The effect of retrograde autologous priming volume on haemodilution and transfusion requirements during cardiac surgery

OBJECTIVES: Many cardiac procedures using cardiopulmonary bypass (CPB) still require intraoperative transfusion. Retrograde autologous priming (RAP) has been introduced to decrease haemodilution and the blood transfusion rate. This study is designed to determine the influence or RAP on intraoperative haematocrit, transfusion and its clinical consequences. METHODS: The RAP effect was retrospectively studied in 753 patients during contemporary cardiac surgery, targeting a haematocrit of 25%. Multivariate linear regression analysis was performed to identify the independent factors influencing intraoperative haematocrit, transfusion rate and transfusion quantity. RESULTS: RAP was used in 498 patients and compared with 255 controls. RAP decreased the haemodilution level (nadir haematocrit 26.8 standard deviation [SD] 4.0% in RAP vs 25.8 SD 3.6% in controls; P= 0.001) and transfusion frequency (26.1 vs 33.3%, P= 0.04), despite smaller patients (body surface area [BSA] 1.86 SD 0.20 m 2 vs 1.91 SD 0.21 m 2 in RAP vs controls; P= 0.002) with lower preoperative haematocrit (38.9 SD 4.4% vs 40.5 SD 4.6%; P< 0.001). Optimal RAP volume was overall 475 ml (ROC area 0.55; 95% confidence interval [CI] 0.50–0.60; P= 0.04) and 375 ml in patients with BSA <1.7 m 2 (ROC area 0.63; 95% CI 0.54–0.73; P= 0.008) to decrease the transfusion incidence. Multivariate analysis revealed RAP volume as a significant determinant of nadir haematocrit (β= 0.003, 95% CI 0.002–0.004, P< 0.001) and transfusion rate (odds ratio (OR) = 0.997, 95% CI 0.996–0.999, P< 0.001), independent of BSA, gender and preoperative haematocrit. CONCLUSIONS: Retrograde autologous priming is an effective adjunct to decrease the blood transfusion rate, coping with the CPBrelated haemodilution and its adverse clinical effects. A RAP volume individualized to each patient offers most benefit as part of a multidisciplinary blood conservation approach.