The Patient Receiving Chronic Renal Replacement with Dialysis

Seth Furgeson

Isaac Teitelbaum

Maintenance dialysis is a treatment for patients with advanced chronic kidney disease (CKD). While dialysis cannot duplicate many functions of a normal kidney, the goals of dialysis are to remove toxins that are normally cleared by the kidney and to maintain euvolemia in the patient. Ideally, chronic dialysis will improve signs and symptoms of uremia and allow patients to return to predialysis functional status. There are two major types of dialysis: hemodialysis (HD; performed in a dialysis unit or at home) and peritoneal dialysis (PD; almost always done at home). There are no well-performed prospective clinical trials comparing the two modalities, so the choice of modality depends on patient preferences, treatment availability, or possible contraindications to either modality.

In the United States, there has been a steady increase in the incidence and prevalence of end-stage renal disease (ESRD) over the last 30 years (Fig. 12-1). Although the utilization of PD is reported to be increasing, at present approximately 93% of patients in the United States use hemodialysis as their initial modality. Worldwide, approximately 89% of patients with ESRD are treated with hemodialysis.

I. INDICATIONS FOR INITIATING DIALYSIS

Starting a patient on dialysis is associated with dramatic changes in the patient’s lifestyle and is frequently associated with medical complications. It is therefore important to thoroughly assess the benefits of initiating dialysis in patients with CKD. In general, life-threatening conditions, such as severe hyperkalemia, severe volume overload, or uremic pericarditis, will mandate prompt initiation of dialysis. Less severe symptoms, such as mild cognitive changes associated with uremia, would warrant dialysis initiation if the patient has appropriate dialysis access [e.g., arteriovenous fistula (AVF) for hemodialysis or catheter for PD]. If the patient does not have access, the benefits of dialysis must be weighed against the risk of a temporary hemodialysis catheter infection.

Ideally, dialysis should be initiated before life-threatening symptoms develop. Possible indications for initiating dialysis are listed in Table 12-1. The most recent guideline recommendations for dialysis initiation come from Kidney Disease: Improving Global Outcomes (K-DIGO). The K-DIGO recommendations suggest initiating dialysis when symptoms or signs of kidney disease develop, blood pressure or volume status is uncontrolled, nutritional status deteriorates, or cognitive dysfunction is present.

Figure 12-1. Incident and prevalent dialysis counts in the United States. (From Atlas of end-stage renal disease in the United States. Am J Kidney Dis 2013; 61(1):e149-e164.) Reprinted with permission.

Table 12-1. Potential Indications for Dialysis Initiation

Volume overload refractory to diuretics

Hyperkalemia

Pleuritis or pericarditis

Peripheral neuropathy

Encephalopathy

Malnutrition

Nausea/vomiting

Uremic bleeding

Metabolic acidosis

Resistant hypertension

Severe hyperphosphatemia

Severe hypocalcemia

Although most patients with a severely depressed glomerular filtration rate (GFR; <10 mL/min) will have some complication of renal failure, there is no specific GFR that mandates dialysis initiation. Possible benefits to starting dialysis earlier (GFR >10 mL/min) include preventing malnutrition and improving volume status. While observational studies have had conflicting results regarding the benefit of starting dialysis early, there has only been one
controlled study to test the timing of dialysis initiation. The Initiating Dialysis Early and Late (IDEAL) study randomized 828 patients to “early start” dialysis (GFR 10 to 15 mL/min) or “late start” dialysis (GFR 5 to 7 mL/min). The primary outcome was death from any cause. In the intention-to-treat analysis, there was no difference in the primary end point between the two groups. After a follow-up of 3.6 years, both groups had a mortality rate over 35%. There was also no difference in secondary outcomes (cardiovascular events, infections) between the groups. In the study, the treating physician was given discretion to initiate dialysis with a GFR above 7 mL/min if dialysis was felt to be warranted. Consequently, most patients in the late start group needed to start dialysis before the GFR reached 7 mL/min. It should also be noted that estimated GFR measurements [by the Modification of Diet in Renal Disease (MDRD) equation] between the two groups were small; 9 mL/min in the early group versus 7.2 mL/min in the late group. While the IDEAL study does not support routinely starting dialysis in patients with a GFR between 10 and 15 mL/min, it also showed that most patients develop a need for dialysis soon after their GFR falls below 10 mL/min.

Education regarding dialysis is an essential part of predialysis care. Therefore, patients should be well informed regarding all possible options (including palliative care). Some patients with significantly reduced life expectancy (severe comorbidity or elderly patients) may not live longer with dialysis and may have a reduction in quality of life with dialysis. For instance, one study found that elderly nursing home patients starting dialysis have a 58% mortality rate at 1 year while only having a 13% chance of maintaining their predialysis functional status. The decision to initiate dialysis in these patients should be a collaborative one between the patient, nephrologist, and family members.

II. HEMODIALYSIS

A. Hemodialysis Procedure.

Hemodialysis is the most common dialysis modality in the United States; it can be performed either at an outpatient dialysis unit or at home. Most patients in the United States receive hemodialysis at a dialysis center. Hemodialysis at dialysis units is usually performed thrice weekly, with each treatment lasting close to 4 hours. Some patients receive longer, nocturnal sessions at dialysis units. Home dialysis patients do shorter treatments more frequently (five or six times weekly, known as short daily dialysis) or nocturnal treatments.

During the hemodialysis procedure, blood is rapidly moved through an extracorporeal circuit. Blood is removed by a needle or through a catheter port and enters the dialysis filter (Fig. 12-2). The dialysis filter contains thousands of hollow tubes with a semipermeable membrane. On the outside of the tube is the dialysate moving in a countercurrent fashion. Solutes in the blood (high concentration) move into the dialysate (low concentration) by diffusion. Blood is then returned via a separate venous needle or port. In a process known as ultrafiltration, fluid is removed by changing hydrostatic pressure across the dialysis membrane.

Conventional hemodialysis has many advantages. With modern filters, the treatment provides for rapid and effective removal of small molecular
weight solutes, over a 4-hour treatment. Also, hemodialysis machines allow for precise control of ultrafiltration, allowing providers to prescribe a specific amount of fluid removal. In dialysis centers, patients can have trained health care professionals perform the treatment and the total treatment time is roughly 12 hours/week. However, in-center hemodialysis does have some limitations as well. Since it is not a continuous treatment, fluid removal is not physiologic and often necessitates removing large volumes of fluid during a 4-hour treatment. Hemodialysis is also not very effective at removing larger molecules or solutes that are protein bound.

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