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2 RENAL > Dialysis > Flashcards

Dialysis Flashcards

1
Q

what are the 3 main concepts in dialysis

A

diffusion
convection
adsorption

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2
Q

what is diffusion

A

movement of solutes from high to low concentration gradient to equalise the concentrations

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3
Q

what does diffusion allow in dialysis

A

removal of toxins and water products
(urea, K and Na)
infusion of bicarbonate

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4
Q

what happens when the blood enters the dialysis machine

A

it looses K Urea and Na through a semi permeable membrane into the dialysis fluid

it gains bicarbonate from the dialysis fluid into the blood

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5
Q

what is in the dialysis fluid (dialysate)

A 
pure H20 
Na 
HCO3 
K
Glucose
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6
Q

how does haemodialysis get rid of water

A

through convection

water (and solutes dissolved in it) are moved across the semipermeable membrane by a PRESSURE gradient

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7
Q

what is ultrafiltration

A

the removal of water from the blood via a pressure gradient

there is negative pressure in the dialysate which pulls the water out

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8
Q

what happens to plasma proteins during haemodialysis

A

they often stick to the membrane surface and get removed by membrane binding

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9
Q

what is the difference between haemodialysis and haemodiafiltration

A

haemodyalisis is mainly diffusive

haemodiafiltration is mainly convective (uses pressure)

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10
Q

what is the effect of the ultra filtrate in haemodiafiltration

A

high convective force produces lots of ultra filtrate

this sets up a solute - drag which pulls out larger ‘middle molecules’

there is diffusion down engineered concentration gradients

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11
Q

what things affects the efficiency of the convective transport in haemodiafiltration

A

water flux
membrane pore size
pressure difference across membrane (hydrostatic)
viscosity of the fluid
size, shape and electrical charge of the molecules

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12
Q

what is the key difference between HD and HDF

A

in HDF replacement fluid is given to the patient to replace the loads of ultra filtrate taken out

High volume HDF has replacement volumes of >20 litres

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13
Q

what are the benefits of HDF

A
  • smoother, less symptomatic treatment
  • enhances recovery time
  • improves survival
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14
Q

what makes dialysis more efficient

A

longer treatment times

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15
Q

what is the minimum HD/HDF prescription

A

4 hours

3 times a week

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16
Q

what happens when you decrease dialysis time by 30 mins

A

it gives a 1% increased risk of death

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17
Q

what restrictions does dialysis put on the patients diet

A
  • Must reduce fluid to 1 L per day
  • Low salt diet (helps reduce thirst and helps fluid balance)
  • Low potassium diet
  • Low phosphate diet
18
Q

what are the options for gaining vascular access for dialysis

A

Tunneled venous catheter
Fistula
Atriovenous graft
HeRO graft

19
Q

what is a tunnelled venous catheter

A

a catheter inserted into a large vein - usually internal jugular

20
Q

what are the pros of a tunnelled venous catheter

A

easy to insert

can be used immediately

21
Q

what are the cons of a tunnelled venous catheter

A
  • high risk of infection
  • can become blocked
  • can cause damage to veins making line insertion difficult in future
22
Q

what infections do you tend to get with tunnelled venous catheters

A

STAPH AUREUS

leads to

  • endocarditis
  • discitis
  • death
23
Q

treatment for tunnelled venous catheter infection

A

antibiotics

-vancomycin +/- gentamicin as empirical until cultures are back

24
Q

what is a arteriovenous fistula

A

the gold standard for vascular access

artery and vein surgically connected to form a thick walled enlarged vessel

25
Q

what are the pros of an arteriovenous fistula

A

good blood flow

less likely to cause infection

26
Q

cons of an arteriovenous fistula

A

required surgery
needs maturation of 6-12 weeks before use
can limit blood flow to distal arm
can thrombose or pentose

27
Q

what is an arteriovenous graft

A

a graft that connects an artery to a vein

28
Q

what is a HeRO graft

A

for complex access

long graft with venous component on one side and arterial much further down

canulation area is in the middle of the graft

29
Q

complications of dialysis

A 
hypotension 
haemorrhage (ruptured fistula) 
loss of vascular access
arrhythmia 
cardiac arrest
30
Q

what is peritoneal dialysis

A

then the solute is removed by diffusion across the peritoneal membrane

water removed by osmosis driven by a high glucose concentration in the dialysate fluid

31
Q

what is continuous ambulatory peritoneal dialysis

A

dialysis that can be done at home

4x2L bag exchanges per day

peritoneal dialysate is drained and a fresh back is installed

takes 20-30 mins per exchange

32
Q

what is automated peritoneal dialysis

A

1 bag of fluid stays in outside the peritoneum all day

an overnight ADP machine controlled fluid drainage in and out for 9-10 hours per night

33
Q

what are the complications of peritoneal dialysis

A

infection
-peritonitis or exit site infection

Peritoneal membrane failure

Hernia

34
Q

what bacterial tend to cause infection in peritoneal dialysis

A

contamination from:
staph
strep
diptheriods

gut commensals:

e.coli
klebseilla

35
Q

how do you manage infection in peritoneal dialysis

A

culture peritoneal dialysate

intraperitoneal antibiotics

may need catheter removal (if entry site)

36
Q

what is peritoneal membrane failure

A

inability of the membrane to remove enough water due to fluid overload

inability to remove enough solutes

needs switch to HD

37
Q

how does PD cause hernias

A

due to the increased intra-abdominal pressure

required hernia repair and smaller fill volumes

38
Q

when should you star dialysis based on bloods

A

resistant hyperkalaemia

eGFR <7

urea >40

Uresponsive metabolic acidosis

39
Q

when should you start dialysis based on symptoms

A

if there is:

nausea 
vomiting 
anorexia 
profound fatigue 
itch 
unresponsive fluid overload
40
Q

how do you start haemodialysis

A

gradual build up

first session lasts 90-120 mins and build up to 4 hours

41
Q

what happens if uraemic. toxin levels are corrected too rapidly

A

disequilibrium syndrome

  • cerebral oedema
  • confusion
  • seizures
  • death (occasionally)
42
Q

when should you stop dialysis

A
  • haemodynamic instability
  • progressive dementia
  • Inability to remain on therapy for full duration due to agitation
  • cardiovascular event
  • terminal cancer

unable to cope at home - increasing frailty

you then need palliative care involvement

2 RENAL (20 decks)

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