Blood clots in the legs or lungs, also known as deep venous thrombosis and pulmonary embolus, are life or limb-threatening complications of surgical procedures. These problems, collectively known as venous thromboembolism (VTE) are feared by clinicians. This is because they can be difficult to diagnose and even harder to treat effectively once they occur.
One in ten patients with symptomatic pulmonary embolus will be dead in 60 minutes; even if the event occurs within the hospital. Survivors of pulmonary embolus may go on to develop lifelong heart dysfunction requiring medications or surgery. Among patients with blood clots with the legs, many go on to develop the post-thrombotic syndrome. This is a condition in which the venous valves are damaged by a clot and cannot be repaired by the body. This allows venous blood to flow backwards toward the feet and produces a chronically swollen, tender, and ulcerated extremity that can be difficult to treat, and may become a lifelong condition. Overall, prevention remains the most impactful strategy for venous thromboembolism management; a concept highlighted by the US Surgeon General in his 2008 “Call to Action” on VTE .
Venous Thromboembolism and surgical patients
Many surgery patients are at high risk for VTE. This makes sense, as conditions that necessitate surgery (such as cancer, inflammatory bowel disease, or obesity) increase a person’s VTE risk, and surgery itself is a recognized risk factor for clotting events.
Existing guidelines for VTE prevention in surgical patients, including those published by the American College of Chest Physicians and surgery specialty societies, generally provide VTE prevention strategies based on individualized, patient specific risk (quantified using a Caprini score or Rogers score, among others) or based on procedure type (such as patients who have abdominal surgery for cancer or cardiac surgery). This is because studies have shown that VTE risk varies from patient to patient as well as from one surgical procedure to another.
For example, a recent meta analysis in surgical patients showed that there are huge variations in VTE risk among the overall population. Even among patients who have the same operative procedure. The study showed that a 15-fold variation (from 0.7% to 10.7%) in VTE risk exists among the overall surgical population. This means that different people having the same operation can have widely different VTE risk. However, knowing this requires that the surgeon consider patient-specific VTE risk using a Caprini score. Importantly, this same study demonstrated that a Caprini score can specifically identify those patients who would benefit from post-operative anticoagulants (about 25% of all patients having surgery), and also those for whom anticoagulants might not be beneficial. Post-operative anticoagulation is discussed extensively below.
The American College of Chest Physicians recommends that surgeons quantify a patient’s VTE risk based on their individual risk factors, using an established risk scoring system like a Caprini score . When data are available, the ACCP recommends that surgeons base their VTE prevention strategy on a patient’s individualized VTE risk. Certainly, the risk reduction strategies undertaken by surgeons, as well as their pre-operative discussions and the informed consent process, would be quite different for patients with a VTE risk of less than 1% versus over 10%. However, this is predicated on surgeons actively quantifying their patient’s risk for VTE.
Surgeons can minimize, but not eliminate, risk for peri-operative VTE. The word “minimize” is used intentionally here. Major payers like the Centers for Medicare and Medicaid Services have dubbed VTE after certain procedures as “never events”; complications which they believe are 100% preventable. However, dozens of high-level studies in various surgical populations over the past 15 years have clearly demonstrated that VTE events routinely occur, especially among high risk patients, despite aggressive prevention strategies. In this Expert’s opinion, risk for VTE in surgical patients can be minimized but never eliminated. Its claims to the contrary are simply unrealistic or uninformed.
Surgeons should actively consider VTE risk in every single patient and for every single surgery. While all VTE events are probably not preventable, surgeons who do not attempt to minimize their patient’s risk for VTE whenever possible are probably outside of the standard of care, and are certainly violating the cardinal rule of “first, do no harm”. This is particularly relevant when malpractice is in question. Below are a few thoughts on what surgeons can do in the pre-, intra-, and post-operative settings to minimize risk for VTE.
For attorneys and surgeons alike, understanding how the risk of VTE can be reduced in the pre, intra, and post-operative settings is vital to the proper practice of both law and medicine.
Pre-operative VTE risk reduction
Studies in surgical patients have shown that patient-level factors can be used to quantify VTE risk. VTE risk assessment scores like the Caprini score and the Rogers score have been designed and validated to provide this risk quantification. Some factors like body mass index, use of oral contraceptives, presence of central venous access, or recent operative procedure, can be modified prior to surgery. For elective operations, surgeons can take a “step back” and try to decrease VTE risk by minimizing or eliminating VTE risk factors. Recognized risk factors like personal or family history of VTE are inherent to the patient and cannot necessarily be eliminated prior to surgery. However, for patients with personal or family history, pre-operative workup for hypercoagulability (blood conditions that cause the blood to clot more easily than most) and/or referral to Hematology might be justified.
Ultimately, surgeons must understand a patient’s VTE risk in order to perform pre-operative risk reduction. Thus, surgeons should inquire about VTE risk factors at the pre-operative clinic visit. Use of an established VTE risk stratification tool such as the Caprini score or Rogers score (both of which are supported by current American College of Chest Physicians guidelines and many surgical society guidelines) can be critical to allow pre-operative VTE risk quantification. As well as identify potential targets for pre-operative VTE risk modification/reduction.
Intra-operative VTE risk reduction
Anesthesia type is a recognized risk factor for VTE. Studies have shown that non-general anesthesia (like local, IV sedation, or spinal anesthesia) carries less VTE risk than general anesthesia. Not all surgeries can be safely performed under a non-general anesthetic. However, if feasible, use of a non-general anesthetic can decrease VTE risk.
Stasis, or blood slowing, is one risk factor for VTE. Stasis will cause venous dilation and small tears in the vein walls, and this can allow a clot to form at the site. The body normally prevents stasis in the legs through the action of the calf muscle pump ; an action that is lost with anesthesia. Calf muscle contraction physically pumps the blood back toward the heart, and the vein valves ensure it will not flow backward. Stasis mitigation can be performed using mechanical prophylaxis, such as elastic compression stockings or preferably sequential compression devices (SCDs). SCDs help to actively pump blood out of the lower extremities, reproducing the physiologic effect of the calf muscle pump. This minimizes risk for stasis and blood clots in the legs.
Increased operative time is a recognized risk factor for VTE. This fact is particularly relevant when surgeons choose to perform multiple procedures, or when separate surgeons perform procedures during the same anesthetic period. For emergent cases, this may be unavoidable. However, when increased operative time occurs to combine, for example, eyelid surgery and a tummy tuck, VTE risk will be increased as a consequence. Surgeons must use their judgment about the safety of combining procedures to balance patient convenience for a single operative session versus increased VTE risk.
Post-operative VTE risk reduction
VTE risk is known to be elevated for weeks to months after surgery. VTE risk has been shown to peak at 3 weeks after outpatient or inpatient surgery, and risk remains elevated for at least 3, and perhaps as long as 12, months.
Immobility is a recognized VTE risk factor. Patients confined to bed and/or not up and walking should receive mechanical VTE prevention strategies like elastic compression and/or SCDs at least until walking, and possibly for the duration of their inpatient stay. Some surgeons choose to provide these devices at home.
Chemical prophylaxis, such as heparin, low-molecular weight heparin, or oral Factor Xa inhibitors, include blood-thinning medications that will decrease the likelihood of blood clot formation. Studies in many different surgical populations have clearly demonstrated that chemical prophylaxis can significantly decrease the likelihood of VTE. However, this risk reduction must be balanced with the risk of bleeding in patients who recently had surgery. Recent studies have supported an individualized approach to provision of VTE chemical prophylaxis. As noted above, there is a wide variation (~15-fold) of VTE risk among the overall surgical population. The risk/benefit relationship of chemical prophylaxis (VTE risk reduction vs. bleeding) varies similarly. Surgeons generally consider these risk/benefit relationships on a case-by-case basis and document their thought process.
Some studies have shown that patients at highest VTE risk (for example, Caprini scores >8) and/or high risk patient populations (such as patients who have surgery for abdominal/pelvic cancer or hip/knee replacement) may benefit from “extended duration” chemical prophylaxis provided after discharge to decrease VTE risk.
Final thoughts and decreasing VTE risk to zero
Some patients, particularly those who request elective operations, may be deemed by their surgeon as too high risk for VTE. For these patients, the surgeon’s judgment to not offer an operation remains their last avenue to minimize VTE risk. For patients who require an operation (for example, in the setting of cancer or trauma), avoidance of a procedure may not be an option. With these patients, surgeons should attempt risk modification and reduction strategies before, during, and after the surgical procedure.
Expert Witness Bio E-067040
This Expert is a board-certified plastic and reconstructive surgeon and is a fellowship-trained microvascular surgeon with a University-based reconstructive surgery practice. He has over ten years of experience specific to VTE in surgical patients. As of January 2017, he serves as Principal Investigator for five active clinical trials that examine VTE risk reduction and optimization of chemical prophylaxis in a broad range of surgical patients (SICU/trauma patients, orthopedic surgery patients, thoracic surgery patients, microvascular surgery patients, and plastic & reconstructive surgery patients).
This Expert’s research currently receives funding from the federal government and several surgical societies. He has published over 65 peer-reviewed manuscripts, the majority of which examine VTE risk stratification and prevention among surgical patients, in a wide variety of medical and surgical journals. He has given over 70 invited talks at national and international scientific meetings, again focused largely on VTE risk stratification and prevention.