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Peritoneal dialysis uses the peritoneum as a natural permeable membrane through which water and solutes can equilibrate. Peritoneal dialysis is less physiologically stressful than hemodialysis, does not require vascular access, can be performed at home, and allows patients much greater flexibility. However, it requires much more patient involvement. Of the total estimated resting splanchnic blood flow of 1200 mL/min, only about 70 mL/min comes into contact with the peritoneum, so solute equilibration occurs much more slowly than in hemodialysis. But because solute and water clearance is a function of contact time and peritoneal dialysis is performed nearly continuously, efficacy in terms of solute removal is equivalent to that obtained with hemodialysis.
In general, dialysate is instilled through a catheter into the peritoneal space, is left to dwell, and then drained. In the double-bag technique, the patient drains the fluid instilled in the abdomen in one bag and then infuses fluid from the other bag into the peritoneal cavity.
Continuous
ambulatory peritoneal dialysis (CAPD) is most commonly used because of ease of performance and lack of need for a machine to perform the exchanges. A typical adult infuses 2 to 3 L (children, 30 to 40 mL/kg) of dialysate 4 to 5 times/day; dialysate is allowed to remain for 4 h during the day and 8 to 12 h at night. The solution is manually drained. Flushing the infusion set before filling reduces peritonitis rates.
Continuous
cyclic peritoneal dialysis (CCPD) uses a long (12 to 15 h) daytime dwell and 3 to 6 nighttime exchanges performed with an automated cycler. Patients have more freedom during the day, but cumbersome equipment inhibits nighttime mobility. Some patients require a combination of CAPD and CCPD to achieve adequate clearances.
Intermittent
peritoneal dialysis (IPD) may be done using manual or automated techniques or both. Manual IPD is simplest, achieves the highest solute clearance, and is useful chiefly in the treatment of acute renal failure. In adults, 2 to 3 L (in children, 30 to 40 mL/kg) of dialysate, warmed to 37° C, is infused over 10 to 15 min, allowed to dwell in the peritoneal cavity for 30 to 40 min, and drained in about 10 to 15 min. Multiple exchanges may be needed over 12 to 48 h. Automated cycler IPD uses an automated system that cycles the infusion and removal of dialysate. The cycler is generally set up at bedtime, and treatment occurs while the patient sleeps.
Access:
Peritoneal dialysis requires intraperitoneal access, usually via a soft silicone rubber or porous polyurethane catheter. The catheter may be implanted in the operating room under direct visualization or at the bedside by blind insertion of a trocar or under visualization through a peritoneoscope. Most catheters incorporate a polyester fabric cuff that allows tissue ingrowth from the skin or preperitoneal fascia, ideally resulting in a watertight, bacteria-impervious seal and preventing introduction of organisms along the catheter tract. Allowing 10 to 14 days between catheter implantation and use improves healing and reduces the frequency of early pericatheter leakage of dialysate. Double-cuff catheters are better than single-cuff catheters. Also, a caudally directed exit site (the opening of the tunnel through which the catheter enters the peritoneal cavity) lowers the incidence of exit site infections (eg, by collecting less water while showering).
Once access is established, the patient undergoes a peritoneal equilibration test, in which dialysate drained after a 4-h dwell time is analyzed and compared with serum to determine solute clearance rates. This procedure helps determine the patient's peritoneal transport characteristics, the dose of dialysis required, and the most appropriate technique. In general, adequacy is defined as a weekly KT/V ≥ 1.7 (where K is the urea clearance in mL/min, T is dialysis time in minutes, and V is volume of distribution of urea [total body water] in mL).
Complications:
(See also Table 2: Renal Replacement Therapy: Complications of Renal Replacement Therapy ). The most important and common are peritonitis and catheter exit site infection. Symptoms and signs of peritonitis include abdominal pain, cloudy peritoneal fluid, fever, nausea, and tenderness to palpation. Diagnosis is made by clinical criteria and testing. A sample of peritoneal fluid is obtained for Gram stain, culture, and WBC count with differential. Gram stain is often unrevealing, but cultures are positive in > 90%. About 90% also have > 100 WBCs/μL, usually neutrophils (lymphocytes with fungal peritonitis). Negative cultures and WBC counts < 100/μL do not exclude peritonitis, so treatment is indicated if peritonitis is suspected based on clinical or laboratory criteria and should begin immediately, before culture results are available. Peritoneal fluid studies may be falsely negative due to prior antibiotic use, infection limited to the catheter exit site or tunnel, or sampling of too little fluid. Empiric treatment should be adapted to microbial resistance patterns of a given facility, but typical recommendations are for initial treatment with drugs active against gram-positive organisms, eg, either vancomycin or a 1st-generation cephalosporin, plus drugs active against gram-negative organisms, such as a 3rd-generation cephalosporin (eg, ceftazidime ) or an aminoglycoside (eg, gentamicin ). Drugs are adjusted based on the result of peritoneal dialysis fluid culture. Antibiotic therapy is usually given IV or IP (intraperitoneally) for peritonitis and orally for exit site infections. Patients with peritonitis are admitted to the hospital if IV treatment is necessary or if hemodynamic instability or other significant complications arise.
Catheter tunnel exit site infection manifests as tenderness over the tunnel or at the exit site along with crusting, erythema, or drainage. Diagnosis is clinical. Treatment of infection without drainage is topical antiseptics (eg, povidone iodine, chlorhexidine); if ineffective, a 1st-generation cephalosporin or a penicillinase-resistant penicillin is used empirically, with culture results guiding subsequent therapy.
Prognosis:
Most cases of peritonitis respond to prompt antibiotic therapy, but those caused by staphylococci or fungi also require dialysis catheter removal. Overall, 5-yr survival rate in peritoneal dialysis patients is similar to that in hemodialysis patients (about 36%).
Last full review/revision December 2007 by James I. McMillan, MD
Content last modified December 2007
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