Fatal Pulmonary Embolism Prevention

From the Desk of
Joseph A. Caprini, MD, MS, FACS, RVT, DFSVS

Fatal pulmonary embolism is the number one preventable cause of death after surgery.

There are many complications that occur following an operation which are beyond the control of physicians; however, most fatal pulmonary emboli can be prevented using proper thrombosis prophylaxis given for the appropriate length of time based on the patient’s risk.^1-3

(The article continues after the video.)

Solution

This requires administration of prophylactic doses of anticoagulation following surgery, commonly heparin or low molecular weight heparin (LMWH), to patients who are “at risk” for developing fatal thrombi. A number of drugs prevent most of these fatalities when given for the period of time shown to be effective in clinical trials. Protecting the patient for the entire time they remain at increased risk is vital to achieve success.

One should remember that not all VTE events can be prevented with anticoagulant prophylaxis; however, most fatal events are avoided with these drugs.

Identification of patients who are “at risk” is possible when a thorough history and physical examination is performed identifying risk factors that could lead to thrombosis.

The number of risk factors present, along with the “strength” of each risk factor to cause thrombosis, needs to be calculated in order to determine the best choice of drug, dose, and duration of prophylaxis, balancing the risks of thrombosis vs. any factors that could increase the incidence of bleeding in the patient. This final step involves a risk-benefit calculation based on the available literature and the individual characteristics of the patient.⁴

The policy of looking at a short list of common risk factors is a recipe for disaster, especially when an important and powerful risk factor is overlooked. A family history of thrombosis is a powerful predictor of thrombosis that is frequently missed. Despite this fact,several highly recommended scoring systems FAIL to track family history of thrombosis.^5,6

The National Surgical Quality Improvement Program (NSQIP) from the American College of Surgeons, containing over 5 million patients, does NOT track past history or family history of thrombosis.⁷ The use and type, duration, and dose of thrombosis prophylaxis methods are surprisingly NOT recorded. Conducting VTE related studies using this database remains problematic and can be misleading.⁸

Using the Caprini Score is One Method to Achieve the Above Goals

What is the Caprini Score?

The essence of this system is a thorough history and physical exam of the patient including 37-40 risk factors that could lead to a thrombotic event.

The strength of each of these risk factors to cause a thrombosis, based on the literature, is graded using numerical values (1-5).

The number of factors present, along with the value of each factor, are added to produce a final score for the patient.

This score is plotted against the incidence of clinical thrombotic events and the score increases in proportion to the observed incidence of clinical events in published trials.

More about the score:

• Scores less than 5 are associated with a low incidence of VTE events, and stockings or compression devices on the legs are sufficient.
• Patients with scores of 5-8 have been shown to be associated with a significant risk of thrombosis and a standard course of therapy (usually 7 to 10 days) should be prescribed.
• Patients with scores greater than 8 have an incidence of thrombosis that is sufficiently high to recommend 30 days or more of anticoagulant prophylaxis.⁹
• These arbitrary divisions cover most general surgical patients, but different populations may be associated with different set points.

Interpretation of the Score Set Points For High and Very High Risk

The essential factor in refining the risk is to plot the score vs. the incidence of clinical thrombotic events in specific patient populations. Here are several examples: 

Otolaryngology

Patients having head and neck surgery, commonly thyroid and parathyroid operations, are thought to have a very low incidence of thrombosis.

Scoring these patients gives us a different picture. No patients with a score of 6 and below suffered a VTE event.

The incidence of VTE with a score of 7-8 was 3.01%, and 13.16% with a score of >9.¹⁰

This is one excellent example of the value of the score to protect truly “at risk” patients from suffering a fatal PE event while avoiding blanket prophylaxis.

Total Joint Replacement

In a recent study in 1078 patients having total joint replacement, 8 VTE events were seen with 7 of these events having scores of 10 or above.¹¹

One patient with a score of 8 suffered a non-fatal PE.

Based on these results the authors suggested a score of 9 or less was associated with a very low incidence of thrombotic events and they suggested using aspirin for future patients.

This same study shows joint replacement patientswith a score of 10 or above may achieve greater benefit from standard anticoagulation since in their study almost all of the VTE victims had high scores.

Hip Fracture

Patients suffering a hip fracture were found to have a significant correlation between the DVT risk assessment scores and preoperative DVT.¹² This study featured preoperative ultrasound screening and a “significant correlation was seen with Caprini score ≥ 12 points and ≥ 13 points (p < 0.05 all).”

Specific Recommendations for Completing the Caprini Score

Scoring of the patient is recommended using the following steps:¹³

The first step is having the patient fill out a preliminary form in advance of the surgery, hopefully with the assistance of loved ones.¹⁴

We would also suggest that this patient-friendly form be finalized by the person responsible for the history and physical and an initial score recorded based on the following considerations:

1. Issues should be discussed including family history of thrombosis, prior obstetrical complications for women, and any questions not clear on the form.
2. Inspection of the legs for swelling and varicose veins should be done at this time.
3. Face-to-face interaction with the patient is mandatory for best results.¹⁵
4. Chart review can be problematic since the reviewer has no idea if all of the questions were properly asked.

The score should be updated during hospitalization when infection, reoperation, central lines, pneumonia or other complications occur.

A final score should be calculated at discharge to determine the need for continued prophylaxis.

The patient should be followed for 90 days to track VTE clinically evident imaging-proven VTE events.

Correlation of the results with the use, type, duration, and dose of anticoagulant prophylaxis should be done to define a picture of the true value of the score.

The score results for patients not receiving anticoagulants are a critical statistic.

These values need to be recorded for different surgical populations.

The incidence of clinical VTE events in a meta-analysis consisting of mainly non-orthopedic trials, in patients not receiving anticoagulants, showed an alarming incidence of VTE in those with a score of >8 (10.7%).¹⁶

Conclusions

• Fatal pulmonary emboli are the number one preventable complication postoperatively.
• Most fatal pulmonary emboli but not all non-fatal VTE events can be prevented with appropriate anticoagulant prophylaxis.
• A thorough risk assessment for the individual patient is necessary for success.
• The Caprini score is recommended as one approach to achieve this goal.
• Scoring needs to be tailored to individual populations to achieve optimal results.
• More research is necessary to incorporate additional risk factors and explore further specific surgical populations.

References

1. Wakefield TW, McLafferty RB, Lohr JM, Caprini JA, Gillespie DL, Passman MA. Call to action to prevent venous thromboembolism. J Vasc Surg 2009;49:1620-3.
2. Collins R, Scrimgeour A, Yusuf S, Peto R. 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 1988;318:1162-73.
3. Haas S, Wolf H, Kakkar AK, Fareed J, Encke A. Prevention of fatal pulmonary embolism and mortality in surgical patients: a randomized double-blind comparison of LMWH with unfractionated heparin. Thromb Haemost 2005;94:814-9.
4. Caprini JA. Thrombosis risk assessment as a guide to quality patient care. Dis Mon 2005;51:70-8.
5. Rosenberg D, Eichorn A, Alarcon M, McCullagh L, McGinn T, Spyropoulos AC. External validation of the risk assessment model of the International Medical Prevention Registry on Venous Thromboembolism (IMPROVE) for medical patients in a tertiary health system. J Am Heart Assoc 2014;3:e001152.
6. Barber S, Noventa F, Rossetto V, et al. A risk assessment model for the identification of hospitalized medical patients at risk for venous thromboembolism: the Padua Prediction Score. J Thromb Haemost 2010;8.
7. Bilimoria KY, Liu Y, Paruch JL, et al. Development and evaluation of the universal ACS NSQIP surgical risk calculator: a decision aid and informed consent tool for patients and surgeons. J Am Coll Surg 2013;217:833-42 e1-3.
8. McAlpine K, Breau RH, Knee C, et al. Venous thromboembolism and transfusion after major abdominopelvic surgery. Surgery 2019.
9. Cassidy MR, Rosenkranz P, McAneny D. Reducing postoperative venous thromboembolism complications with a standardized risk-stratified prophylaxis protocol and mobilization program. J Am Coll Surg 2014;218:1095-104.
10. Yarlagadda BB, Brook CD, Stein DJ, Jalisi S. Venous thromboembolism in otolaryngology surgical inpatients receiving chemoprophylaxis. Head Neck 2014;36:1087-93.
11. Krauss ES, Segal A, Cronin M, et al. Implementation and Validation of the 2013 Caprini Score for Risk Stratification of Arthroplasty Patients in the Prevention of Venous Thrombosis. Clin Appl Thromb Hemost 2019;25:1-9.
12. Luksameearunothai K, Sa-Ngasoongsong P, Kulachote N, et al. Usefulness of clinical predictors for preoperative screening of deep vein thrombosis in hip fractures. BMC Musculoskelet Disord 2017;18:208.
13. Golemi I, Adum JPS, Tafur A, Caprini J. Venous thromboembolism prophylaxis using the Caprini score. Disease-a-Month 2019;65:249-98.
14. Fuentes HE, Paz LH, Al-Ogaili A, et al. Validation of a Patient-Completed Caprini Risk Score for Venous Thromboembolism Risk Assessment. TH Open 2017;1:e106-e12.
15. Pannucci CJ, Fleming KI. Comparison of face-to-face interaction and the electronic medical record for venous thromboembolism risk stratification using the 2005 Caprini score. J Vasc Surg Venous Lymphat Disord 2018;6:304-11.
16. Pannucci CJ, Swistun L, MacDonald JK, Henke PK, Brooke BS. Individualized Venous Thromboembolism Risk Stratification Using the 2005 Caprini Score to Identify the Benefits and Harms of Chemoprophylaxis in Surgical Patients: A Meta-analysis. Ann Surg 2017;265:1094-103.