Safety of care

Improving patient safety and reducing risks

Anticoagulant, antiplatelet agent and thrombolytic therapy: Amedico-legal perspective

Originally published June 2009

This paper explores the medico-legal issues arising from the use of anticoagulant, antiplatelet and thrombolytic agents. The CMPA had previously identified these three classes of drugs as having great clinical benefit but also important patient safety concerns.

For this reason, the CMPA analyzed 117 medico-legal cases closed between 2002 and 2007 that involved the use of anticoagulants, antiplatelet agents and thrombolytics. These included both legal actions and complaints made to a regulatory authority (College).

Figure 1: Distribution of all closed cases per medication category, CMPA, 2002-2007

Figure 1: Distribution of all closed cases per medication category, CMPA, 2002-2007

Note: Although there were 117 closed cases, two cases involved medications from two categories and therefore appear twice, bringing the total number of case combinations to 119.

Search criteria

January 1, 2002 to
December 31, 2007
Code: All cases with an
antithrombotic/thrombolytic intervention code
Code: Legal actions & College complaints
Type of work: All

The distribution of cases by medication category is summarized in Figure 1.


The following case studies illustrate the two predominant risk concerns associated with the prescribing and management of anticoagulants, namely:

  • Delay or failure to prescribe an anticoagulant when indicated
  • Inadequate monitoring once the medication is prescribed

Case # 1

Failure to prescribe an anticoagulant

A 26-year-old diabetic woman with a history of deep vein thrombosis (DVT) presented to the emergency department (ED) with right lower quadrant pain, nausea and vomiting. An abdominal ultrasound revealed acute appendicitis and urgent surgery was booked. Although the general surgery resident assessed the patient and documented her history of DVT, the staff general surgeon was unaware of this clinical fact. A laparotomy was performed for a ruptured appendix and periappendiceal abscess. The patient was slow to mobilize after surgery. On the second postoperative day, the nurses recorded that the patient's lower extremities were edematous, and anti-embolic stockings were applied. It is unclear whether this information was verbally communicated to the physicians.

The patient was discharged on the fifth postoperative day. Four days later, she presented to the ED via ambulance with acute onset of shortness of breath and loss of consciousness. A cardiac arrest ensued with successful resuscitation. Subsequent investigations confirmed massive pulmonary embolism (PE). Anoxic brain injury complicating the PE left the patient with marked cognitive impairments and spastic quadriparesis. The family commenced a legal action alleging failure to obtain an adequate medical history and failure to prescribe heparin and compression stockings postoperatively.

Legal outcome

Peer experts were of the opinion that the general surgeon should have been aware of the patient's history of DVT, and the fact that he did not review the information contained in the medical records fell below the standard of care. The experts also maintained that a person at risk for venous thromboembolism (VTE), as this patient was, should have received antithrombotic prophylaxis perioperatively. As there was no expert support, the CMPA paid a settlement to the patient on the member's behalf.

Case # 2

Inadequate monitoring of an anticoagulant

A 62-year-old man with a longstanding history of smoking was followed by his family physician (FP) for diabetes mellitus and coronary artery disease. The patient had a history of two myocardial infarctions (MI) and stenting of the right coronary artery. When the patient developed congestive heart failure, the FP referred him to a cardiologist for investigations and treatment. A coronary angiogram showed left ventricular dysfunction and an apical thrombus. The cardiologist prescribed warfarin and forwarded the consultation report to the FP requesting that he monitor the patient's International Normalized Ratio (INR) levels. This report was received three days later, but the FP did not reassess the patient for approximately one more month. He reviewed the cardiologist's report with the patient during that visit and advised him to continue the medications that the cardiologist had prescribed. However, the FP failed to institute measures to monitor the INR levels. Three weeks later, the patient presented to the ED complaining of dizziness, nausea and vision difficulties. Investigations revealed uncontrolled diabetes and a urinary tract infection. The patient was kept overnight for observation and treatment. His condition stabilized by the following morning, and he was discharged.When leaving the hospital, the patient collapsed. He was subsequently diagnosed with a right cerebellar hemorrhage; his INR level at that time was 16. Mild cognitive deficits and limited use of the right arm persisted. A legal action was commenced by the patient alleging the FP failed to monitor his INR levels as instructed by the cardiologist.

Legal outcome

A family physician expert expressed concern about the family physician's failure to monitor the patient's INR levels as directed by the cardiologist. The expert maintained that INR monitoring should have been initiated in a timely manner.Without expert support, a settlement was paid to the patient by the CMPA on behalf of the family physician.

Statistical overview

Figure 2: Comparison of case outcomes for all closed legal actions involving anticoagulants
versus case outcomes for all closed CMPA legal actions, 2002-2007

Figure 2: Comparison of case outcomes for all closed  legal actions involving anticoagulantsversus case outcomes for all closed CMPA legal  actions, 2002-2007

Case outcomes

• Legal actions (60 cases)

In comparison with the overall CMPA experience with legal actions, cases involving anticoagulant therapy resulted in fewer favourable outcomes for the physician. In the overall CMPA experience, 60 per cent of the legal cases were dismissed and seven per cent resulted in judgment for the physician; in the anticoagulant cases, only 48 per cent were dismissed and two per cent resulted in judgment for the physician. (Figure 2)

• College cases (25 cases)

The College expressed concerns related to patient care, inadequate record keeping and communication problems with the patient and family in 15 cases; two of these cases resulted in voluntary retirement or imposed practice limitations. Conversely, the College was not critical of the physician's care in eight cases. The outcome was unknown in two cases.

Type of Work distribution

The study revealed that medico-legal difficulties with anticoagulants crossed a broad range of specialties, with family physicians being the most frequent group involved.

Clinical findings

The experts identified issues related to the prescribing and management of anticoagulants in 58 of the 85 cases. The other 27 cases were excluded from analysis for the following reasons:

  • In 15 cases, experts expressed the view that undesirable patient outcomes occurred despite appropriate care by the physician
  • In seven cases, the anticoagulant was not the focus of the case
  • In five cases, there was insufficient information to determine responsibility for the identified issue or the legal action was dismissed or discontinued

Of the 58 cases analyzed, 36 cases involved oral anticoagulants, of which all but two involved the use of warfarin; 15 cases involved unfractionated heparin; and five cases involved low-molecular-weight heparin. The name of the medication was not specified in two cases.

Of these 58 cases, the majority had more than one issue; two to three issues per case was the most common finding. Hence, the percentages exceed 100 per cent:

  • Forty-five per cent of the cases (26 cases) represented a delay or failure to prescribe an anticoagulant when indicated, most often in the following situations:
    • prophylactic anticoagulation in the postoperative period, especially in the presence of identified risk factors, such as a history of DVT
    • clinical conditions for which an anticoagulant would be considered the treatment of choice, such as atrial fibrillation (AF)
  • Inadequate monitoring of the anticoagulant occurred in 38 per cent of the cases (22 cases). This was most often related to inadequate INR monitoring of oral anticoagulant therapy.
  • In 38 per cent of the cases (22 cases), a diagnostic issue at the time of evaluation of the patient's presenting condition or during the course of anticoagulant therapy also affected the prescribing and management of anticoagulants. A delay or failure to perform or follow up on appropriate investigations (e.g., CT scan, ultrasound, electrocardiogram, heparin-induced thrombocytopenia [HIT] test) as well as failure to consider information in the medical record were key contributing factors.
  • Other areas of concern included:
    • communication problems between physicians during the transfer of care
    • delay or failure to consult a specialist
    • other prescribing issues, (e.g., failure to reverse warfarin prior to an invasive procedure and not considering the effect of potential interactions between anticoagulants and other medications, e.g., antibiotics)

Patient clinical outcomes

As expected, thromboembolic and major bleeding events were the most common adverse events.

Thromboembolic events ? 48 per cent of the cases (28 cases)

  • Pulmonary embolism occurred in 11 of these cases. In the majority, the PE developed postoperatively, most frequently after gynecologic or orthopedic surgeries.
    • Almost two-thirds of these patients died
  • Ischemic strokes developed in 10 of these cases, primarily either related to inadequate INR monitoring or due to failure to prescribe an anticoagulant for patients with mechanical heart valves or medical conditions such as AF.
    • In all of the cases with inadequate INR monitoring, the INR values were subtherapeutic
    • Over 50 per cent of these patients were left with major functional disabilities and one patient died
  • Other thromboembolic events included peripheral arterial occlusions, mechanical heart valve occlusions and an embolic event to the spleen.

Major bleeding events ? 43 per cent of the cases (25 cases)

  • There were 10 cases of intracranial hemorrhage, of which five were associated with inadequate INR monitoring.
    • Six of the 10 patients had serious clinical outcomes; three of them died
  • Of the other 15 cases, bleeding occurred most frequently at the site of diagnostic, therapeutic and surgical procedures. Other patients developed spontaneous bleeding such as hemopericardium and rectal bleeding.
    • Approximately half of these patients died

Other complications ? 9 per cent of the cases (5 cases)

  • Other complications included paradoxical hypercoagulable state (warfarin) and heparin-induced thrombocytopenia.
    • Two of these patients died

Risk management considerations for anticoagulants

Based on the expert opinions obtained in the medico-legal cases related to anticoagulants, the following risk management considerations have been identified:

  • Are you aware of conditions in your patient that may warrant the use of an anticoagulant?
  • Have the appropriate diagnostic investigations been performed and reviewed?
  • Have you considered the current clinical practice guidelines for the prescribing and management of anticoagulants for both active treatment and prophylaxis?
  • Have you considered potential interactions with other drugs or natural health and food products?
  • Would consultation with a specialist be helpful?
  • Has there been effective communication between physicians during the transfer of care of patients on anticoagulant therapy?
  • Has there been effective communication with your patient about the anticoagulant therapy and the monitoring requirement?
  • Have you arranged appropriate follow up and INR monitoring when your patient is on oral anticoagulant therapy? Is there a systematic process in place to review the INR results, adjust the dosage as appropriate, and document the dose change?
  • Does the medical record reflect the risk discussion about anticoagulant therapy and other treatment options?

Antiplatelet agents

Analysis of the 16 antiplatelet cases closed between 2002 and 2007 did not reveal sufficient information to draw meaningful conclusions specific to this class of drug. Most often, risk concerns could not be attributed solely to the use of an antiplatelet agent because of coincident risks related to thrombolytic or antithrombotic therapy used in conjunction with the antiplatelet agent.

Thrombolytic agents

Despite the current widespread clinical usage of thrombolytic agents, and despite their recognized potential for serious bleeding, only 18 thrombolytic cases closed between 2002 and 2007. Moreover, the single key finding of this review was that a delay or failure to prescribe a thrombolytic agent when indicated was a far greater medico-legal risk than the risk associated with complications arising from its use. In fact, of the 11 cases in which experts identified issues involving thrombolytic agents, there was a delay or failure to prescribe a thrombolytic agent in 10 cases as the result of a
misdiagnosis or a delay in diagnosis of the patient's presenting condition.

Note: The other seven cases were excluded for the following reasons:

  • In five cases, experts expressed the view that adverse patient outcomes resulted despite appropriate care by the physician
  • In one case, even though a thrombolytic was prescribed, it was not the focus of the case
  • In one case, the court dismissed the legal action before responsibility for the identified issue could be determined

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.