Flashcards in Dialysis- Final Exam Deck (84)
filtering metabolic waste products from blood; separation of dissolved substances from a solution by allowing the solution to diffuse through a semipermeable membrane
Removing waste products such as creatinine and urea, as well as free water from the blood when the kidneys are in renal failure
Peritoneal Dialysis (PD)
a Tx for patients with severe chronic kidney disease; uses patient's peritoneum as a membrane across which fluids and dissolved substances are exchanged
What substances are exchanged with peritoneal dialysis?
Electrolytes, urea, glucose, albumin and other small molcules
Continuous Ambulatory Peritoneal Dialysis (CAPD)
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
What is used as an alternative to hemodialysis, especially in kids?
Peritoneal dialysis (PD)
dialysis solution in the dialyzer helps remove wastes/fluid from blood.
artificial kidney filter designed to provide controllable transfer of solutes and water across a semi-permeable membrane separating flowing blood and dialysate streams
What does a dialysate solution contain?
Chemicals in concentrations similar to blood, a mixture of purified water and measured chemicals, which flows countercurrent on the outside.
What substances that must remain in the blood stream?
Glucose sodium calcium magnesium
Substances that must remain the in blood stream are in what concentrations in the dialysate solution?
Concentrations similar to blood
What does the composition of dialysate determine?
Which solutes pass out of and which stay in teh blood during dialysis
What transfer processes occur in a dialyzer?
Diffusion (dialysis) and convection (ultrafiltration)
What are the three basic dialyzer designs?
Coil, parallel plate, hollow fiber configurations
What is one of the major modes of mass transfer?
Convection (diffusion is another; diffusive transport)
What type of kidney failure do we create on bypass?
Acute renal failure
Acute renal failure (ARF)
A sudden loss of kidney function caused by an illness, an injury, or a toxin that stresses the kidneys (kidney function may recover)
Chronic Kidney Disease (CKD)
A long and usually slow process where the kidneys lose their ability to function
Why type of kidney failure will you get with stenosis in the renal artery?
End-stage renal disease (ESRD)
When the kidneys have completely and permanently shut down
Would we give mannitol for ESRD?
no because it's cleared in the kidneys
Renal failure defintiion
decrease in GFR
How is renal failure detected biochemically?
Elevated serum creatinine level
How do we characterize ARF?
1. Rapid loss of kidney function (hypovolemia)
2. Causes include low blood volume
3. Exposure to harmful substances
4. Obstruction of urinary tract
What lab findings help us diagnose acute kidney injury?
Elevated blood urea nitrogen level (BUN)
Inability of the kidneys to produce sufficient amounts of urine
What are some complications of ARF?
High K+ levels
Changes in body fluid balance (big shift)
Effects to other organ systems
How is chronic kidney disease identified?
Significantly elevated creatinine
What do higher levels of creatinine indicate?
Falling GFR; and as a result decreased capability of the kidneys to excrete waste products
What are creatinine levels in early stages of chronic kidney disease?
may be normal
Problems frequently encountered in kidney malfunction
-Abnormal fluid levels in body
-deranged acid levels
-Abnormal potassium, calcium, phosphate
-hematuria (blood loss in urine)
-proteinuria (protein loss in urine)
Long-term kidneys problems have significant repercussions on other diseases such as what?
Removed total body water on the principle of hydrostatic pressure gradients
What is used to treat renal failure?
Dialysis; removal of diffusable solutes based on the principle of concentration gradient and solute drag established by dialysate solution
Describe the diffusion of molecules.
How do you control water?
Controlling transport of sodium
influence exerted by a flow of solvent through a membrane on the simultaneous movement of a solute through the membrane
Types of dialyzers
Describe the blood compartment of a coil dialyzer.
Blood compartment consisted of one or two long membrane tubes placed between support screen and wound around a plastic core
Why are coil dialyzers restricted in use?
Serious performance limitations; coil design did not produce uniform dialysate flow distribution across the membrane
Describe the setup of a parallel plate dialyzer.
Sheets of membrane are mounted on plastic support screens, and then stacked in multiple layers range from 2 or 20 or more.
What do parallel plate dialyzers allow?
Multiple parallel blood and dialysate flow channels (lower resistance to flow)
Major improvements in parallel plate dialyzer allow what (3)?
1. Thinner blood and dialysate channels with uniform dimensions
2. Minimal masking or blocking of membranes on the support
3. Minimal stretching or deformation of membranes across the supports
What dialyzer has the most effective design?
Hollow Fiber Dialyzer
Describe the design of the hollow fiber dialyzer.
Low-volume high efficiency with low resistance to flow. Fiber bundle are potted in polyurethane at each end of the fiber bundle in the tube sheet, which serves as the membrane support.
__________ machines offer tremendous flexibility in adjusting dialysis regimens.
What type of system do hemodialysis machines use?
Single pass system where the dialysate circulates through the dialyzer once and is then discarded
What 3 components do all dialysis systems require?
1. Dialysate Heater (to warm to body temp)
2. Dialysate pump/flow meter (regulate rate of delivery)
3. Sensors/alarms (pressure, temp, conductivity, air or blood leaks)
When dialyzing, patient blood is on one side and what type of solution is on the other side?
Hypotonic solution (dialysate)
What creates movement of molecules across membrane in hemodialysis?
Movement from hypertonic blood to hypotonic solution (dialysate)
What substances in the blood decrease in hemodialysis?
BUN, creatinine, electrolytes
HOw can fluid pass through semipermeable filter membrane in hemodialysis?
By applying suction on the far side of the membrane
What creates a transmembrane pressure gradient?
What happens when you use vacuum?; What is meant by convective transport or solvent drag?
Small solute molecules get dragged out through the membrane pores along with the water
The movement of solutes through the membrane ("convective flux") is calculatable
Almost all single-patient hemodialysis machines use a ______________, where the dialysate circulates through the dialyzer once and is then discarded.
What temperature should the dialysate be?
Body temp, 37
What is more effective: peritoneal dialysis or hemodialysis?
When is peritoneal dialysis effective?
Very labile cardiac states
Tx of choice in kids
What is an advantage of peritoneal dialysis?
Allows more patient freedom
What are some convection based alternative hemodialytic techniques?
CAVH (continuous arteriovenous hemofiltration)
CVVH (continuous venovenous hemofiltration)
What are some diffusive therapy based alternative hemodialytic techniques?
CAVHD (continuous arteriovenous hemodialysis)
CVVHD (continuous venovenous hemodialysis)
How does blood circulate in continuous arterio-venous hemofiltration?
With or without a blood pump thrugh a small hollow-fiber hemofilter; through the hemofilter wherein the plasma and water is filtered and collected in the collection bag
Where do you get access in CAVH?
Femoral artery and vein
Where is heparin infused in CAVH?
Proximal to the dialyzer
Where is replacement volume infused in CAVH?
Into venous return line
Why is CVVH replacing CAVH mode?
Pump assisted and achieves higher clearance. Because of its effectiveness, it is replacing the pumpless CAVH mode
Where do you get access in CVVH?
Double lumen catheter in the femoral, SC, or IJ vein
How is continuous diffusive solute transport achieved in CVVH?
Infusing a dialysate flui
What is the counter-current rate in CVVH?
15 ml/min or 1 L/hr
CAVH/CVVH Mechanism of Action
-Solute removed by solvent drag
-roller pump creates hydrostatic pressure
-drives solute through membrane
-pore size limits transfer
-more efficient removal of larger molecules than diffusion
-enhanced cleared of autologous cytokines
CAVH/CVVH has enhanced clearance of what?
Describe the technique of CAVHD.
Infusion pump, dialyzer membrane and dialysate solution.
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.
What process does CAVHD use to rid the body of wastes?
What wastes does CAVHD get rid of?
Fluid, electrolytes, nitrogenous wastes
What is the preferred arterial access site for CAVHD?
What is more effective: CAVHD or CVVHD? Why?
CAVHD, becuase the lower pressure venous system does not filter as much blood per unit of time
CAVHD/CVVHD Mechanism of Action
-Solute diffuses electrochemical gradient
-diffusive movement; smaller molecule have greater KE removed based on size of gradient
-convection due to UF
-solute removed proportion to size
-dialysate flow is low that BFR
-solute removal directly proportion to dialysate flow rate
What type of cannulas are used for dialysis access?
duel lumen dialysis catheters
Surgically created arteriovenous fistulas are preferred over catheters for patients with chronic renal failure for ease of access and a lower infection risk
What is one the most common errors of dual lumen cathters?
Placement of arterial and venous ports on the catheters
What is used for anticoagulation?
What are some advantages of Citrate as an anticoagulant?
Citrate has the effect of anticoagulating the CVVVH system itself.
Citrate interrups the clotting cascade by soaking up (chelating) free ionized calcium. the citrate is cooked off (metabolized) into the form of bicarb