End-Stage Renal Disease



End-Stage Renal Disease


Edward C. Kohaut



DIALYSIS

Deciding when to initiate dialytic therapy in the child with chronic renal failure (CRF) often is difficult. No given level of serum creatinine or creatinine clearance is used as an absolute guide to the need for dialysis. Most children who require dialysis have residual renal functions of less than 10% of normal [a glomerular filtration rate (GFR) of less than 15 mL/minute/1.73M2]. Even within this group, however, the need for dialytic therapy varies. When the child nearing end-stage renal disease (ESRD) no longer can function normally, is lethargic, cannot attend school, and has a poorer quality of life, dialytic therapy is indicated. Poor or absent growth once was an indication for considering dialysis, although growth may not normalize after dialysis is initiated. The use of supraphysiologic doses of recombinant human growth hormone has been shown to normalize growth velocity in children with chronic renal insufficiency (CRI), and, therefore, poor growth no longer is an indication for undergoing dialysis. Indications for infant dialysis may be different and are discussed separately.


Hemodialysis

Hemodialysis is a process by which blood is passed over an artificial semipermeable membrane, allowing the transfer of small molecules from the blood into surrounding dialysate. The rate of transfer of the solute depends on the concentration gradient of the solute, the blood flow over the membrane, and the permeability of the membrane to the solute. Movement of water across the membrane is a function of hydrostatic pressure. Hemodialysis is a relatively efficient process. Blood flows of 100 mL/minute through the dialyzer are possible, even in small patients. At that rate, using modern dialyzers, urea can be cleared at 70 to 80 mL/minute. Thus, during the treatment, the patient will have almost normal renal function. However, to hemodialyze a child for more than 4 to 5 hours, three times a week, is impractical. Aggressive hemodialysis performed for 15 hours a week would be equivalent to only 10% of normal renal function, which is an important point that should be stressed to children with renal failure and their parents. The expectation that once a child is placed on dialysis everything will return to normal is common, but that certainly is not the case.


Vascular Access

Vascular access always has been a particular problem for children undergoing hemodialysis. The blood vessel used must be large enough to permit the blood flow necessary for effective dialysis. In the small, frequently malnourished child with renal failure, femoral vessels often are the only option for vascular access.

Internal jugular catheters are used most often for semipermanent vascular access. This advance, coupled with the development of single-needle dialysis technology, has eliminated the need for using external shunts. Although the possibility of infection still is present, these newer catheters can be removed easily and a new one inserted at another site if infection is suspected. With this method, no loss of vascular integrity occurs. Many programs now use internal jugular catheters to hemodialyze infants. If the patient is thought to require long-term hemodialysis, a subcutaneous access should be created, which usually is accomplished by forming an arteriovenous fistula (the anastomosis of an artery directly to a vein) or by placing a graft (using a foreign material, usually polytetrafluoroethylene, to connect an artery to a vein). Either procedure usually provides long-term access for hemodialysis. Ideally, these procedures should be performed in the upper extremity, usually the forearm, but in smaller children, grafts may have to be placed in the femoral vessels to achieve adequate blood flow.

Some of the major complications of hemodialysis are related to access devices. Subcutaneous access devices can bleed from trauma, although trauma more often causes hematomas around the vessels, which may lead to compression and loss of flow or thrombosis. Infection was a common complication in patients with transcutaneous (Scriber) shunts, and it remains a problem with internal jugular catheter access. Infection seldom develops when subcutaneous access is used, but a strict sterile technique must be used when entering the vessels. These devices also may become infected when a patient becomes bacteremic. Administering prophylactic antibiotics before procedures when bacteremia can be expected (e.g., dental procedures) may be wise. Despite our best efforts, shunts and fistulas thrombose more frequently in children than in adults. This difference presumably is related to the smaller vessels and relatively lower blood flow in children. The pediatrician caring for these children always should examine these access devices and be aware of the frequent complications associated with them.


Procedure

The hemodialysis procedure itself is technically more demanding in children than in adults. The size of the dialyzer and blood tubing should be determined by the patient’s blood volume. Ideally, no more than 10% of the child’s blood volume should be in the extracorporeal circuit. Unfortunately, dialysis equipment and supplies are produced for the larger adult market, and compromises or innovations are required to meet the requirements for small children.

Another major complication of hemodialysis is a result of its efficiency. The child may begin dialysis with an elevated blood urea nitrogen (BUN) level that, with a large, efficient dialyzer, is lowered rapidly, leading to a sharp reduction in extracellular osmolality. If an equally rapid reduction in intracellular osmolality of brain cells does not follow, cerebral edema results; this event is termed dysequilibrium syndrome. This syndrome includes headache, abdominal pain, nausea, vomiting, and muscle cramps, followed by convulsions and coma. The syndrome can be avoided if clearances of urea are restricted to 3 or, at the most, 4 mL/kg/minute. Disequilibrium syndrome occurs more often in pediatric centers because of the availability of dialyzers that are more efficient than needed for the patient’s
size. Nonetheless, pediatric nephrologists have developed the required strategies to avoid the development of this syndrome in even the smallest patients.

Hypotension is a common complication of hemodialysis, and it occurs more frequently in children than in adults. During the hemodialysis procedure, excess fluid is removed from the extracellular fluid space, where it has accumulated since the last dialysis session. If the volume of blood is reduced rapidly and equilibration from the remaining extracellular fluid space is slow, hypovolemia usually results. Normally, an increase in peripheral vascular resistance would compensate, thus maintaining a normal blood pressure. However, vascular tone is deficient during dialysis, and hypotension often results. The lack of response of peripheral vessels to hypovolemia is thought to be caused by the activation of certain vasoactive substances by exposure of blood to the dialysis membrane. Less biologically active dialysis membranes are being studied. The incidence of hypotension can be limited by slow, regular removal of fluid.

Many other complications, including sudden death from many causes, occur with dialysis. The incidence of mechanical complications can be lowered by carefully maintaining equipment and having a vigilant nursing staff. This supervision is especially important when dialyzing small children, whose inquiring minds and busy fingers may not be aware of the dangers surrounding them.

At an experienced pediatric dialysis center, symptom-free dialysis of even the smallest child is possible. This goal is more difficult to achieve if interdialytic intake of salt and water has caused such excessive changes in body composition that vigorous dialysis cannot be avoided. Most centers limit the intake of protein in children treated with hemodialysis to 1 g/kg/day, with variability based on age and the needs of individual patients. The intake of sodium is restricted to less than 1.5 mEq/kg/day, which may be too low for some patients with residual function and salt wasting. High-potassium foods should be avoided, and specific restrictions of potassium sometimes are required. Some children treated with hemodialysis chronically have large intakes of water. They should be encouraged to limit fluids to 1.0 to 1.5 L/m2/day.


Adjunctive Therapy

Many of the therapeutic recommendations discussed in Chapter 322 for children with chronic renal failure (CRF) who do not yet require dialysis also apply to children treated with hemodialysis. As previously discussed, certain dietary restrictions are required in the management of these patients, but more of the chronic complications noted in these children are related to malnutrition than to dietary noncompliance. After undergoing vigorous hemodialysis treatments, children may be anorexic secondary to the disequilibrium syndrome; then, as the concentration of uremic toxins increases before the next dialysis, they may become anorexic from uremia. This anorexic cycle leads to malnutrition, which may perpetuate poor intake. Poor intake of dietary protein can cause a decrease in the BUN level, which may lead a less experienced physician to think that the patient is improving with dialysis, when actually the child is becoming malnourished. Malnutrition causes muscle wasting and a reduction in creatinine, which again can suggest the patient is improved, when actually the patient’s health is failing. Careful and frequent dietary assessments must be made, and taking caloric dietary supplements should be encouraged if energy intake decreases to less than 100% of the recommended dietary allowance (RDA). Protein supplements occasionally are needed in severely anorexic patients. Too little intake of protein is as harmful as too much in children treated with hemodialysis. Increasingly, pediatric dialysis centers are using nasogastric tube or gastrostomy tube feedings in these patients to ensure they have adequate intake.

The intake of dietary phosphate also must be reduced. In the past, the absorption of phosphate was decreased through the use of aluminum hydroxide phosphate binders. This therapy now is contraindicated because patients receiving dialysis may develop aluminum toxicity, manifested by dementia or worsening of renal osteodystrophy. Calcium carbonate, now recommended as a replacement for aluminum hydroxide, acts as both a phosphate binder and a calcium supplement. Vitamin supplements, including 1,25-dihydroxycholecalciferol supplementation, are required by children with ESRD who are treated with hemodialysis. Folate and other water-soluble vitamins are removed by hemodialysis; therefore, the intake of a daily multivitamin supplement with folate is recommended.


Results

The treatment of the larger child with hemodialysis usually is successful. Dialyzing small infants remains difficult, although limited data suggest success. The mortality rate associated with hemodialysis is low in children weighing more than 15 kg who are treated at a pediatric dialysis center. However, this success does not mean that improvement is unnecessary. Children treated with hemodialysis rarely grow normally unless they also are treated with supraphysiologic doses of growth hormone, and they have great difficulty maintaining a reasonably normal lifestyle. Children have not been recommended for home hemodialysis treatment in the past, and hemodialysis performed in a specialized center results in a disrupted school schedule and reduced peer interaction. However, when this therapy is performed in a pediatric unit dedicated to the needs of chronically ill children, patients who for medical or social reasons cannot be treated with home therapy can thrive while being treated with hemodialysis.


Peritoneal Dialysis

The use of peritoneal dialysis as a renal replacement therapy for children has a relatively short history. In the 1950s and 1960s, peritoneal dialysis was used to treat acute renal failure. Treatment of CRF with peritoneal dialysis was unsuccessful until reliable peritoneal access was developed in the late 1960s. At that time, several pediatric programs using intermittent peritoneal dialysis were developed. Because of the parallel development of a more efficient therapy (hemodialysis), intermittent peritoneal dialysis never was used widely to treat CRF in either children or adults.


Continuous Ambulatory Peritoneal Dialysis and Continuous Cycling Peritoneal Dialysis

In 1976, a new form of peritoneal dialysis that later became known as continuous ambulatory peritoneal dialysis (CAPD) was described. CAPD overcomes the relative inefficiency of the peritoneal membrane by exposing it continually to dialysate. In the early 1980s, this form of dialysis was introduced as a form of therapy for children with CRF. In 1981, another form of continuous peritoneal dialysis was introduced and subsequently was named continuous cycling peritoneal dialysis (CCPD). CCPD has been adapted to children with ESRD. The descriptions of CAPD and CCPD have rekindled the interest of many pediatric nephrologists in peritoneal dialysis.

Only gold members can continue reading. Log In or Register to continue

Jul 24, 2016 | Posted by in ORTHOPEDIC | Comments Off on End-Stage Renal Disease
Premium Wordpress Themes by UFO Themes