From the Desk of
Joseph A. Caprini, MD, MS, FACS, RVT, DFSVS
Many years ago when I was a student and surgical resident we spent a great deal of time perfecting our history-taking and physical exam skills. In those days these skills were essential for best patient care since we had no ultrasound, CAT scans, or MRI exams available. It is not surprising that when becoming interested in thrombosis prophylaxis, I searched the literature looking for all reasons why people developed venous thrombosis and created a list of historical and physical factors associated with the development of venous thromboembolism (VTE). Surrounded by brilliant colleagues we searched the literature to find appropriate clinical trial data to substantiate each item on the list and discovered that the relative risk of VTE was different depending on the risk factors involved.1 A past VTE or active cancer has a much greater effect on VTE incidence than does obesity, age, or swollen legs. Additional literature suggested that the same risk factor may have different levels of power associated with VTE. Age represents one of those variables — as age increases so does the VTE rate.2
This led to assigning a relative risk score to each factor depending on the incidence of VTE found in prospective clinical trials. Further research revealed that the more risk factors present, the greater was the risk of VTE.3 Putting all of this information together, a risk score was calculated to indicate the relative likelihood of an individual patient developing VTE.4 The score allowed prophylaxis to be tailored to the individual to obtain the best balance between efficacy and safety. Patients with low scores can receive physical methods of prophylaxis which are effective but have no bleeding risk.5 Higher-risk patients should receive heparin or low molecular weight heparin (LMWH), which have been shown to significantly reduce the VTE rate, and cut the death rate from fatal pulmonary emboli (PE) in half compared to placebo.6
The highest-risk patients should receive a combination of physical and pharmacologic methods which have been shown to reduce the VTE rate to < 2% in studies over the past 25 years.7 Literature has also demonstrated that the length of prophylaxis, timing of the first dose, and selection of anticoagulant can be tailored according to the level of risk.8,9
(The article continues below the video.)
The Caprini score utilizes all of the above principles to calculate the individual’s VTE risk and recommend a prophylaxis regime unique to each patient.10 The key element is a thorough history and physical including 37 elements. This results in a risk profile for that patient that one could term “thrombosis risk baggage.” The total risk of the patient is based on combining the baggage with the inherent risk of the operation based on complexity.
The score was first tested in more than 500 medical and 500 surgical patients admitted to a community hospital within the Northwestern University system.11,12 Patients with a score of three or more were considered to be “at risk” and this represented 80% of medical patients and 65% of surgical patients. Furthermore, patients with a score of five or more were found in 46% of medical and 46% of surgical patients. These results demonstrated that a majority of hospitalized patients were “at risk” for developing a thrombotic event, and prophylactic measures should be targeted to those with such scores rather than use blanket prophylaxis that was recommended for all hospitalized patients during the 1990’s.
The University of Michigan developed a risk assessment method based on the Caprini score which was validated retrospectively in 8216 patients and published in 2010.13 The Michigan program included mandatory compliance with recommended prophylaxis modalities based on the risk score. The physician had the ability to “opt out” if the patient had a high risk of bleeding. Overall 97% of the time the surgeons complied with the recommended prophylaxis method. The VTE rate has dropped since the program started in 2008 and excellent results continue to this day.
A second major study appeared in 2011 involving the Venous Thromboembolism Prevention Study (VTEPS) Network. This was a consortium of 5 tertiary referral centers that examined venous thromboembolism (VTE) in 1125 plastic surgery patients. The authors reported that “The Caprini RAM effectively risk-stratifies plastic and reconstructive surgery patients for VTE risk. “Among patients with Caprini score >8, 11.3% of these individuals followed for 60 days suffered a postoperative VTE when chemoprophylaxis was not provided.”14
CHEST 2012 guidelines recommend either the Caprini or Rodgers score to be used for surgical patients. The Caprini score was described as follows: “It is relatively easy to use and appears to discriminate reasonably well among patients at low, moderate, and high risk for VTE.”15 The Rodgers score was more complex and not further validated in any additional studies. The University of Michigan and the VTEP consortium data led to this critical endorsement of the Caprini score.
Since the 2012 guidelines endorsed the concept of tabulating patient-specific risk factors (baggage), a more comprehensive estimate of risk could be achieved than was seen with the group specific guidelines in the 2008 version. A patient having a low-risk (minor) procedure who has multiple risk factors resulting in a high Caprini score may have the same risk of VTE as someone having a high-risk (major) surgical procedure without additional risk factors with a similar high Caprini score.
It is fascinating to quote from the CHEST 2001 guidelines– “For surgical patients, the incidence of DVT is affected by the preexisting factors just listed and by factors related to the procedure itself, including the site, technique, and duration of the procedure, the type of anesthetic, the presence of infection, and the degree of postoperative immobilization.”16 One is reminded of the quote “Those who cannot remember the past are condemned to repeat it.” (George Santayana (1863 – 1952), The Life of Reason, Volume 1, 1905.
The philosophy regarding individual risk assessment is stated a different way in The American Society of Hematology 2019 Guidelines For Thrombosis Prophylaxis In The Surgical Patient.17 “For clinicians different choices will be appropriate for individual patients, and clinicians must help each patient to arrive at a management decision consistent with the patient’s values and preferences. Decision aids may be useful in helping individuals to make decisions consistent with their individual risks, values, and preferences.” Since many of their recommendations include the following statement: conditional recommendation based on very low certainty in the evidence of effects, it appears prudent for the clinicians to incorporate validated risk assessment models as part of the decision-making process to protect individual patients.”
The following statement is included near the end of the ASH 2019 Thrombosis Prophylaxis Guidelines In The Surgical Patients—”A widely used high-quality guideline is the 2012 Guideline of the American College of Chest Physicians (ACCP), which places a strong emphasis on patients’ VTE risk scores. In the guideline recommendations for VTE prevention in non-orthopedic surgical patients, patient oriented VTE risk calculators, such as the Caprini score and Rogers score, were adopted.”
The Caprini score is the most extensively used assessment tool worldwide appearing in 130 publications to date. Further blogs will discuss aspects of the score in many clinical situations, patient populations, and centers from around the world. The use of this tool is one way to achieve the goal of providing protection of the surgical patient from the number one PREVENTABLE cause of death postoperatively. Overall combining the inherent risk of thrombosis associated with the surgical procedure with the individual patient’s risk factors is critical to achieve this goal. In the final analysis there is no substitute for a thorough history and physical.
REFERENCES
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17. Anderson DR, Morgano GP, Bennett C, Dentali F, Francis CW. American Society of Hematology 2019 guidelines for management of venous thromboembolism- prevention of venous thromboembolism in surgical hospitalized patients. American Society of Hematology 2019;3:3898-944.