**2. Principles modalities of renal replacement therapy**

Prior to the late 1980s, RRT was limited to peritoneal dialysis (PD) and hemodialysis (HD). In intensive care, all the renal therapy methods (peritoneal dialysis, conventional hemodialysis, and continuous extracorporeal purification, such as hemofiltration (HF) and hemodiafiltration (HDF)) have been developed in children to supplement renal function when it becomes insufficient in all or part, whether in primary or secondary way. These methods became quickly very popular, especially in Europe, and gradually gained prominence in intensive care units. HD is based essentially on diffusion, hemofiltration on convection, and hemodiafiltration on the diffusion/convection combination.

The advent of hemofiltration (HF) methods has provided resuscitators with therapies that they have been able to appropriate more easily while reducing hemodynamic complications but at the cost of reduced efficacy (clearance), thus justifying their continued use [7].

For the convective modality, the exchanges take place through a semipermeable membrane according to a hydrostatic pressure gradient. An ultrafiltrate is then removed from the patient's blood, composed of plasma water and molecules of a molecular weight less than the diameter of the pores of the membrane. A large quantity of plasma water is thus withdrawn from the patient, requiring replacement with a replacement liquid, either upstream of the filter (predilution) or downstream (post-dilution).

The DP, therefore, does not require an extracorporeal blood circuit, the peritoneum acts as a semi-permeable membrane, and the exchanges between the blood and the dialysis solution (infused into the peritoneal cavity by a catheter placed by the resuscitator in the peritoneal cavity) take place through the walls of the rich vascular network of the peritoneal membrane, according to the concentration gradients. Water extraction is possible by adding glucose polymers to the dialysate, creating an oncotic pressure gradient that generates water transfer from the vascular sector to the dialysate.

PD is the most commonly initiated technique in infants and newborns because of the hemodynamic stability it provides, and the age and weight of the child.

The advantages and disadvantages of each method are summarized in **Table 1**.



*IPD intermittent peritoneal dialysis, VP ventriculoperitoneal, ICU intensive care unit.*

#### **Table 1.**

*Comparison of the advantages and disadvantages of continuous renal replacement therapies (CRRT) and peritoneal dialysis (PD) and intermittent hemodialysis (IHD).*
