SACCM 178: Renal Replacement Therapies Flashcards

1
Q

How does timing of initiation of RRT affect survival in humans with AKI?

A

does not affect survival according to recent systematic review of RCTs

Gaudry et al., 2020, the Lancet

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2
Q

What are the three most commonly prescribed extracorporeal RRT in veterinary medicine?

A

Continuous renal replacement therapy (CRRT)
Intermittent hemodialysis (IHD)
prolonged intermittend renal replacement therapy

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3
Q

What are the four modalities of CRRT?

A
  • continuous ultrafiltration - convective - fluid removal
  • continous venovenous hemofiltration -convective - solute removal
  • continous venovenous hemodialysis (CVVHD) - diffusive - solute removal
  • continous venovenous hemodiafiltration (CVVHDF) - diffusive and convective - solute removal

solute removal prescriptions can be altered to achieve fluid removal

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4
Q

What is the definition of “Dialysis”?

A

Dialysis is the movement of solutes between two aqueous solutions separated by a semipermeable membrane

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5
Q

What does the rate of solute removal by diffusion depend on?

A
  • concentration gradient
  • solute charge
  • solute molecular weight
  • surface area
  • permability
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6
Q

How do diffusion and convection differ in the size of solutes they remove?

A
  • diffusion removes small molecular weight solutes, e.g., BUN and creatinine, and some middle molecular weight
  • convection removed small and middle molecular weight solutes (500 - 60,000 Da) + some large (>60,000)
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7
Q

What is the molecular weight of BUN?

A

60 Da

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8
Q

What is the molecular weight of creatinine?

A

113 Da

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9
Q

What is the molecular weight of albumin?

A

66,400 Da

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10
Q

What does the rate of solute removal by convection depend on?

A
  • amount of water movement across the membrane (osmotic and hydrostatic pressures)
  • membrane pore size
  • membrane surface area
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11
Q

Does IHD work by diffusion or convection?

A

primarily diffusion

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12
Q

Explain how dwell time and exchange frequency can be altered to improve removal of small or larger molecular sized molecules during PD.

A
  • Small solutes are cleared by diffusion - therefore to maximize small solute removal freuquent dialysate exchange keeps up a high cc gradient
  • Middle to large solutes are removed by convection - therefore longer dwelling times permit better solute equillibration
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13
Q

How is ultrafiltration achieved in IHD and CRRT?

A

by application of a negative transmembrane pressure to the dialyzer

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14
Q

What are the indications for dialysis?

A

AEIOU

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15
Q

Why does IHD and CRRT improve electrocardiogram abnormalities rapidly - even if total body K remains elevated?

A

returning blood with low K levels - returns directly into the right atrium and coronary circulation

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16
Q

Name 3 contraindications and how to adjust for them in IHD and CRRT

A
  • severe hypotension - stabilized with pharmacotherapy and volume restoration
  • severe preexisting coagulopathies - adjust anti-coagulatn prescriptions
  • small patient size - prime the extracorporeal circuit with colloid solutions, blood, or both
17
Q

What are contraindications to PD in small animal patients?

A
  • peritonitis
  • recent abdominal or thoracic surgery
  • hypoalbuminemia
  • severe hypercatabolic states
18
Q

How much heparin should be used to lock the catheter lumens?

A

100-2000 units/mL depending on the patient’s size

19
Q

In what dialysis modalities does the dialysate flow countercurrent to the blood?

A

IHD, CVVHD, CVVHDF

20
Q

Why do CRRT dialyzers have larger pore sizes than IHD ones?

A

because CRRT relies on diffusion and convection - solute removal in IHD is mostly by diffusion

21
Q

What are complications from local citrate anticoagulation?

A

hypocalcemia
arrhythmias
alkalosis
citrate toxicity

22
Q

What are the components of the dialysis prescription?

A
  • type of RRT most appropriate for the patient
  • dialyzer
  • blood flow rate
  • dialysis time
  • dialysate composition
  • flow rate
  • ultrafiltration
  • type of anticoagulation
23
Q

What rate should not be exceeded for volume removal by ultrafiltration?

A

most patients can tolerate < 10 ml/kg/hr

24
Q

What are clinical signs of excessive rate of ultrafiltration?

A
  • hypotension
  • hypothermia
  • nausea
  • cramping
25
Q

List 8 acute complications of IHD and CRRT

A
  • hypotension
  • hemorrhage from systemic heparinization
  • hypocalcemia or alkalemia from citrate anticoagulation
  • dialysis disequilibrium syndrome
  • air embolism
  • dialyzer membrane reaction
  • blood loss through clotting of the extracorporeal circuit
  • catheter occlusion
26
Q

List 8 complications of PD

A
  • catheter occlusion
  • catheter site infection
  • dialysate leakage
  • septic periotnitis
  • fluid retention
  • hypoalbuminemia
  • dyspnea from increased abdominal pessure
  • hyperglycemia