Clinical factors influencing the decision to transfuse after percutaneous native kidney biopsy

Background: Transfusion of erythrocytes is the most common intervention after a complicated percutaneous renal biopsy (PRB). Anemia is considered to be a leading risk factor for bleeding following a PRB, and based on recent studies of transfusions in hospitalized patients, many institutions are restricting the threshold for erythrocyte transfusion to a lower hemoglobin concentration (Hgb). The purpose of this study is to analyze factors that influence the transfusion decision after a PRB, and to determine whether anemia is truly a risk factor for bleeding or anemic patients are simply more likely to receive a transfusion because of their already lower pre-PRB Hgb. Methods: PRB of native kidneys was performed using real-time ultrasound with automated biopsy needles from January 1990 to April 2014. All patients were prospectively followed for bleeding with a 24-h inpatient observation. An intervention for a bleeding complication (BL-I) was defined by undergoing a procedure (cystoscopy, embolization), receiving a blood transfusion (BL-T), death and/or readmission related to the biopsy. To further define the effect of anemia, patients were divided into three pre-PRB Hgb groups: <9.0 g/dL (n = 79), 9.0-11.0 g/dL (n = 266) and >11.0 g/dL (n = 565). Results: BL-I occurred in 71/910 (7.8%) of PRBs. The majority of these were BL-T (57/71, 80%; 57/910, 6.3% overall). Patients with BL-I had lower pre-PRBHgb than those without BL-I (mean +/- SD; 10.3 +/- 2.0 versus 12.0 +/- 2.1 g/dL, P < 0.0001) and a greater change (Delta) in Hgb (2.1 +/- 1.6 versus 1.0 +/- 0.8 g/dL, P < 0.0001). When compared with higher Hgb, patients with Hgb < 9.0 g/dL had more traditional risk factors for bleeding (older age: 49 +/- 18 versus 48 +/- 18 versus 45 +/- 16 years, P = 0.02; female: 72 versus 70 versus 56%, P < 0.0001; higher serum creatinine: 4.0 +/- 2.9 versus 2.9 +/- 2.6 versus 1.7 +/- 1.4mg/dL, P < 0.0001; higher systolic blood pressure: 138 +/- 18 versus 133 +/- 19 versus 133 +/- 18 mmHg, P = 0.06; higher bleeding time: 7.6 +/- 1.8 versus 7.4 +/- 2.0 versus 6.7 +/- 1.8min, P < 0.0001). When BL-T was stratified by pre-PRBHgb, there were more transfusions in those with lower pre-PRBHgb (24 versus 9 versus 3%, P < 0.0001). However, these patients not only had fewer hematomas (58 versus 83 versus 87%, P = 0.04) but also demonstrated a smaller Delta Hgb post-PRB (1.3 +/- 1.0 versus 1.8 +/- 0.8 versus 3.2 +/- 1.6, P < 0.0001) compared with patients with higher pre-PRB Hgb, yet still received a transfusion. Conclusions: While patients with lower pre-PRB Hgb have more of the traditional risk factors for a complication after PRB, there was actually less clinically evident bleeding in these patients who were transfused. Although anemia itself has been considered to be a risk factor for a complication in the past, it more accurately represents only a predictor of receiving an erythrocyte transfusion. In the setting of the PRB, the decision for transfusion is influenced more by the severity of anemia at baseline as opposed to clinically evident bleeding.