1126
UNIT X
Disorders of Renal Function and Fluids and Electrolytes
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
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
Old
solution
New
solution
Catheter
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.
