Plastic and Reconstructive Surgery Advance Online Article DOI: 10.1097/PRS.0000000000000061 The Limitations of Using a National Database to Investigate Risk Factors for Venous Thromboembolism Eric Swanson, M.D.
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Corresponding author: Eric Swanson, M.D., Swanson Center, 11413 Ash Street , Leawood, KS 66211 931 663-1030, [email protected]
DISCLOSURE
A
C
C
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The author has no financial interest in any of the products, devices, or drugs mentioned in this manuscript. The author has no conflicts of interest to disclose. There was no outside funding for this study.
1
Copyright © American Society of Plastic Surgeons. All rights reserved.
Sir: Wes et al.1 mine a national database in an effort to identify risk factors for venous thromboembolism after body contouring surgery. Using Current Procedural Terminology (CPT)
TE D
codes, these investigators identify a number of risk factors – age, obesity, inpatient surgery, trunk contouring, a contaminated wound, and contouring more than two regions. The authors1
acknowledge that information regarding venous thromboembolism prevention is unavailable, so that no conclusion is possible regarding the efficacy, safety, or timing of chemoprophylaxis.
In their previous study,2 breast surgery patients accounted for 14.1 percent of the total. The
EP
patient makeup in this retrospective study is quite different, with 66.8 percent of the patients
undergoing contouring of the breast.1 Breast procedures are normally considered separately from body contouring procedures.3 Unfortunately, the inclusion of mammaplasties skews the data
C
analysis for the other 33.2 percent of patients undergoing body contouring surgery.
Thirty percent of the patients were treated by general surgeons.1 Unless general surgeons are
C
performing breast contouring surgery, this means that most trunk contouring cases were performed by general surgeons. Almost half of the patients (and likely more if breast surgery
A
patients were excluded) were obese, consistent with a large representation of bariatric patients.1 By contrast, obese patients account for about 20 percent of body contouring cases treated by plastic surgeons.4
The wound class and physical status data require explanation. Elective body contouring surgery should be a clean procedure. A clean-contaminated wound is a surgical wound in which the 2
Copyright © American Society of Plastic Surgeons. All rights reserved.
respiratory, alimentary, genital, or urinary tract is entered. In this database, 8.2 percent of patents were categorized as clean-contaminated, contaminated, or infected. All breast surgery (66.8 percent) is expected to be clean. Therefore, 24.7 percent (8.2/33.2) of patients undergoing
TE D
body contouring surgery (excluding the breasts) had contaminated wounds.
The American Society of Anesthesiologists physical status classification5 for elective body
contouring surgery is typically Class 1 or 2. A patient labeled Class 3 has a severe systemic
disease such as poorly-controlled diabetes, chronic obstructive pulmonary disease, or morbid
obesity (BMI ≥ 40 kg/m2).5 This series included 3899 Class 3 patients (21.9 percent), 220 Class
EP
4 patients (whose life is constantly threatened), and even 2 moribund Class 5 patients.
The authors believe that their risk factors are “independent predictors,”1 but do not control for the procedure or history of massive weight loss. Bariatric patients have higher rates of anemia, hypertension, diabetes, and malnutrition. An apparent risk differential is created by including a
C
large low-risk (and arguably unrelated) breast surgery group. Mammaplasty patients are, on average, younger and leaner6 than bariatric patients.1 Their operating times tend to be shorter.6
C
One cannot conclude that treating more than two areas with contouring is a risk factor if the majority of the low-risk breast surgery patients underwent breast surgery without simultaneous
A
body contouring procedures. Patients undergoing contouring of more than two areas are more likely to be treated with an abdominoplasty, which places them at higher risk already. The same reasoning applies to age, sex (breast surgery patients being all female) and body mass index comparisons. To compare “apples with apples,” it would have been preferable to exclude breast patients (and, ideally, massive weight loss patients), or just study the breast patients. By the
3
Copyright © American Society of Plastic Surgeons. All rights reserved.
same logic, it is unfair to indict general surgeons because they are operating on a higher-risk patient group. Correlation does not imply causation; inpatients are admitted because they are at higher risk by virtue of a medical issue or the extent of planned surgery.
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Data from the Venous Thromboembolism Prevention Study7 shows that high-risk patients (Caprini score ≥ 7) experienced a 3.0 percent risk of venous thromboembolism, compared with a 1.2 percent risk overall.8 Wes et al.1 report a very similar complication rate, 2.95 percent, for
their highest-risk group. The relevant question is whether anticoagulating 100 percent of these
patients is justified if (1) 97 percent of the patients will not develop this complication1,8 (making
EP
the treatment unnecessary) and (2) the treatment introduces iatrogenic complications.8
The 2012 Guidelines of the American College of Chest Physicians9 do not include individual risk stratification or Caprini scores as risk reduction strategies. This fact may surprise plastic surgeons who believe that such scores are endorsed by national guidelines. Despite our best
C
efforts, we cannot reliably predict who will develop a venous thromboembolism.8,10 Retrospective reviews of disparate patient groups, even large ones that do not include objective
C
diagnostic data (and are affected by sampling bias)1 are unlikely to be fruitful. Our efforts are
better directed at (1) improving anesthesia to reduce risk for all patients,8 and (2) learning more
A
about the natural history of this complication using ultrasound surveillance, which can also provide early detection and treatment for affected patients.10
4
Copyright © American Society of Plastic Surgeons. All rights reserved.
References
1. Wes AM, Wink JD, Kovach SJ, Fischer JP. Venous thromboembolism in body
TE D
contouring: An analysis of 17,774 patients from the National Surgical Quality Improvement databases. Plast Reconstr Surg. 2015;135:972e.
2. Fischer JP, Wes AM, Serletti JM, Kovach SJ. Complications in body contouring
procedures: An analysis of 1797 patients from the 2005 to 2010 American College of Surgeons National Surgical Quality Improvement Program databases. Plast Reconstr
EP
Surg. 2013;132:1411–1420.
3. Plastic and Reconstructive Surgery website. Collections. Cosmetic: Body
C
Contouring/Liposuction. Available at:
http://journals.lww.com/plasreconsurg/pages/collectiondetails.aspx?TopicalCollectionId=
C
10. Accessed May 30, 2015.
4. Swanson E. Prospective clinical study reveals significant reduction in triglyceride level
A
and white cell count after liposuction and abdominoplasty and no change in cholesterol levels. Plast Reconstr Surg. 2011;128:182e-197e.
5
Copyright © American Society of Plastic Surgeons. All rights reserved.
5. American Society of Anesthesiologists Physical Status Classification System. Available at: http://asahq.org/resources/clinical-information/asa-physical-status-classificationsystem. Accessed May 30, 2015.
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6. Swanson E. Prospective comparative clinical evaluation of 784 consecutive cases of breast augmentation and vertical mammaplasty, performed individually and in combination. Plast Reconstr Surg. 2013;132:30e-45e; discussion 46e-47e.
7. Pannucci CJ, Dreszer G, Fisher Wachtman C, et al. Postoperative enoxaparin prevents symptomatic venous thromboembolism in high-risk plastic surgery patients. Plast
EP
Reconstr Surg. 2011;128:1093-1103.
8. Swanson E. The case against chemoprophylaxis for venous thromboembolism prevention and the rationale for SAFE anesthesia. Plast Reconstr Surg Glob Open 2014;2:e160.
C
9. Kearon C, Akl EA, Comerota AJ, et al. Antithrombotic therapy for VTE disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of
C
Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012;141(2
A
Suppl):e419S-494S.
10. Swanson E. Ultrasound screening for deep venous thrombosis detection: Prospective evaluation of 200 plastic surgery outpatients. Plast Reconstr Surg Glob Open 2015;3:e332.
6
Copyright © American Society of Plastic Surgeons. All rights reserved.
TE D
Corresponding author: Eric Swanson, M.D., Swanson Center, 11413 Ash Street , Leawood, KS 66211 931 663-1030, [email protected]
DISCLOSURE
A
C
C
EP
The author has no financial interest in any of the products, devices, or drugs mentioned in this manuscript. The author has no conflicts of interest to disclose. There was no outside funding for this study.
1
Copyright © American Society of Plastic Surgeons. All rights reserved.
Sir: Wes et al.1 mine a national database in an effort to identify risk factors for venous thromboembolism after body contouring surgery. Using Current Procedural Terminology (CPT)
TE D
codes, these investigators identify a number of risk factors – age, obesity, inpatient surgery, trunk contouring, a contaminated wound, and contouring more than two regions. The authors1
acknowledge that information regarding venous thromboembolism prevention is unavailable, so that no conclusion is possible regarding the efficacy, safety, or timing of chemoprophylaxis.
In their previous study,2 breast surgery patients accounted for 14.1 percent of the total. The
EP
patient makeup in this retrospective study is quite different, with 66.8 percent of the patients
undergoing contouring of the breast.1 Breast procedures are normally considered separately from body contouring procedures.3 Unfortunately, the inclusion of mammaplasties skews the data
C
analysis for the other 33.2 percent of patients undergoing body contouring surgery.
Thirty percent of the patients were treated by general surgeons.1 Unless general surgeons are
C
performing breast contouring surgery, this means that most trunk contouring cases were performed by general surgeons. Almost half of the patients (and likely more if breast surgery
A
patients were excluded) were obese, consistent with a large representation of bariatric patients.1 By contrast, obese patients account for about 20 percent of body contouring cases treated by plastic surgeons.4
The wound class and physical status data require explanation. Elective body contouring surgery should be a clean procedure. A clean-contaminated wound is a surgical wound in which the 2
Copyright © American Society of Plastic Surgeons. All rights reserved.
respiratory, alimentary, genital, or urinary tract is entered. In this database, 8.2 percent of patents were categorized as clean-contaminated, contaminated, or infected. All breast surgery (66.8 percent) is expected to be clean. Therefore, 24.7 percent (8.2/33.2) of patients undergoing
TE D
body contouring surgery (excluding the breasts) had contaminated wounds.
The American Society of Anesthesiologists physical status classification5 for elective body
contouring surgery is typically Class 1 or 2. A patient labeled Class 3 has a severe systemic
disease such as poorly-controlled diabetes, chronic obstructive pulmonary disease, or morbid
obesity (BMI ≥ 40 kg/m2).5 This series included 3899 Class 3 patients (21.9 percent), 220 Class
EP
4 patients (whose life is constantly threatened), and even 2 moribund Class 5 patients.
The authors believe that their risk factors are “independent predictors,”1 but do not control for the procedure or history of massive weight loss. Bariatric patients have higher rates of anemia, hypertension, diabetes, and malnutrition. An apparent risk differential is created by including a
C
large low-risk (and arguably unrelated) breast surgery group. Mammaplasty patients are, on average, younger and leaner6 than bariatric patients.1 Their operating times tend to be shorter.6
C
One cannot conclude that treating more than two areas with contouring is a risk factor if the majority of the low-risk breast surgery patients underwent breast surgery without simultaneous
A
body contouring procedures. Patients undergoing contouring of more than two areas are more likely to be treated with an abdominoplasty, which places them at higher risk already. The same reasoning applies to age, sex (breast surgery patients being all female) and body mass index comparisons. To compare “apples with apples,” it would have been preferable to exclude breast patients (and, ideally, massive weight loss patients), or just study the breast patients. By the
3
Copyright © American Society of Plastic Surgeons. All rights reserved.
same logic, it is unfair to indict general surgeons because they are operating on a higher-risk patient group. Correlation does not imply causation; inpatients are admitted because they are at higher risk by virtue of a medical issue or the extent of planned surgery.
TE D
Data from the Venous Thromboembolism Prevention Study7 shows that high-risk patients (Caprini score ≥ 7) experienced a 3.0 percent risk of venous thromboembolism, compared with a 1.2 percent risk overall.8 Wes et al.1 report a very similar complication rate, 2.95 percent, for
their highest-risk group. The relevant question is whether anticoagulating 100 percent of these
patients is justified if (1) 97 percent of the patients will not develop this complication1,8 (making
EP
the treatment unnecessary) and (2) the treatment introduces iatrogenic complications.8
The 2012 Guidelines of the American College of Chest Physicians9 do not include individual risk stratification or Caprini scores as risk reduction strategies. This fact may surprise plastic surgeons who believe that such scores are endorsed by national guidelines. Despite our best
C
efforts, we cannot reliably predict who will develop a venous thromboembolism.8,10 Retrospective reviews of disparate patient groups, even large ones that do not include objective
C
diagnostic data (and are affected by sampling bias)1 are unlikely to be fruitful. Our efforts are
better directed at (1) improving anesthesia to reduce risk for all patients,8 and (2) learning more
A
about the natural history of this complication using ultrasound surveillance, which can also provide early detection and treatment for affected patients.10
4
Copyright © American Society of Plastic Surgeons. All rights reserved.
References
1. Wes AM, Wink JD, Kovach SJ, Fischer JP. Venous thromboembolism in body
TE D
contouring: An analysis of 17,774 patients from the National Surgical Quality Improvement databases. Plast Reconstr Surg. 2015;135:972e.
2. Fischer JP, Wes AM, Serletti JM, Kovach SJ. Complications in body contouring
procedures: An analysis of 1797 patients from the 2005 to 2010 American College of Surgeons National Surgical Quality Improvement Program databases. Plast Reconstr
EP
Surg. 2013;132:1411–1420.
3. Plastic and Reconstructive Surgery website. Collections. Cosmetic: Body
C
Contouring/Liposuction. Available at:
http://journals.lww.com/plasreconsurg/pages/collectiondetails.aspx?TopicalCollectionId=
C
10. Accessed May 30, 2015.
4. Swanson E. Prospective clinical study reveals significant reduction in triglyceride level
A
and white cell count after liposuction and abdominoplasty and no change in cholesterol levels. Plast Reconstr Surg. 2011;128:182e-197e.
5
Copyright © American Society of Plastic Surgeons. All rights reserved.
5. American Society of Anesthesiologists Physical Status Classification System. Available at: http://asahq.org/resources/clinical-information/asa-physical-status-classificationsystem. Accessed May 30, 2015.
TE D
6. Swanson E. Prospective comparative clinical evaluation of 784 consecutive cases of breast augmentation and vertical mammaplasty, performed individually and in combination. Plast Reconstr Surg. 2013;132:30e-45e; discussion 46e-47e.
7. Pannucci CJ, Dreszer G, Fisher Wachtman C, et al. Postoperative enoxaparin prevents symptomatic venous thromboembolism in high-risk plastic surgery patients. Plast
EP
Reconstr Surg. 2011;128:1093-1103.
8. Swanson E. The case against chemoprophylaxis for venous thromboembolism prevention and the rationale for SAFE anesthesia. Plast Reconstr Surg Glob Open 2014;2:e160.
C
9. Kearon C, Akl EA, Comerota AJ, et al. Antithrombotic therapy for VTE disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of
C
Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012;141(2
A
Suppl):e419S-494S.
10. Swanson E. Ultrasound screening for deep venous thrombosis detection: Prospective evaluation of 200 plastic surgery outpatients. Plast Reconstr Surg Glob Open 2015;3:e332.
6
Copyright © American Society of Plastic Surgeons. All rights reserved.
