A Study on the Efficacy and Safety of Continuous Renal Replacement Therapy (CVVHDF) Using a Commercial Citrate-containing Replacement Fluid (Prismocitrate 18/0)
A Study on the Efficacy and Safety of Continuous Renal Replacement Therapy (CVVHDF) Using a Commercial Citrate-containing Replacement Fluid (Prismocitrate 18/0)
The investigators aim to examine the efficacy and safety of using a new citrate containing
 commercially available solutions (Prismocitrate 18/0) as the regional citrate anticoagulation
 in continuous renal replacement therapy for critically ill patients.
Acute kidney injury is common in critically ill patients, and continuous renal replacement
 therapy is the preferable mode of treatment to remove the metabolic waste while avoiding the
 hemodynamic instability associated with intermittent hemodialysis. Thrombosis frequently
 occurs in the hemofilter which could reduce the circuit lifespan, jeopardize the efficacy of
 renal replacement, result in loss of blood cells and increased transfusion requirement.
 Anticoagulants including conventional heparin and low molecular weight heparin, introduced
 via the arterial port of the circuit, are widely used to reduce clotting within the
 extracorporeal circuit. However, significant amount of heparin is not removed in the circuit
 and will be carried into patient's circulation, which could lead to bleeding complications.
 Regional citrate anticoagulation (RCA) has been used for intermittent haemodialysis since
 1983, and its use has extended to that for continuous renal replacement therapy (CRRT) since
 1987. Citrate is introduced at therapeutic level at the arterial limb of the dialysis
 circuit, where it chelates calcium ions in the blood to prevent clotting within the
 hemofilter. While some calcium-citrate complex is removed in the filter, the residual will be
 circulated to the patient and be metabolized in liver. Patient's systemic ionized calcium
 level remains normal, by hemodilution and also calcium replacement. Therefore, the
 anticoagulant effect from citrate is regional and confined to the extracorporeal circuit. RCA
 has the potential to extend circuit life during renal replacement therapy without systemic
 anticoagulation. In a recent meta-analysis of randomized controlled trials, RCA was as
 efficacious as heparin anticoagulation in term of maintaining circuit function, and RCA was
 associated with decreased risk of bleeding with no significant increase in incidence of
 metabolic alkalosis.(5) Hypocalcemia was more common in patients receiving citrate, but of
 note, no clinical adverse event was reported in the included studies. Although citrate
 anticoagulation had repeatedly been demonstrated to prolong filter life, many hospitals still
 refrained from using it, as a result of limited experience, different patient variety, or
 other reasons.

 The investigators' group has performed a pilot study (HKU/HA HKW IRB No: UW 08-221) to assess
 the efficacy and safety of continuous venous-venous hemodiafiltration(CVVHDF) using a
 commercial citrate containing replacement fluid (Prismocitrate 10/2, Gambro) which contains
 10mmol/l citrate and 2 mmol/l citric acid. 15 subjects were recruited from July 2008 to June
 2011. No serious adverse events were reported, including severe hypocalcemia, hypercalcemia,
 citrate toxicity and severe acid base disturbances. Metabolic acidosis due to renal failure
 were only partially corrected by CRRT with citrate anticoagulation in the initial study
 subjects, the problem was subsequently solved by adding supplemental bicarbonate to the
 dialysate. Since then, all the patients were able to complete the treatment protocols with
 adequate kidney lifespan, correction of metabolic abnormalities and fluid imbalance. However,
 since additional bicarbonate is needed to correct the metabolic acidosis during CRRT, there
 is room for improvement regarding the formulation of the citrate-containing solution to
 reduce acid liberation while increasing the alkali bicarbonate production. Prismocitrate
 18/0, which contains 18mmol/l citrate (one mmol citrate could be metabolized to produce 3
 mmol bicarbonate) and no citric acid, could potentially result in better acid-base control
 during CRRT.
Inclusion Criteria:

 -  The patient requires CRRT as treatment for renal failure, as decided by the attending
 physician

 -  The patient fulfils at least one of the following clinical criteria for initiating
 CRRT:

 1. According to the RIFLE criteria, (11) patients satisfying the "injury" criteria
 (increase creatinine by 2 fold or urine output<0.5ml/kg/hr for 12hr) will be
 considered for CRRT

 2. Hyperkalemia ([K+] > 6.5 mmol/L).

 3. Severe acidemia (pH < 7.2).

 4. Urea > 25 mmol/liter.

 5. Clinically significant organ oedema in the setting of ARF.

 Exclusion Criteria: