Dialysis access loss is most often the result of thrombosis, which is usually a
consequence of venous stenosis. Prospective monitoring of access function (e.g.,
intra-access flow; static or dynamic venous pressures; measurement of access
recirculation; and physical findings, such as swelling of the arm, clotting of the graft,
prolonged bleeding after needle removal, or altered character of the pulse or thrill) is
paramount to the prevention of thrombosis. Fistula patency generally is much greater
than synthetic graft patency, although thrombosis and loss of function may occur in
6 The stenosis may be corrected by percutaneous transluminal angioplasty or, if
necessary, surgical revision of the access site. Successful correction is effective as a
means to prevent thrombosis. Once it occurs, thrombosis is managed by surgical or
mechanical thrombectomy, or use of thrombolytic agents. Alteplase, reteplase, and
tenecteplase appear to be effective for thrombolysis of the vascular access site.
Thrombolytic therapy should be avoided in those patients with an increased risk of
For patients who have tunneled, cuffed hemodialysis catheters for hemodialysis,
the success rates for clearing occlusions was greatest with reteplase at 88% ± 4%,
then alteplase at 81% ± 37%, and tenecteplase at 41% ± 5% with no serious adverse
bleeding events reported for thrombolytic therapy.
47 Catheter-locking regimens of
heparin 3 times per week or recombinant tissue plasminogen activator instead of
heparin at the midweek hemodialysis session was found to reduce the incidence of
catheter malfunction and bacteremia.
Anticoagulants and antiplatelet agents have been evaluated in the prevention of
graft thrombosis. A large, multicenter, randomized, placebo-controlled trial found a
modest effect of extended-release dipyridamole and low-dose aspirin in reducing
HD graft stenosis during the period immediately after graft placement, and improving
49 However, approximately three-fourths of patients had
loss of graft patency at 1 year. Bleeding occurred at a similar rate (12%) in the
treatment and placebo groups. In a cost–utility analysis, aspirin alone was found to
be the most cost effective approach,
50 but no prospective studies have evaluated
normalized ratio of 1.4 to 1.9 or combination therapy with clopidogrel and aspirin in
patients with polytetrafluoroethylene grafts showed no benefit in the prevention of
thrombosis or prolongation of graft survival.
In both studies, patients receiving
active treatment experienced a significantly increased risk of bleeding. A small
single-center, randomized, placebo-controlled clinical trial found that fish oil
; however, this benefit was not borne out in a larger,
multicenter, randomized, controlled trial.
Based on these studies, oral anticoagulants or antiplatelet agents have no defined
role for prophylaxis of graft thrombosis.
CASE 30-1, QUESTION 9: Assessment of the hemodialysis access site is performed at every treatment to
Access infections, usually involving grafts to a greater extent than a native fistula,
are predominantly caused by Staphylococcus aureus or Staphylococcus epidermidis.
Infections with gram-negative organisms as well as Enterococcus species occur with
6 Access infections can lead to bacteremia and sepsis with or
without local signs of infection.
There is no evidence that prophylactic antibiotics are of value; to the contrary,
indiscriminate use of antibiotics could lead to colonization with resistant organisms.
Thus, R.W. should not receive a prophylactic antibiotic. However, if evidence of
infection is present, a prompt response is important. K/DOQI clinical practice
guidelines for vascular access also advocate surgical incision and resection of
infected grafts. Fistula infections are rare and should be treated as subacute bacterial
endocarditis with 6 weeks of antibiotic therapy.
QUESTION 1: D.B. a 56-year-old, 75 kg woman who undergoes high-flux hemodialysis 3 times a week
suspected hemodialysis catheter-related infection?
Antibiotics that permit dosing during or after each dialysis session or antibiotics
whose pharmacokinetics are unaffected by dialysis should be chosen. Treatment
usually is initiated with vancomycin 20 mg/kg loading dose infused during the last 60
to 90 minutes of dialysis, and then 500 mg during the last 30 minutes of each
subsequent dialysis session, depending on the type of dialysis being used.
dialysis results in greater removal of vancomycin than conventional dialysis.
Intradialytic dosing of vancomycin is a convenient mode of drug administration in
patients receiving high-flux dialysis. It avoids the need for additional intravenous
access, longer stays in the hemodialysis unit, or home antibiotic administration.
Cefazolin 20 mg/kg after each dialysis session can be used instead of vancomycin in
dialysis units with a low prevalence of methicillin-resistant staphylococci.
antibiotic therapy should also include coverage for gram-negative bacilli, with
antibiotic selection based on the local antibiogram. For example, gentamicin (or
tobramycin) 1 mg/kg, not to exceed 100 mg infused after each dialysis session can be
used for empiric gram-negative coverage with appropriate serum concentration
CASE 30-2, QUESTION 2: What are your dosing recommendations for intravenous vancomycin and
gentamicin therapy for D.B., and how are the infusions prepared?
D.B. weighs 75 kg, therefore she should receive a vancomycin loading dose of
1,500 mg. Parenteral vancomycin is prepared by reconstituting 10 g of sterile
vancomycin powder with 96 mL of Sterile Water for Injection for a concentration of
100 mg/mL. Fifteen mL of the vancomycin 100 mg/mL solution is further diluted in
500 mL of 5% dextrose or 0.9% sodium chloride injection, and infused during the
last 90 minutes of hemodialysis. For the maintenance dose, vancomycin 500 mg IV
(premixed bag) is infused during the last 30 minutes of each subsequent dialysis
session. D.B. should receive gentamicin 75 mg infused over 30 minutes after
dialysis. Parenteral gentamicin is prepared by diluting the 75 mg dose with 50 to 100
mL of 5% dextrose or 0.9% sodium chloride injection. Vancomycin and gentamicin
doses are adjusted according to serum concentrations measured before the next
hemodialysis session targeting predialysis concentrations of approximately 20
mg/mL for vancomycin and 3 mg/mL for gentamicin. Subsequent antibiotic therapy
should be tailored based on culture and sensitivity results. Antibiotic therapy is
continued until blood cultures are negative, no other source of infection is identified,
and signs and symptoms of infection have resolved (e.g., resolution of fever and
Other long-term complications associated with HD include aluminum toxicity,
amyloidosis, and malnutrition.
Aluminum accumulation in patients undergoing HD was a significant problem before
water sources were adequately treated to remove aluminum. Major complications of
aluminum toxicity include dementia, aluminum bone disease, and anemia. Aluminum
accumulation still occurs in patients treated with aluminum-containing phosphate
binders, although not to the degree associated with water supplies. (See Chapter 28,
Chronic Kidney Disease, for further discussion.)
Amyloidosis is a painful complication of ESRD caused by the deposition of β2
microglobulin–containing amyloid in joints and soft tissues over time. Carpal tunnel
syndrome, manifested as weakness and soreness in the thumb from pressure on the
median nerve, is the most common symptom. Bone cysts also appear along with joint
deposition of amyloid, which can lead to chronic arthralgias, joint immobility, bone
fractures, and substantial disability. The incidence of amyloidosis is approximately
50% after 12 years of dialysis and nearly 100% after 20 years. β2
(molecular weight, 11,800 Da) is normally eliminated by filtration and tubular
catabolism in the intact nephron. Renal failure leads to reduced elimination and
accumulation of this substance even during dialysis. High-flux membranes are more
effective than conventional membranes for the removal of β2
wrists and analgesics for pain relief. Newer generations of dialysis membranes may
hold some promise in reducing the development of amyloidosis.
Chronic kidney disease produces a catabolic state in patients and, along with the
multifactorial complications of ESRD, leads to malnutrition. Serum albumin
concentrations less than 3.0 g/dL are associated with an increased mortality rate
compared with higher values. Inadequate dietary intake and losses of amino acids by
dialysis contribute to protein malnutrition, which in turn can lead to additional
complications, such as impaired wound healing, susceptibility to infection, and
others. (See Chapter 28, Chronic Kidney Disease, for further discussion.)
L-Carnitine supplementation has been used in patients with ESRD to relieve
in both plasma and tissue as free carnitine, the active component, or bound to fatty
acids as acylcarnitine. The primary source of carnitine is dietary intake, primarily
from red meat and dairy products. Carnitine is a small water-soluble molecule that is
freely dialyzed, thus its levels are reduced in hemodialysis. The potential benefits of
correcting this relative carnitine deficiency have been primarily studied in patients
having chronic HD. Although some have suggested that carnitine supplementation
benefits muscle cramps and hypotension during dialysis (as well as minimizing
fatigue, skeletal muscle weakness, cardiomyopathy, and anemia resistant to large
doses of erythropoietic therapy), no evidence supports its routine use in patients
Peritoneal dialysis is performed using several different modalities, including the
most common, CAPD. Development of specialized devices to facilitate the exchange
process and improve patient convenience has led to processes referred to as APD,
including continuous cycling peritoneal dialysis (CCPD) and nocturnal intermittent
dialysis (NIPD). CAPD is the most common method for chronic PD, but the APD
methods have grown in popularity, especially among the pediatric population.
Although lower rates of peritonitis are observed in APD compared with CAPD,
other outcomes measures, such as need for transition to HD and mortality, are similar
Principles and Transport Processes
Continuous ambulatory peritoneal dialysis is performed by the instillation of 2 to 3 L
of sterile dialysate solution into the peritoneal cavity through a surgically placed
resident catheter. The solution dwells within the cavity for 4 to 8 hours, and then it is
drained and replaced with a fresh solution. This process of fill, dwell, and drain is
performed 3 to 4 times during the day, with an overnight dwell by the patient in his or
her normal home or work environment (Fig. 30-2). Conceptually, the process is
similar to HD in that uremic toxins are removed by diffusion down a concentration
gradient across a membrane into the dialysate solution. In this case, the peritoneal
membrane covering the abdominal contents serves as an endogenous dialysis
membrane, and the vasculature embedded in the peritoneum serves as the blood
supply to equilibrate with the dialysate. A primary difference is that because the
dialysate solution is resident, the result is a very slow dialysate flow rate of
approximately 7 mL/minute when 10 L of fluid is drained per day. Solute loss occurs
by diffusion for small molecules, and through convection for larger, middle
Hemodialysis provides constant perfusion of fresh dialysate, thereby maintaining a
large concentration gradient across the dialysis membrane throughout the dialysis
treatment. Unlike hemodialysis, during a typical dwell period for CAPD, urea and
other substances increase in the dialysate relative to unbound plasma concentrations.
For a daytime dwell period of 4 hours, urea achieves nearly equal concentrations
with plasma; therefore, the rate of elimination can become very small. Instillation of
fresh dialysate solution will reestablish the diffusion gradient, leading to an
increased rate of urea removal. For a patient making four exchanges of 2 L each per
day, assuming the urea dialysate concentration equals the plasma concentration, and 2
L are removed by ultrafiltration, the urea clearance would be approximately 7
mL/minute. This is substantially lower than urea clearances achieved with HD;
therefore, CAPD must be performed continually (daily) throughout the week to
achieve adequate urea removal. Clearance depends on blood flow; dialysate flow;
and peritoneal membrane characteristics such as size, permeability, and thickness.
Dialysate flow, the only easily adjusted variable to alter clearance, has been used
effectively in acute PD to achieve relatively high clearances with 30- to 60-minute
dwell periods in a cycling system. CCPD uses this concept of shorter dwell periods
during the sleeping hours with automatic fill, dwell, and drain periods, leaving a
high-dextrose dialysate in the peritoneal cavity throughout the day until the next
cycling session. NIPD is similar, with nightly exchanges, but the peritoneum is left
unfilled, or dry, during the daytime. As a result, urea clearance is lower with NIPD,
but it may be suitable for many patients, and preferable to the volume load in the
peritoneal cavity throughout the day with CCPD.
58 Electrolyte concentrations in the
dialysate solution are near physiologic concentrations to prevent substantial shifts in
serum electrolyte levels (Table 30-1). A potential advantage of PD compared with
HD is the continuous dialysis of larger, middle molecules that have been implicated
as a possible source of toxic effects. These molecules are cleared through convection
and follow water as it is removed through ultrafiltration. Clearance of these
molecules depends less on flow and more on duration of dialysis. The continuous
process of PD, although associated with low clearance values, provides for a more
physiologic condition in patients, rather than the intermittent treatment provided with
Medical-Surgical Nursing. 9th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2000.
Fluid is removed by ultrafiltration through adjustment of the transmembrane pressure
during HD. Because this pressure is not easily adjusted in PD, fluid is removed by
altering the osmotic pressure within the dialysate. This is accomplished by the
addition of dextrose (glucose monohydrate) to the dialysate in varying
concentrations, depending on the degree of fluid removal necessary in the patient.
Concentrations of dextrose in commercially available solutions include 1.5%, 2.5%,
and 4.25%, with net fluid losses during a 4-hour dwell period of 200 mLand 400 mL
for the 1.5% and 2.5% solutions, respectively, and approximately 700 mL for the
4.25% solution after an overnight dwell.
59 As the dwell time persists, the dextrose is
absorbed and is diluted by the movement of fluid from the vascular space, so that
most ultrafiltration occurs early during the dwell period.
Bicarbonate is not compatible with the calcium and magnesium in the dialysate and
can lead to precipitation; therefore, lactate is used in the dialysate. Acid–base
balance is achieved through the absorption of lactate from the dialysate, which
subsequently is metabolized to bicarbonate in vivo.
Delivery of dialysate into the peritoneal cavity is accomplished through an
indwelling catheter inserted through the abdominal wall. The most common design is
the Tenckhoff catheter, made of silicone rubber or polyurethane; it consists of a tube,
straight or curled, with many holes in the distal end for fluid inflow and outflow. The
catheter also has a single or double cuff, which serves to anchor it to the internal and
external attachment sites by promoting fibrous tissue growth; this also serves as a
barrier to bacterial migration. Several modifications to the original catheter have
appeared on the market, mostly in an attempt to overcome problems related to
outflow of dialysate. Maintaining an unobstructed outlet port is essential for
Delivery of dialysate through the catheter is accomplished using Y sets and
double-bag systems. The Y transfer set uses three limbs of tubing, with fresh
dialysate attached to the upper arm of the Y, an empty bag to the lower arm, and the
stem connected to the catheter. Clamping the inflow arm and opening the stem and
outflow arm allow dialysate to drain from the peritoneum into the empty bag.
Reversing the clamps then permits infusion of the fresh dialysate solution after a
small rinse of the line is performed with the fresh solution. Clamping of the catheter
allows removal of the Y transfer set and bags from the patient. The double-bag
system uses pre-attached bags to both limbs and the patient and makes only a single
connection to the catheter. Use of the Y transfer set has reduced episodes of
peritonitis from approximately one for every 9 to 12 patient-months to one for every
60 PD performed with the cycler involves only two
disconnections of the system, compared with four for CAPD.
increased to as high as 4.25% in some situations?
The initial CAPD prescription for most patients consists of three exchanges during
the day with 1.5% dextrose and a fourth, overnight, exchange with 4.25% dextrose.
This would be expected to achieve fluid removal of approximately 1,300 mL, based
on 200 mL from each daytime exchange and 700 mL overnight. Based on the
assessment of the patient’s fluid status, it may be necessary to increase or decrease
the dialysate prescription to achieve fluid balance. Fluid retention is solved by
increasing the dextrose content of the daytime exchanges, beginning with 2.5% in
place of one of the 1.5% solutions. This is expected to result in an additional
removal of 200 mL, and therapy can be further adjusted as necessary. For patients
with excessive fluid removal, it may be possible to decrease the number of
exchanges per day as long as adequate solute removal is present. If four exchanges
are needed, the fluid intake can be liberalized to maintain adequate hydration.
Dextrose is the dextrorotatory form of glucose. Glucose is a small molecule that
rapidly diffuses across the peritoneal membrane. As glucose is absorbed, the osmotic
gradient of the dwell progressively dissipates, reducing ultrafiltration. Toward the
end of the long dwell, more dialysate fluid may be absorbed than ultrafiltered,
resulting in a negative net ultrafiltration volume where the drained volume is less
than the infused volume. A negative net ultrafiltration volume is undesirable. Greater
ultrafiltration and fluid management are predictors of survival.
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