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.

Introduction: Operating theatres are a crucial learning environment for trainee surgeons developing surgical skills. There is no structured framework for teaching during surgery or its evaluation. Objective assessment of the learning experience can assess quality and highlight areas for improvement, maximizing benefit. Methods: A 5-point Likert rating scale was devised to assess surgical teaching experience. Positive and negative teaching attributes were established with a literature review and interviews of trainees and teachers. Sixty surgical trainees at a major London teaching hospital, operating under consultant supervision, evaluated the supervisor teaching using the tool. Significance of test results from the assessment tool was analysed using repeated measures analysis of variance for Likert scoring. A P value 50.05 was considered statistically significant. Results: There was consensus between trainees on the relevance of tool themes, with most ranked important or absolutely essential and no difference across grades (P 5 0.05). There was no difference in the overall supervisor scores between trainees with different levels of experience (P 5 0.05) or between procedures with different levels of complexity (P 5 0.05). Junior supervisors scored more highly overall than senior supervisors (P = 0.024). Discussion: The study demonstrated that the assessment tool is feasible, practical and applicable, with face and content validity. Discrimination between supervisors with different levels of experience shows discriminative validity. The tool facilitates objective assessment of the teaching experience in surgery. We hope this will aid improvements in teaching quality, an area for further study.