Download Peritoneal dialysis

Peritoneal dialysis
Dr Ejaz Ahmed
Barrier to transport
• Mesothelium
– Does not hinder transport
• Interstitium
– Hinders transport to some extent
• Endothelium
– Main barrier
Peritoneal transport principles
• Diffusion
– Depends on concentration gradient
• Convection(filtration)
– Depends on hydrostatic pressure and osmotic
pressure
Diffusion
• Dr=p×a×c
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•
•
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Dr=diffusion rate
P=solute permeability
A=area of membrane
C=concentration gradient
Ultrafiltration
• UFr=p×a×(Hp+Op)
– UFr=ultrafiltration rate
– P=permeability of water
– A=surface area
– Hp=hydrostatic pressure gradient
– Op=osmotic pressure gradient
Material of catheter
• Silicone rubber
– Milky white material
• Polyurethane
– Clear material
Catheter design
• Three portions
– Intraperitoneal
– Extraperitoneal
– External
• Cuffs
– Dacron material
– One or two
Placement of catheter
• Open surgical placement
• Peritoneoscopic placement
• Blind placement
Proper location of catheter
• Intraperitoneal portion
– Directed towards pelvis
• Cuff
– Deep: within medial or lateral border of rectus
sheath
– Superficial: about 2 cms from skin exit
Composition of peritoneal dialysis fluid
Sodium(mmol/L)
132-134
Potasium(mmol/L)
0-2
Calcium(mmol/L)
1.0-1.75
Magnesium(mmol/L)
0.25-0.75
Chloride(mmol/L)
95-106
Lactate(mmol/L)
35-40
Bicarbonate(mmol/L)
34
Bicarbonate/lactate
25/15
Glucose(g/dl)
1.36-4.25
lcodextrin(g/dl)
7.5
Amino acids(g/dl)
1.1
Osmotic agents
• Low molecular weight
– Glucose- 1.5%,2.5%,4.25%
– Glycerol
– Amino acids
• High molecular weight
– Albumin
– Glucose polymer
– peptides
Clearance
• Theoretical concept
• “Volume of plasma from which all the substance has been
removed and excreted into the urine per unit time”
Amount excreted = Urine volume x urine concentration
Excretion rate = Urine volume x urine concentration
Time
Clearance Example
Clearance of a substance x
• Excretion rate = 100 mg/ml x 1 ml = 100 mg/min
1 minute
• Concentration of substance x in plasma = 1 mg/ml
• Amount of plasma cleared per minute =
100 mg/min = 100 ml
1 mg/ml
Clearance = U x V
TxP
Principles of Clearance
Principles of Clearance
Clearance
of Inulin
Substance
(L/wk)
Urea
kidney
CAPD
750
HD
HD
standard High flux
130
130
Vit B12
1200
30
80
40
Inulin
1200
10
40
20
β2 Microg
1000
0
300
250
70
Small solute clearance
• Urea clearance (Kt/V)
– Normalised to total body water
• Creatinine clearance (CrCl)
– Normalised to body surface area
Total clearance
• Sum of
– Residual renal clearance
– Peritoneal dialysis clearance
Method of calculating dialysate
clearance of urea
• 24 hr collection of peritoneal dialysate
effluent
• Measure urea concentration in dialysate
• Estimate total urea content
– Urea concentration × volume of effluent
• Calculate clearance
– Kt =
Urea content in dialysate
Serum urea level
Method of calculating renal
clearance of urea
• Collect 24 hr urine
• Measure urea concentration in urine
• Estimate total urea content
– Urea concentration × urine volume
• Calculate renal clearence of urea
– Kt =
Urea content in urine
serum urea level
Total and normalised clearance
• Total clearance
– Dialysate clearance + renal clearance
• Normalised clearance (Kt/V)
– Dialysate clearance + renal clearance
Total body water
Calculate clearance
• A 50 yr old man weighing 66 Kg has no
urine output. He is on CAPD with four 2.5
L exchanges daily. His blood urea is 160
mg/dl and dialysate urea concentration of
24 hr collection is 140 mg/dl.calculate his
daily clearance
Complications of peritoneal dialysis
• Mechanical complication of catheter
– Catheter obstruction/inadequate drain
– Perforation and laceration of organs
– Peritoneal catheter leaks
• Infectious complications
– Exit site infection
– Peritonitis
Clinical presentation of peritonitis
(percentages)
Cloudy fluid
98-100
Abdominal pain
67-97
Abdominal tenderness
62-79
Fever
34-36
Chills
18-23
Nausea
30-35
Vomiting
25-30
Diarrhoea
7-15
Route of entry for peritonitis
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•
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Touch contamination
Catheter related
Enteric
Haematogenous
Gynaecological
Organisms causing peritonitis
• Gram-positive
– Staphylococcus epidermidis
– Staphylococcus aureus
– Streptococcus
– Enterococcus
• Gram-negative
• Fungal
• Mycobacterial
Differential diagnosis of cloudy effluent
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Infectious peritonitis
Eosinophilic peritonitis
Sclerosing peritonitis
Chylous ascites
Malignant ascites
Pancreatitis
Chemical peritonitis
Treatment of peritonitis
• Antibiotics
– Intraperitoneal route
• Continuous
• Intermitent
– Intravenous route
• Pain control
Outcome and sequelae
•
•
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•
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Resolution-60-90%
Abscess formation-1%
Transfer to hemodialysis(technique failure)-30%
Sclerosing peritonitis-1-2%
Death-1-6%
Types of peritoneal dialysis
• Manual
– CAPD-Continuous ambulatory peritoneal
dialysis
• Automated
– CCPD-Continuous cyclic peritoneal dialysis
– NIPD-Nocturnal intermittent peritoneal dialysis
– TDP-Tidal peritoneal dialysis
TYPE
Day
exchange
Night
exchange
Volume of
exchange
CAPD
2-3
1-2
1-3
CCPD
1
3-4
1-3
NIPD
0
3-5
2-3
TDP
0
20
1-1.5
Peritoneal transport assessment
• PET test
– Concentration of creatinine in dialysis solution
at four hrs
– Concentration of creatinine in plasma at same
time
– Ratio of dialysate creatinine to plasma
creatinine is calculated
– Subject is classified into different transporter
group
Improving outcomes: equal or better survival in first 2–3 years
Better preservation of RRF versus HD
Higher haemoglobin levels; less erythropoietin use
Preservation of vascular access for HD
Provides continuous UF for improved blood pressure and
volume control
Better outcomes post-transplant
Less risk of acquiring blood borne virus (hepatitis C)
Patient benefits including more flexible holidays and travel and
higher employment rates; better quality of life than
maintenance HD
Ability to expand patient numbers in a dialysis centre with
limited need for resources and major capital investments
Lower staff to patient ratio than maintenance HD
Less costly than maintenance HD