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Nephrology > Renal replacement therapy > Flashcards

Renal replacement therapy Flashcards

1
Q

What are the indications for RRT?

A

-uremia
-volume overload
-metabolic acidosis
-hyperkalemia

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2
Q

What is the mortality difference between IHD and CRRT?

A

none

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3
Q

What is ultrafiltration?

A

movement of fluid across semipermeable membrane secondary to pressure gradient

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4
Q

What is diffusion?

A

solute transport across a semipermeable membrane
-movement is concentration based
-best for small molecule clearance

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5
Q

What is convection?

A

solute transport across a semipermeable membrane
-solute moves with solvent d/t transmembrane pressures
-removes broad spectrum of solute sizes

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6
Q

Does CVVH use diffusion or convection to clear solutes?

A

convection

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7
Q

What differentiates hemodialysis from hemofiltration?

A

-HD = removes solutes by diffusion; solutes diffuse down a concentration gradient
-HF = removes solutes by convection; solutes and water are pulled across a semipermeable membrane via pressure difference

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8
Q

What size molecules is hemodialysis good for?

A

smaller molecules 10-100 kDa (i.e. creatinine and urea)

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9
Q

What size molecules is hemofiltration good for?

A

middle sized molecules 10 - 10,000kDa

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10
Q

What are the components of a CRRT prescription?

A

-modality
-blood flow rate
-replacement fluid rate
-type of replacement fluid
-how much UF to remove

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11
Q

How do you calculate CRRT dose?

A

dose = replacement fluid rate / patient’s weight

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12
Q

What is the recommend CRRT dose?

A

20 - 25 mL/kg/hr
-however surgical pts w/ frequent interruptions in the system it is good to target a dose of 25-30mL/kg/hr to make up for breaks

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13
Q

What CRRT mode can be used to help pts w/ sepsis and AKI and why?

A

CVVH
-HF good for clearing medium sized molecules; inflammatory cytokines fit this category

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14
Q

What factors increase risk of dialysis related hypotension?

A

-advanced age
-female
-hypotension prior to dialysis
-hypoalbuminemia
-higher BMI

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15
Q

How do you calculate filtration fraction?

A

FF = replacement fluid + UF / blood flow rate + replacement fluid rate
-to minimize blood clot target a FF of < 25%

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16
Q

What is the average increase in circuit life associated w/ use of citrate as anticoagulation for CRRT?

A

30hrs

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17
Q

How is citrate metabolize? Into what

A

-hepatically metabolized
-into Ca and bicarb
-might need replacement fluids w/ lower bicarb to avoid metabolic alkalosis

18
Q

How does toxicity d/t citrate manifest in pts w/ liver failure?

A

low serum ionized Ca

19
Q

What is the total calcium : ionized calcium ratio indicative of citrate toxicity?

A

> 2.5

20
Q

What is the recommended maximum prescription for net UF while on CRRT?

A

no to exceed 1.5 - 2mL/kg

21
Q

What is the minimum blood flow rate needed to maximize clearance for prefilter replacement fluid rates of up to 1500mL/hr and dialysis fluid rates of up to 3600mL/hr?

A

150mL/min

22
Q

Does iHD or CRRT tend to correct hyponatremia more quickly?

A

iHD

23
Q

What makes up the total UF rate?

A

UF rate = (preblood pump/prefilter replacement fluid rate) + (postfilter replacement fluid rate)

24
Q

What are the KDIGO guidelines for catheter sites to be used for CRRT?

A
  1. RIJ
  2. femoral
  3. LIJ
    try not to use subclavian
25
Q

What are the KDIGO guidelines for length of catheters to use for CRRT?

A

-12 - 15cm for RIJ
-19 - 24cm for femoral
-15 - 20cm for LIJ
recommend 11.5 - 14F catheters

26
Q

What does the filtration fraction represent?

A

the fraction of plasma that is removed from the blood during hemofiltration

27
Q

Which type of CRRT modes (convection versus diffusion) have higher filtration fractions?

A

convection

28
Q

For convection modes what can be done to reduce filtration fraction and prolong hemofilter survival?

A

-using higher blood flow rates
-predilution replacement fluids

29
Q

What value of iCa indicates optimal regional AC when using citrate?

A

iCa < 0.35mmol/L

30
Q

What did a meta-analysis show were the big differences between using citrate and heparin?

A

when using citrate see:
-less risk of bleeding
-prolonged filter life span
-more episodes of hypocalcemia
-no difference in mortality

31
Q

What lab abnormalities indicate citrate excess?

A

-metabolic alkalosis
-tot Ca/iCa < 2.5

32
Q

How do you treat citrate excess?

A

-decrease blood flow rate
-increase dialysate flow rate or decrease buffer concentration in other CRRT solutions

33
Q

What lab abnormalities indicate citrate toxicity?

A

-anion gap metabolic acidosis
-tot Ca/iCa > 2.5
-escalating Ca infusion rate

34
Q

How do you manage citrate toxicity?

A

-decrease blood flow rate
-increase dilaysate rate
-discontinue citrate
(can try one or two, don’t necessarily need to do all 3)

35
Q

What lab abnormalities are seen in citrate deficit?

A

-metabolic acidosis
-tot Ca/iCa < 2.5

36
Q

What blood flow rates should be used to limit the effects of citrate?

A

100 - 180mL/min

37
Q

What 3 medication characteristics help predict if it will be removed by CRRT?

A

-volume of distribution (Vd)
-molecular weight (MW)
-protein binding

38
Q

What Vd, protein binding, and MW predict that a drug will be removed by convection?

A

-low Vd < 2L/kg
-low protein binding < 80%
-small MW < 20,000Da (or at least smaller than the size of the filter pores)

39
Q

What type of relationship does convective clearance have to replacement fluid?

A

positive linear relationship

40
Q

What is the creatinine clearance of a UF of 2.5L/hr?

A

40mL/min
(creat clearance = 2500mL/60min)

41
Q

How much should the creatinine clearance increase per 0.5L/hr increase in convection?

A

10mL/min

Nephrology (3 decks)

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