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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)
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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 • 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
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 T x P
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
Route of entry for peritonitis • 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 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 • 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