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Venous Thromboembolic Events: How Low Can You Go?
Caroline E. Jones*, Allison A. Gullick, Melanie S. Morris
Surgery, University of Alabama-Birmingham, Birmingham, AL

Postoperative venous thromboembolisms (VTEs) are a publically reported quality measure and are targeted in pay-for-performance programs. However, elimination of VTEs may not be possible. We reviewed postoperative chemical VTE prophylaxis administration records to determine the preventability of VTEs at our institution.

A retrospective cohort analysis was performed using the 2011-2015 American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) single institution database. All adult patients diagnosed with VTE within 30 days of major surgery were identified. Cases of VTE present on admission were excluded. Preoperative risk assessment was performed using the Caprini Score. The number of missing doses of chemical VTE prophylaxis (enoxaparin or subcutaneous heparin) with documented reasons was obtained by chart abstraction. Number of missing days of prophylaxis was assessed to compare patients with different dosing regimens. Chi-square and Wilcoxon Rank Sums tests were used to determine the differences among categorical and continuous variables, respectively.

Of 83 patients with postoperative VTE, 65.1% had lower extremity deep venous thrombosis (LE DVT), compared to 27.7% with upper extremity (UE) DVT and 7.2% with visceral thrombosis. Caprini scores ranged from 2 to 12 with mean 6.49. The majority of patients (90.4%) were considered at highest risk for VTE by the Caprini risk scoring method, followed by 8.4% at high risk, and 1.2% at moderate risk; no patient with VTE was considered low risk. Nearly half of all VTEs (45.7%) occurred in spine or oncologic operations. The majority of VTEs (60.2%) were not preventable (37.3% of LE DVTs, 65.2% of UE DVTs, 66.7% of visceral thromboses) because patients did not miss any prophylactic doses, and VTEs were not catheter-related. Of the patients that missed doses (62.6% of cohort), most missed only 1 dose (21.7%), followed by 2 doses (10.8%), 3 doses (6.0%), 4 doses (4.8%), and 5+ doses (19.2%). Patients with VTEs diagnosed during their index hospital stay were more likely to have missed doses (mean 3.71) compared to patients whose VTE was diagnosed after discharge (mean 1.08) with p=0.021. Of the 28.9% VTEs diagnosed after hospital discharge, 25.0% were associated with operations for gynecologic cancers, despite frequent continuation of prophylactic anticoagulation at home. Of 187 total doses missed among 52 patients, 39.0% were missed for unknown reasons, 26.2% for bleeding concerns, 15.5% following spinal surgery, 13.4% for upcoming procedure, 2.7% for epidural catheter removal, and 2.7% due to ordering error.

Post-operative VTEs happen despite appropriate, guideline driven care in more than half of patients. Thus, the utility of VTEs as a valid measure of hospital quality should be questioned.

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