Postoperative venous thromboembolism (VTE) is a significant source of morbidity, mortality, and cost.1,2 Colorectal surgery patients are at particularly high risk for VTE due to positioning during surgery, pelvic dissection, and other conditions often found in these patients, such as cancer and inflammatory bowel disease.3 A National Surgical Quality Improvement Program (NSQIP) analysis demonstrated an overall rate of VTE in colorectal surgery patients of 2.4%, although other studies have demonstrated rates up to 9%, even in those receiving appropriate chemoprophylaxis.4-6 Many of these VTEs occur in the postdischarge setting. In a NSQIP study of colorectal surgery patients, the rate of VTE between discharge and 30 days was 0.47%.7 The cost burdenfor a postoperative VTE has been estimated to be more than $18,000.8
Studies from NSQIP have identified multiple factors associated with VTE in colorectal surgery patients, but NSQIP does not record ambulation as a standard variable.9 Multiple strategies have been implemented to reduce postoperative VTE. Often, these studies focus on increasing compliance with appropriate chemoprophylaxis, risk stratification, or bundling multiple strategies.10,11 However, despite the fact that postsurgical ambulation is widely encouraged and recommended by the American Society of Colon and Rectal Surgeons clinical practice guidelines, there is little evidence demonstrating the role of ambulation alone in the reduction of VTE.4,12 The purpose of this study was to create a multidisciplinary protocol to increase postoperative ambulation and evaluate its effect on VTE.
Methods
Setting
This study was conducted at a single academic tertiary care center.
Patients and Outcome Measures
All patients undergoing colectomy or proctectomy by surgeons in the section of colon and rectal surgery at a single institution between January 2011 and March 2017 were included. Colectomy and proctectomy were defined by CPT codes 44140, 44141, 44143, 44144, 44145, 44146, 44147, 44150, 44151, 44155, 44156, 44157, 44158, 44160, 44204, 44205, 44206, 44207, 44208, 44210, 44211, 44212, 44213, 45110, 45111, 45112, 45113, 45114, 45116, 45119, 45120, 45121, 45123, 45126, 45160, 45395, and 45397. The primary outcome of VTE within 30 days, including deep venous thrombosis (DVT) and pulmonary embolism (PE), was measured using institution-specific data from NSQIP in both the pre-intervention and postintervention setting. The occurrence of both DVT and PE in 1 patient was counted as a single event of VTE. Ambulation rate on postoperative day (POD) 0, 1, and 2 was calculated by NSQIP in the pre-intervention setting (our institution-specific NSQIP recorded ambulation data for an unrelated project) and by review of the electronic health record in the postintervention setting, as this institution-specific variable was no longer being collected. Ambulation was defined as getting out of bed and taking at least 1 step. The threshold for ambulating each day was once on POD 0 and twice on PODs 1 and 2. Patients with missing ambulation data were excluded from the analysis. Both prior to and throughout the intervention, all patients were given VTE chemoprophylaxis with either low-dose unfractionated heparin or low-molecular-weight heparin prior to induction of anesthesia, with chemoprophylaxis extending an additional 21 days after discharge (unless specifically contraindicated); sequential compression devices; and standard orders to ambulate 3 times daily from POD 0 as part of the standard Enhanced Recovery After Surgery protocol.
Analysis
Statistical analysis was performed using univariate analysis. Chi-square test and univariate logistic regression were used to determine the association between ambulation rates and VTE in the pre-intervention group. Chi-square test was also used to compare ambulation and VTE rates between the pre-intervention and postintervention groups. Plan-Do-Study-Act (PDSA) cycle fidelity (the degree to which a PDSA cycle is carried out in accordance with the guiding principles of its use) was measured by recording the ambulation rates both before and after the intervention.13 Statistical analysis was performed using SAS Version 9.4 (SAS Institute, Cary, NC). This study was reviewed by the Washington University School of Medicine Institutional Review Board and deemed to be quality improvement, not human subjects research, and therefore did not require formal approval.