As emphasized in the preceding sections, abdominal pain during dialysis remains the main indication for TPD. Other less common indications for TPD are conditions in which higher solute clearances or UF are desired without increasing dialysis duration.

The ideal TPD prescription, therefore, is one that is targeted to the indication for TPD, and in general is one that would achieve the goal of pain- and alarm-free therapy with optimal clearances and UF, while delivering a safe treatment that avoids overfilling.

When contemplating a TPD prescription, the prescriber must decide on the following parameters, as mandated by the Baxter Home Choice® software (the most commonly used home cycler for pediatric patients in the USA), to ensure a safe and effective treatment:

1.

The percentage of the initial fill volume that should be exchanged with each cycle (the TV) and amount that should stay in the peritoneal cavity (the residual volume);

2.

Frequency of tidal full drain, i.e., how often to fully drain the peritoneal cavity; and

3.

The net UF goal for the day.

There is no absolute recommended TV percentage necessary to keep the catheter afloat and decrease pain and drain alarms, and there is great variation in the literature on what has been used. In a cross-sectional survey of 6 adult dialysis units in Ontario, Canada, the TV percentage most frequently used varied between 75 and 80%; the most common indication for TPD in this cohort was drain pain [29]. As a general recommendation, the TV should be kept as high as possible (at least ≥ 50%), since only a small volume of residual dialysate is typically needed to keep the catheter afloat. This recommendation is aligned with the published pediatric experience with TPD, in which a TV of 50% was used and led to alarm- and pain-free dialysis treatments [5, 8, 20]. In a small subset of patients, such as those with prolonged drain times due to malfunctioning PD catheters, such an increase of TV may not be possible without compromising clearances; in such instances, a combination of high intraperitoneal fill volumes (e.g., initial fill volume 3 L in an adult-sized patient) combined with low TV (800–1000 mL) may allow dialysis to proceed without alarms [21].

In the few instances when TPD is considered for solute clearance, a TV of at least 50% has been proposed to achieve comparable clearances to standard APD prescriptions [11, 14]. This is in contrast to lower TVs (25%) which are associated with lower clearances as demonstrated in the previously referenced studies. To achieve higher clearances without prolonging dialysis duration, large-dose TPD can be considered, with a dialysate flow rate of at least 50 mL/kg/h [18, 20], using frequent exchanges (ranging from 20 to 35 per night) [5, 18] and a TV of 50%.

After determining the TV percentage, the prescriber must decide on the frequency of complete drainage of the peritoneal cavity. The main goal of complete drainage is to avoid overfilling (increased IIPV) and increased intraperitoneal pressure that can have grave consequences including death [29]. A commonly used practice is to completely drain the abdomen every three to four cycles. In the new model of the Baxter Home Choice® Cycler, the settings default to a complete drain every third cycle. This is a safety measure to prevent overfilling, but it can be modified by the prescriber. This may be desired and made less frequent in instances where patients are experiencing severe drain pain with each complete drain.

The final step is to enter the total anticipated (goal) UF for the therapy. This step is necessary to ensure that the volume that is ultrafiltered is removed along with the TV, and not retained until therapy is completed since that would lead to an overfilled state and its associated risks. The expected UF must be estimated carefully as adverse events may occur if the UF entered in the cycler program is set too low or too high. If the expected UF is set too low, progressive overfilling of the abdomen can occur from retention of the UF in the abdomen increasing the residual volume, which may lead to increased intraperitoneal pressure causing patient discomfort and as mentioned above, other serious complications. If the anticipated UF is set too high, the residual volume will be progressively depleted. This may lead to drain pain and would defeat the very purpose of initiating TPD. One way of estimating a patient’s UF is to review the previous actual UF achieved in the patient, the week prior to initiating TPD, and using 70% of that as the anticipated UF on TPD. Once tidal therapy is started, re-evaluating and re-assessing the actual UF is crucial to prevent overfilling or depleting the residual volume. In the new model of Baxter Home Choice® cycler, the minimum anticipated UF value defaults to 1000 mL per day. The prescriber can modify this number; the value entered has be greater than zero.