Retrograde Autologous Priming: Is It Really Effective in Reducing Red Blood Cell Transfusions during Extracorporeal Circulation?

Background: Retrograde autologous priming (RAP) is known to be useful in decreasing the need of transfusions in cardiac surgery because it prevents excessive hemodilution due to the crystalloid priming of cardiopulmonary bypass circuit. However, there are also negative side effects in terms of blood conservation. We analyzed the intraoperative blood-conserving effect of RAP and also investigated the efficacy of autotransfusion and ultrafiltration as a supplemental method for RAP. Material and Method: From January 2005 to December 2007, 117 patients who underwent isolated coronary artery bypass operations using cardiopulmonary bypass (CPB) were enrolled. Mean age was 63.9$\pm$9.1 years (range 36$\sim$83 years) and 34 patients were female. There were 62 patients in the RAP group and 55 patients in he control group. Intraoperative autotransfusion was performed via the arterial line. RAP was done just before initiating CPB using retrograde drainage of the crystalloid priming solution. Both conventional (CUF) and modified (MUF) ultrafiltrations were done during and after CPB, respectively. The transfusion threshold was less than 20% in hematocrit. Result: Autotransfusions were done in 79 patients (67.5%) and the average amount was 142.5$\pm$65.4 mL (range 30$\sim$320 mL). Homologous red blood cell (RBC) transfusion was done in 47 patients (40.2%) and mean amount of transfused RBC was 404.3$\pm$222.6 mL. Risk factors for transfusions were body surface area (OR 0.01, 95% CI 0.00 $\sim$ 0.63, p=0.030) and cardiopulmonary bypass time (OR 1.04, 95% CI 1.01 $\sim$ 1.08, p=0.019). RAP was not effective in terms of the rate of transfusion (34.5% vs 45.2%, p=0.24). However, the amount of transfused RBC was significantly decreased (526.3$\pm$242.3ml vs 321.4$\pm$166.3 mL, p=0.001). Autotransfusion and ultrafiltration revealed additive and cumulative effects decreasing transfusion amount (one; 600.0$\pm$231.0 mL, two; 533.3$\pm$264.6 mL, three; 346.7$\pm$176.7 mL, four; 300.0$\pm$146.1 mL, p=0.002). Conclusion: Even though RAP did not appear to be effective in terms of the number of patients receiving intraoperative RBC transfusions, it could conserve blood in terms of the amount transfused and with the additive effects of autotransfusion and ultrafiltration. If we want to maximize the blood conserving effect of RAP, more aggressive control will be necessary - such as high threshold of transfusion trigger or strict regulation of crystalloid infusion, and so forth.

역행성 자가혈액 충전법: 체외순환 중 동종적혈구 수혈량을 줄일 수 있는가?

배경: 역행성자가혈액충전(RAP)은 체외순환으로 인한 과도한 혈희석을 예방하여 심장수술과 관련된 수혈량을 줄일 수 있는 유용한 방법으로 알려져 있으나 그 효과에 대한 반론도 여전하다. 저자들은 RAP의 혈액보존효과를 분석하고 보조적 수단으로서 자가수혈과, 초여과법의 유용성을 알아보고자 하였다. 대상 및 방법: 2005년 1월부터 2007년 12월까지 심폐기를 사용한 단독 관상동맥우회수술을 시행한 117명의 환자를 대상으로 하였다. 평균나이는 63.9$\pm$9.1세(범위 36$\sim$83세), 남여 성비는 83 : 34였고 RAP군은 62명, 대조군은 55명이었다. RAP는 체외순환 시작 전 동맥 및 정맥라인을 통해 정질성 충전액이 배액되도록 하였다. 초여과법은 체외순환 중 시행하는 고전적방법과, 체외순환 직후 시행하는 변형법을 적용하였다. 동종적혈구의 수혈기준은 적혈구용적량 20% 미만으로 하였다 결과: 79예(67.5%)에서 수술 중 자가수혈을 시행하였고 채혈량은 평균 142.5$\pm$65.4 mL (범위 30$\sim$320 mL)였다. 체외순환 중 동종적혈구 수혈은 47예(40.2%)에서 시행되었으며 평균 수혈량은 404.3$\pm$222.6 mL였다. 수혈의 위험인자는 체표면적(OR 0.01, 95% CI 0.00$\sim$0.63, p=0.030)과 심폐기 가동시간(OR 1.04, 95% CI 1.01$\sim$1.08, p=0.019)이었다. RAP는 수혈빈도를 감소시키는 효과는 없었지만(34.5% vs 45.2%, p=0.24), 수혈량은 통계적으로 의미있게 감소하였고(526.3$\pm$242.3 mL vs 321.4$\pm$166.3 mL, p=0.001) 자가수혈과 초여과법을 병합 적용할 경우 누진적으로 수혈량 감소효과가 있는 것으로 나타났다(한가지; 600.0$\pm$231.0 mL, 두가지; 533.3$\pm$264.6 mL, 세가지; 346.7$\pm$176.7 mL, 네가지; 300.0$\pm$146.1 mL, p=0.002). 결론: RAP는 체외순환 중 동종적혈구 수혈빈도를 감소시키지는 못했지만 수혈량은 의미있게 감소시키는 효과가 있었고, 자가수혈과 초여과법은 추가적인 수혈량 감소효과를 보였다. 체외순환 중 수혈빈도를 감소시키기 위해서는 수혈기준이 되는 적혈구용적량을 낮추고 정질성 수액의 투여를 제한하는 등의 적극적 노력이 필요할 것으로 생각된다.