**5. Continuous hemofiltration (HF, HDF, continuous HD)**

These techniques are preferred in respiratory and/or hemodynamic failure situations; they require the placement of a dialysis catheter), an HF machine, and a biocompatible filter. The preferred ultrasound insertion site is the right internal jugular vein in terms of purification quality [10, 11].

The femoral site is a perfectly acceptable alternative in the context of extreme urgency and remains the most used in the English literature [12].

Machinery pumps (blood, dialysate, restitution) guarantee the accuracy of the water balance. Pediatric filters with areas ranging from 0.2 to 1.2 m2 are available in all commercial markets depending on the brand of dialysis generator used (**Figure 1**).

A wide range of pediatric and neonatal Hemofilters, made of MediSulfone® proprietary membrane, has been developed to create the best treatment for low-bodyweight patients.

Frequently, the circuit must be de-coagulated with heparin therapy (10 to 20 IU/ kg/hour to achieve an activated cephalin time between 50 and 65 seconds) or with regional citrate anticoagulation (ionized calcium monitoring).

*Dialytic Treatment of Acute Renal Failure in Children DOI: http://dx.doi.org/10.5772/intechopen.111621*

#### **Figure 1.** *Diagram of a pediatric hemofilter.*

#### **Figure 2.**

*Circuit diagrams for the various modes of continuous kidney replacement therapy (CKRT) by ref. [14] in Indian J Pediatr. Blood flows from left to right from the patient to the blood pump and then to the filter, from which it is returned to the patient. (a) Slow continuous ultrafiltration (SCUF): In this modality, there is no diffusive clearance and only ultrafiltrate (UF) is generated across the filter; this method is preferred for isolated UF removal when kidney function is normal, (b) Continuousvenovenous hemofiltration (CVVH): Replacement fluid is run eitherpre- or post-filter in a volume to replace the effluent; excess effluent is removed to ensure the UF desired for negative fluid balance; clearance is convective rather than diffusive. (c) Continuous venovenous hemodialysis (CVVHD): Blood flows across the filter in a countercurrent fashion with the dialysate fluid, and the effluent predominantly consists of dialysate fluid with minimal, if any, UF, as in intermittent hemodialysis. (d) Continuous venovenous hemodiafiltration (CVVHDF): This modality combines CVVH with CVVHD, such that the blood and dialysis fluid run in counter-current directions, the replacement fluid is either pre- or post-filter, and the effluent comprises the dialysate and replacement fluids.*

Blood flow (BF) ranges from 3 to 10 mL/kg/minute. The blood pump flow rate should be at least 50 mL/min to maintain a filtration fraction <20%, which is easily achieved with a functioning 8 Fr catheter and HF of 0.3 m2 [13].

This corresponds approximately to 2000 mL/h for 1.73 m2 (in HDF, it is necessary to take into account the dialysate flow rate, or QD: total dose = QUF + QD).

In all cases, a filtration fraction (FF = QUF/[1 - Ht] x QS) of less than 15–20% should be maintained to avoid coagulation of the filter.

In pure continuous hemofiltration (CVVH, CAVH) and in the course of the derived methods which are the techniques without restitution (SCUF), the clearance is ensured by convection (**Figure 2**).

The following table describes the advantages and disadvantages of each treatment modality.
