SEARCH

SEARCH BY CITATION

Keywords:

  • venous thromboembolism;
  • pulmonary embolus;
  • thromboprophylaxis;
  • hospitalised-associated thrombosis;
  • mortality

Summary

  1. Top of page
  2. Summary
  3. Changes in clinical practice
  4. Recognising hospital-acquired venous thromboembolism as a safety issue
  5. Defining the population at risk
  6. Identifying individual patients in need of thromboprophylaxis
  7. Refining risk assessment
  8. Conclusion
  9. Conflict of interest
  10. References

Venous thromboembolism in adults is related to recent hospitalisation in approximately half of all cases and approximately half of all hospitalised adult patients are considered to be at risk by conventional criteria. Due to advances in surgical practice, the identification of surgical patients in need of prophylaxis has become less rather than more certain. Faster surgical technique, regional anaesthesia and early mobilisation are considered to reduce the risk of venous thromboembolism and hence possibly obviate the need for prophylaxis after early discharge from hospital. An increasing proportion of patients with hospital-acquired venous thromboembolism are medical patients, but the need to identify medical patients that require thromboprophylaxis is a new aspect of clinical practice for many physicians and prophylaxis remains under-utilised in non-surgical hospitalised patients. In this review prevention of hospital-acquired venous thromboembolism is considered as a patient safety issue in the context of changing clinical practice. Strategies for refining and validating risk assessment models and evaluating the effect of risk assessment and thromboprophylaxis are suggested.

Deep vein thrombosis (DVT) and pulmonary embolus (PE) are referred to collectively as venous thromboembolism (VTE) or venous thrombosis (VT). VTE related to hospitalisation in adults has been referred to as hospital-acquired thrombosis (HAT). However, at least 50% of episodes of VTE in adults attributable to hospitalisation are diagnosed following discharge from hospital and presentation may occur up to 3 months after leaving hospital (Goldhaber & Tapson, 2004; Spencer et al, 2007; Sweetland et al, 2009). Whilst the initiation of thrombus may occur during the period of hospitalisation it is likely that in cases of late presentation the propagation of thrombus often occurs following discharge and in some cases the initiation process may actually occur following discharge from hospital. Therefore, the term hospital-associated VTE might be more correct. Nevertheless, to avoid expansion of terminology ‘hospital-acquired’ is used throughout this article to refer to VTE occurring as a consequence of hospitalisation in the previous 3 months.

In 2007 the Independent Expert Working Group for the prevention of VTE in hospitalised patients reported to the Chief Medical Officer (CMO) for England (Department of Health 2007). In response to that report the CMO stated (Department of Health 2008a): ‘The dangers of venous thromboembolism in hospitalised patients have long been recognised, but our challenge was to find a systematic approach to identify patients most at risk. Creating a standardised national preventive strategy on this scale is a world first.…..by implementing risk assessment for all patients admitted to hospital, we can make the goal of reducing death from venous thromboembolism more attainable. This simple step has the potential to save thousands of lives each year’.

Many studies have been performed to determine the incidence of DVT and PE in different groups of patients and to identify risk factors. The risk of VTE associated with hospitalisation depends not only on the reason for admission (procedural risk) but also on co-existing patient-related factors (patient-related risk). The decision as to whether a patient requires thromboprophylaxis depends on the absolute thrombosis risk and the choice of prophylaxis depends on the balance between absolute thrombosis and bleeding risks. For each patient an assessment of risk should be undertaken on admission and ideally reviewed periodically during hospitalisation, particularly in medical patients whose risk may escalate. Depending on the degree of risk patients should receive advice and treatment to reduce this. Patients should be mobilised early and pharmacological or mechanical thromboprophylaxis should be given to patients at moderate to high risk. Numerous studies have demonstrated that rates of VTE associated with hospitalisation can be reduced by more than 50% by daily administration of low dose heparins (standard unfractionated or low molecular weight heparins) or in some cases by the effective application of mechanical methods of thromboprophylaxis (Geerts et al, 2008). Therefore, defining the population at risk is a pre-requisite for targeted prophylaxis to reduce the incidence of hospital-acquired VTE. However, defining this population is not as ‘simple’ as it might at first appear. With advances in surgical practice, identification of surgical patients in need of prophylaxis has become less certain whilst the need to identify medical patients that require thromboprophylaxis is a new aspect of clinical practice for many physicians.

Changes in clinical practice

  1. Top of page
  2. Summary
  3. Changes in clinical practice
  4. Recognising hospital-acquired venous thromboembolism as a safety issue
  5. Defining the population at risk
  6. Identifying individual patients in need of thromboprophylaxis
  7. Refining risk assessment
  8. Conclusion
  9. Conflict of interest
  10. References

VTE is related to recent hospitalisation in approximately half of all adult cases (Heit et al, 2002). In addition approximately half of all hospitalised patients are considered to be at risk by conventional criteria (Cohen et al, 2008). Amongst seven million patients discharged from nearly 1000 American acute care hospitals, postoperative VTE was the second most common complication, the second-most-common cause of excess length of stay, and the third most common cause of excess mortality and excess cost (Zhan & Miller, 2003). Despite the recognition of a strong association between surgery and subsequent thrombosis, changing patterns in surgical practice have confused clinicians as to which patients require prophylaxis and for how long. For example, in orthopaedic surgery the need for pharmacological prophylaxis is still questioned by some orthopaedic surgeons as the incidence of VTE appears to have been reduced by faster surgical technique (Sharrock et al, 1992), regional anaesthesia (Prins & Hirsh, 1990) and early mobilisation (Pearse et al, 2007). In all modalities of surgery, length of stay has been significantly shortened with many patients discharged within 2 or 3 d. The clinical trials that demonstrated benefit of low dose heparins typically randomised patients to 7–10 d of prophylaxis. With rapid mobilisation and discharge the question now is whether pharmacological prophylaxis for the duration of the hospital admission is sufficient for some patients or whether all patients considered to be at sufficient risk to commence low dose heparin in hospital should continue heparin after discharge for at least 7 (or 10) d, with extended prophylaxis for longer in some patients. Late onset VTE after hospitalisation is increasingly recognised in both surgical and medical patients (Huo & Muntz, 2009) and the development of Risk Assessment Models (RAMs) for use at the time of discharge to determine which patients require extended prophylaxis are a likely development.

An increasing proportion of patients with hospital-acquired VTE are medical patients (Cohen et al, 1996; Goldhaber et al, 2000). This probably relates to increasing use of thromboprophylaxis in surgical patients over the last 30 years and a relative reduction of DVT in this population of patients. This changing pattern was reported more than 10 years ago in a long-term study at Kings College Hospital in London where a significant reduction in the rate of venographically diagnosed postoperative DVT was observed with a constant rate of non-postoperative DVT over the same period (Cohen et al, 1996). Post mortem studies indicate that the majority of patients dying due to VTE acquired during hospitalisation are medical patients (Alikhan et al, 2004; Baglin et al, 1997; Lindblad et al, 1991; Sandler & Martin, 1989; Stein & Henry, 1995). Hospital-acquired VTE is now recognised to be as much a problem in medical patients as in surgical patients (Cohen et al, 2005; Department of Health 2007, Francis, 2007; Geerts, 2009; Geerts et al, 2008; Thromboembolism Risk Factors (THRIFT) Consensus Group 1992).

Recognising hospital-acquired venous thromboembolism as a safety issue

  1. Top of page
  2. Summary
  3. Changes in clinical practice
  4. Recognising hospital-acquired venous thromboembolism as a safety issue
  5. Defining the population at risk
  6. Identifying individual patients in need of thromboprophylaxis
  7. Refining risk assessment
  8. Conclusion
  9. Conflict of interest
  10. References

Kakkar et al (1969) studied the natural history of post-operative VTE in 132 consecutive patients during the post-operative period using 125I-labelled fibrinogen leg scanning. The labelled fibrinogen was injected intravenously on the day before surgery and radioactivity over the legs was measured 1 h later, again after surgery and on the third and sixth post-operative days. In 40 of the 132 patients (30%) an increase in radioactivity over the legs was observed and venography demonstrated DVT in 39 of these 40 patients. In 14 patients the increased radioactivity resolved within 72 h and in these patients venography had demonstrated a small thrombus confined to the calf veins. In the other 26 patients the increased radioactivity persisted and extension of DVT into the proximal veins was demonstrated by venography in nine of these patients with four developing symptoms and signs of PE. This landmark study indicated that, after elective surgery, initiation of thrombus began in the calf veins in 30% of patients with clot propagating into the larger proximal veins in 7% of all patients.

Subsequent randomised trials have convincingly shown that the development of post-operative VTE is reduced by more than 50% by administration of low dose unfractionated heparin with a consequent reduction in fatal pulmonary embolus (Collins et al, 1988; Kakkar et al, 1977; Sagar et al, 1975). The administration of low dose low molecular weight heparins has been shown to be at least equally effective (Koch et al, 2001; Leizorovicz et al, 1992; Nurmohamed et al, 1992).

The high risk of fatal PE in medical patients is similarly reduced by more than 50% by the administration of low dose low molecular weight heparins (Dentali et al, 2007).

Despite this 40-year history of increasing recognition of hospital-acquired VTE and a mass of evidence showing that simple intervention reduces mortality due to fatal PE, it is only in the last 5 years that prevention of hospital-acquired VTE has been designated as a national priority for patient safety in England, with the prevention of fatal PE as the primary driving force (House of Commons Health Committee 2005). However, clarification of many issues is still required before comprehensive effective implementation becomes a reality (Baglin, 2008). The Third Annual Report of the All Party Parliamentary Thrombosis Committee published in November 2009 indicated that still only 41% of hospitals were able to provide audit data for documented risk assessment and appropriate thromboprophylaxis (http://www.dvtreport.com/). At a meeting of the UK Thromboprophylaxis Forum held at the Royal College of Physicians in London on 10th December 2008, ten ‘hurdles’ to implementation of risk assessment and thromboprophylaxis were formulated, including the fundamental issue of which patients require thromboprophylaxis (Table I).

Table I.   Ten ‘hurdles’ to implementation of risk assessment and thromboprophylaxis formulated at a meeting of the UK Thromboprophylaxis Forum held at the Royal College of Physicians in London on 10th December 2008.
Perception of problem by clinicians– many clinicians remain unaware of the risk of hospital-associated thrombosis (HAT)
Agreement on RAM– within hospitals, specialties and even in clinical teams there is often disagreement on the preferred risk assessment model, including whether an opt-in or opt-out strategy should be used
Agreement on intervention– within hospitals, specialties and even in clinical teams there is often disagreement on the preferred modality for prevention of HAT
Extended prophylaxis– amongst clinicians there is uncertainty and disagreement on the need for extended prophylaxis after discharge from hospital
Who assesses & prescribes?– should doctors or nurses perform the risk assessment?
Training & competency– how will it be ensured that the RAM is completed correctly? One simple method is to review the RAMs on post-take and post-operative ward rounds when a senior clinician can review the RAMs and validate and train staff
Implementation– process audit will measure application but effectiveness is more difficult to measure. As post mortems are now performed infrequently it is not possible to monitor fatal HAT. Therefore, non-fatal thrombosis should be monitored, for example through anticoagulant clinics and ICD codes with a register of patients with VTE developing within a defined period of hospitalisation. This allows hospitals to distinguish between a failure to risk assess and give appropriate thromboprophylaxis and a failure of appropriate thromboprophylaxis to prevent thrombosis
Funding– no funding has been designated for the process, training or the interventions. However prevention of HAT was included in the Commissioning for Quality and Innovation (CQUIN) payment framework from December 2009
Change management– bringing about change in the NHS culture is difficult. Unless prevention of HAT is embedded in the Healthcare Commission and NHS Litigation Authority procedures, implementation is likely to be unnecessarily slow and incomplete. There is also a need to incorporate prevention of HAT into the commissioning process and inclusion in CQUIN will facilitate this. Lessons learnt from the prevention of hospital-acquired infection need to be transferred
Patient empowerment & engagement– patient knowledge can help to prompt risk assessment and encourage health care staff to take steps to prevent thrombosis. Unfortunately, for much of the public DVT is something they associate with flying and not hospitalisation. The risk of fatal PE following an airflight is <1 per 1 000 000. Given that 7% of hospital deaths are due to PE, even with an optimistic hospital inpatient mortality of only 1%, the risk of dying from PE as a consequence of hospitalisation is at least 1000 times greater than after an airflight

Defining the population at risk

  1. Top of page
  2. Summary
  3. Changes in clinical practice
  4. Recognising hospital-acquired venous thromboembolism as a safety issue
  5. Defining the population at risk
  6. Identifying individual patients in need of thromboprophylaxis
  7. Refining risk assessment
  8. Conclusion
  9. Conflict of interest
  10. References

The report from the House of Commons Health Committee published in 2005 stated that each year over 25 000 people in England die from VTE developing during hospitalisation (House of Commons Health Committee 2005). The basis for this statement was not readily evident in the report. In 2007 the VTE Impact Assessment Group in Europe (VITAE) published their estimate of fatal PE in six European countries for the year 2004 (Cohen et al, 2007). The study group highlighted that epidemiological studies of diagnosed VTE underestimated the total burden of disease as many cases are undiagnosed and studies do not include unrecognised thrombosis-related deaths. The VITAE study estimated the number of VTE-related deaths from the number of treated episodes of VTE and assumed that 90% of all cases of VTE are undiagnosed. Based on other defined parameters in their model, the likelihood of diagnosed DVT being fatal was estimated at 0·6% with a 3·7% probability of undiagnosed DVT being fatal. Therefore, the model was strongly weighted by undiagnosed VTE and a relatively higher mortality in undiagnosed patients. Deaths that occurred as a consequence of hospital-acquired VTE were considered to comprise the majority of all VTE-related deaths and were estimated to be approximately 250 000 in 2004. Given the population of these countries, the annual mortality due to hospital-acquired VTE based on this estimate is about 1 per 1150 of the population. In epidemiological studies of diagnosed VTE the incidence of VTE is 1–2 per 1000. (Naess et al, 2007; Silverstein et al, 1998). Therefore, the VITAE calculations suggest that almost as many patients die of VTE as are diagnosed with the condition, with about 85% of these deaths occurring without the diagnosis being suspected in life. This estimate is compatible with the finding of the post mortem studies that demonstrate that about 85% of deaths in hospital due to hospital-acquired VTE occur without a diagnosis of VTE before death (Table II) (Alikhan et al, 2004; Baglin et al, 1997; Lindblad et al, 1991; Sandler & Martin, 1989; Stein & Henry, 1995).

Table II.   Post-mortem studies recording death due to pulmonary embolus.
LocationAuthor (year)Number of post-mortems (post-mortem rate)Total PE at post-mortemDeaths attributable to PE at post mortemProportion of fatal cases with venous thrombosis not suspected in life
  1. *The study reported by Alikhan et al (2004) is a continuation of a previous analysis at King’s College Hospital, London, Cohen et al, 1996).

  2. †Adult post-mortems only.

SheffieldSandler and Martin (1989)2388 (47%)313 (13%)239 (10%)95%
MalmoLindblad et al (1991)994 (77% in final year of study)260 (26%)93 (9·4%)
DetroitStein and Henry (1995)404 (–)59 (15%)20 (5·0%)70%
CambridgeBaglin et al (1997)400 (–)45 (11·25%)29 (7·25%)90%
LondonAlikhan et al (2004)*5107† (42%)265 (5·2%)
Total 9293 646 7% (95%CI 6·4–7·5) 

The population of the UK is approximately 60 million and so the VITAE calculation equates to about 52 000 deaths per year due to hospital-acquired VTE. The ENDORSE (Evaluation of Patients at Risk for Venous Thromboembolism in the Acute Hospital Care Setting) study indicated that only about 50% of at risk patients receive appropriate thromboprophylaxis in the UK (Cohen et al, 2008). On the basis that prophylaxis reduces the rate of fatal PE by 60%, the ratio of deaths due to PE in patients not receiving prophylaxis compared to those who do would be about 1·7 and so 33 000 deaths would be in patients not receiving prophylaxis, of which 20 000 (60%) could be prevented by low dose low molecular weight heparin. As 85% of the UK population live in England the figure would be about 17 000 for England alone. This estimate would vary if the rates for England and the UK were different to the European rate and if prophylaxis was considered to reduce the rate of fatal PE by more than 60%. In addition, some of the patients dying from PE would have terminal illness. The most recent post-mortem study indicated that 22% of deaths due to fatal PE in hospitalised patients occurred in those with cancer (Alikhan et al, 2004) and so the number of preventable deaths annually might be closer to 14 000 based on these estimates.

UK-specific data using the VITAE and ENDORSE methodologies are now on file and indicate that the annual number of preventable deaths in the UK is higher than previously thought (Alexander Cohen, Kings College Hospital, London, personal communication). The annual number of hospital deaths in England is now approximately 270 000. Postmortem studies show that 7% of deaths in hospitalised patients are due to PE (Table II) (Alikhan et al, 2004; Baglin et al, 1997; Lindblad et al, 1991; Sandler & Martin, 1989; Stein & Henry, 1995). This equates to 19 000 deaths. At least 50% of episodes of VTE become apparent only after discharge from hospital (Goldhaber et al, 2000; Goldhaber & Tapson, 2004; Huber et al, 1992; Spencer et al, 2007; Sweetland et al, 2009), and so the total number of deaths due to hospital-acquired thrombosis may be significantly >19 000 and possibly approach, or even exceed, the proposed figure of 25 000.

Identifying individual patients in need of thromboprophylaxis

  1. Top of page
  2. Summary
  3. Changes in clinical practice
  4. Recognising hospital-acquired venous thromboembolism as a safety issue
  5. Defining the population at risk
  6. Identifying individual patients in need of thromboprophylaxis
  7. Refining risk assessment
  8. Conclusion
  9. Conflict of interest
  10. References

In 1986 a Consensus Conference Statement was issued from the US National Institutes of Health (National Institutes of Health 1986). One of the questions addressed by the consensus development panel was ‘What is the level of risk of DVT and PE in various patient groups?’ The question was answered primarily by reference to rates of DVT, identified by radio-labelled fibrinogen leg scanning or venography, in control arms of randomised studies of thromboprophylaxis in surgical patients. The conclusion was that groups of high risk patients could be identified and the incidence of VTE could be significantly reduced by prophylactic regimens, which the statement concluded should be used more extensively. Nine questions that remained to be answered about prevention of VTE were formulated. Notably, none of these questions related specifically to improving methods for defining the population in need of thromboprophylaxis.

In 1992 the Thromboembolic Risk Factors (THRIFT) Consensus Group issued a similar statement but with the addition of a list of risk factors for thromboembolism and summarising the classification of risk into low, moderate and high (Thromboembolism Risk Factors (THRIFT) Consensus Group 1992) as originally proposed by Salzman and Hirsh (1982).

The American College of Chest Physicians Guideline has been adopted as an international guideline (Cohen et al, 2008; Tapson et al, 2007). The 8th edition describes two general approaches to deciding who needs thromboprophylaxis (Geerts et al, 2008). One approach is to consider the risk of VTE in each patient based on individual risk factors and the risk associated with their current illness or procedure. Thromboprophylaxis is then prescribed based on the composite risk estimate. This approach requires the use of RAMs (Cohen et al, 2005). Many RAMs have been published but are limited by a lack of understanding of how the various risk factors interact in a quantitative manner to determine the absolute risk of VTE in an individual. However, this may be more of a theoretical concern than a real problem. The alternative approach is to implement group-specific prophylaxis routinely for all patients belonging to a major at-risk group, for example, major orthopaedic surgery. With the recognition of a high risk of hospital-acquired thrombosis in medical as well as surgical patients, recent RAMs have tended to combine these two general approaches with identification of procedural risks, identifying general groups of patients with the degree of risk refined in relation to patient-specific risk factors. The potential disadvantage of this approach is perceived complication and consequently suboptimal implementation. The advantage is that a single RAM at the point of entry to hospital can be applied to all patients so that at-risk patients will not be missed, regardless of the indication for admission. Furthermore, all hospital staff will quickly become familiar with the model and so implementation becomes routine.

In recognition of these advantages combined with the need for simplicity, the Implementation Working Group, working with stakeholders such as the National Institute for Clinical Excellence (NICE), proposed a simplified RAM in which any single defined risk factor (procedural or personal) qualified a patient as sufficiently high risk to be considered for thromboprophylaxis (Department of Health 2008b). In relation to surgical patients the procedural risk remains the major determinant of VTE risk. However, in an individual the patient-related risk factors may increase the perceived level of risk such that a patient undergoing a low risk procedure (such as knee arthroscopy) might ‘qualify’ for prophylaxis based on their personal risk profile, for example a history of PE after a previous minor surgical procedure. Alternatively, a patient undergoing abdominal surgery who might normally be considered to be at moderate risk and prescribed 20 mg enoxaparin or 2500 units of dalteparin daily, might be prescribed 40 mg or 5000 units, respectively, due to additional medical risk factors that ‘elevate’ them to high risk, for example active chronic inflammatory bowel disease. The NICE Clinical Guideline 92 ‘Venous Thromboembolism: reducing the risk’ was published in January 2010 (NICE 2010) and replaces NICE Clinical Guideline 46. The RAM included in Guideline 92 is a development of the Implementation Working Group’s RAM published in 2008 but with some notable differences:

  • 1
     Medical patients are considered to be at risk if their mobility is reduced for 3 d or more, or they are expected to have ongoing reduced mobility;
  • 2
     The procedural risk of surgery is defined in relation to duration of a procedure as total anaesthetic plus surgical time >90 min or >60 min if surgery involves the pelvis or lower limb.

Refining risk assessment

  1. Top of page
  2. Summary
  3. Changes in clinical practice
  4. Recognising hospital-acquired venous thromboembolism as a safety issue
  5. Defining the population at risk
  6. Identifying individual patients in need of thromboprophylaxis
  7. Refining risk assessment
  8. Conclusion
  9. Conflict of interest
  10. References

The risk of VTE in relation to surgical procedures is still largely dependent on procedural risk and a simple RAM based on procedure and age is frequently used in practice (Geerts et al, 2008; Kearon & Hirsh, 2001; Salzman & Hirsh, 1982). Nevertheless, despite the availability of simple, cheap and effective prophylaxis, it is still underused in surgical patients (Kakkar et al, 2004; Yu et al, 2007). RAMs are not as well established for medical patients and only a minority currently receive prophylaxis (Amin et al, 2007; Cohen et al, 2008; Kahn et al, 2007; Tapson et al, 2007; Yu et al, 2007). Risk factors for VTE in medical patients have been identified from registries, epidemiological, case control, observational cohorts and control arms of randomised interventional studies. The risks of VTE and the benefits of prophylaxis have been reviewed and a comprehensive RAM derived for medical patients (Cohen et al, 2005). This relatively simple RAM combines medical conditions associated with VTE risk with individual patient risks, classified as evidence-based or consensus-based. The output from the RAM is either ‘yes’ or ‘no’ when deciding whether a medical patient should receive thromboprophylaxis.

Regardless of the approach to risk assessment, further refinements in defining at-risk patients are required as clinical practice continually changes and hence, the risk attributable to individual factors changes. Furthermore, how the various risk factors interact to determine risk is still unknown and so RAMs may yet be further simplified after multivariate analysis of large databases of patient demographics and outcomes in relation to hospital episodes. Hospital Episode Statistics (HES) is the national statistical data warehouse relating to care provided by NHS hospitals and for NHS hospital patients treated elsewhere and this may become a reliable resource that may enable identification of the majority of patients at risk by a minimum number of clinical risk factors. A large dataset would enable identification of risk factors and interaction by comparing regional or national patient and control cohorts.

There are reasons to prevent VTE other than death; namely morbidity from DVT and PE including long term complications, such as post-thrombotic syndrome and chronic pulmonary hypertension, risk of bleeding from therapeutic intensity anticoagulation, delayed discharge and re-admission. For example, the severity of hospital-acquired thrombosis and the complications due to having to administer therapeutic intensity anticoagulation were highlighted by a study in which 3·4% of patients died, with PE considered to be a major contributory factor in 40% of these, and 5% of all treated patients suffered gastrointestinal haemorrhage with one fatal cerebral bleed (Goldhaber et al, 2000). Despite many reasons for preventing hospital-acquired thrombosis the primary declared reason for risk assessment and prophylaxis in England, if not the UK, is prevention of hospital deaths due to PE (Department of Health 2008b). It is unlikely that reduction of hospital-acquired infection would have been achieved without prioritisation at the highest level of management within the NHS and appropriate allocation of resources. However, equally important was the ability to directly measure hospital-acquired infection by microbiological identification so that the effect of intervention could be monitored by measurement of the primary target, i.e. infection. In contrast measurement of fatal PE is problematic. At least 80% of fatal hospital-acquired emboli are not suspected before death and therefore the only way to monitor the primary outcome is by post mortem examination. However, due to procedural changes and public perceptions regarding post mortems it was predicted that post mortem rates would fall in the UK (Alikhan et al, 2004; Carr et al, 2002) and this has been confirmed. For example, post mortem rates at Addenbrooke’s Hospital have fallen by 95% since the post mortem study of fatal hospital-acquired thrombosis was reported (Baglin et al, 1997) (Fig 1). Therefore, the effort to reduce hospital-acquired thrombosis will be hindered by an inability to measure the effect of strategic interventions on the primary outcome of death. Instead, measurement of the surrogate marker of symptomatic non-fatal VTE will have to suffice. Events could theoretically be achieved by monitoring completed hospital episodes coded according to the International Classification of Disease (ICD 10th edition – I26 & I80 with Y83 identifying surgical intervention). However, inaccurate coding and overlap between primary and secondary coding may hamper this approach for some time in many hospitals. A likely, more reliable approach to monitoring, at least at present, is identification of patients referred for anticoagulant treatment within 3 months of hospitalisation. This process of identification can be supplemented with reports of positive ultrasounds and lung imaging from radiology departments. However, this method of monitoring is only likely to be informative if the majority of patients are referred to the same hospital for diagnosis and treatment of VTE as in which they were originally hospitalised. Thus, for many cities in the UK it is quite possible, indeed likely, that many patients will move between hospitals. Defining an episode of VTE as hospital-acquired requires validation at least by notes review and is likely to be most beneficial if linked by feedback to the initial clinical team. With this in mind a ‘Look Back’ programme was introduced at Addenbrookes’s Hospital in January 2008. Patients developing VTE in hospital or within 3 months of discharge are identified and the RAM, modelled on the Department of Health RAM (Department of Health 2008b), is retrospectively completed from the patient’s clinical record taken at the time of initial hospitalisation. It is then possible to determine if hospital-acquired VTE was the result of a failure of risk assessment, a failure to implement prophylaxis or a prophylaxis failure. This analysis is important as a report from a hospital with a high rate of thromboprophylaxis demonstrated that most fatal hospital-acquired thrombosis was due to failed prophylaxis rather than omitted prophylaxis (Goldhaber et al, 2000). In the Addenbrooke’s Look Back programme individual results are fed back to the responsible consultant and collectively results are incorporated into a hospital-wide dataset (Table III).

image

Figure 1.  Post mortem rates for Addenbrooke’s Hospital, Cambridge. Data supplied by Simon Brown, Department of Histopathogy, Addenbrooke’s Hospital, Cambridge.

Download figure to PowerPoint

Table III.   Proposed model for a Look Back programme.
  1. *Definition of hospital-associated venous thrombosis should be pre-determined with respect to time since discharge, e.g. 3 months, and should include events occurring during hospitalisation and after discharge.

Identification*Referrals to anticoagulant service for treatment of DVT or PERadiology report listsICD codes I26 & I80
FeedbackIndividual patient reports to clinical team responsible for initial period of hospitalisation indicating if:  
 Failure of risk assessment
 Failure to implement prophylaxis
 Prophylaxis failure with refinement of local RAM and prophylaxis strategy over time
MonitoringCumulative dataset  
 Hospital wide rates
 By division (medical, surgical, orthopaedic, other)

Conclusion

  1. Top of page
  2. Summary
  3. Changes in clinical practice
  4. Recognising hospital-acquired venous thromboembolism as a safety issue
  5. Defining the population at risk
  6. Identifying individual patients in need of thromboprophylaxis
  7. Refining risk assessment
  8. Conclusion
  9. Conflict of interest
  10. References

Despite the prioritisation of prevention of hospital-acquired thrombosis at a national level in England since 2007, considerable effort is needed to achieve universal risk assessment of hospitalised patients and to make death due to a failure to implement prophylaxis a ‘never event’. The same effort is required throughout the UK. Dr Foster Intelligence published The Hospital Guide for 2009 in relation to patient safety and quality accounts (http://www.drfosterhealth.co.uk/quality-accounts/) and in response to the question ‘What percent of patients are risk assessed for VTE on admission’ only 31% of Trusts reported that they risk-assessed more than 90% of patients on admission (Fig 2). Audit frequently indicates that more patients receive prophylaxis than are risk-assessed and so process audits should include both risk assessment and administration of prophylaxis as standards to be measured. As the quality of national data regarding hospital-acquired thrombosis linked to patient demographics and hospital episodes improves it will be possible to develop models of care based on absolute-risk-reduction and which optimise cost-effectiveness.

image

Figure 2.  Answer to question ‘What percent of patients are risk assessed for venous thromboembolism on admission?’ by 123 hospitals in The Hospital Guide for 2009 published by Dr Foster Intelligence (http://www.drfosterhealth.co.uk/quality-accounts/).

Download figure to PowerPoint

Conflict of interest

  1. Top of page
  2. Summary
  3. Changes in clinical practice
  4. Recognising hospital-acquired venous thromboembolism as a safety issue
  5. Defining the population at risk
  6. Identifying individual patients in need of thromboprophylaxis
  7. Refining risk assessment
  8. Conclusion
  9. Conflict of interest
  10. References

T Baglin is grateful to Dr Julian Flower, Director of the Eastern Region Public Health Observatory, Institute of Public Health, Cambridge, for helpful discussion & Caroline Baglin, Nurse Consultant at Addenbrooke’s Hospital, for helpful discussion and development of the Look Back programme. TB was a member of the Implementation Working Group and the Department of Health Venous Thromboemblism Expert Group and has received honoraria from Sanofi-Synthelabo, Boerhinger and Bayer in the last 5 years.

References

  1. Top of page
  2. Summary
  3. Changes in clinical practice
  4. Recognising hospital-acquired venous thromboembolism as a safety issue
  5. Defining the population at risk
  6. Identifying individual patients in need of thromboprophylaxis
  7. Refining risk assessment
  8. Conclusion
  9. Conflict of interest
  10. References
  • Alikhan, R., Peters, F., Wilmott, R. & Cohen, A.T. (2004) Fatal pulmonary embolism in hospitalised patients: a necropsy review. Journal of Clinical Pathology, 57, 12541257.
  • Amin, A., Stemkowski, S., Lin, J. & Yang, G. (2007) Thromboprophylaxis rates in US medical centers: success or failure? Journal of Thrombosis and Haemostasis, 5, 16101616.
  • Baglin, T. (2008) Venous thromboembolism in hospitalised patients: a public health crisis? British Journal of Haematology, 141, 764770.
  • Baglin, T.P., White, K. & Charles, A. (1997) Fatal pulmonary embolism in hospitalised medical patients. Journal of Clinical Pathology, 50, 609610.
  • Carr, N.J., Burke, M.M., Corbishley, C.M., Suarez, V. & McCarthy, K.P. (2002) The autopsy: lessons from the National Confidential Enquiry into Perioperative Deaths. Journal of the Royal Society of Medicine, 95, 328330.
  • Cohen, A.T., Edmondson, R.A., Phillips, M.J., Ward, V.P. & Kakkar, V.V. (1996) The changing pattern of venous thromboembolic disease. Haemostasis, 26, 6571.
  • Cohen, A.T., Alikhan, R., Arcelus, J.I., Bergmann, J.F., Haas, S., Merli, G.J., Spyropoulos, A.C., Tapson, V.F. & Turpie, A.G. (2005) Assessment of venous thromboembolism risk and the benefits of thromboprophylaxis in medical patients. Thrombosis and Haemostasis, 94, 750759.
  • Cohen, A.T., Agnelli, G., Anderson, F.A., Arcelus, J.I., Bergqvist, D., Brecht, J.G., Greer, I.A., Heit, J.A., Hutchinson, J.L., Kakkar, A.K., Mottier, D., Oger, E., Samama, M.M. & Spannagl, M. (2007) Venous thromboembolism (VTE) in Europe. The number of VTE events and associated morbidity and mortality. Thrombosis and Haemostasis, 98, 756764.
  • Cohen, A.T., Tapson, V.F., Bergmann, J.F., Goldhaber, S.Z., Kakkar, A.K., Deslandes, B., Huang, W., Zayaruzny, M., Emery, L. & Anderson, Jr, F.A. (2008) Venous thromboembolism risk and prophylaxis in the acute hospital care setting (ENDORSE study): a multinational cross-sectional study. Lancet, 371, 387394.
  • Collins, R., Scrimgeour, A., Yusuf, S. & Peto, R. (1988) Reduction in fatal pulmonary embolism and venous thrombosis by perioperative administration of subcutaneous heparin. Overview of results of randomized trials in general, orthopedic, and urologic surgery. New England Journal of Medicine, 318, 11621173.
  • Dentali, F., Douketis, J.D., Gianni, M., Lim, W. & Crowther, M.A. (2007) Meta-analysis: anticoagulant prophylaxis to prevent symptomatic venous thromboembolism in hospitalized medical patients. Annals of Internal Medicine, 146, 278288.
  • Department of Health (2007) Report of the independent expert working group on the prevention of venous thromboembolism in hospitalised patients. http://www.dh.gov.uk/en/Publicationsandstatistics/Publications/PublicationsPolicyAndGuidance/DH_073944 .
  • Department of Health (2008a) Hospital patients to be assessed for risk of blood clots. http://nds.coi.gov.uk/content/detail.aspx?NewsAreaId=2&ReleaseID=379218&SubjectId=16&AdvancedSearch=true .
  • Department of Health (2008b) Risk assessment for venous thromboembolism. http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/@dh/@en/documents/digitalasset/dh_088216.pdf .
  • Francis, C.W. (2007) Clinical practice. Prophylaxis for thromboembolism in hospitalized medical patients. New England Journal of Medicine, 356, 14381444.
  • Geerts, W. (2009) Prevention of venous thromboembolism: a key patient safety priority. Journal of Thrombosis and Haemostasis, 7(Suppl. 1), 18.
  • Geerts, W.H., Bergqvist, D., Pineo, G.F., Heit, J.A., Samama, C.M., Lassen, M.R. & Colwell, C.W. (2008) Prevention of venous thromboembolism: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th edition). Chest, 133, 381S453S.
  • Goldhaber, S.Z. & Tapson, V.F. (2004) A prospective registry of 5,451 patients with ultrasound-confirmed deep vein thrombosis. American Journal of Cardiology, 93, 259262.
  • Goldhaber, S.Z., Dunn, K. & MacDougall, R.C. (2000) New onset of venous thromboembolism among hospitalized patients at Brigham and Women’s Hospital is caused more often by prophylaxis failure than by withholding treatment. Chest, 118, 16801684.
  • Heit, J.A., O’Fallon, W.M., Petterson, T.M., Lohse, C.M., Silverstein, M.D., Mohr, D.N. & Melton, 3rd, L.J. (2002) Relative impact of risk factors for deep vein thrombosis and pulmonary embolism: a population-based study. Archives of Internal Medicine, 162, 12451248.
  • House of Commons Health Committee (2005) The Prevention of Venous Thromboembolism in Hospitalised Patients, Second Report of Session 2004–2005. May 2007. http://www.publications.parliament.uk/pa/cm200405/cmselect/cmhealth/99/99.pdf.
  • Huber, O., Bounameaux, H., Borst, F. & Rohner, A. (1992) Postoperative pulmonary embolism after hospital discharge. An underestimated risk. Archives of Surgery, 127, 310313.
  • Huo, M.H. & Muntz, J. (2009) Extended thromboprophylaxis with low-molecular-weight heparins after hospital discharge in high-risk surgical and medical patients: a review. Clinical Therapeutics, 31, 11291141.
  • Kahn, S.R., Panju, A., Geerts, W., Pineo, G.F., Desjardins, L., Turpie, A.G., Glezer, S., Thabane, L. & Sebaldt, R.J. (2007) Multicenter evaluation of the use of venous thromboembolism prophylaxis in acutely ill medical patients in Canada. Thrombosis Research, 119, 145155.
  • Kakkar, V.V., Howe, C.T., Flanc, C. & Clarke, M.B. (1969) Natural history of postoperative deep-vein thrombosis. Lancet, 2, 230232.
  • Kakkar, V.V., Corrigan, T.P., Fossard, D.P., Sutherland, I. & Thirwell, J. (1977) Prevention of fatal postoperative pulmonary embolism by low doses of heparin. Reappraisal of results of international multicentre trial. Lancet, 1, 567569.
  • Kakkar, A.K., Davidson, B.L. & Haas, S.K. (2004) Compliance with recommended prophylaxis for venous thromboembolism: improving the use and rate of uptake of clinical practice guidelines. Journal of Thrombosis and Haemostasis, 2, 221227.
  • Kearon, C. & Hirsh, J. (2001) Prevention of venous thromboembolism. In: Hemostasis and Thrombosis: Basic Principles and Clinical Practice (ed. by R.Colman, J.Hirsh, V.Marder, A.Clowes & J.George), pp. 13931404. Lippincott Williams & Wilkins, Philadelphia.
  • Koch, A., Ziegler, S., Breitschwerdt, H. & Victor, N. (2001) Low molecular weight heparin and unfractionated heparin in thrombosis prophylaxis: meta-analysis based on original patient data. Thrombosis Research, 102, 295309.
  • Leizorovicz, A., Haugh, M.C., Chapuis, F.R., Samama, M.M. & Boissel, J.P. (1992) Low molecular weight heparin in prevention of perioperative thrombosis. British Medical Journal, 305, 913920.
  • Lindblad, B., Sternby, N.H. & Bergqvist, D. (1991) Incidence of venous thromboembolism verified by necropsy over 30 years. British Medical Journal, 302, 709711.
  • Naess, I.A., Christiansen, S.C., Romundstad, P., Cannegieter, S.C., Rosendaal, F.R. & Hammerstrom, J. (2007) Incidence and mortality of venous thrombosis: a population-based study. Journal of Thrombosis and Haemostasis, 5, 692699.
  • National Institutes of Health (1986) Prevention of venous thrombosis and pulmonary embolism. NIH Consensus Development. Journal of the American Medical Association, 256, 744749.
  • NICE (2010) Venous thromboembolism: reducing the risk. Clinical Guideline 92, January http://guidance.nice.org.uk/CG92.
  • Nurmohamed, M.T., Rosendaal, F.R., Buller, H.R., Dekker, E., Hommes, D.W., Vandenbroucke, J.P. & Briet, E. (1992) Low-molecular-weight heparin versus standard heparin in general and orthopaedic surgery: a meta-analysis. Lancet, 340, 152156.
  • Pearse, E.O., Caldwell, B.F., Lockwood, R.J. & Hollard, J. (2007) Early mobilisation after conventional knee replacement may reduce the risk of postoperative venous thromboembolism. Journal of Bone and Joint Surgery, 89-B, 316322.
  • Prins, M.H. & Hirsh, J. (1990) A comparison of general anesthesia and regional anesthesia as a risk factor for deep vein thrombosis following hip surgery: a critical review. Thrombosis and Haemostasis, 64, 497500.
  • Sagar, S., Massey, J. & Sanderson, J.M. (1975) Low-dose heparin prophylaxis against fatal pulmonary embolism. British Medical Journal, 4, 257259.
  • Salzman, E. & Hirsh, J. (1982) Prevention of venous thromboembolism. In: Hemostasis and Thrombosis: Basic Principles and Clinical Practice (ed. by R.Colman, J.Hirsh, V.Marder & E.Salzman), pp. 986992. Lippincott, New York.
  • Sandler, D.A. & Martin, J.F. (1989) Autopsy proven pulmonary embolism in hospital patients: are we detecting enough deep vein thrombosis? Journal of the Royal Society of Medicine, 82, 203205.
  • Sharrock, N.E., Go, G., Mineo, R. & Harpel, P.C. (1992) The hemodynamic and fibrinolytic response to low dose epinephrine and phenylephrine infusions during total hip replacement under epidural anesthesia. Thrombosis and Haemostasis, 68, 436441.
  • Silverstein, M.D., Heit, J.A., Mohr, D.N., Petterson, T.M., O’Fallon, W.M. & Melton, 3rd, L.J. (1998) Trends in the incidence of deep vein thrombosis and pulmonary embolism: a 25-year population-based study. Archives of Internal Medicine, 158, 585593.
  • Spencer, F.A., Lessard, D., Emery, C., Reed, G. & Goldberg, R.J. (2007) Venous thromboembolism in the outpatient setting. Archives of Internal Medicine, 167, 14711475.
  • Stein, P.D. & Henry, J.W. (1995) Prevalence of acute pulmonary embolism among patients in a general hospital and at autopsy. Chest, 108, 978981.
  • Sweetland, S., Green, J., Liu, B., Berrington de Gonzalez, A., Canonico, M., Reeves, G. & Beral, V. (2009) Duration and magnitude of the postoperative risk of venous thromboembolism in middle aged women: prospective cohort study. British Medical Journal, 339, b4583.
  • Tapson, V.F., Decousus, H., Pini, M., Chong, B.H., Froehlich, J.B., Monreal, M., Spyropoulos, A.C., Merli, G.J., Zotz, R.B., Bergmann, J.F., Pavanello, R., Turpie, A.G., Nakamura, M., Piovella, F., Kakkar, A.K., Spencer, F.A., Fitzgerald, G. & Anderson, Jr, F.A. (2007) Venous thromboembolism prophylaxis in acutely ill hospitalized medical patients: findings from the International Medical Prevention Registry on Venous Thromboembolism. Chest, 132, 936945.
  • Thromboembolism Risk Factors (THRIFT) Consensus Group (1992) Risk of and prophylaxis for venous thromboembolism in hospital patients. Thromboembolic Risk Factors (THRIFT) Consensus Group. British Medical Journal, 305, 567574.
  • Yu, H.T., Dylan, M.L., Lin, J. & Dubois, R.W. (2007) Hospitals’ compliance with prophylaxis guidelines for venous thromboembolism. American Journal of Health-System Pharmacy, 64, 6976.
  • Zhan, C. & Miller, M.R. (2003) Excess length of stay, charges, and mortality attributable to medical injuries during hospitalization. Journal of the American Medical Association, 290, 18681874.