Porth's Pathophysiology, 9e

1126

UNIT X Disorders of Renal Function and Fluids and Electrolytes

­performed in an automated manner, usually at night, with the person connected to an automatic cycler, which then performs four or five cycles, while the person sleeps. In the morning, the person, with the last exchange remaining in the abdomen, is disconnected from the cycler and goes about his or her usual activities. In NIPD, the person is given approximately 10 hours of automatic cycling each night, with the abdomen left dry during the day. Potential problems with peritoneal dialysis include infec- tion, catheter malfunction, dehydration caused by excessive fluid removal, hyperglycemia, and hernia. The most serious complication is infection, which can occur at the catheter exit site, in the subcutaneous tunnel, or in the peritoneal cavity ( i.e., peritonitis). Transplantation.  Greatly improved success rates have made kidney transplantation the treatment of choice for many patients with CKD. The availability of donor organs continues to limit the number of transplantations performed each year. Donor organs are obtained from cadavers and living related donors ( e.g., parent, sibling). Transplants from living unre- lated donors ( e.g., spouse) have been used in cases of suitable ABO blood type and tissue compatibility. The success of transplantation depends on multiple vari- ables such as the general health of the person, the degree of histocompatibility with the donor, the degree of end-organ disease the person may have, and how well the immuno- logical response is managed. Maintenance immunosuppres- sive therapy typically consists of prednisone, azathioprine, and cyclosporine (or tacrolimus). IL-2, a cytokine, plays an essential role in T- and B-cell activation. Cyclosporine and tacrolimus, calcineurin inhibitors, inhibit IL-2 synthesis. IL-2 receptor antagonists such as basiliximab and daclizumab are more frequently being used. 39 Monoclonal antibodies such as alemtuzumab is starting to be used. 39 OKT-3 (directed against the CD3 T-cell receptor), and ATGAM, which is a polyclonal antibody, are used rarely such as when the person is expe- riencing steroid resistance and allograft rejection. The Janus kinase (JAK) 3 inhibitors are a new classification of immu- nosuppressive therapy that are also starting to be in use and have effective results. 39 Two examples of this drug category include AEB-071, which inhibits protein kinase, and LEA29Y or Belatacept, which have both improved transplant patients’ rate of rejection. However, most of these immunosuppres- sive drugs have serious side effects such as cardiovascular ­problems, metabolic dysfunction, and cancer. 39 Rejection, which is categorized as acute and chronic, can occur at any time. Acute rejection most commonly occurs dur- ing the first several months after transplantation and involves a cellular response with the proliferation of T lymphocytes. Chronic rejection can occur months to years after transplan- tation. Because chronic rejection is caused by both cellular and humoral immunity, it does not respond well to increased immunosuppressive therapy. Maintenance immunosuppressive therapy and increased use of immunosuppression to treat rejection predispose

New solution

Catheter

Old solution

Peritoneal cavity

FIGURE 42.6  •  Peritoneal dialysis. A semipermeable membrane, richly supplied with small blood vessels, lines the peritoneal cavity. With dialysate dwelling in the peritoneal cavity, waste products diffuse from the network of blood vessels into the dialysate.

tissue and exits on the side of the abdomen (Fig. 42.6). The dialysis process involves instilling a sterile dialyzing solution (usually 1 to 3 L) through the catheter over a period of approx- imately 10 minutes. The solution then is allowed to remain, or dwell, in the peritoneal cavity for a prescribed amount of time, during which the metabolic end products and extracellular fluid diffuse into the dialysis solution. At the end of the dwell time, the dialysis fluid is drained out of the peritoneal cavity by gravity into a sterile bag. Glucose in the dialysis solution accounts for water removal. Commercial dialysis solution is available in 1.5%, 2.5%, and 4.25% dextrose concentrations. Solutions with higher dextrose levels increase osmosis, caus- ing more fluid to be removed. As with hemodialysis, Kt / V val- ues are used to evaluate adequacy of peritoneal dialysis. Peritoneal dialysis can be performed at home or in a dialysis center and can be carried out by continuous ambula- tory peritoneal dialysis (CAPD), continuous cyclic peritoneal dialysis (CCPD), or nocturnal intermittent peritoneal dialysis (NIPD)—all with variations in the number of exchanges and dwell times. 2 Individual preference, manual ability, lifestyle, knowledge of the procedure, and physiologic response to treat- ment are used to determine the type of dialysis that is used. The most common method is CAPD, a self-care procedure in which the person manages the dialysis procedure at home. CAPD involves instilling the dialysate into the peritoneal cav- ity and rolling up the bag and tubing and securing them under clothing during the dwell. After the dwell time is completed (usually 4 to 6 hours during the day), the bag is unrolled and lowered, allowing the waste-containing dialysis solution to drain from the peritoneal cavity into the bag. Each exchange, which involves draining the solution and infusing a new solu- tion, requires approximately 30 to 45 minutes. Four exchanges usually are performed each day. In CCPD, exchanges are