**7.1 Optimal RRT modality**

The choice of RRT depends on the institution, resources available, nurses training and patient's clinical status. Either IHD, PD, PIKRT such as SLED or CRRT can be used in ICU. CRRT tends to be the preferred modality in most ICUs. Given, CRRT does not require blood flow rates as high as IHD, CRRT tends to be the preferred modality for hemodynamically unstable patients. However, there is not any evidence that supports one modality over another.

A systematic review and meta-analysis published in 2021 (by Ye et al.) [11] compared different modalities of RRT through 31 randomized controlled trials. The review concluded that there was no overall difference in mortality between CRRT and IHD. However, CRRT was noted to increase renal recovery compared to IHD. Slow-efficiency extended dialysis with hemofiltration may be the most effective intervention at reducing mortality, but more research is needed. PD is associated with good efficacy and the least number of complications but may not be practical in all settings. ICU clinicians should feel comfortable that the differences between CRRT, IHD, slow efficiency extended dialysis, and PD are small, and any of these modalities is a reasonable option to employ in critically ill patients.

SLED can be useful if the patient requires multiple procedures that would interrupt CRRT, Since CRRT needs to be operating with as few interruptions as possible over 24 hours. Some institutions use SLED to transition patients from CRRT to standard IHD as hemodynamic stability improves.

One meta-analysis found no statistically significant difference between SLED and CRRT regarding patient-centered outcomes such as mortality, kidney function, recovery, dialysis dependence, length of stay in ICU, and fluid rate. SLED is also generally less expensive to administer and has similar safety for patients as CRRT.

**Timing of onset:** Multiple trials have compared the timing of RRT initiation in critically ill patients with AKI. Early RRT initiation (within 12 hours of identification) was not associated with improved outcomes and may be associated with increased risk of adverse events. Delayed RRT initiation (until indications develop) is preferred [12], but there are likely to be limits to how long RRT can be safely delayed. The optimal timing of RRT initiation is still unknown.


• The AKIKI-2 trial [15] found that mortality was higher in patients who had RRT deferred until an urgent indication developed or the BUN exceeded 140 mg/dL, but the difference was not statistically significant.

Based on the available evidence, delayed RRT initiation is preferred in critically ill patients with AKI. However, the optimal timing of RRT initiation is still unknown and may vary depending on individual patient characteristics.

**Session length**: Session length depends on the modality of dialysis and patients' ability to tolerate it. IHD is about 3–4 hours 2–3 times a week. PIKRT is 3 times a week but for 8–16 hours a day. CRRT is optimally applied for 24 hours a day.

**Dialysate flow rate**: The flow rate ranges from 100 to 400 ml/min. The dialysate flow rate is adjusted for the anticipated duration of the session. There is a finite amount of dialysate volume per session, based on how much the machine can accommodate. If the session is needed to last more than 8 hours for example, a lower flow rate may be needed. The dialysis flow rates for CRRT and PIKRT are lower than IHD 100–200 ml/min compared to IHD 300-400 ml/min.

**CRRT dialysate dosing**: The 'Randomized Evaluation of Normal versus Augmented Level of RRT' (RENAL) trial [16] and the 'Acute Renal Failure Trial Network' (ATN) [17] trials were two large clinical trials that evaluated the higher intensity (40 or 35 cc/kg/h) vs. lower intensity (25 or 20 cc/kg/h) dosing of CRRT. There was no difference found between lower intensity vs. higher intensity groups. Lower intensity dosing is currently recommended.

**Ultrafiltration rate**: The rate is determined by hemodynamic stability and urgency to remove excess fluid. With hemodynamically unstable patients, UF of 50 ml/h is a good starting place and can increase over time, However, if a patient is severely volume overloaded and can tolerate higher volume removal, a much higher ultra filtration rate can be targeted. For IHD, multiple liters of fluid negativity per session can be targeted based on hemodynamic stability.

**Blood flow**: The highest blood flow that the catheter will allow is used. It is usually initiated at100mL/min for CRRT and gradually increased to 200 cc/min. The higher the blood flow, the less likely a clot forms in the extracorporeal circuit. IHD can be initiated at 300–400 ml/min.

**Drug Dosing**: Volume of distribution, Vd and protein binding determine the effectiveness of a drug for a patient on CRRT 24 hours a day. Ideally, an ICU pharmacist should help dose medications for patients on CRRT 24 hours a day. If a drug is less than 2000 Da in weight, it might be readily removed on CRRT. Such drugs may need a higher dosing than usual dosing. The higher the protein bound content, the lesser the likelihood the drug will be cleared during CRRT. If a patient is volume overloaded, the higher Vd should be accounted for compared to ideal body weight and drug should be dosed accordingly. When possible and where available, follow plasma concentrations of drugs to achieve therapeutic levels. If a patient is on intermittent dialysis, it may be possible to dose a drug whose clearance may be affected by dialysis outside the dialytic time.

**Complications**: The major complications Include hypotension and abnormalities in electrolytes, albumin, calcium, and phosphate. As far as hypotension, PIKRT or SLED is well tolerated. Like CRRT, the slow blood flow rates and low UF allows hemodynamically unstable patients to tolerate it well. Hypophosphatemia only occurs with prolonged or frequent PIKRT and requires phosphate supplementation.

It is typically recommended that electrolytes and acid–base status be monitored every 6–12 hours initially for CRRT. Should the patient remain stable with minimal

### *Renal Replacement Therapy in Intensive Care Unit DOI: http://dx.doi.org/10.5772/intechopen.112139*

electrolyte changes after 24–48 hours, lab monitoring frequency can be further spaced to every 12–24 hours.

In recent years, there have been some updates in CRRT monitoring technology, aimed at improving the accuracy and efficiency of the process. For example, newer CRRT machines now incorporate advanced sensors and algorithms that can detect changes in blood flow and pressure, helping to prevent clotting and other complications.

Another recent development is the use of electronic medical records (EMRs) and data analytics tools to track patient outcomes and identify potential areas for improvement. This approach has been shown to reduce errors and improve overall quality of care in CRRT patients.
