Purpose:
Concerns related to postoperative hematoma formation influence use of enoxaparin for venous thromboembolism (VTE) prophylaxis after surgery. The PSEF-funded Venous Thromboembolism Prevention Study (VTEPS) was designed to evaluate the efficacy of post-operative enoxaparin for VTE prevention in plastic surgery patients. In preliminary analysis of the VTEPS database, we evaluated rates of re-operative hematoma formation with post-operative enoxaparin. Additionally, we examined the relationship between procedure type and hematoma formation in patients not receiving enoxaparin prophylaxis.
Methods:
The VTEPS network consists of four academic institutions. In June 2009, each implemented a clinical protocol for VTE prophylaxis, which included pre-operative risk stratification and post-operative enoxaparin. For patients scoring three or higher in the Caprini risk stratification system, prophylactic-dose enoxaparin was initially dosed 6-8 hours after surgery and subsequently administered for the duration of inpatient stay. For comparison, from 2006 to June 2009, a control group of historic patients who did not receive enoxaparin was identified. Chart reviews identified thromboembolic and bleeding complications for 60 days after surgery. Preliminary analysis of our data examined rates of re-operative hematoma, stratified by receipt of enoxaparin and procedure type. Multivariable logistic regression examined independent predictors of re-operative hematoma.
Results:
Analysis of the database identified 1006 patients who received post-operative enoxaparin and 1614 historic controls that did not receive enoxaparin. The hematoma rate requiring surgical drainage, irrespective of procedure, showed no significant difference (p=0.757) between patients who received post operative enoxaparin (3.38%) and those who did not (3.16%). Similarly, subgroup analysis demonstrated no significant differences in re-operative hematoma rates for breast reconstruction (4.41% vs. 4.52%, p=0.946), breast reduction (9.38% vs. 8.81%, p=0.917), or non-breast plastic surgery (2.53% vs. 1.58%, p=0.163) (Graph 1). When compared to those having non-breast surgery, breast reconstruction patients (4.52% vs. 1.58%, p=0.002) and breast reduction patients (8.81% vs. 1.58%, p<0.001) were significantly more likely to have a re-operative hematoma in the historic control group. Breast reduction patients were significantly more likely to have a re-operative hematoma when compared to breast reconstruction patients (8.81% vs. 4.52%, p=0.048). We performed multivariable logistic regression using age, body mass index; receipt of intra-operative heparin product; receipt of intra- or post-operative aspirin; microsurgical procedure; total operative time; and receipt of post-operative enoxaparin as independent variables. No factor was independently associated with re-operative hematoma.
Conclusion:
Post-operative enoxaparin did not significantly affect re-operative hematoma rates in the overall patient population or those in the breast surgery subgroup. For all patients studied, breast surgery patients were at disproportionately increased risk for re-operative hematomas compared to other patients having plastic and reconstructive surgery.