Venous thromboembolism (VTE) is a major, and often unrecognised cause of patient morbidity and mortality in hospitalised patients . Pulmonary embolism (PE) accounts for 5-10% of hospital deaths and is, therefore, often quoted as the most preventable cause of death in hospital [1–5]. Hospitalised patients are at a 100 times greater risk than primary care patients  and between 25-30% of non-fatal VTEs occur in patients with prior hospitalisation .
The prevention of VTE has been identified as a major health need nationally and internationally to improve patient safety . A recent multinational, observational, cross-sectional study carried out in 358 hospitals from 32 different countries (the ENDORSE study) showed that 51.8% of patients were at risk of VTE and only 50.2% of patients who were deemed to be at risk received prophylaxis . A retrospective review of patients with a diagnosis of VTE was performed in 2010 in New Zealand and supported these findings. It demonstrated that 25% of patients with a VTE had been admitted to hospital in the preceding three months. Of these patients, two thirds had not received appropriate prophylaxis .
Several trials have been performed studying the use of single and multiple implementation strategies [5, 8–10]. Single strategies such as passive dissemination are the least effective method of implementing guidelines, whereas combined systems of education, reminders, audit and feedback are believed more effective . Many studies, however, presented short term data, so it is not known whether these implementation programmes had lasting effects [5, 8]. In addition, many are examining the implementation of local guidelines.
This study presents data from the implementation of a new national guideline issued by the National Institute for Health and Clinical Excellence (NICE) in the UK in February 2010 (see below) .
NICE Clinical Guideline 92, 2010 
Assess patients for risk of VTE on admission to hospital
Assess patients for bleeding risk
Weigh up benefits and risks of prescribing prophylaxis and prescribe if appropriate
Prophylactic measures to be taken if indicated:
Pharmacological measures, e.g., fondaparinux sodium, LMWH, unfractionated heparin (UFH) in patients with renal failure
Mechanical prophylaxis, e.g., anti-embolism stockings, foot impulse devices and intermittent pneumatic compression devices
General measures should also be taken:
The aim of this study was to evaluate the implementation of the NICE guideline across four hospitals in the NHS South of England region, and its impact on patient safety using the following outcome measures:
The percentage of patients for whom a risk assessment was documented.
The percentage of patients who received VTE prophylaxis amongst those who were not risk assessed.
The percentage of patients who received VTE prophylaxis amongst those with a contraindication to VTE prophylaxis.
The percentages were compared between the years prior to (2009) and following (2010) publication of the NICE guideline.