The American Journal of Surgery (2015) 209, 640-644
Society of Black Academic Surgeons
Lower extremity arterial reconstruction in obese patients Olumayowa Pitan, M.D., Mark Williams, B.S., Augustine Obirieze, M.B.B.S., M.P.H., Daniel Tran, M.D., David Rose, M.D., Terrence Fullum, M.D., Edward Cornwell, III, M.D., Kakra Hughes, M.D.* Department of Surgery, Howard University College of Medicine and Hospital, 2041 Georgia Avenue, #4B-04, Washington, DC 20060, USA
KEYWORDS: Obesity; Outcomes; Lower extremity revascularization
Abstract BACKGROUND: Previous reports have noted that obese patients undergoing lower extremity arterial reconstruction have higher complication rates compared with nonobese patients. We evaluated the effect of obesity on outcomes following open infrainguinal arterial reconstruction on a national level. METHODS: A query of the American College of Surgeons’ National Surgical Quality Improvement Program Database was conducted to identify all adult patients who underwent open infrainguinal lower extremity arterial reconstruction from 2005 to 2009. Postoperative outcomes were analyzed in different body mass index groups. RESULTS: Obese and morbidly obese patients had a higher risk of wound infection when compared with normal weight patients (odds ratios 2.1 and 2.7, P , .05). Obese patients had a lower mortality when compared with normal weight patients (odds ratio .83, P , .05). CONCLUSIONS: Obesity was associated with an increase in wound infection after open lower extremity arterial reconstruction. Obesity, but not morbid obesity, was associated with decreased mortality. Ó 2015 Elsevier Inc. All rights reserved.
The condition of obesity in the United States, and around the globe, has been gradually escalating over the last few decades,1 such that it has been defined as a public health issue of pandemic magnitude.2 Currently, in the United States, over 35% of adults are estimated to be obese,1 with adults aged 60 and over more likely to be
The authors declare no conflicts of interest. * Corresponding author. Tel.: 11-202-865-1281; fax: 11-202-8656432. E-mail address: [email protected] Manuscript received March 31, 2014; revised manuscript December 4, 2014 0002-9610/$ - see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.amjsurg.2014.12.012
obese than younger adults.3 Obesity has been implicated in the pathophysiology of a variety of conditions including cardiovascular disease, diabetes, dyslipidemia, hypertension, and stroke.4 The medical costs associated with obesity were estimated at $147 billion in 2008,1 with a direct medical cost of approximately 5% to 10% of the US healthcare expenditure.5,6 This increase in cost is also seen in patients undergoing surgical procedures.7,8 Studies evaluating the effect of obesity on various diseases9–11 have shown a correlation between obesity and various comorbidities.12,13 It is, therefore, not surprising that obesity has often been associated with an increased risk of perioperative complications.14–16 Specifically, an increasing body mass index
O. Pitan et al.
Infrainguinal bypass in obese patients
641
(BMI) has been associated with an increase in infection rate.15,17 The effect of obesity on patients undergoing vascular surgery has also been investigated.18–20 Patel et al20 noted that obese patients while having similar limb salvage rates, perioperative cardiac morbidity, long-term survival rates, and long-term graft patency rates as nonobese patients, nevertheless manifested an increased risk of surgical site wound infection. In another study, Chang et al reported that Class I obesity was associated with a decrease in perioperative stroke benefit in patients undergoing carotid endarterectomy.19 Many of these studies, however, have been single institution studies and some have included all types of vascular reconstructive procedures, making generalization somewhat difficult.18 We undertook this study to evaluate the effect of obesity on outcomes in a large cohort of patients undergoing lower extremity arterial reconstruction on a national scale.
complications included acute renal failure, progressive renal insufficiency, or urinary tract infection. Overall complications included any of the above complications or a return to the operating room. Bivariate analyses were done, using the Pearson’s chisquare test for categorical variables and analysis of variance test for continuous variables. Multivariate logistic regression analyses were performed to assess the odds of postoperative complications and mortality, comparing the groups, while controlling for patient demographics, preoperative comorbidities, functional status before surgery, procedure type, and smoking history. All statistical analyses were done using STATA/MP, version 12.0 (StataCorp, College Station, TX). Statistical significance was defined as P value less than .05.
Methods
Description of the study population
A retrospective study was conducted using data from the American College of Surgeons’ National Surgical Quality Improvement Program (NSQIP) Database from 2005 to 2009. Using the American Medical Association’s Current Procedural Terminology codes, adult patients who had all undergone an open infrainguinal arterial reconstruction were identified. Patients were then categorized according to BMI into 4 comparison groups: normal weight (BMI 18.5 to 24.9), overweight (BMI 25.0 to 29.9), obese (BMI 30.0 to 39.9), and morbidly obese (BMI R 40). Additional data were retrieved from the database including age, sex, ethnicity, smoking status (current smoker within 1 year of operation), and preoperative functional status (categorized as independent, partially dependent, or totally dependent), as well as preoperative comorbidities. Comorbidities were classified into 4 groups: cardiac comorbidity was defined as congestive heart failure within 30 days before surgery, a history of myocardial infarction 6 months before surgery, previous percutaneous coronary intervention, previous cardiac surgery, and a history of angina within 1 month of surgery. Renal comorbidity was defined as acute renal failure and/or preoperative dialysis dependence. Pulmonary comorbidity was defined as a history of chronic obstructive pulmonary disease, current (active) pneumonia, and ventilator dependence greater than 24 hours. Diabetic comorbidity was defined as a diagnosis of diabetes mellitus. Outcomes evaluated included postoperative mortality and complications. Postoperative complications were further identified as amputation, graft failure, wound infection, respiratory, cardiac, renal, and overall complications. Pulmonary complications included pneumonia, unplanned intubation, pulmonary embolism, or ventilator use for greater than 48 hours. Wound infection complication included superficial surgical site infection (SSI), deep incisional SSI, and organ space SSI. Cardiac complications included cardiac arrest or myocardial infarction. Renal
The study population comprised 17,789 patients in the NSQIP database who all underwent an open infrainguinal lower extremity arterial reconstructive operation from 2005 to 2009. Of these, 35% were normal weight (BMI 18.5 to 24.9), 36% were overweight (BMI 25.0 to 29.9), 26% were obese (BMI 30.0 to 39.9), and 3% were morbidly obese (BMI R 40). This was a primarily male (64%) population with a mean age of 67 (standard deviation [SD] 11) years. The mean BMI was 27.8 (SD 5.9). A majority of patients was older than 60 years comprising 73% of the cohort. Patients less than 40 years comprised 1% of the study population. Forty-one percent of the patients were current smokers and 83% were fully independent with regards to their functional status. The population was predominantly white (74%), with a significant prevalence of preoperative cardiac comorbidities (41%) and diabetes mellitus (41%) (Table 1).
Results
Outcomes There was a low overall mortality rate of 2.4%, with a 30-day graft failure rate of 4.7%. Cardiac complications occurred in 2% of the patients, 3.8% had respiratory complications, 3% had renal complications, 11% had wound infections, and 17% required reoperation within 30 days. The mean postoperative length of stay was 6 days (SD 7.5). On bivariate analysis, obese patients had a mortality rate of 1.5% compared with 3.1% in normal weight patients (P , .05). Obese patients had a 15% rate of wound infection, morbidly obese patients had a 21.2% rate compared with 7.8% in normal weight patients (P , .05). On multivariate regression, obese patients had a 22% increased risk of overall complications and morbidly obese patients had a 48% increased risk when compared with normal weight patients (OR 1.2, P , .05 and OR 1.44, P , .05 respectively). Obese patients were less likely to die when compared with normal weight patients (OR .83,
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The American Journal of Surgery, Vol 209, No 4, April 2015
Table 1
Preoperative patient characteristics
Mean age (years) Age ,40 40–49 50–59 .60 Mean BMI (kg/m2) Female sex Current smoker Functional status Independent Partially dependent Totally dependent Cardiac disease Pulmonary disease Renal disease Diabetes mellitus
Normal weight (%) BMI 18.5–24.9 (n 5 6,242)
Overweight (%) BMI 25–29.9 (n 5 6,368)
Obese (%) BMI 30–39.9 (n 5 4,581)
Morbidly obese (%) BMI . 40 (n 5 598)
69
67
64
60
63 (1.0) 267 (4.4) 978 (16.2) 4,730 (78.3) 22.4 2,480 (39.7) 2,893 (46.4)
64 306 1,108 4,792 27.3 1,931 2,480
5,018 1,076 148 2,329 987 456 1,865
5,401 859 108 2,641 797 417 2,582
(80.4) (17.2) (2.4) (35.1) (15.8) (7.3) (29.9)
(1.0) (4.9) (17.7) (76.4) (30.3) (38.9)
49 322 1,079 3,110 33.4 1,645 1,693
(1.1) (7.1) (23.7) (68.2) (35.9) (37.0)
18 (3.0) 71 (11.9) 175 (29.3) 333 (55.8) 45.4 322 (53.4) 221 (37.0)
(84.8) (13.5) (1.7) (41.5) (12.5) (6.6) (40.6)
3,915 686 81 2,035 621 325 2,480
(85.5) (12.8) (1.8) (44.4) (13.6) (7.1) (54.1)
485 97 16 259 77 58 392
(81.1) (16.2) (2.7) (43.3) (12.9) (9.7) (65.6)
Values in parenthesis represent percentages, other values represent actual number of patients in each category. BMI 5 body mass index.
P , .05). The odds of wound infection increased with increasing BMI: obese patients had twice the risk and morbidly obese patients were almost 3 times as likely to have a wound infection compared with normal weight patients (ORs 1.3, 2.1, 2.7, respectively, P , .05) (Table 2). The types of operations performed among the various groups were similar in complexity (Table 3). The infection rates among the different procedure types were analyzed and no significant difference was found.
Comments The American College of Surgeons’ NSQIP is a multicenter, multispecialty surgical database. Data are collected on preoperative risk factors, intraoperative variables, and 30-day postoperative mortality and morbidity outcomes for patients undergoing major surgical procedures in both inpatient and
Table 2
outpatient settings.21 Employing this database, we were able to analyze various postoperative complications across BMI classifications on a national level. Interestingly, this study population consisted primarily of overweight (36%) and obese patients (26%), with proportions higher than that of the general population. The overall key finding was that an increase in BMI was strongly associated with an increase in postoperative wound infection even after adjusting for potential confounders such as diabetes mellitus, smoking, and procedure type. One interesting finding in this study was that obesity, but not morbid obesity, appeared to offer a significant survival advantage during the 30-day postoperative period following lower extremity arterial reconstruction when compared with normal weight patients. Although this was unexpected, it is, in fact, consistent with a previous report by Davenport et al18 that also describes a protective benefit of obesity as compared with normal weight, underweight, and morbidly obese individuals undergoing vascular procedures. Similarly, Mullen et al17 reported this
Postoperative complications
Mortality Amputation Graft failure Cardiac complications Pulmonary complications Renal complications Wound infection Overall complications
Normal weight (n 5 6,242)
Overweight (P value) (n 5 6,368)
Obese (P value) (n 5 4,581)
Morbidly obese (P value) (n 5 598)
Reference Reference Reference Reference Reference Reference Reference Reference
.8 1.0 .9 .9 1.0 1.0 1.3 1.0
.5 1.6 1.0 .9 .9 1.2 2.0 1.2
.8 (.36) No amputations 1.0 (.79) .6 (.22) .9 (.69) 1.5 (.07) 2.7 (.00) 1.5 (.00)
Values represent odds ratios with P values in parenthesis.
(.14) (.98) (.40) (.43) (.79) (.64) (.00) (.30)
(.00) (.44) (.77) (.35) (.58) (.20) (.00) (.00)
O. Pitan et al. Table 3
Infrainguinal bypass in obese patients
643
Operations performed
Femoral–popliteal bypass Femoral–distal bypass Femoral–popliteal endarterectomy Femoral–femoral bypass Popliteal–distal bypass Tibioperoneal endarterectomy Distal–distal bypass
Normal weight (%)
Overweight (%)
Obese (%)
Morbidly obese (%)
41 24 18 9 6 .9 .06
42 24 19 8 7 .7 .03
44 22 19 7 7 .6 .09
43 22 18 8 8 .8 .17
survival advantage in patients undergoing nonbariatric general surgery. This has often been referred to as the ‘‘obesity paradox’’17,22 and is a phenomenon that has been observed in other vascular operations such as carotid endarterectomy19 as well as in nonsurgical patients with established heart failure.23 Various theories have been postulated to explain the obesity paradox. A possible explanation for this paradoxical advantage that obesity confers is that the obese patients might not be as critically ill as those patients with unintentional weight loss and wasting as a result of the severity of their chronic conditions thereby increasing their mortality. No studies have clearly explained the etiology of this paradox. There are several limitations to this studydindeed the established pitfalls of NSQIP have been well described.24 Its retrospective nature necessarily places heavy reliance on proper coding, which may not necessarily be guaranteed to be universally accurate. Second, the database only gives 30-day postoperative outcomes, precluding the ability to evaluate long-term outcomes. Third, critical outcomes such as amputation and graft failure rates necessitate long-term follow-up, which this study is not able to provide. One distinctive advantage of using this multi-institutional surgical outcomes large database, however, is the increased statistical power that it affords and the ability to evaluate outcomes on such a large scale.
Conclusions In summary, in this population of patients who all underwent open infrainguinal arterial reconstruction, obesity was associated with an increase in wound infection when compared with normal weight patients. Obesity, but not morbid obesity, was associated with a decrease in mortality as compared with normal weight individuals. Further research would be helpful to further elucidate this paradoxical advantage conferred by nonmorbid obesity to guide future recommendations for patient weight and operative risk assessment.
References 1. Overweight and Obesity. 2012; Available at: http://www.cdc.gov/ obesity/data/adult.html. Accessed April 1, 2013.
2. Hennekens CH, Andreotti F. Leading avoidable cause of premature deaths worldwide: case for obesity. Am J Med 2013;126:97–8. 3. Ogden CL, Carroll MD, Kit BK, et al. Prevalence of obesity in the United States, 2009-2010. NCHS Data Brief 2012;82:1–8. 4. Brixner D, Ghate SR, McAdam-Marx C, et al. Association between cardiometabolic risk factors and body mass index based on diagnosis and treatment codes in an electronic medical record database. J Manag Care Pharm 2008;14:756–67. 5. Tsai AG, Williamson DF, Glick HA. Direct medical cost of overweight and obesity in the USA: a quantitative systematic review. Obes Rev 2011;12:50–61. 6. Wang YC, McPherson K, Marsh T, et al. Health and economic burden of the projected obesity trends in the USA and the UK. Lancet 2011; 378:815–25. 7. Hawn MT, Bian J, Leeth RR, et al. Impact of obesity on resource utilization for general surgical procedures. Ann Surg 2005;241:821–6; discussion, 826–8. 8. Richards NG, Beekley AC, Tichansky DS. The economic costs of obesity and the impact of bariatric surgery. Surg Clin North Am 2011;91:1173–80. vii–viii. 9. Sabharwal S, Root MZ. Impact of obesity on orthopaedics. J Bone Joint Surg Am 2012;94:1045–52. 10. O’Donnell DE, O’Donnell CD, Webb KA, et al. Respiratory consequences of mild-to-moderate obesity: impact on exercise performance in health and in chronic obstructive pulmonary disease. Pulm Med 2012;2012:818925. 11. Patterson RE, Frank LL, Kristal AR, et al. A comprehensive examination of health conditions associated with obesity in older adults. Am J Prev Med 2004;27:385–90. 12. Fontaine KR, Redden DT, Wang C, et al. Years of life lost due to obesity. JAMA 2003;289:187–93. 13. Poirier P, Giles TD, Bray GA, et al. Obesity and cardiovascular disease: pathophysiology, evaluation, and effect of weight loss: an update of the 1997 American Heart Association Scientific Statement on Obesity and Heart Disease from the Obesity Committee of the Council on Nutrition, Physical Activity, and Metabolism. Circulation 2006; 113:898–918. 14. Bickenbach KA, Denton B, Gonen M, et al. Impact of obesity on perioperative complications and long-term survival of patients with gastric cancer. Ann Surg Oncol 2013;20:780–7. 15. Nam JH, Gahtan V, Roberts AB, et al. Influence of incisional complications on infrainguinal vein bypass graft outcome. Ann Vasc Surg 1999;13:77–83. 16. Ramsey AM, Martin RC. Body mass index and outcomes from pancreatic resection: a review and meta-analysis. J Gastrointest Surg 2011; 15:1633–42. 17. Mullen JT, Moorman DW, Davenport DL. The obesity paradox: body mass index and outcomes in patients undergoing nonbariatric general surgery. Ann Surg 2009;250:166–72. 18. Davenport DL, Xenos ES, Hosokawa P, et al. The influence of body mass index obesity status on vascular surgery 30-day morbidity and mortality. J Vasc Surg 2009;49:140–7. 147.e1; discussion, 147.
644 19. Jackson RS, Black 3rd JH, Lum YW, et al. Class I obesity is paradoxically associated with decreased risk of postoperative stroke after carotid endarterectomy. J Vasc Surg 2012;55:1306–12. 20. Patel VI, Hamdan AD, Schermerhorn ML, et al. Lower extremity arterial revascularization in obese patients. J Vasc Surg 2007;46: 738–42. 21. ACS NSQIP Participant User Data File User Guide. Available at: http://site.acsnsqip.org/downloads/. Accessed August 8, 2012.
The American Journal of Surgery, Vol 209, No 4, April 2015 22. Kastorini CM, Panagiotakos DB. The obesity paradox: methodological considerations based on epidemiological and clinical evidence–new insights. Maturitas 2012;72:220–4. 23. Curtis JP, Selter JG, Wang Y, et al. The obesity paradox: body mass index and outcomes in patients with heart failure. Arch Intern Med 2005;165:55–61. 24. Nguyen LL, Barshes NR. Analysis of large databases in vascular surgery. J Vasc Surg 2010;52:768–74.
Society of Black Academic Surgeons
Lower extremity arterial reconstruction in obese patients Olumayowa Pitan, M.D., Mark Williams, B.S., Augustine Obirieze, M.B.B.S., M.P.H., Daniel Tran, M.D., David Rose, M.D., Terrence Fullum, M.D., Edward Cornwell, III, M.D., Kakra Hughes, M.D.* Department of Surgery, Howard University College of Medicine and Hospital, 2041 Georgia Avenue, #4B-04, Washington, DC 20060, USA
KEYWORDS: Obesity; Outcomes; Lower extremity revascularization
Abstract BACKGROUND: Previous reports have noted that obese patients undergoing lower extremity arterial reconstruction have higher complication rates compared with nonobese patients. We evaluated the effect of obesity on outcomes following open infrainguinal arterial reconstruction on a national level. METHODS: A query of the American College of Surgeons’ National Surgical Quality Improvement Program Database was conducted to identify all adult patients who underwent open infrainguinal lower extremity arterial reconstruction from 2005 to 2009. Postoperative outcomes were analyzed in different body mass index groups. RESULTS: Obese and morbidly obese patients had a higher risk of wound infection when compared with normal weight patients (odds ratios 2.1 and 2.7, P , .05). Obese patients had a lower mortality when compared with normal weight patients (odds ratio .83, P , .05). CONCLUSIONS: Obesity was associated with an increase in wound infection after open lower extremity arterial reconstruction. Obesity, but not morbid obesity, was associated with decreased mortality. Ó 2015 Elsevier Inc. All rights reserved.
The condition of obesity in the United States, and around the globe, has been gradually escalating over the last few decades,1 such that it has been defined as a public health issue of pandemic magnitude.2 Currently, in the United States, over 35% of adults are estimated to be obese,1 with adults aged 60 and over more likely to be
The authors declare no conflicts of interest. * Corresponding author. Tel.: 11-202-865-1281; fax: 11-202-8656432. E-mail address: [email protected] Manuscript received March 31, 2014; revised manuscript December 4, 2014 0002-9610/$ - see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.amjsurg.2014.12.012
obese than younger adults.3 Obesity has been implicated in the pathophysiology of a variety of conditions including cardiovascular disease, diabetes, dyslipidemia, hypertension, and stroke.4 The medical costs associated with obesity were estimated at $147 billion in 2008,1 with a direct medical cost of approximately 5% to 10% of the US healthcare expenditure.5,6 This increase in cost is also seen in patients undergoing surgical procedures.7,8 Studies evaluating the effect of obesity on various diseases9–11 have shown a correlation between obesity and various comorbidities.12,13 It is, therefore, not surprising that obesity has often been associated with an increased risk of perioperative complications.14–16 Specifically, an increasing body mass index
O. Pitan et al.
Infrainguinal bypass in obese patients
641
(BMI) has been associated with an increase in infection rate.15,17 The effect of obesity on patients undergoing vascular surgery has also been investigated.18–20 Patel et al20 noted that obese patients while having similar limb salvage rates, perioperative cardiac morbidity, long-term survival rates, and long-term graft patency rates as nonobese patients, nevertheless manifested an increased risk of surgical site wound infection. In another study, Chang et al reported that Class I obesity was associated with a decrease in perioperative stroke benefit in patients undergoing carotid endarterectomy.19 Many of these studies, however, have been single institution studies and some have included all types of vascular reconstructive procedures, making generalization somewhat difficult.18 We undertook this study to evaluate the effect of obesity on outcomes in a large cohort of patients undergoing lower extremity arterial reconstruction on a national scale.
complications included acute renal failure, progressive renal insufficiency, or urinary tract infection. Overall complications included any of the above complications or a return to the operating room. Bivariate analyses were done, using the Pearson’s chisquare test for categorical variables and analysis of variance test for continuous variables. Multivariate logistic regression analyses were performed to assess the odds of postoperative complications and mortality, comparing the groups, while controlling for patient demographics, preoperative comorbidities, functional status before surgery, procedure type, and smoking history. All statistical analyses were done using STATA/MP, version 12.0 (StataCorp, College Station, TX). Statistical significance was defined as P value less than .05.
Methods
Description of the study population
A retrospective study was conducted using data from the American College of Surgeons’ National Surgical Quality Improvement Program (NSQIP) Database from 2005 to 2009. Using the American Medical Association’s Current Procedural Terminology codes, adult patients who had all undergone an open infrainguinal arterial reconstruction were identified. Patients were then categorized according to BMI into 4 comparison groups: normal weight (BMI 18.5 to 24.9), overweight (BMI 25.0 to 29.9), obese (BMI 30.0 to 39.9), and morbidly obese (BMI R 40). Additional data were retrieved from the database including age, sex, ethnicity, smoking status (current smoker within 1 year of operation), and preoperative functional status (categorized as independent, partially dependent, or totally dependent), as well as preoperative comorbidities. Comorbidities were classified into 4 groups: cardiac comorbidity was defined as congestive heart failure within 30 days before surgery, a history of myocardial infarction 6 months before surgery, previous percutaneous coronary intervention, previous cardiac surgery, and a history of angina within 1 month of surgery. Renal comorbidity was defined as acute renal failure and/or preoperative dialysis dependence. Pulmonary comorbidity was defined as a history of chronic obstructive pulmonary disease, current (active) pneumonia, and ventilator dependence greater than 24 hours. Diabetic comorbidity was defined as a diagnosis of diabetes mellitus. Outcomes evaluated included postoperative mortality and complications. Postoperative complications were further identified as amputation, graft failure, wound infection, respiratory, cardiac, renal, and overall complications. Pulmonary complications included pneumonia, unplanned intubation, pulmonary embolism, or ventilator use for greater than 48 hours. Wound infection complication included superficial surgical site infection (SSI), deep incisional SSI, and organ space SSI. Cardiac complications included cardiac arrest or myocardial infarction. Renal
The study population comprised 17,789 patients in the NSQIP database who all underwent an open infrainguinal lower extremity arterial reconstructive operation from 2005 to 2009. Of these, 35% were normal weight (BMI 18.5 to 24.9), 36% were overweight (BMI 25.0 to 29.9), 26% were obese (BMI 30.0 to 39.9), and 3% were morbidly obese (BMI R 40). This was a primarily male (64%) population with a mean age of 67 (standard deviation [SD] 11) years. The mean BMI was 27.8 (SD 5.9). A majority of patients was older than 60 years comprising 73% of the cohort. Patients less than 40 years comprised 1% of the study population. Forty-one percent of the patients were current smokers and 83% were fully independent with regards to their functional status. The population was predominantly white (74%), with a significant prevalence of preoperative cardiac comorbidities (41%) and diabetes mellitus (41%) (Table 1).
Results
Outcomes There was a low overall mortality rate of 2.4%, with a 30-day graft failure rate of 4.7%. Cardiac complications occurred in 2% of the patients, 3.8% had respiratory complications, 3% had renal complications, 11% had wound infections, and 17% required reoperation within 30 days. The mean postoperative length of stay was 6 days (SD 7.5). On bivariate analysis, obese patients had a mortality rate of 1.5% compared with 3.1% in normal weight patients (P , .05). Obese patients had a 15% rate of wound infection, morbidly obese patients had a 21.2% rate compared with 7.8% in normal weight patients (P , .05). On multivariate regression, obese patients had a 22% increased risk of overall complications and morbidly obese patients had a 48% increased risk when compared with normal weight patients (OR 1.2, P , .05 and OR 1.44, P , .05 respectively). Obese patients were less likely to die when compared with normal weight patients (OR .83,
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The American Journal of Surgery, Vol 209, No 4, April 2015
Table 1
Preoperative patient characteristics
Mean age (years) Age ,40 40–49 50–59 .60 Mean BMI (kg/m2) Female sex Current smoker Functional status Independent Partially dependent Totally dependent Cardiac disease Pulmonary disease Renal disease Diabetes mellitus
Normal weight (%) BMI 18.5–24.9 (n 5 6,242)
Overweight (%) BMI 25–29.9 (n 5 6,368)
Obese (%) BMI 30–39.9 (n 5 4,581)
Morbidly obese (%) BMI . 40 (n 5 598)
69
67
64
60
63 (1.0) 267 (4.4) 978 (16.2) 4,730 (78.3) 22.4 2,480 (39.7) 2,893 (46.4)
64 306 1,108 4,792 27.3 1,931 2,480
5,018 1,076 148 2,329 987 456 1,865
5,401 859 108 2,641 797 417 2,582
(80.4) (17.2) (2.4) (35.1) (15.8) (7.3) (29.9)
(1.0) (4.9) (17.7) (76.4) (30.3) (38.9)
49 322 1,079 3,110 33.4 1,645 1,693
(1.1) (7.1) (23.7) (68.2) (35.9) (37.0)
18 (3.0) 71 (11.9) 175 (29.3) 333 (55.8) 45.4 322 (53.4) 221 (37.0)
(84.8) (13.5) (1.7) (41.5) (12.5) (6.6) (40.6)
3,915 686 81 2,035 621 325 2,480
(85.5) (12.8) (1.8) (44.4) (13.6) (7.1) (54.1)
485 97 16 259 77 58 392
(81.1) (16.2) (2.7) (43.3) (12.9) (9.7) (65.6)
Values in parenthesis represent percentages, other values represent actual number of patients in each category. BMI 5 body mass index.
P , .05). The odds of wound infection increased with increasing BMI: obese patients had twice the risk and morbidly obese patients were almost 3 times as likely to have a wound infection compared with normal weight patients (ORs 1.3, 2.1, 2.7, respectively, P , .05) (Table 2). The types of operations performed among the various groups were similar in complexity (Table 3). The infection rates among the different procedure types were analyzed and no significant difference was found.
Comments The American College of Surgeons’ NSQIP is a multicenter, multispecialty surgical database. Data are collected on preoperative risk factors, intraoperative variables, and 30-day postoperative mortality and morbidity outcomes for patients undergoing major surgical procedures in both inpatient and
Table 2
outpatient settings.21 Employing this database, we were able to analyze various postoperative complications across BMI classifications on a national level. Interestingly, this study population consisted primarily of overweight (36%) and obese patients (26%), with proportions higher than that of the general population. The overall key finding was that an increase in BMI was strongly associated with an increase in postoperative wound infection even after adjusting for potential confounders such as diabetes mellitus, smoking, and procedure type. One interesting finding in this study was that obesity, but not morbid obesity, appeared to offer a significant survival advantage during the 30-day postoperative period following lower extremity arterial reconstruction when compared with normal weight patients. Although this was unexpected, it is, in fact, consistent with a previous report by Davenport et al18 that also describes a protective benefit of obesity as compared with normal weight, underweight, and morbidly obese individuals undergoing vascular procedures. Similarly, Mullen et al17 reported this
Postoperative complications
Mortality Amputation Graft failure Cardiac complications Pulmonary complications Renal complications Wound infection Overall complications
Normal weight (n 5 6,242)
Overweight (P value) (n 5 6,368)
Obese (P value) (n 5 4,581)
Morbidly obese (P value) (n 5 598)
Reference Reference Reference Reference Reference Reference Reference Reference
.8 1.0 .9 .9 1.0 1.0 1.3 1.0
.5 1.6 1.0 .9 .9 1.2 2.0 1.2
.8 (.36) No amputations 1.0 (.79) .6 (.22) .9 (.69) 1.5 (.07) 2.7 (.00) 1.5 (.00)
Values represent odds ratios with P values in parenthesis.
(.14) (.98) (.40) (.43) (.79) (.64) (.00) (.30)
(.00) (.44) (.77) (.35) (.58) (.20) (.00) (.00)
O. Pitan et al. Table 3
Infrainguinal bypass in obese patients
643
Operations performed
Femoral–popliteal bypass Femoral–distal bypass Femoral–popliteal endarterectomy Femoral–femoral bypass Popliteal–distal bypass Tibioperoneal endarterectomy Distal–distal bypass
Normal weight (%)
Overweight (%)
Obese (%)
Morbidly obese (%)
41 24 18 9 6 .9 .06
42 24 19 8 7 .7 .03
44 22 19 7 7 .6 .09
43 22 18 8 8 .8 .17
survival advantage in patients undergoing nonbariatric general surgery. This has often been referred to as the ‘‘obesity paradox’’17,22 and is a phenomenon that has been observed in other vascular operations such as carotid endarterectomy19 as well as in nonsurgical patients with established heart failure.23 Various theories have been postulated to explain the obesity paradox. A possible explanation for this paradoxical advantage that obesity confers is that the obese patients might not be as critically ill as those patients with unintentional weight loss and wasting as a result of the severity of their chronic conditions thereby increasing their mortality. No studies have clearly explained the etiology of this paradox. There are several limitations to this studydindeed the established pitfalls of NSQIP have been well described.24 Its retrospective nature necessarily places heavy reliance on proper coding, which may not necessarily be guaranteed to be universally accurate. Second, the database only gives 30-day postoperative outcomes, precluding the ability to evaluate long-term outcomes. Third, critical outcomes such as amputation and graft failure rates necessitate long-term follow-up, which this study is not able to provide. One distinctive advantage of using this multi-institutional surgical outcomes large database, however, is the increased statistical power that it affords and the ability to evaluate outcomes on such a large scale.
Conclusions In summary, in this population of patients who all underwent open infrainguinal arterial reconstruction, obesity was associated with an increase in wound infection when compared with normal weight patients. Obesity, but not morbid obesity, was associated with a decrease in mortality as compared with normal weight individuals. Further research would be helpful to further elucidate this paradoxical advantage conferred by nonmorbid obesity to guide future recommendations for patient weight and operative risk assessment.
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