Bubble chamber clotting during continuous renal replacement therapy: Vertical versus horizontal blood flow entry

Background: The continuous renal replacement therapy (CRRT) bubble trap chamber is a frequent site of clotting. Aims: To assess clot formation when comparing our standard 'vertical' blood entry chamber (BEC) with a new 'horizontal' BEC. Methods: Adult ICU patients requiring CRRT were treated with the vertical BEC and then a similar subsequent cohort with the horizontal BEC in continuous veno-venous haemofiltration mode. Results: 40 chambers were assessed for each design. Circuit life was 13.9 ± 9.5 h for the vertical and 17.7 ± 15.9 h for the horizontal BEC (p = 0.33). APTT, however, was higher for the horizontal BEC (55.7 ± 34.7 vs. 37.4 ± 9.0, p < 0.002) and no difference in circuit life was found after multivariable analysis. A clotting score ≥3 was observed in 85% of all chambers. There was no difference in chamber clotting score (vertical 3.6 ± 1.03 vs. horizontal 3.8 ± 1.0, p = 0.5). In addition, no difference was found when scores were divided into two groups using a 'likelihood' to clot analysis (p = 1.0). Conclusion: CRRT horizontal BEC were not associated with less clotting compared to our standard vertical BEC.