels (lower resistance to flow).

Question 33

PARALLEL PLATE DIALYZER improvements

Answer 33

(1) thinner blood and dialysate channels with uniform dimensions,  (2) minimal masking or blocking of membranes on the support, and  (3) minimal stretching or deformation of membranes across the supports.

Question 34

HOLLOW FIBER DIALYZER

Answer 34

 Most effective design ->low-volume high efficiency with low resistance to flow. The fiber bundle are potted in polyurethane at each end of the fiber bundle in the tube sheet, which serves as the membrane support.

Question 35

MECHANICAL ASPECTS OF DIALYSIS SYSTEMS

Answer 35

hemodialysis machines offer tremendous flexibility in adjusting dialysis regimens. Hemodialysis machines use a single pass system where the dialysate circulates through the dialyzer once and is then discarded.

Question 36

MECHANICAL ASPECTS OF DIALYSIS SYSTEMS |  All systems require the same basic components:

Answer 36

dialysate heater to warm dialysate to body temperature  dialysate pump and flow meter to regulate the rate of dialysate delivery  sensors and alarms to monitor dialysate pressure, temperature, conductivity, and air or blood leaks.

Question 37

DIALYSIS TYPES

Answer 37

 Hemodialysis  Peritoneal Dialysis

Question 38

When you dialyze someone, you put their blood

Answer 38

(hypertonic – very full of stuff that needs removing) on one side of a membrane – and put some hypotonic solution on the other side (that’s the dialysate)

Question 39

hemodialysis decreases

Answer 39

number of BUN and creatinine molecules in the blood decreases (along with a bunch of even smaller ones like the electrolytes, which is why we spend so much time worrying about giving them back).

Question 40

HOWEVER – YOU HAVEN’T REMOVED ANY FLUID YET... |  Fluid can passes thru semipermeable filter membrane, by

Answer 40

applying suction on the far side of the membrane, vacuum “creates a transmembrane pressure gradient” It turns out that when you do this, small solute molecules get dragged out through the membrane pores along with the water (this is what they mean by “convective transport”, or “solvent drag”)

Question 41

CONVECTIVE FLUX

Answer 41

The movement of solutes through the membrane (“convective flux”) is calculatable using all sorts of horrid and bizarre renal mathematics Happily, I will leave that to the engineers (or Harry)

Question 42

MECHANICAL ASPECTS CIRCUIT COMPONENTS

Answer 42

Allsystemsrequirethesamebasiccomponents:  Aheatertowarmdialysateto37C  Adialysatepumpandflowmetertoregulatetherateof dialysate delivery  Sensorsandalarmstomonitordialysatepressure, temperature, conductivity, and air or blood leaks.

Question 43

Almost all single-patient hemodialysis machines use a

Answer 43

single pass system where the dialysate circulates through the dialyzer once and is then discarded.

Question 44

PERITONEAL DIALYSIS

Answer 44

 Less efficient at removal vs. hemodialysis  Effective in very labile cardiac states  Treatment of choice in kidlets  Allows more patient freedom

Question 45

ALTERNATIVE HEMODIALYTIC TECHNIQUES | I. Convection based

Answer 45

a. CAVH (continuous arteriovenous hemofiltration) b. CVVH (continuous venovenous hemofiltration)

Question 46

ALTERNATIVE HEMODIALYTIC TECHNIQUES | II. Diffusive Therapy

Answer 46

a. CAVHD (continuous arteriovenous hemodialysis) b. CVVHD (continuous venovenous hemodialysis)

Question 47

CAVH | continuous arterio-venous hemofiltration

Answer 47

 Blood circulates with or without a blood pump through a small hollow-fiber hemofilter.  Access - femoral artery and vein.  Heparin is infused proximal to the dialyzer.  Blood circulates through the hemofilter wherein the plasma and water is filtered and collected in the collection bag. Replacement volume is infused into the venous return line.

Question 48

CVVH | continuous veno-venous hemofiltration

Answer 48

 Pump assisted and achieves higher clearance. Because of its effectiveness, it is replacing the pumpless CAVH mode.  Access - double lumen catheter in the femoral, SC, or IJ vein.  Continuous diffusive solute transport is achieved by infusing a dialysis fluid  counter-current at 15 ml/min or 1 L/hr.

Question 49

CAVH/CVVH MECHANISMS OF ACTION | Convection

Answer 49

 Solute is removed by “Solvent Drag”. The solvent carries the solute through a semi-permeable membrane.  The roller pump creates hydrostatic pressure, which drives the solvent thru membrane.  The pore size limits molecular transfer  More efficient removal of larger molecules than diffusion  Enhanced clearance of autologous cytokines

Question 50

CAVHD | continuous arteriovenous hemodialysis

Answer 50

This technique uses an infusion pump, dialyzer membrane and dialysate solution.  An infusion pump pushes a flow of dialysis fluid dialyzer. The blood/dialysate interfaces on the membrane. CAVHD uses the process of diffusion dialysis to rid the body of fluid, electrolytes, and nitrogenous wastes. The preferred arterial access site is the common femoral artery

Question 51

CVVHD | continuous veno-venous hemodialysis

Answer 51

 The process of continuous diffusion dialysis in CVVHD is less effective than the CAVHD because the lower pressure venous system does not filter as much blood per unit of time.

Question 52

CAVHD/CVVHD MECHANISMS OF ACTION

Answer 52

Diffusion (predominantly)  Solute diffuses down an electrochemical gradient through a semi- permeable membrane in response to an electrolyte solution running counter current to the flow through the filter.  Diffusive movement of the solute- smaller molecules (ie urea) have greater kinetic energy and are removed based on the size of the concentration gradient  Convection occurs due to UF  Solute removal is proportional to the concentration gradient/size  Dialysate flow rate is slower than BFR (limiting factor to solute removal)  Solute removal is directly proportional to dialysate flow rate

Question 53

ARTERIOVENOUS FISTULA

Answer 53

Surgically created arteriovenous fistulas are preferred over catheters for patients with chronic renal failure for ease of access and a lower infection risk.  One of the most common errors of dual lumen catheters is the placement of the arterial and venous ports on the catheters

Question 54

ANTICOAGULATION | Citrate (CPD) Citrate advantages

Answer 54

 citrate has the effect of anticoagulating the CVVH system itself.  Citrate interrupts the clotting cascade by soaking up (chelating) free ionized calcium. the citrate is cooked off (metabolized) into the form of bicarb – (a safe result)

Question 55

heparin used with

Answer 55

both CVVH and CVVHD