Preoperative Hemoglobin and Body Mass Index as Predictors of Safe Aspirate Volume in Liposuction

Background: Liposuction is one of the most frequently performed aesthetic procedures worldwide. Although generally safe, excessive blood loss and postoperative anemia remain potential complications, particularly in large-volume cases. Current safety guidelines rely on fixed aspirate thresholds rather than individualized physiological parameters. This study aimed to develop and validate a mathematical model to predict the maximum safe fat aspirate volume based on preoperative hemoglobin and body mass index. Methods: A prospective observational study was conducted between January and December 2022 at a tertiary hospital in western Mexico. Female patients aged 18 years or older undergoing primary liposuction were included. Pre- and postoperative hemoglobin levels were measured within 24 hours. The predictive model was defined as: where constant was adjusted by body mass index (0.75 for normal weight, 0.70 for overweight, and 0.60 for obese patients). Correlations between predicted and observed hemoglobin decreases and aspirated volumes were analyzed using the Pearson test. Results: A total of 308 female patients (mean age, 32.2 ± 9.1 y) were analyzed. The mean aspirated volume was 5.17 L. Predicted and observed hemoglobin decreases showed a strong correlation ( r = 0.864, P < 0.05). Total aspirated volume correlated significantly with both expected ( r = 0.951) and observed (r = 0.793) hemoglobin changes ( P < 0.05). No transfusions or major complications occurred. Conclusions: This model accurately estimates postoperative hemoglobin changes and defines individualized aspirate limits, offering a simple and reliable tool to enhance perioperative safety in liposuction.