(to promote ultrafiltration), increasing the dialysate pressure could reduce
the filtration rate in desired circumstances- Blood priming
Blood priming refers to filling the circuit volume with blood prior to its
connection to the patient circulation. It is particularly needed when the
circuit volume exceeds 10-15% of the estimated blood volume of the child.
[5]- Anticoagulant
Anticoagulation is needed to keep the circuit patent.
a. Heparin. It is delivered in the pre-filter area of the circuit and titrated
to achieve a post-filter PTT of 1.5 times normal or an ACT of 180 s.
Heparin is given continuously at a rate of 10-20 units/kg/h after a
bolus of 20-30 units/kg. Bleeding complications are more common
with heparin [9]
b. Citrate based anticoagulation. It is better tolerated in children and
has lower complication rates. Citrate binds free calcium ions thus
preventing coagulation. Sodium citrate is delivered to the initial part
of the circuit providing a local anticoagulation effect. Calcium
chloride is added to the blood before it is returned to the patient.
Citrate is converted to bicarbonate in the liver which could cause
metabolic alkalosis. Be careful in patients with hepatic insufficiency
because citrate overload could cause metabolic acidosis.Buffering agents.
Bicarbonate and lactate based dialysate solutions are the two main
buffering agents used during CVVHD and CVVHDF. Conversion of lactate
to bicarbonate in the liver limits the use of lactate based solutions in