Renal Replacement Therapies

Question 1

Renal Replacement Therapies

Answer 1

Chapter 178 CCM 3rd edition

Question 2

What are the indications for renal replacement therapy

Answer 2

life-threatening electrolyte and acid-base derangements nonresponsive to medical management, refractory hyperkalemia, and severe fluid overload with oligoanuria

Question 3

What are the most common forms of renal replacement?

Answer 3

intermittent hemodialysis (IHD), continuous renal replacement therapy (CRRT), and prolonged intermittent renal replacement therapy

Question 4

What is the difference between intermittent and continuous renal replacement?

Answer 4

Intermittent hemodialysis allows a high maximum removal rate of low molecular weight solutes per unit of time,2 whereas CRRT is a continuous modality, which most closely mimics endogenous renal function. Once CRRT is started, therapy is continued until the patient’s renal function recovers, the goal of the treatment is met (removal of exogenous toxin and/or excessive fluid burden), the patient is transitioned to IHD, or death occurs.

Question 5

What is the advantage of prolonged IHD?

Answer 5

Can remove solute however is prescribed over 6-12hrs lessening the haemodynamic burden and staffing burden

Question 6

Is there a clear mortality benefit of IHD or CRRT?

Answer 6

No, no clear difference in humans

Question 7

Principles of dialysis

Question 8

What are the two major factors that contribute to solute movement?

Answer 8

diffusion and convection

Question 9

What does diffusion depend on?

Answer 9

oncentration gradient between the two compartments, the solute charge and molecular weight, and the surface area and permeability of the membrane.
BUN and crea are low molecular weight so diffuse easily

Question 10

What is convective solute removal

Answer 10

Convective solute removal occurs when solutes are dragged with plasma water across the dialysis membrane as a result of an osmotic or hydrostatic pressure gradients (solvent drag). The rate of solute removal is dictated by the amount of water movement across the membrane, the membrane pore size, and the membrane surface area. Convection allows for effective removal of middle molecular weight solutes (molecular weight 500 to 60,000 Da) and small amounts of large (molecular weight >60,000 Da) molecular weight solutes during dialysis, if membrane pores are of sufficient size.

Question 11

During peritoneal dialysis how does dwell time effect solute removed?

Answer 11

Short dwell time = small molecules (urea and crea)
Long dwell time = larger molecules (albumin)

Question 12

What is the goal of ultrafiltration?

Answer 12

Fluid removal - convective process that refers to removal of excess plasma water from the intravascular compartment.
application of negative transmembrane pressure to the dialyzer allows plasma water to shift across the membrane into the dialysate compartment and out of the patient.
In peritoneal this is through the use of hyperosmolar dialysate to draw fluid into the dialysate

Question 13

Where should the dialysis catheter tip be placed?

Answer 13

In the right atrium

Question 14

What are the two most common forms of anti-coagulation used in dialysis

Answer 14

systemic heparinisation (increased risk of bleeding) and regional citrate (hypocalcemia, arrhythmias, alkalosis

If already overtly coagulopathic can go without or use low dose hep - May increase the risk of clotting.

Question 15

Dialysis prescription

Question 16

What are the most important aspects of dialysis prescription?

Answer 16

selection of the most appropriate RRT platform, dialyzer, blood flow rate, dialysis time, dialysate composition and flow rate, ultrafiltration, and type of anticoagulation.

Question 17

What occurs during dialysis disequilibrium syndrome

Answer 17

Rapid removal of osmotically active solutes (primarily BUN) from the blood compartment creates temporary acute osmotic pressure gradients between the blood, extravascular, and intracellular compartments. This gradient can allow plasma water to shift from the vascular compartment and into the intracellular compartments. When this phenomenon occurs in brain tissue, secondary swelling occurs, and this can lead to irreversible neurologic damage or death.

Question 18

What are the potential complications of excessively fast ultrafiltrate removal

Answer 18

hypotension, hypothermia, nausea, and cramping.

Question 19

What is the normal peritoneal dialysis volume?

Answer 19

the normal dialysate volume is about 30 to 40 ml/kg per exchange cycle. If fluid balance becomes positive or returning volume decreases to less than 90% of what was administered, the dialysate should be changed to encourage ultrafiltration.

Question 20

What are the complications associated with dialysis ?

Answer 20

hypotension, haemorrhage due to anti-coag, hypocalcaemia, alkalaemia, disequilibrium syndrome, air embolism, blood loss due to extracorporeal circuit clotting, catheter occlusion

Question 21

What complications are associated with PD?

Answer 21

catheter occlusion, catheter site infection, dialysate leakage, septic peritonitis, fluid retention, hypoalbuminemia, dyspnea due to increased abdominal pressure, and hyperglycemia from dialysate with a high glucose concentration.

Question 22

Prog

Answer 22

SMall studies but somewhere around 50%