Regional citrate anticoagulation for RRTs in critically ill patients with AKI

Abstract

Hemorrhagic complications have been reported in up to 30% of critically ill patients with AKI undergoing RRT with systemic anticoagulation. Because bleeding is associated with significantly increased mortality risk, strategies aimed at reducing hemorrhagic complications while maintaining extracorporeal circulation should be implemented. Among the alternatives to systemic anticoagulation, regional citrate anticoagulation has been shown to prolong circuit life while reducing the incidence of hemorrhagic complications and lowering transfusion needs. For these reasons, the recently published Kidney Disease Improving Global Outcomes Clinical Practice Guidelines for Acute Kidney Injury have recommended regional citrate anticoagulation as the preferred anticoagulation modality for continuous RRT in critically ill patients in whom it is not contraindicated. However, the use of regional citrate anticoagulation is still limited because of concerns related to the risk of metabolic complications, the complexity of the proposed protocols, and the need for customized solutions. The introduction of simplified anticoagulation protocols based on citrate and the development of dialysis monitors with integrated infusion systems and dedicated software could lead to the wider use of regional citrate anticoagulation in upcoming years.

Keywords: AKI; CRRT; SLED; citrate; regional anticoagulation.

Figure 1.

RCA in continuous RRT: basic principles. *Sampling for systemic ionized calcium is from the circuit arterial line or the patient’s arterial line (to avoid the effects of vascular access recirculation). Systemic total calcium can be measured from a central venous line. CVVH, continuous venovenous hemofiltration; CVVHD, continuous venovenous hemodialysis; CVVHDF, continuous venovenous hemodiafiltration; Qb, blood flow rate; RCA, regional citrate anticoagulation.

Figure 2.

Schematic representation of RCA for the different continuous RRT modalities. In protocols adopting high-concentration citrate solutions, the use of a low-sodium dialysate and/or replacement fluid is generally required to prevent hypernatremia. In protocols adopting low-concentration citrate solutions, citrate acts as both an anticoagulant and a predilution replacement fluid, thus contributing to the total continuous RRT dose. Sections A and C display RCA circuits in predilution-only CVVH and CVVHD modalities, respectively. The dotted boxes in B and D indicate the possibility of using a calcium-free predilution replacement fluid along with a separate hypertonic citrate solution to obtain predilution and postdilution CVVH or CVVHDF.

Figure 3.

Schematic representation of a simplified regional citrate anticoagulation protocol for SLED using a calcium-containing dialysate. Detailed protocol is shown as supplemental material in ref. . *Sampling for systemic ionized calcium is from the circuit arterial line or the patient’s arterial line (to avoid the effects of vascular access recirculation). Systemic total calcium can be measured from a central venous line. ACD-A, anticoagulant citrate dextrose solution A; SLED, sustained low-efficiency dialysis; Uf, ultrafiltration.

Figure 4.

Composition of commercially available citrate and CRRT solutions for RCA. To design the appropriate RCA protocol (CVVHD, CVVH, CVVHDF), each citrate solution should be combined with the correctly matched dialysate and/or replacement fluid. Availability and trade name of each solution may vary according to different countries. The list of commercially available citrate and CRRT solutions derives from the more recently reported RCA protocols and could be partial. N/A, not applicable or not available.