With the continuous flow tech- nique,* dialysis ... several hours until the fluid be- ..... Orlando. FL. 1985 Mar 16-17. Semln Oneal. 1985:12(3 Suppl4):1·123. 17.
Peritoneal dialysis Current technology and techniques
Zbylut J. Twardowski, MD, PhD
Preview Peritoneal dialysis is the most common form of home dialysis. Although used predominantly for the treatment of renal failure, other clinical uses have become practical because of recent dramatic improvements in methods. In this article, Dr Twardowski discusses regimens and techniques for peritoneal dialysis, as well as promising new developments. In the 1920s and 1930s, two techniques of peritoneal dialysis--COntinuous flow and intermittent flow-were developed. 1 With the continuous flow technique,* dialysis solution is infused through a trocar or tubing into the upper alxlomen and drained simultaneously through another trocar or tubing introduced into the lower abdomen. Fluid retained in the peritoneal cavity during dialysis (sump volume) is drained at the end of the session. With the intermittent flow techilique, a single trocar or rubber catheter is used. Fluid is
infused into the peritoneal cavity, equilibrated for a short time, and drained as completely as possible through the same trocar or catheter. The flow is interrupted after outflow and before the next
inflow.
After their introduction, both techniques continued to evolve, and 101 cases of peritoneal dialysis were reported in the literature between 1923 and 1948. 3 In themte1950s,phannaceuticru companies started to produce fluid in 1-liter bottles and developed a closed system of fluid drainage. 4 A nylon catheter with multiple sm&l perlorations at the distal end was designed spectficruly for peritoneal dialysis. 4 •5 *Note the difference between continuous In the early 1960s, a regimen* and lntennittent peritoneal dialysis techniques and regimens. The term of intermittent peritoneal dialysis ''technique" refers to the method of for chronic renal failure was dialysis solution flow dwing a single introduced. It gained popularity d1alysts session. The term "regimen" refers to the overall systematic plan of after two crucial improvements dialysis. Intermittent means that cUalysts by Tenckhoff: (1) a safe and sessions are performed several times a permanent access for chronic week, with periods without dialysiS Intervening; conttnuous means that the peritoneal dialysis6 and (2) an dialysis solution Is present 1n the peritone- automated sterilization and delival cavity continuously. See Twardowsld2 ery system that allowed therapy for full discussion of peritoneal dialysis athome. 7 terminology.
VOL 85/NO 5/APRIL 1989/POSTGRAOUATE MEDICINE • PERITONEAL DIALYSIS
The Tenckhoff catheter -is still the one most widely used for peritoneal dialysis. Intermittent peritoneal dialysis, however, could not compete successfully with hemodialysis because of low efficiency, and its use for chronic renal failure began to wane in the early 1970s. Hemodialysis made rapid progress as new, efficient dialyzers were developed and arteriovenous fistulas were devised for blood access. In 1978, Popovich and associates8 reported on a new method--continuous ambulatory peritoneru dialysis. The concept and practice of this method contradict the objectives of intermittent peritoneru diruysis. Instead of sophisticated automation to increase efficiency by delivering large amounts of fluid intraperttoneally, continuous ambulatory peritoneal dialysis uses a manual method of fluid delivery and drainage and overcomes the inefficiency of intermittent dialysis by a continuous regtmen. With continuous ambulatory peritoneal dialysis, dialysis is performed around the clock every day while the patient is ambulatory or asleep. Instead of being confined to bed three or four times weekly to have large amounts of fluid delivered into and drained from the peritoneal cavity, as is required with intermittent peritoneal diruysis, the continued
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With CAPD, dialysis is performed around the clock every day while the patient is ambulatory or asleep.
Figure 1. Commonly used catheters for chronic peritoneal dialysis. All catheters are made of silicone rubber tubing and provided with Dacron cuffs. a. Double-cuff Tenckhoff cathe· ter with straight intraperitoneal segment. b. Toron to Western Hospital catheter with flange and bead at inner cuff to pre· veni leaks of dialysate and intraperitoneal disks to prevent catheter-tip migration. c. Swan· neck catheters With various intraperitoneal designs.
patient infuses dialysis solution into the peritoneal cavity and returns to daily activities for several hours until the fluid becomes equilibrated with plasma; the fluid is then drained and replaced with fresh solution. Types of peritoneal catheters9 Two types of peritoneal catheters are currently in use: (1) a variety of stylet catheters for treatment of acute conditions and (2) permanent catheters for chronic conditions. STYLET CATHETER&--These catheters consist of semirigid plastic tubing with multiple holes at the intraperitoneal end, a connector to the peritoneal delivery system, and a metal stylet protruding from the end that provides a sharp cutting tip for penetration of the abdominal wall. After the wall is penetrated, the stylet is removed and the
catheter tip is positioned in the true pelvis. The catheter is removed when a dialysis session is completed. The use of stylet catheters is becoming less frequent. even for treatment of acute conditions, because several dialysis sessions are usually necessary. A permanent catheter eliminates the need for repeated punctures of the abdominal wall. PERMANENTCATHETER&--
Most of the commonly used permanent catheters (figure 1) are made of silicone rubber tubing and provided \vith Dacron cuffs. Growth of fibrous tissue into the cuffs seals the catheter and prevents pericatheter fluid leaks and bacterial penetration into the peritoneal cavity. The original Tenckhoff, swanneck Tenckhoff, and swan-neck coil catheters may be Inserted at bedside and are used for acute and chronic diseases. An attri-
bute of swan-neck catheters is a permanent bend between cuffs that enables catheter Implantation in an unstressed condition with intraperitoneal and external segments directed downward. This decreases the incidence of the most frequent catheter complications: infection of exit and tunnel, poor drainage due to catheter-tip migration out of the pelvis, and external cuff extrusion. Other permanent catheters require surgical implantation and are more suitable for chronic diseases. Current regimens and techniques5 ·1o-12 Intermittent peritoneal dialysis and continuous ambulatory peritoneal dialysis are the regimens in current use. Intermittent dialysis sessions last 10 to 24 hours several times a week. With continuous ambulatory dialysis. the dialysate is present in the peritoneal cavity continuously seven days a week for as long as the patient requires dialysis. Only short, insignificant interruptions occur between fluid exchanges. The continuous flow technique, described earlier. is not currently employed. Rather, the intermittent flow technique is used. It may be performed either manually or with the assistance of a dialysis machine (figure 2). With the latter. a cycler precontinued
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PERITONEAL DIALYSIS • VOL 85/NO 5/ APRIL 1989/POSTGRADUATE MEDICINE
CAPD is a manual method of dialysis with a cycle time of four to ten hours.
a Figure 2. Systems for automated peritoneal dialysis. a. Peritoneal dialysis cycler. Before dialysis, containers of premixed solutions are hung and connected with peritoneal dialysis catheter through system of tubing with occlusors. A device heats and delivers specified volumes of solutions into peritoneal cavity and drains
dialysate at.preset time intervals and/or volumes. b. Reverse osmosis-proportioning system. Dialysis solution is produced from concentrate and treated water. System performs all functions of cycler. P. pump; X, occlusors. ·
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Figure 3. Y-set system of manual fluid exchange for continuous ambulatory peritoneal dialysis. a. Preparation of set before exchange. b. Operation of system during exchange. Step 1: After attaching tubing to catheter and spiking fresh solution bag, small amount of fluid is flushed from fresh solution bag to drainage· VOL 85/NO 5/APRIL 1989/POSTGRAOUATE MEDICINE • PI!RITONI!AL DIALYSIS
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bag to deaerate set. Step 2: Dialysate is drained from peritoneal cavity to drainage bag. Step 3: Fresh solution is infused into peritoneal cavity. With this system, flow of solution to drainage bag immediately after connection washes out any contamination.
163
Worldwide, more than 35,000 patients with chronic renal failure are on forms of chronic peritoneal dialysis.
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Based on data published and distributed by Health care Financing Administration, Department of Health and Human Services, Washington, DC.
warms the solution, instills set volumes at predetermined times, and allots time for dwell and drainage. An alarm is activated if inflow or outflow is disrupted. The usual cycle time from the beginning of infusion to the end of drainage is 30 to 60 minutes, and the usual volume of solution used per cycle is 2liters. Fully automated machines that prepare dialysis solutions from concentrate and pretreated water are no longer manufactured because of low demand. For continuous ambulatory peritoneal dialysis, only a manual method is used by the patient or helper. In adults, 211ters of fluid are usually instilled into the peritoneal cavity for each exchange. The cycle time is gener-
ally four to ten hours. Most patients perform three exchanges during the daytime and one exchange overnight. Two connecting systems of fluid delivery from the dialysis solution bag into the peritoneal cavity are used: (1) a single-pronged system introduced in 1978 and (2) a recently introduced Y-set system. With the first system, simple single-pronged connecting tubing is attached to the catheter. The other end of the tubing is attached to a bag of dialySis solution by a spike or other connector, and the fluid is instilled into the peritoneal cavity. The tubing is then clamped, and the bag and fluid-filled connecting tubing are folded and carried under the clothing.
After dwell time, the bag and tubing are unfolded and lowered, the tubing is unclamped, and the fluid is drained into the bag as completely as possible. Using sterile precautions, the connecting tubing is disengaged from the full bag and reattached to a fresh bag of dialysis solution. With this method, dialysis solution is infused into the peritoneal cavity after the connection is made (the infuse :first, drain later principle). Hence, if the system becomes contaminated during a connection procedure, the contaminant is introduced directly into the peritoneal cavity. With theY-set system (figure 3), the extension tubing has two branches; one is attached to a drainage bag, and the other has continued
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PERITONEAL DIALYSIS • VOL 85/1'10 5/APRIL 1989/POSTGRAOUATE MEDICINE
Home hemodialysis requires a dedicated helper, whereas peritoneal dialysis is basically self-administered.
a spike for a fresh solution bag. This system is more expensive than the single-pronged system, but solutions always flow to the drainage bag immediately after connection (the drain first, infuse later principle). This feature seems to be crucial in lowering the incidence of peritoneal· infections, because any contaminants introduced during connection are washed into the drainage bag instead of into the peritoneal cavity. Continuous cyclic peritoneal dialysis is a hybrid of continuous ambulatory peritoneal dialysis and intermittent peritoneal dialysis. Three or more short-dwell exchanges are performed overnight on a cycler, and one longdwell exchange is done during the daytime. Table 1 shows the number of patients on various forms of dialysis in the United States between 1980 and 1987.
Uses of peritoneal dialysis 13 The list Qf reported clinical uses for peritoneal dialysis is lengthy (table 2). However, the procedure is widely used only for the four clinical conditions that are discussed here. CHRONIC RENAL FAILURE 1" -
Worldwide, more than 35,000 patients with chronic renal fail- · tn"e are currently on forms of chronic peritoneal dialysis. Most are treated with continuous
ambulatory peritoneal dialysis. Other forms of peritoneal dialysis are used for patients who cannot be treated with continuous ambulatory dialysis; they may want to be on home dialysis, but they either do not have facilities or their physical condition is not appropriate for home hemodialysis. In most cases, home hemodialysis requires a dedicated helper (usually a spouse), whereas peritoneal dialysis is basically self-administered. If the patient does need a helper, continuous cyclic peritoneal dialysis is easier for the helper to learn and perform than hemodialysis. This seems to be a reason for the growing popularity of peritoneal dialysis as opposed to home hemodialysis. The few contraindications to chronic peritoneal dialysis are summarized in table 3. The only absolute contraindication is a loss of more than 50% of the peritoneal surface area due to previous surgery andjor severe peritonitis. Patients with conditions aggravated by high intraabdominal pressure are treated with intermittent peritoneal dialysis; because it is performed with the patient supine, intraabdominal pressure is kept low. Indications for chronic peritoneal dialysis instead of hemodialysis are more social than medical, and the results with either are similar.
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