Predicting Blood Loss and Transfusion Requirements During Radical Prostatectomy: The Significant Negative Impact of Increasing Body Mass Index

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Abstract
Purpose: Radical retropubic prostatectomy (RRP) has been associated with significant blood loss and/or transfusion requirement. While still a concern, routine autologous blood donation has not been standard at our institution for more than a decade. We assessed recent blood loss and transfusion requirements in contemporary patients undergoing RRP and examined the possible predictive impact of preoperative variables. Materials and Methods: A retrospective review of 436 consecutive patients who underwent RRP between July 1999 and December 2001 was performed with the primary purpose of analyzing estimated blood loss (EBL) and blood transfusion requirements as well as possible preoperative risk factors, including clinical demographic characteristics, body mass index (BMI), defined as weight in kg/height in m2, comorbidities, American Society of Anesthesiologists classification and Charlson index score. Results: A total of 436 consecutive patients with a mean age of 60 years (range 39 to 78) underwent RRP under general anesthesia. Mean American Society of Anesthesiologists class was 2.3 (range 1 to 3) and the mean BMI was 27.7 (range 18.2 to 44.3). Mean preoperative and postoperative hematocrit was 43.9% and 32.5%, respectively. Overall mean EBL was 603 cc (range 100 to 3500) and the transfusion rate was 4.8%. On multivariate analysis the only significant correlative predictor of EBL was BMI. There was a significantly lower EBL in patients with an acceptable BMI (less than 25) vs overweight (25 to 30) and obese (greater than 30) patients (p = 0.021). Likewise the rate of transfusion was significantly higher in the overweight (6.9%) and obese (5.6%) groups compared to the normal BMI group (1.9%) (p = 0.009). Conclusions: Our series demonstrates that blood loss during RRP continues to decrease. The respectable blood loss and low transfusion rates in this series were due to refinements in surgical technique rather than to perioperative modifications. To our knowledge the identification of BMI as a predictor of blood loss and transfusion is novel. These data serve as a benchmark for future comparisons and argue for continued refinements in techniques to decrease blood loss, particularly in overweight and obese patients.