Non anti-coagulant factors associated with filter life in continuous renal replacement therapy (CRRT): a systematic review and meta-analysis

Abstract

BackgroundOptimising filter life and performance efficiency in continuous renal replacement therapy has been a focus of considerable recent research. Larger high quality studies have predominantly focussed on optimal anticoagulation however CRRT is complex and filter life is also affected by vascular access, circuit and management factors. We performed a systematic search of the literature to identify and quantify the effect of vascular access, circuit and patient factors that affect filter life and presented the results as a meta-analysis.MethodsA systematic review and meta-analysis was performed by searching Pubmed (MEDLINE) and Ovid EMBASE libraries from inception to 29th February 2016 for all studies with a comparator or independent variable relating to CRRT circuits and reporting filter life. Included studies documented filter life in hours with a comparator other than anti-coagulation intervention. All studies comparing anticoagulation interventions were searched for regression or hazard models pertaining to other sources of variation in filter life.ResultsEight hundred nineteen abstracts were identified of which 364 were selected for full text analysis. 24 presented data on patient modifiers of circuit life, 14 on vascular access modifiers and 34 on circuit related factors. Risk of bias was high and findings are hypothesis generating.Ranking of vascular access site by filter longevity favours: tunnelled semi-permanent catheters, femoral, internal jugular and subclavian last. There is inconsistency in the difference reported between femoral and jugular catheters.Amongst published literature, modality of CRRT consistently favoured continuous veno-venous haemodiafiltration (CVVHD-F) with an associated 44% lower failure rate compared to CVVH. There was a trend favouring higher blood flow rates. There is insufficient data to determine advantages of haemofilter membranes.Patient factors associated with a statistically significant worsening of filter life included mechanical ventilation, elevated SOFA or LOD score, elevations in ionized calcium, elevated platelet count, red cell transfusion, platelet factor 4 (PF-4) antibodies, and elevated fibrinogen.Majority of studies are observational or report circuit factors in sub-analysis. Risk of bias is high and findings require targeted investigations to confirm.ConclusionThe interaction of patient, pathology, anticoagulation, vascular access, circuit and staff factors contribute to CRRT filter life. There remains an ambiguity from published data as to which site and side should be the first choice for vascular access placement and what interaction this has with patient factors and timing. Early consideration of tunnelled semi-permanent access may provide optimal filter life if longer periods of CRRT are anticipated. There remains an absence of robust evidence outside of anti-coagulation strategies despite over 20 years of therapy delivery however trends favour CVVHD-F over CVVH.

Hemodialysis without anticoagulation: Less clotting in conventional hemodialysis than in predilution hemodiafiltration

“…Likewise, in continuous renal replacement therapy, the meta‐analysis conducted by Brain et al . also suggests that purely convective techniques such as continuous veno‐venous hemodiafiltration (CVVH) are associated with shorter filter life span than techniques containing diffusive flux (CVVHD and CVVHDF) …”

Better late than never: the true results of CARRESS‐HF

“…Disconcerting is also the unprecedented incidence of filter clotting which occurred in 23/64 (36%) patients no longer on UF at 96 h. The estimated UF rates were 83 [46–109] mL/h; 140 [83–178] mL/h; 107 [32–178] mL/h; and 70 [21–115] mL/h for each sequential 24 h period from baseline to 96 h, respectively. Low UF rates, such as those reported by Grodin and colleagues, should indeed reduce, rather than increase, filter clotting by decreasing filtration fraction . Therefore, the most plausible cause of the high incidence of filter clotting was the use of excessively low blood flows which, in contrast to slow UF rates, augment the risk of haemofilter clotting by increasing the filtration fraction.…”

“…Therefore, the most plausible cause of the high incidence of filter clotting was the use of excessively low blood flows which, in contrast to slow UF rates, augment the risk of haemofilter clotting by increasing the filtration fraction. Furthermore, the risk of this event increases over time due to the haemoconcentration induced by fluid removal itself . Between randomization and primary endpoint evaluation, UF was terminated in 10/64 (16%) because of hypotension or evidence of volume depletion.…”

“…Because such choice is separate from the other listed causes of therapy discontinuation, including achievement of optimal volume status, haemodynamic instability, evidence of volume depletion, increased sCr, filter clotting and vascular access failure, the suspicion arises that UF was prematurely terminated either for convenience, lack of familiarity with the therapy, or both. 1 7 Therefore, the most plausible cause of the high incidence of filter clotting was the use of excessively low blood flows which, in contrast to slow UF rates, augment the risk of haemofilter clotting by increasing the filtration fraction. Furthermore, the risk of this event increases over time due to the haemoconcentration induced by fluid removal itself.…”

“…Furthermore, the risk of this event increases over time due to the haemoconcentration induced by fluid removal itself. 7 Between randomization and primary endpoint evaluation, UF was terminated in 10/64 (16%) because of hypotension or evidence of volume depletion. Notably, UF rates at 48 and 72 h were higher than those used at 24 h. This fact alone suggests disregard of the physiological principles of fluid shift between the interstitium and the vascular space described by Starling.…”