A regional citrate anticoagulation protocol for pre-dilutional CVVHDf: the 'Modified Alabama Protocol'

The use of citrate to anticoagulate the Continuous Renal Replacement Therapy (CRRT) circuit has not been widely adopted in Australia as an alternative to heparin due to treatment complexity and risks of metabolic complications and availability of suitable solutions. However, interest persists in citrate anticoagulation as a viable alternative when heparin is either contraindicated or has failed to provide an adequate circuit lifespan due to dialyser clotting.

This paper will describe a regional citrate anticoagulation protocol based on the 'Alabama Protocol' (AP) for pre-dilutional continuous veno-venous haemodiafiltration (CVVHDf) adapted to meet local requirements of an Australian tertiary medical-surgical intensive care unit.

The 'Modified Alabama Protocol' (MAP) uses base solutions which are now commercially available in Australia to produce a 0.5% citrate concentrate as the replacement fluid and a bicarbonate based, calcium-free solution as the dialysate. A number of additives are required to be added to the base solutions in order to match the requirements of the protocol. The anticoagulatory effects of citrate are monitored by reviewing simultaneous blood samples taken from the patient's arterial line and the post-dialyser sample port of the CRRT circuit. Post-dialyser and systemic ionised calcium levels in addition to the patient's base excess are easily obtainable by processing the blood samples through a blood gas analyser on site in the intensive care unit. Acid-base and electrolyte disturbances are controlled by adjusting the flow rate of replacement fluid and dialysate. As the protocol provides consistent directions on how to achieve desired biochemical values and when medical intervention is required, the approach offers an ideal opportunity for trained nursing staff to follow such a protocol at the bedside.

This paper describes a practical protocol for the delivery of regional citrate anticoagulation for pre-dilutional CVVHDf. The protocol maintains the flexibility in dialysis/haemofiltration dose prescription and advises on the requirement for monitoring and necessary adjustments to prevent the development of metabolic disturbances. This may assist regional citrate to achieve wider acceptance as an alternative anticoagulation strategy for critically ill patients.