Peritoneal dialysis (PD) can be provided in the form of several techniques.

Choosing a modality for chronic peritoneal dialysis

 

Peritoneal dialysis (PD) can be provided in several techniques. First, it is noteworthy to mention that peritoneal blood and dialysate flows during PD are extremely lower that that with hemodialysis (HDX) (both are > 400 mL/min). Consequently, urea (toxin) clearance per unit time is too much lesser with PD than that via HDX. Nevertheless, PD is usually provided in a continuous manner with net weekly solute clearance approached that via HDX.

 

TYPES OF PD 

PD modality can be provided in either a continuous or intermittent manner. Continuous ambulatory PD (CAPD) encompasses several exchanges during the day (often 3) with an overnight dwell usually added. A modification for this regimen is to include one nighttime exchange via an exchange device, leading to 2 overnight exchanges and 3 exchanges per day. This modification of CAPD is rarely used. An automated PD (APD) may use a cycler to perform many overnight exchanges. To modify this technique a continuous cycler PD (CCPD), nightly intermittent PD (NIPD), and tidal PD (TPD) can be performed:

Ø Continuous cycler PD (CCPD) hs a long per day dwell with multiple cycles overnight. A small number of patients on CCPD do not perform daytime dwell.

Ø An intermittent module, e.g., nightly intermittent PD (NIPD) or intermittent PD (IPD), that provide periods ("wet" abdomen) with alternate times at which peritoneal cavity could be drained of dialysate ("dry" abdomen).

Ø Tidal PD (TPD), composed of exchanges with peritoneal cavity always contains some dialysate (at least one-half full), this manner may improve sense of comfort and fasten drainage in certain patients. 

CAPD VERSUS APD

Whether there’re any clinical progress in providing the CAPD or APD modules, a crucial question that’s still unanswered. Despite paucity of data, CAPD and APD modalities may behave similarly in regard to the clinical outcome.

 

DIALYSIS PRESCRIPTION

Choice of modality

With institution of PD, most patients still have a reasonable residual kidney function, so, they can cope with any type of PD. However, once the residual kidney function starts to fade out, patient choice should be directed to a more suitable modality to achieve the optimum level of fluid and solute (toxin) clearance. At the beginning, dwell timing as well as dwell volumes should be individualized first according to the current patient’s status.

Two current guides for PD adequacy, first, total Kt/V/week (adequacy equation) for urea should be at least 1.7 and, or rather to consider CrCl to be at least 50-60 L/week per 1.73 m² body surface area. These targets should be monitored by time to guarantee an adequate PD modality. As residual kidney function went away and the peritoneal membrane starts to lose its physiological transport criteria by time, it is mandatory to augment the DX prescription (either by increasing the number of exchanges or dwell volumes).

 

Residual renal function

Patient maintained on PD usually have some preserved residual kidney function when they commenced in this modality. However, this residual kidney function gradually declines with time, to match “dwell time” to “transport type” gains more importance in this situation.  

 

CHOICE OF PD MODALITY

Both CAPD or CCPD modalities are currently required by patients maintained on PD dialysis. In regard to CAPD, 4 manual exchanges per day, 2 L each in addition to another overnight exchange.  Modification of this system can be achieved via timing, volumes, and number of exchanges per day.

On the other hand, CCPD is an automated module of PD in wch a cycler delivers 3-6 exchanges while the is sleeping in addition to 12-15 hour per day dwell. The net weekly clearance is simulating that gained with CAPD but greater amount of dialysate is generally warranted per day. Patient’s preference between CAPD and CCPD depends to a great extent on lifestyle or personal desires (e.g., need to work, refusing to do exchange in day time, or, lack of ability to perform the exchanges by themselves).

However, CCPD may provide more time for work, family, and social activities as compared to CAPD. Sleep apnea may also complicate the nocturnal PD. Generally, automated PD is superior to CAPD in fluid and solute removal optimization in certain patients. The automated module can provide larger amounts of dwells, longer nocturnal sessions, in addition to the daytime exchange, hence, a greater amounts of solute and fluid removal can be achieved.

N.B. This Blogger is created to declare different modalities in peritoneal dialysis.