Guidelines for VTE prophylaxis are available and widely disseminated. The guidelines from the American College of Chest Physicians (ACCP) are often considered the definitive resource [11]. This group has specific recommendations for prophylaxis in non-orthopedic surgery patients [39]. Guidelines for specific populations at risk, such as trauma patients and orthopedic surgical patients, are available from specialty societies such as the Eastern Association for the Surgery of Trauma (EAST) and the American Academy of Orthopedic Surgeons (AAOS), respectively [40, 41].

Most protocols use subcutaneous (SC) injection of unfractionated heparin or low molecular weight heparins (LWMH) such as enoxaparin, dalteparin, or fondaparinux for VTE prophylaxis. Trauma and orthopedic literature typically supports the use of LMWH over unfractionated heparin [40]. Patients with unstable renal function or creatinine clearance less than 30 mL/min should receive unfractionated heparin instead of LMWH due to risks associated with bioaccumulation of some LMWHs in patients with reduced renal clearance. Newer oral anticoagulants are being promoted for VTE prevention, although at this time, the only well-studied indication is for patients undergoing hip or knee replacement surgery.

VTE prophylaxis should generally be provided throughout the inpatient hospitalization, but some literature also supports extending prophylaxis to the outpatient setting for a limited duration after discharge from the hospital. This may be of particular use in patients at high risk for perioperative VTE including orthopedic surgery patients, or those with major abdominopelvic oncologic resections. Dosing of unfractionated heparin is typically 5000 units SC every 8 h for many patients, while less frequent dosing (5000 units SC every 12 h) may be appropriate for some patients at lower risk. Dosing for a common LMWH, enoxaparin, is typically once daily with 40 mg SC for most surgical patients yet should be 30 mg twice daily for trauma patients [42]. VTE prophylaxis is typically administered 1–2 h before any major surgical procedure and resumed 12–24 h postoperatively. Contraindications to pharmacologic prophylaxis include active bleeding, high risk of bleeding, systemic anticoagulation, coagulopathy with international normalized ratio (INR) ≥1.5, or thrombocytopenia (platelet count <50,000).

Mechanical prophylaxis may include sequential compression devices (SCDS) and thromboembolic deterrent stockings (TEDS). SCDS are preferred over TEDS alone, and TEDS may be associated with ulcers or skin breakdown, especially in patients with stroke, peripheral vascular disease, or chronic lower extremity wounds [43]. Compliance with these devices in surgical patients is poor even without any specific contraindications, and efforts to improve compliance by addressing misconceptions will be discussed later in the chapter. Although very little data support its use, ambulation has been suggested as an effective adjunct to VTE prophylaxis when feasible [44]. However, this should not be considered an acceptable replacement to pharmacologic and/or mechanical prophylaxis in hospitalized patients at risk for VTE.

Inferior vena cava (IVC) filters have been used as prophylaxis in certain high-risk patients without VTE who are unable to receive pharmacologic prophylaxis. The strongest data for this indication come from the trauma literature [45]. EAST offers a level III recommendation (based on retrospective data and/or expert opinion) that a prophylactic IVC filter may be considered in very high-risk trauma patients who are unable to receive pharmacologic VTE prophylaxis [40]. This recommendation may apply to patients with both increased bleeding risk and an injury pattern rendering them immobile for a prolonged period (e.g., severe closed-head injury, spinal cord injury with paraplegia or quadriplegia, or multiple long-bone fractures). However, there is considerable disagreement on this topic, and the ACCP states that “for major trauma patients, we suggest that an IVC filter should not be used for primary VTE prevention (Grade 2C)” [39].

While the trauma literature has identified a potential benefit, IVC filters may also be associated with increased morbidity and mortality in other patient populations. In the bariatric surgery literature, prophylactic IVC filters are associated with higher mortality and higher risk of DVT [46]. Further research is needed to truly understand the implications and safety considerations for IVC filter use in different patient populations.

If a retrievable IVC filter is used, it is important to remove the IVC filter as soon as the patient’s acute risk of VTE decreases. In many cases, patients do not return for IVC filter removal. One study of 446 trauma patients who received retrievable IVC filters demonstrated that only 22 % actually had their IVC filter removed [47]. Filter endothelialization may occur as soon as 3 weeks after placement, yet many can still be recovered years later. Patients may experience complications from prolonged indwelling IVC filters, including perforation of the IVC noted on subsequent CT imaging and strut fracture and embolization [48, 49].

Numerous efforts are underway to identify strategies to ensure better rates of filter retrieval. One group has applied the DMAIC (Define, Measure, Analyze, Improve, Control) methodology of the Six Sigma paradigm and increased filter retrieval rates from a baseline of 8 to 52 % by employing automated clinic visit scheduling for 4 weeks after IVC filter placement [50]. A group in New Zealand implemented an “IVC filter pathway” and increased retrieval rates from 63 to 100 % [51]. Focused efforts to improve poor IVC filter removal rates in trauma have been successful and increased rates to 59 % at one US hospital and 87 % at a Canadian trauma center [52, 53].

One approach to improve documentation of VTE risk status and compliance with evidence-based guidelines is to utilize a mandatory computerized provider order entry (CPOE) clinical decision support (CDS) tool, as suggested by the AHRQ [8, 9]. Computer order entry system requires the prescribing provider to complete a checklist of VTE risk factors and contraindications specific for the patient. Based on this checklist, the patient is risk stratified, and the appropriate prophylaxis, according to current guidelines, is determined. The provider is then prompted to order the appropriate prophylaxis regimen. This approach has demonstrated dramatic improvements in both prescription of risk-appropriate VTE prophylaxis for medical and surgical patients and an associated decrease in the rate of preventable harm from VTE [14, 15]. When this strategy was implemented at the Johns Hopkins Hospital, compliance with guideline-appropriate prophylaxis in trauma patients increased from 66.2 to 84.4 % (p < 0.001), and the rate of preventable harm from VTE decreased from 1.0 to 0.17 % (p = 0.04).

It is important to ensure that interventions designed to improve prescription of VTE prophylaxis are targeted at the appropriate individuals. At many academic institutions, quality measures attributed to attending physicians (e.g., rate of compliance with appropriate VTE prophylaxis) may actually reflect the average performance of both highly compliant and noncompliant residents. One study compared the proportion of risk-appropriate VTE prophylaxis orders written by each resident and attributed to attending physicians [54]. While there was no difference in proportion of risk-appropriate VTE prophylaxis when attributed to attending physicians, there was a significant difference among residents. Over half of the residents prescribed optimal prophylaxis for every patient they admitted, but there was a minority of residents (9.3 %) who failed to prescribe optimal prophylaxis for any of the patients they admitted. This study demonstrates the importance of targeting the providers actually responsible for entering the prophylaxis orders. Furthermore, this suggests that an educational intervention with the limited number of residents not prescribing appropriate prophylaxis might be most effective. Accordingly, a system designed to audit resident compliance with VTE prophylaxis and provide individualized performance feedback was implemented and has been shown to significantly improve compliance with guidelines, reduce incidence of VTE, and improve residents’ satisfaction with their education [55].

Once risk-appropriate VTE prophylaxis is ordered, it does not necessarily mean that all ordered doses of prophylaxis will actually be administered. Even missing one dose of VTE prophylaxis is associated with VTE events as demonstrated by a 2014 analysis of 202 trauma and general surgery patients [56]. This study showed an overall incidence of DVT of 15.8 %, and 58.9 % of patients had missed at least one dose of prescribed VTE prophylaxis. DVT occurred in 23.5 % of patients who missed at least one dose of prophylaxis and in 4.8 % of patients who missed no doses of prophylaxis (p < 0.01). A 2015 study examined 128 medical and surgical patients with hospital-acquired VTE and determined that 72 % (92 patients) of these VTE events were potentially preventable [17]. The VTE events that were not preventable were attributed to the presence of a central venous catheter [57]. Of the 92 patients who experienced potentially preventable VTE events, 79 (86 %) were prescribed optimal prophylaxis, yet only 43 (47 %) received defect-free care. Of the 49 patients (53 %) who were noted to have defects in their care, 13 (27 %) were not prescribed risk-appropriate VTE prophylaxis, and 36 (73 %) missed at least one dose of appropriately prescribed prophylaxis. A retrospective review examined the medication administration record for patients prescribed VTE prophylaxis over a 7-month period at one academic medical center [58]. Over 100,000 doses of VTE prophylaxis were ordered, but 12 % of these doses were not actually administered to patients. Patient refusal was the most commonly documented reason for nonadministration in about 60 % of cases. This study also demonstrated that a small group of patients (approximately 20 %) constituted the majority (80 %) of all nonadministered doses. Heterogeneity in terms of administration of VTE prophylaxis across nursing floors was noted which suggests that targeting interventions to specific nursing floors, individual nurses, or individual patients may be effective.

Many patients are not aware of VTE or its potential consequences, which may lead some patients to refuse VTE prophylaxis without a clear understanding of the risks and benefits of this decision. An APHA telephone survey established that fewer than one in ten Americans know about DVT and are familiar with its symptoms or risk factors [6]. Recently, for World Thrombosis Day (October 13, 2014), Wendelboe surveyed 7233 participants in nine countries to determine the awareness of VTE. They found awareness to be lowest for DVT (44 %) and PE (54 %) compared to other common conditions such as breast cancer (85 %), stroke (85 %), prostate cancer (82 %), and heart attack (88 %) [59]. Initiatives to increase awareness among patients and the public are also important to decrease the incidence of VTE. For example, US Congress has designated the month of March as DVT Awareness Month to help highlight the symptoms of this common disease. Ongoing efforts must incorporate patient-centered interventions to ensure that patients understand the importance of VTE prophylaxis and the inherent risks associated with refusal of prophylaxis. Recently, our group has been funded to address this problem by the Patient-Centered Outcomes Research Institute (PCORI) for a project titled “Preventing Venous Thromboembolism: Empowering Patients and Enabling Patient-Centered Care via Health Information Technology” [60]. Patient educational materials are readily available in both paper (http://​www.​Hopkinsmedicine.​org/​Armstrong/​bloodclots) and video (http://​bit.​ly/​bloodclots) formats, which can be used for this purpose.

Efforts to improve VTE prophylaxis in accordance with best-practice guidelines may require addressing obstacles attributed to hospital culture [61]. For example, mechanical VTE prophylaxis with SCDS is often prescribed but commonly underutilized in about 50 % of patients [62]. Noncompliance may be largely related to patient discomfort and the ease with which these devices may be removed by the patient. Another well-known contributing factor is lack of available SCD equipment at the time of patient admission. Some hospitals have addressed this issue by assigning SCD equipment to each hospital bed, ensuring that the patient will be provided with clean SCD equipment at the time the bed is made available. There may be a tendency for multidisciplinary staff members to remove SCDS to help a patient out of bed without reapplying the SCDS when returning the patient to bed. This problem requires education of a broader multidisciplinary group including nursing assistants, physical therapists, occupational therapists, and transport teams. A common misconception held by some hospital staff and contributing to noncompliance is that SCDS may cause patient falls. A retrospective study examined the incidence of SCD-related falls and determined that only 0.45 % of falls in the hospital are related to SCDS and SCD-related falls are not more harmful than other types of falls [63].

Active attempts to understand nursing practices and beliefs identified barriers to administration of prescribed VTE prophylaxis in a mixed methods study published in 2014 [16]. The study revealed a nursing belief that nurses are responsible for assessing individual patient risks and benefits of prescribed pharmacological VTE prophylaxis before administering the medication to the patient. One nurse who participated in a focus group during this study stated “We make the clinical decision all the time as to whether a patient needs VTE prophylaxis every day, based on how much the patient is ambulating.” This study was able to identify misconceptions held by many nurses and introduced an opportunity to provide additional education to this group.

There is no consensus regarding DVT screening of high-risk asymptomatic patients, and practices among surgeons may vary significantly [66]. ACCP does not recommend routine screening for DVT in critically ill patients [11]. EAST recognizes that some patients at high risk may benefit from routine screening for DVT [40]. However, the clinical importance of asymptomatic DVT detected by routine screening remains unclear. Supporters of routine screening see benefit in performing a relatively inexpensive and noninvasive test (Duplex ultrasonography), in order to diagnose and treat asymptomatic DVT before it progresses to symptomatic or fatal PE. Others feel that increased medical testing, associated costs, and treatment of asymptomatic DVT (which may never have come to clinical attention otherwise) incur not only the risk associated with anticoagulation but also unnecessary costs.

Surveillance bias (“the more you look, the more you find”) is a common concern when screening asymptomatic patients for VTE. Studies have clearly shown that increasing screening is associated with increasing rates of VTE, primarily in trauma patients [20, 67, 68]. However, this phenomenon has also been shown in a large sample of nearly one million Medicare patients undergoing a wide range of surgical procedures [69]. While national and regional bodies recognize low incidence of VTE as a marker of quality, this is a biased measurement since hospitals that less commonly screen patients for VTE are going to identify fewer VTE events regardless of associated healthcare quality.

The standard of patient safety and quality care should not only focus on the incidence of VTE (outcome measure) alone but also consider how frequently patients are prescribed and administered VTE prophylaxis according to best-practice guidelines (process measure). Rather than measuring incidence of VTE alone, some experts argue for a pure process measure approach or combined process and outcome measure instead [12, 13, 20, 21]. Outcome measures are of considerable interest and have been commonly used to determine the quality of care [70]. However, poor outcomes provide no information about how to actually address the underlying problem. Interventions to improve the quality of care must be directed at the process of care [71]. Using the VTE and Outcome Measures example, linking the process measures (prescription and administration of risk-appropriate VTE prophylaxis) and the outcome measure (incidence of VTE) estimates one of the most valuable markers of patient safety and excellent care: the true rate of preventable harm [20, 21].