Safety of care

Improving patient safety and reducing risks

Perils in the prevention of venous thromboembolism

Originally published June 2012

Today the management of patients at risk of developing venous thromboembolism is undergoing greater scrutiny than in the past.

Venous thromboembolism (VTE) refers collectively to the conditions of deep venous thrombosis and pulmonary embolism. Pulmonary embolism secondary to deep venous thrombosis is the leading cause of preventable hospital deaths, accounting for about 10% of in-hospital mortality.1 Non-fatal VTE events are important causes of morbidity and prolonged hospitalization.2

Most venous thromboembolism cases develop during hospitalization and in the weeks and months after discharge. Different approaches to preventing VTE — drug and non-drug strategies — have been studied extensively for hospitalized patients with a wide range of medical and surgical conditions. Overall, appropriate pharmacological prophylaxis reduces the incidence of venous thromboembolism by 50% to 60% in patients at risk.3

Patients who are at risk for venous thromboembolism must be identified and managed appropriately. When evaluating a patient's risk and deciding on a treatment, patient-specific features should also be considered. Often, even during a single admission, the risk of VTE and bleeding events varies due to many factors such as patient immobility and the need for invasive procedures. Anticoagulants may increase the risk of bleeding, and that risk must be considered when making decisions about VTE prophylaxis. Several anticoagulation protocols aimed at preventing venous thromboembolism are available. These protocols rely on different agents, timing, and routes of administration. As it is not the CMPA's mandate to set standards of practice, the Association does not endorse any particular approach.

Despite the publication of regularly-updated evidence-based guidelines, large published multi-national studies indicate VTE prophylaxis is underused in hospitalized patients at risk.45 One of the recommendations of a major guideline review is that every general hospital should develop a strategy to prevent venous thromboembolism.6

Accreditation Canada has developed Required Organizational Practices in which medical and surgical services are required to address prevention of venous thromboembolism. These practices include VTE Prophylaxis and Safe Surgery Checklist which state that adult surgical centres should have a written VTE prophylaxis policy or guideline, and that a safe surgery checklist should be used in operating rooms in Canada7. The checklists now in use by many Canadian hospitals include a reminder to consider the patient's need for VTE prophylaxis.

VTE cases from the CMPA

During the six-year period from 2006 to 2011, the CMPA had 242 medico-legal cases involving venous thromboembolism. Many of the medico-legal problems in these cases were the result of allegations that the physician failed to diagnose and treat venous thromboembolism. The cases also identified medico-legal problems related to VTE prophylaxis such as failing to consider risk factors specific to an individual patient, and underestimating the risk of developing VTE due to illness.

Case examples

Case 1: Failure to recognize a patient at increased risk of VTE

A family physician referred a 50-year-old woman with a history of postpartum deep venous thrombosis (DVT) to an orthopaedic surgeon for bilateral hallux rigidus.

Approximately two months after surgery on her left foot, the patient developed a DVT in the lower left leg. Warfarin therapy, with appropriate monitoring, was prescribed for several months. The family physician did not advise the orthopaedic surgeon of this complication. Although the patient reported the deep venous thrombosis to the surgeon at a follow-up appointment, the surgeon did not document it in the medical record.

Without the family physician's knowledge, the patient returned to the orthopaedic surgeon one year later for surgery on the other foot. As the office record did not contain the history of deep venous thrombosis and the surgeon did not specifically ask about past DVT during history taking, venous thromboembolism prophylaxis was not prescribed. The surgery was uneventful, and there was no clinical evidence of deep venous thrombosis throughout the post-operative period. When the family physician learned a second surgery had been performed, he was concerned about the need for anticoagulation. However, the patient advised him that she was instructed to do exercises to prevent deep venous thrombosis. Believing anticoagulation was being addressed by the orthopaedic surgeon who the patient would be seeing the following day, the family physician did not prescribe prophylactic anticoagulants. Ten days later, the patient died from a pulmonary embolism secondary to deep venous thrombosis. The family initiated a legal action.

What the experts said

Peer experts in the case expressed the view the patient probably would have had a decreased likelihood of venous thromboembolism after the second surgery had post-operative anticoagulant prophylaxis been prescribed. The experts also maintained that a lack of communication between the physicians and deficiencies in history taking and documentation contributed to this omission.

Without expert support, the CMPA, on behalf of the family physician and orthopaedic surgeon, paid a settlement to the patient's family. While the medical literature does not provide evidence for prophylaxis in this type of surgery, given the prior deep venous thrombosis after similar surgery, a reasonable expectation in this case was to provide pharmacologic prophylaxis.


Case 2: Decision to not use VTE prophylaxis

An elderly patient, with severe oxygen-dependent chronic obstructive pulmonary disease (COPD), had acute cholecystitis related to cholelithiasis.

In hospital, she did not significantly improve with intravenous fluids and antibiotics, and an ultrasound revealed fluid surrounding the gallbladder. A laparoscopic cholecystectomy was performed, and a Jackson-Pratt drain was placed because of minor bleeding from the hepatic bed. Given the bleeding and severe co-morbidities, the patient was not considered a good candidate for VTE prophylaxis. She was admitted to an intensive care unit for observation and within 24 hours was sent to the ward in stable condition. Days later, she became rapidly unwell with shortness of breath and sinus bradycardia, followed by cardiac arrest with unsuccessful resuscitation. An autopsy identified a large pulmonary embolism as the cause of death. A legal action followed.

Experts' opinion

Peer experts for the defence in this case supported the care provided. Ultimately the matter was resolved with a consent dismissal (a document provided by the parties in a legal action stating the dispute is resolved and the parties agree the court should dismiss the claim).


The experts' concerns in the VTE cases

In each CMPA case, the defence retained different peer experts to review the care. The following summarizes the concerns identified from all of the cases:

  • failure to obtain or consider relevant patient-specific risk factors (e.g. age over 70; personal or family history of deep venous thrombosis, pulmonary embolism, or thrombophilia; cancer; congestive heart failure; acute stroke or MI; certain drug therapies predisposing the patient to clotting; obesity; lack of mobility; and others)
  • underestimation of venous thromboembolism risk caused by illness
  • inappropriate risk stratification when determining appropriate candidacy for venous thromboembolism prophylaxis (overestimation of the risk of perioperative hemorrhage was not supported by the experts)
  • inadequate informed consent discussions
  • verbal or written communication issues between treating physicians, and also between physicians and other healthcare professionals, that impeded the transmission of important information
  • incomplete discharge instructions to inform patients about the importance of continuing anticoagulant strategies post-discharge, and providing information on the symptoms of possible thromboembolic disease and the need to seek medical attention should these occur
  • inadequate documentation of consent, clinical care, and discharge instructions in the medical record

Managing the medico-legal risks of VTE

The following risk management considerations are based on the experts' opinions in the analyzed CMPA cases:

  • Are you aware of your hospital's formal VTE prophylaxis policy or guidelines?
  • Do you consider current clinical practice guidelines for venous thromboembolism prevention when assessing individual patients?
  • If a patient's clinical risk factors for venous thromboembolism change, do you reassess the need for prophylaxis?
  • Do you appropriately adjust and resume anticoagulation as required?
  • Do you provide patients with a consent discussion related to VTE prophylaxis?
  • When a patient's particular features cause you to modify your usual approach to VTE prophylaxis, is your decision-making process reflected in your discussion with the patient and in your notes in the medical record?
  • If appropriate, do you provide anticoagulation therapy at discharge and provide advice on the symptoms of possible VTE disease?
  • Do you adequately document consent, clinical care, and discharge discussions?
  • If the patient returns with symptoms and findings suspicious of deep venous thrombosis or pulmonary embolism, do you arrange appropriate investigations in a timely way?

Two key points

  1. Physicians should be aware of their institution's guidelines for VTE prophylaxis.
  2. Physicians should consider a careful evaluation of each patient's history for risks of venous thromboembolism and bleeding when making decisions about VTE prophylaxis. Evidence-based guidelines from authoritative sources should also be consulted.


  1. Sandler, D.A., Martin, J.F., "Autopsy proven pulmonary embolism in hospital patients: are we detecting enough deep vein thrombosis?," Journal of the Royal Society of Medicine (1989) Vol. 82, p.203-205.
  2. Zhan, C., Miller, M.R., "Excess length of stay, charges, and mortality attributable to medical injuries during hospitalization," Journal of the American Medical Association (2003) Vol. 290, p.1868-1874.
  3. Leizorovicz, A., Mismetti, P., "Preventing venous thromboembolism in medical patients," Circulation (December 14, 2004), Vol. 110 (Suppl IV), p. IV 13-19.
  4. Kahn, S.R., et al., "Prevention of venous thromboembolic disease in surgical patients," Thrombosis Research (2007), Vol. 119(2), p.145.
  5. Cohen, A., et al., "Venous thromboembolism risk and prophylaxis in the acute hospital setting (ENDORSE study): a multi-national cross-section study," The Lancet, (February 2, 2008), Vol. 371, no.9610 p.387-394.
  6. American College of Chest Physicians, "Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidenced-Based Clinical Practice Guidelines (8th Edition)," Chest, (June 2008), Vol. 133, no.6 p.382S.
  7. Accreditation Canada, "Accreditation Canada. Required organizational practices," September 2011. Retrieved on March 20, 2012, p.28, 54-55, from:

DISCLAIMER: The information contained in this learning material is for general educational purposes only and is not intended to provide specific professional medical or legal advice, nor to constitute a "standard of care" for Canadian healthcare professionals. The use of CMPA learning resources is subject to the foregoing as well as the CMPA's Terms of Use.