Cyclers:

Cyclers are an automated device capable of delivering a measured volume of dialysate into the peritoneal cavity and providing automated drainage of spent dialysate after specific dwell time.

Functions:

1.Measurs the volume of dialysate to be infused.

2.Warm the dialysate to body temperature before infusion.

3.Time the frequency and numbers of exchanges

4.Measure ultrafiltration.

5.Mix dextrose concentrations to achieve the desired ultrafiltration.

Modern electronic and computerized programs are used to improve the functions of the traditional mechanical cyclers. The new cyclers generation are reliable , efficient , simple and capable to perform many functions.

The early cyclers used the gravity for infusion and drainage of dialysate into and out of the peritoneal cavity. Further improvement in some designs a pump is used to force the dialysate up to a raised containers , from which it is allowed to enter the peritoneal cavity. Timers and clamps of the cyclers regulate the time of inflow , dwell, and outflow of dialysate. Advanced cyclers measure the total amount of dialysate infused and drained and display the net difference between the two i.e. e volume of ultrafiltration. Most of the cyclers have alarms that will sounds or light and shut off the cyclers if failure to achieve the exact inflow or outflow volume occurs. In some cyclers pneumatic pressure pumps to regulate the inflow -after warming -, dwell, and outflow of dialysate. Sensitive pressure monitoring devices are required to avoid accidental infusion of large volumes of dialysate  and to avoid suction of the mesentery or tissues during draining.

Tubing sets:

Disposable one step set up cassettes, including all the necessary tubing for the cyclers has simplified the procedure of setting up the equipment. Multiple use of tubing sets and the utilization of empty solution bags as the next day's drain has been tried to reduce the cost and patient effort in setting up their equipment. Large dialysate containers are used to reduce the number of connections.

Connectors:

APD has shared the same connectors developed for CAPD of the same system. The use of external occlusion for the disconnection procedure during APD has markedly simplified the procedure and reduces peritonitis rate.

Solute clearance with some PD modalities:

 N, Nocturnal -  D, Diurnal  -   TV, Tidal volume  -  RV, Residual volume

Intermittent Peritoneal Dialysis (IPD)

This mode of peritoneal dialysis ,alternate dialysis of various duration (10-48 hours) with interdialytic phases lasts for one or more days according to the patient needs. The exchange volume can be adjusted  according to patient’s size , volume of peritoneal cavity , and cardiopulmonary tolerance. Introduction of automated techniques (Cyclers and reverse osmoses machines) increased the safety by reducing risk of infection and also the effectiveness of PD by insuring the regularity of the exchanges.

Initially patients with residual renal function do well on 40 hours per week of IPD, but as the endogenous renal function decreases the effectiveness of IPD fails.

Nocturnal Peritoneal Dialysis (NPD).

Nocturnal Peritoneal Dialysis (NPD) is Intermittent Peritoneal Dialysis (I'D) performed nightly. The total exchange time in this mode of therapy is 8-10 hours using the cycle times up to 60 minutes. No. dialysis fluid in the abdomen during the daytime

Prescription (sample)

Dialysate volume: 2-liter exchange [16-20 liter/night]

Session length: Over 8-10 hours

Exchange time: On 10 p.m.            -----      Off  8 p.m.

                        One exchange every hour or more

                        Abdomen left dry in the morning.

Ultrafiltration: Use.....liters 1.5% and......liters 4.25%

Additives: Heparin , potassium , insulin ................etc

Indication

1. in patients with increased membrane permeability (high peritoneal transfer rates) . The use of short frequent peritoneal exchanges will results in adequate ultrafiltration and improved solute removal.

2.in patient suffering from complications associated with increased intraabdominal pressure. Patients suffering from ;  hernias , bladder and uterine prolapse , low backache , restrictive lung disease , severe cardiovascular instability , gastrointestinal reflux and abdominal pain associated with dialysate infusion may benefit from NPD.

Disadvantages:

1.NPD has the disadvantages of not providing  a steady physiological state.

2.Expensive due to the relatively high dialysate flows and the need of cycle.

Continuous Cyclic Peritoneal Dialysis (CCPD)

Continuous Cyclic Peritoneal dialysis is a form of automated peritoneal dialysis. Cyclers with timers that allow dwell times of several hours is necessary.CCPD users must carry out 3-5 nightly exchanges over 10-12 hours, plus a daytime exchange remain in the peritoneal cavity to control uremia. 10-18 % of urea cleared by the daytime exchange It avoid  interrupting daytime activities and may also reduce the incidence of PD complications.

Prescription (sample)

Dialysate volume: 2-liter exchange [10 liter/day]

                            4 exchanges at night and 1 at day time

Session length: Over 10 hours

Exchange time: On 10 p.m.            -----      Off  8 p.m.

                        One exchange every 2.5 hour at night

                        The fifth exchange left in the peritoneal cavity in the morning morning.

Ultrafiltration: Use.....liters 1.5% and......liters 4.25% at nighttime and ......% at daytime.

Additives: Heparin , potassium , insulin ................etc

The use of hypertonic solution [4,25]during daytime is recommended because of prolonged dwell time and significant absorption of dextrose after4-6 hour dwell.

Indications:

1.Patients who needs partner assistance

2.In patient suffering from complications associated with increased intraabdominal pressure. See TAD

3.Inadequate dialysis with other modalities,

Advantages:

1.The efficiency of  COD in removing small and middle molecule is comparable to CAPD. Adequate BP control is also achieved.

2.It provide a relatively continuous therapy without necessity for on and off procedure during the active hours

3.The risk of hernias and pericatheter leak are lower in COD than CAPD.

4.Less peritonitis rate.

5.CCPD is the treatment of choice in children.

Disadvantages:

1.The need of cycle

2.Expensive , related to the cycle and its disposable tubing.

3.Protein loss and hyperlipidaemia

Tidal Peritoneal Dialysis (TPD)

Tidal peritoneal dialysis is a therapy in which the patient abdomen is filled with dialysate, and a portion of the dialysate is drained and replaced by fresh dialysate. The rationale behind this technique is that a sufficient residual volume always in contact with peritoneal membrane while partial exchanges are carried out throughout the night. It is one form of automated peritoneal dialysis which permits a reduction in dialysis time and improves the efficiency of dialysis by keeping the abdomen full while drain and fill times. The peritoneal cavity is drained completely only at the end of dialysis session.

This technique uses  a modified cycle regulated by volume rather than time and high dialysate flows , unlike COD and NYPD in which the cycle regulated by time rather than volume..

Example ; Exchange volume = 3 liters , (Reserve volume =1.5 liter , Tidal volume 1.5 liter) , for a total of 30 liters over 8-10 hour. Cycles are short; usually less than 20 minutes.

Advantages:

1.The high dialysate flow rate provides increased diffusion and minimizes the formation of unstirred layers of dialysate next to the peritoneum.

2.The presence of reserve volume provides continuous contact between the dialysate and the peritoneal membrane , i.e. continuous excellent  clearance and ultrafiltration.

Disadvantages:

1.The peritoneal dialysis catheter must have excellent inflow and outflow

2.The need of special volume controlled cycle.

3.Very high dialysate flows.

4.The ultrafiltration volume must be calculated and added to the drain volume with each exchange.

5.Clearance of larger molecule is high.

6.Expensive