[Factors affecting blood loss in total knee arthroplasty patients]

The aim of the study was to identify the factors affecting major blood loss in patients undergoing total knee arthroplasty (TKA), in order to reduce blood loss and requirements for blood transfusion. This prospective randomized study included 80/184 patients treated by TKA at University Hospital of Traumatology, Zagreb, Croatia, from January 2005 till December 2007. The following parameters were analyzed: patient age, sex, body mass index (BMI), arterial blood pressure, preoperative hemoglobin level and hemoglobin level preceding blood transfusion, length of surgery, blood loss and volume of blood transfused. According to patient age, there were no differences in the length of surgery, blood loss volume, hemoglobin level before blood transfusion and use of blood transfusion. Older patients had lower hemoglobin level before blood transfusion and received greater volumes of blood transfusion, but the difference was not statistically significant. Male patients had a significantly higher preoperative hemoglobin level as compared to female patients (P = 0.012). The mean volume of blood loss and of transfused blood was larger in male than female patients, however, the difference did not reach statistical significance. According to BMI, there were no differences in the length of surgery, blood loss, volume of transfused blood and hemoglobin level before transfusion. Patients with a lower preoperative hemoglobin level did not lose more blood during and after surgery, but the requirement for blood transfusion was significantly higher (P = 0.014). Hypertensive patients had a statistically greater perioperative blood loss (P = 0.038), but did not receive more transfused blood (P = 0.494). Preoperative hemoglobin level was higher in patients with elevated arterial blood pressure than in those with normal blood pressure, but the difference was not statistically significant (P = 0.595). Hemoglobin level before blood transfusion was also higher in hypertensive patients than in those with normal blood pressure, but it was not statistically significant (P = 0.288). In patients with longer duration of surgery, blood loss and volume of blood transfused blood were statistically significantly greater (P = 0.003 and P = 0.015, respectively). Study results yielded a significant positive correlation between the length of surgery and the volume of blood loss (r = 0.282; P = 0.011) as well as between the length of surgery and the volume of blood transfused (r = 0.362; P = 0.001). A significant negative correlation was established between the preoperative hemoglobin level and application of blood transfusion (r = -0.250; P = 0.025). Patients with hypertension had a significantly larger blood loss volume as compared to patients with normal arterial pressure (P = 0.038) and received more blood transfusions than patients with normal blood pressure, but the difference was not statistically significant (P = 0.494). Age, sex and BMI had no statistically significant effect on blood loss volume and application of blood transfusion. Male patients had a significantly higher preoperative hemoglobin level (P=0.012), larger mean blood loss volume (P = 0.057) and received more blood transfusions than female patients, however, the difference did not reach statistical significance (P = 0.562). Based on study results, it is concluded that requirements for blood transfusion will be greater in patients with hypertension and lower preoperative hemoglobin level as well as in all cases with longer duration of surgery. To reduce the use of allogeneic blood transfusion, it is necessary to correct arterial blood pressure before surgery in hypertensive patients and also to magnify preoperative hemoglobin level if it is lower.