Automated regional citrate anticoagulation: technological barriers and possible solutions.
BACKGROUND
Large-scale adoption of regional citrate anticoagulation (RCA) is prevented by risks of the technique as practiced traditionally. Safe RCA protocols with automated delivery on customized dialysis systems are needed.


METHODS
We applied kinetic analysis of solute fluxes during RCA to design a protocol for sustained low-efficiency dialysis (SLED) for critically ill patients. We used a high-flux hemodialyzer, a zero-calcium (Ca) dialysate, a dialysis machine with online clearance and access recirculation monitoring, and a separate optical hematocrit (Hct) sensor. Flow rates were Q(B) = 200 ml/min for blood; Q(D) = 400 ml/min for dialysate, with Na = 140 mmol/l and HCO(3) = 32 mmol/l; Q(citrate) = 400 ml/h of acid citrate dextrose A; ultrafiltration as indicated. The Q(Ca) was infused into the return blood line, adjusted hourly based on online Hct and a <24-hour-old albumin level.


RESULTS
Using the SLED-RCA protocol in an anhepatic, ex vivo dialysis system, ionized Ca (iCa) was >1 mmol/l in the blood reservoir and <0.3 mmol/l in the blood circuit after citrate but before Ca infusion (Q(Ca)) with normal electrolyte composition of the blood returning to the reservoir. Clinically, SLED-RCA completely abrogated clotting, without adverse electrolyte effects. The Q(Ca) prediction algorithm maintained normal systemic iCa (0.95-1.4 mmol/l) in all patients. The high citrate extraction on the dialyzer prevented systemic citrate accumulation even in shock liver patients. Safety analysis shows that building a dialysis system for automated SLED-RCA is feasible.


CONCLUSIONS
Using predictive Q(Ca) dosing and integrating control of the infusion pumps with the dialysis machine, SLED-RCA can be near-automated today to provide a user-friendly and safe system.
Szamosfalvi
Balazs
B
Division of Nephrology and Hypertension, Henry Ford Health System, Detroit, Mich., USA. bszamos1@hfhs.org
Frinak
Stanley
S
Yee
Jerry
J
D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics; D001331:Automation; D001639:Bicarbonates / Q000008:administration & dosage; D002118:Calcium / Q000008:administration & dosage / Q000097:blood; D002614:Chelating Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics; D019343:Citric Acid / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics; D004867:Equipment Design; D004868:Equipment Failure; D004869:Equipment Safety; D005947:Glucose / Q000008:administration & dosage; D015312:Hemodialysis Solutions / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics; D006801:Humans; D006996:Hypocalcemia / Q000209:etiology / Q000517:prevention & control; D007260:Infusion Pumps; D007676:Kidney Failure, Chronic / Q000097:blood / Q000628:therapy*; D019300:Medical Errors / Q000517:prevention & control; D009862:Online Systems; D010710:Phosphates / Q000008:administration & dosage; D011188:Potassium / Q000008:administration & dosage; D006435:Renal Dialysis / Q000295:instrumentation / Q000379:methods*; D012709:Serum Albumin / Q000032:analysis
D000925:Anticoagulants; D001639:Bicarbonates; D002614:Chelating Agents; D015312:Hemodialysis Solutions; D010710:Phosphates; D012709:Serum Albumin; D019343:Citric Acid; D005947:Glucose; D011188:Potassium; C018279:sodium phosphate; D002118:Calcium