Abstract
Introduction:
The incidence of metabolically unhealthy obesity is rising nationally. In this study, we compare wound and overall complications between metabolically unhealthy obese and healthy patients undergoing elective plastic surgery and model how operative time influences a complication risk.
Methods:
Patients undergoing elective breast and body plastic surgery procedures in the 2009–2019 National Surgical Quality Improvement Program (NSQIP) dataset were identified. Complications were compared between metabolically unhealthy obese (body mass index [BMI] > 30 with diabetes and/or hypertension) versus metabolically healthy obese patients (BMI > 30 without diabetes or hypertension). Logistic regression was used to model the probability of wound complications across operative times stratified by metabolic status.
Results:
Of 139,352 patients, 13.4% (n = 18,663) had metabolically unhealthy obesity and 23.8% (n = 33,135) had metabolically healthy obesity. Compared to metabolically healthy patients, metabolically unhealthy patients had higher incidence of wound complications (6.9% versus 5.6%; P < 0.001) and adverse events (12.4% versus 9.6%; P < 0.001), in addition to higher 30-d readmission, returns to the operating room, and length of stay (all P < 0.001). After adjustment, BMI (Odds ratio [OR] 7.86), hypertension (OR 1.15), and diabetes (OR 1.25) were independent risk factors for wound complications (all P < 0.001). Among metabolically unhealthy patients, the operative time was log-linear with a wound complication risk (OR 1.21; P < 0.001).
Conclusions:
Diabetes and hypertension are additive risk factors with obesity for wound complications in elective plastic surgery. Among patients with metabolically unhealthy obesity, a risk of wound complications increases logarithmically with operative time. This distinction with regard to metabolic state might explain the unclear impact of obesity on surgical outcomes within existing surgical literature.
Keywords: Diabetes, Metabolic syndrome, Obesity, Operative time, Plastic surgery, Wound healing
Introduction
Obesity is a growing epidemic across the United States, affecting more than 40% of the population in 2018.1 Within this population, a growing number of patients have a constellation of metabolic derangements referred to collectively as metabolic syndrome, defined to be excess abdominal fat as measured by the waist circumference with concurrent metabolic risk factors including hypertension, diabetes, and dyslipidemia.2,3 Metabolic syndrome is a complex inflammatory state associated with a spectrum of biochemical and hormonal disturbances2,4,5 and has been associated with worse cardiovascular outcomes and all-cause mortality compared to obese patients without metabolic derangement (metabolically healthy obesity).6,7 In surgical patients, metabolic syndrome has also been shown to lead to higher 30-d postoperative complications across subspecialties including general surgery, orthopedic surgery, and neurosurgery.8–14
In plastic surgery, obesity has been well established as a risk factor for wound complications and adverse events, particularly in breast and body procedures.15–21 In addition, many plastic surgeons use body mass index (BMI) cutoffs in their practice when considering candidacy for elective cases to reduce the complication risk.22–24 However, despite a growing body of literature demonstrating an exponential risk of surgical complications in metabolically unhealthy obese patients,8–14,25 how metabolic derangement influences complication rates in obese patients undergoing plastic surgery has not been studied. Furthermore, how the risk of wound complications varies by the operative time within the metabolically unhealthy obese population remains unknown.
In this study, we use the 2009–2019 American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) to study the influence of metabolically unhealthy obesity on wound healing complications and adverse events across elective plastic surgery breast and body procedures. We also model the association between operative time and cumulative wound complication risk in both metabolically healthy and unhealthy patients. Ultimately, we aim for this study to guide surgical decision making regarding the pursuit of and timing of elective plastic surgery procedures within the growing population of metabolically unhealthy obese patients nationally.
Methods
After an institutional review board approval, the ACS NSQIP database was queried for all elective plastic surgery cases from 2009 to 2019. Cases included were primary plastic surgery cases that were coded as nonemergency (elective) procedures involving breast and body procedures (Supplementary Table 1 for included Current Procedural Terminology [CPT] codes) in adult patients aged ≥18 years who had available BMI data and operative time at least ≥30 min. Patient demographics and comorbidities collected included age, race/ethnicity, gender, BMI, hypertension (HTN) requiring medication, diabetes mellitus with or without the need for insulin, tobacco use, congestive heart failure (CHF), bleeding disorder, steroid use, chronic obstructive pulmonary disease (COPD), and American Society of Anesthesiologists (ASA) classification (1–4). Intraoperative variables and postoperative complications collected included operative time, length of stay, 30-d mortality, superficial/deep surgical site infections, wound disruption, pneumonia, unplanned intubation, deep vein thrombosis (DVT), pulmonary embolism (PE), acute renal failure, urinary tract infection, sepsis, return to the operating room (OR), and 30-d readmission. Wound healing complications were defined to include any superficial incisional surgical site infection (SSI), deep incisional surgical site infection (SSI), organ/space surgical site infection (SSI), or wound disruption. BMI (kg/m2) was calculated using the following formula:
Underweight was classified as BMI < 18.5, normal weight BMI 18.5–25, overweight BMI 25–30, obese BMI 30–35, severely obese BMI 35–40, morbidly obese BMI 40–50, and super obese BMI > 50. In this study, metabolically unhealthy obesity was defined to be the presence of obesity (BMI > 30) with diabetes and/or hypertension, whereas metabolically healthy obesity was defined to be BMI > 30 without diabetes or hypertension.
Study outcome
The primary outcome of interest was the influence of metabolically unhealthy obesity on wound healing complications and adverse events across elective breast and body plastic surgery procedures. Secondary outcomes included the interaction between metabolic risk factors with operative time on incidence of wound healing complications.
Statistical analysis
Demographic and clinical characteristics were summarized with numbers and percentages for categorical variables and median (interquartile range [IQR]) for continuous variables stratified by BMI and metabolically unhealthy versus healthy obesity. Median and IQR were used in this study because none of the continuous variables used in this study (patient age, BMI, operative time, and hospital length of stay) were normally distributed. Normality was checked using Shapiroe–Wilk tests (all P values less than 0.001). Differences between the cohorts were tested using the Chi-squared tests for categorical variables and Wilcoxon signed-rank tests for continuous variables, as appropriate. A logistic regression model was used to model the effect of obesity, diabetes, HTN, and operative time on wound healing complications, after the adjustment for confounders. The probability of wound healing complications stratified by the log of operative time was modeled for metabolically healthy and unhealthy patients. All tests were two-sided and were considered statistically significant for values of P < 0.05. The analysis was conducted in Excel and R.
Results
A total of 139,352 patients undergoing elective breast and body plastic surgery procedures in the 2009–2019 NSQIP dataset were included for an analysis. Briefly, most patients were female (98.3%), Caucasian, or African American (58.2% and 12.1%, respectively) and underwent surgery in an outpatient setting (75.4%). Most patients were normal weight (29.6%), overweight (32.1%), or obese (21.8%), with severe obesity present in 9.8%, morbid obesity in 4.8%, and super obesity in 0.8% patients. Tobacco use was present in 9.1% of the cohort. Diabetes was present in 5.8% and HTN in 21.8% of patients. Across the cohort, wound healing complications occurred in 3.9% (n = 5409) of cases (Table 1).
Table 1 –
Demographics and comorbidities across the cohort (total n = 139,352).
| Variables | Response | n | % |
|---|---|---|---|
|
| |||
| Incidence of wound healing complications | Yes | 5406 | 3.9 |
| Incidence of any adverse events | Yes | 10,900 | 7.8 |
| BMI category | Underweight | 1543 | 1.1 |
| Normal weight | 41,288 | 29.6 | |
| Overweight | 44,723 | 32.1 | |
| Obese | 30,385 | 21.8 | |
| Severely obese | 13,666 | 9.8 | |
| Morbidly obese | 6661 | 4.8 | |
| Super obese | 1086 | 0.78 | |
| Patient gender | Female | 136,964 | 98.3 |
| Male | 2388 | 1.7 | |
| Patient race/ethnicity | Asian | 3260 | 2.3 |
| African American | 16,835 | 12.1 | |
| Hispanic | 7350 | 5.3 | |
| Caucasian | 81,057 | 58.2 | |
| Other | 729 | 0.5 | |
| Missing | 30,121 | 21.6 | |
| Smoking status | Yes | 12,619 | 9.1 |
| No | 126,733 | 90.9 | |
| Diabetes status | Yes | 8133 | 5.8 |
| No | 131,219 | 94.2 | |
| Hypertension | Yes | 30,373 | 21.8 |
| No | 108,979 | 78.2 | |
| Surgery class | Inpatient | 34,320 | 24.6 |
| Outpatient | 105,032 | 75.4 | |
Demographics and complications between metabolically unhealthy versus healthy patients
Demographic characteristics stratified by health status are shown in Table 2. Overall, 18,663 patients (14.9%) were deemed to have metabolically unhealthy obesity defined as having obesity concurrent with either HTN or diabetes, whereas 33,135 patients (26.5%) had metabolically healthy obesity without diabetes or HTN and 73,078 patients (58.5%) were healthy without obesity, hypertension, or diabetes as comorbidities. Compared to metabolically healthy obese patients, patients with metabolically unhealthy obesity were more likely to have ASA 3 (48.0% versus 20.8%) or ASA four status (1.3% versus 0.23%), had higher median BMI (34.8 versus 33.6), incidence of bleeding disorders (1.2% versus 0.5%), steroid use (2.5% versus 1.4%), and COPD (2.2% versus 0.6%) (all P < 0.001). Diabetes was present in 29.3% and HTN was present in 91.2% of the metabolically unhealthy cohort.
Table 2 –
Demographics stratified by health status (total n = 124,876).
| Variables | Healthy (n = 73,078) | Metabolically healthy obesity* (n = 33,135) | Metabolically unhealthy obesity* (n = 18,663) | P value† |
|---|---|---|---|---|
|
| ||||
| Age (median, IQR) | 46 (18) | 45 (18) | 56 (15) | <0.001 |
| ASA classification | ||||
| 1 (normal healthy patient) | 25.4% | 12.3% | 0.66% | <0.001 |
| 2 (patient with mild systemic disease) | 63.0% | 66.6% | 50.0% | <0.001 |
| 3 (patient with severe systemic disease) | 11.4% | 20.8% | 48.0% | <0.001 |
| 4 (patient with severe systemic disease) | 0.075% | 0.23% | 1.3% | <0.001 |
| Operative time (min) (median, IQR) | 132 (124) | 158 (128) | 156 (128) | <0.001 |
| Race | ||||
| Caucasian | 62.0% | 50.9% | 53.2% | <0.001 |
| African American | 6.3% | 17.9% | 24.1% | <0.001 |
| Asian | 3.2% | 0.78% | 0.89% | 0.200 |
| BMI (median, IQR) | 24.9 (5.0) | 33.6 (5.3) | 34.8 (6.5) | <0.001 |
| HTN | 0% | 0% | 91.2% | <0.001 |
| Diabetes | 0% | 0% | 29.3% | <0.001 |
| Tobacco use | 8.9% | 9.5% | 8.6% | <0.001 |
| CHF | 0.016% | 0.027% | 0.33% | <0.001 |
| Bleeding disorder | 0.44% | 0.49% | 1.2% | <0.001 |
| Steroid use | 1.3% | 1.4% | 2.5% | <0.001 |
| COPD | 0.39% | 0.59% | 2.2% | <0.001 |
Metabolically healthy defined to be a patient without obesity with concurrent diabetes or hypertension. Metabolically unhealthy obesity defined to be the presence of obesity with diabetes and/or hypertension. Other groups defined to have obesity alone, hypertension alone, and diabetes alone without other metabolic risk factors.
Metabolically unhealthy versus metabolically healthy obesity.
Incidence of postoperative complications between the patients stratified by health status is shown in Table 3. Data for 11,820 patients with hypertension alone and 1115 patients with diabetes alone without other metabolic risk factors are shown in Supplementary Table 1. Adverse events were more likely to occur in patients with metabolically unhealthy obesity (12.4%) compared to those with metabolically healthy obesity (9.6%) (P < 0.001) and healthy patients (5.8%). Incidence of wound healing complications was also significantly higher among patients with metabolically unhealthy obesity (6.9%) compared to those with metabolically healthy obesity (5.6%) (P < 0.001), in addition to superficial SSI (P = 0.017), deep SSI (P < 0.001), and wound disruption (P < 0.001). Furthermore, when comparing patients with metabolically unhealthy versus metabolically healthy obese patients, incidence of many postoperative complications was higher including superficial SSI (3.7% versus 3.3%), deep SSI (1.1% versus 0.8%), sepsis (0.59% versus 0.36%), and need for transfusions (2.1% versus 1.4%) (all P < 0.05). In addition, return to the OR (5.5% versus 3.9%), readmission (4.8% versus 3.1%), and length of stay (median one versus 0 d) was higher in those with metabolically unhealthy obesity compared to those in the metabolically healthy group (P < 0.001). Complications including DVT (0.32% versus 0.31%), PE (0.29% versus 0.25%), and 30-d mortality (0.03% versus 0.02%) were similar in both groups (P > 0.05) (Table 3).
Table 3 –
Adverse events among patients of different health statuses (total n = 124,876).
| Variables | Healthy (n = 73,078) | Metabolically healthy obesity* (n = 33,135) | Metabolically unhealthy obesity* (n = 18,663) | P value† |
|---|---|---|---|---|
|
| ||||
| Any adverse event (n%) | 5.8% | 9.6% | 12.4% | <0.001 |
| Complications | ||||
| Any wound healing complications | 2.4% | 5.6% | 6.9% | <0.001 |
| Superficial SSI | 1.3% | 3.3% | 3.7% | 0.017 |
| Deep SSI | 0.35% | 0.78% | 1.1% | <0.001 |
| Organ/Space SSI | 0.42% | 0.71% | 1.1% | <0.001 |
| Wound disruption | 0.44% | 1.1% | 1.5% | <0.001 |
| Pneumonia | 0.052% | 0.13% | 0.25% | 0.001 |
| Unplanned intubation | 0.016% | 0.033% | 0.12% | <0.001 |
| DVT | 0.11% | 0.31% | 0.32% | 0.983 |
| Pulmonary embolism | 0.10% | 0.25% | 0.29% | 0.435 |
| Acute renal failure | 0.0014% | 0.0060% | 0.070% | <0.001 |
| Urinary tract infection | 0.22% | 0.31% | 0.44% | 0.018 |
| Sepsis | 0.13% | 0.36% | 0.59% | <0.001 |
| Septic shock | 0.011% | 0.012% | 0.11% | <0.001 |
| Myocardial infarction | 0.0068% | 0.015% | 0.086% | <0.001 |
| Need for transfusions | 1.0% | 1.4% | 2.1% | <0.001 |
| Return to the OR | 3.2% | 3.9% | 5.4% | <0.001 |
| Readmission | 2.0% | 3.1% | 4.8% | <0.001 |
| Mortality within 30 d after operation | 0.0096% | 0.021% | 0.027% | 0.916 |
| Length of stay (d) (median, IQR) | 0 (1) | 0 (1) | 1 (1) | <0.001 |
Metabolically healthy defined to be a patient without obesity with concurrent diabetes or hypertension. Metabolically unhealthy obesity defined to be the presence of obesity with diabetes and/or hypertension. Other groups defined to have obesity alone, hypertension alone, and diabetes alone without other metabolic risk factors.
Metabolically unhealthy versus metabolically healthy obesity.
Postoperative complications by obesity class
Demographics and complications were then stratified by obesity class (Table 4), including underweight patients (median BMI 17.8), normal weight (median BMI 22.7), overweight (median BMI 27.4), obese (median BMI 32.1), severely obese (median BMI 37.0), morbidly obese (median BMI 42.7), and super obese patients (median BMI 54.7). As BMI class increased, incidence of wound healing complications increased across obesity classes (Normal Weight: 1.1% versus Obese: 3.6% versus Super Obese: 7.8%) and incidence of adverse effects similarly increased across obesity classes (Normal Weight: 5.3% versus Obese: 9.4% versus Super Obese: 19.1%). Across obesity classes, more obese patients tended to more frequently undergo inpatient surgery and have comorbid diabetes and HTN (Table 4).
Table 4 –
Demographics, comorbidities, and wound healing incidence between classes of obesity (total n = 139,352).
| Variables | Underweight (n = 1543) | Normal weight (n = 39,546) | Overweight (n = 42,354) | Obese (n = 28,547) | Severely obese (n = 12,761) | Morbidly obese (n = 6159) | Super obese (n = 954) |
|---|---|---|---|---|---|---|---|
|
| |||||||
| BMI, median (IQR) kg/m2 | 17.8 (1.0) | 22.7 (2.7) | 27.4 (2.5) | 32.1 (2.5) | 37.0 (2.4) | 42.7 (3.8) | 54.7 (8.2) |
| Wound complication (n %) | 28 (1.8%) | 426 (1.1%) | 948 (2.2%) | 1023 (3.6%) | 593 (4.6%) | 402 (6.5%) | 74 (7.8%) |
| Adverse events (n %) | 68 (4.4%) | 2194 (5.3%) | 3156 (7.1%) | 2870 (9.4%) | 1499 (11.0%) | 906 (13.6%) | 207 (19.1%) |
| Age, median (IQR) y | 44 (20.5) | 47 (18) | 13.4 (19) | 49 (19) | 49 (18) | 49 (18) | 49 (19) |
| Operative time, median (IQR) min | 95 (94.5) | 122 (119) | 144 (127) | 155 (131) | 160 (127) | 162 (117) | 165 (110) |
| Male gender (n %) | 15 (1.0%) | 359 (0.9%) | 688 (1.6%) | 548 (1.9%) | 288 (2.3%) | 188 (3.1%) | 101 (10.6%) |
| Race (n %) | |||||||
| African American | 62 (4.0%) | 1705 (4.3%) | 4348 (10.2%) | 4809 (16.8%) | 2975 (23.3%) | 1714 (27.8%) | 252 (26.4%) |
| Caucasian | 1064 (69.0%) | 26,322 (66.6%) | 24,355 (57.3%) | 14,722 (51.7%) | 6400 (50.2%) | 3098 (50.3%) | 540 (56.6%) |
| Tobacco use (n %) | 200 (13.0%) | 3549 (9.0%) | 3681 (8.7%) | 2487 (8.7%) | 1238 (9.7%) | 588 (9.5%) | 93 (9.7%) |
| Inpatient class (n %) | 269 (17.4%) | 7805 (19.7%) | 10,010 (23.5%) | 7034 (24.6%) | 3051 (23.9%) | 1460 (23.7%) | 318 (33.3%) |
| Diabetes (n %) | 20 (1.3%) | 672 (1.6%) | 1964 (4.4%) | 2575 (8.5%) | 1617 (11.8%) | 1029 (15.4%) | 256 (23.6%) |
| Hypertension (n %) | 125 (8.1%) | 4182 (10.6%) | 8221 (19.3%) | 8054 (28.2%) | 4579 (35.9%) | 2549 (41.4%) | 572 (49.5%) |
| Metabolically unhealthy obesity (n %) | 8851 (31.0%) | 4998 (39.2%) | 2807 (45.6%) | 514 (53.9%) | |||
Independent predictors of wound healing complications
Logistic regression was then used to model the risk of wound healing complications and adverse effects across the cohort adjusted by individual CPT code (Table 5). Across characteristics, log of BMI was most correlated with incidence of wound healing complications, with higher BMI increasing the wound complication risk (Odds Ratio [OR] 7.86; P < 0.001). Hypertension (OR 1.15; P < 0.001) and diabetes (OR 1.25; P < 0.001) were also independent risk factors for the occurrence of wound healing complications. The odds ratios of the log of BMI, hypertension, and diabetes are all greater than one indicating a cumulative risk, meaning that patients with metabolically unhealthy obesity have a higher cumulative risk of developing wound healing complications compared to other patients with single metabolic risk factors alone. The risk of wound healing complications increases by 25.4% for diabetic patients (OR 1.254), the presence of hypertension increases the risk of wound complications by 14.6% (OR 1.146), and if log of BMI increases by 1 unit, the wound complication risk increases by 686% (OR 7.86). Other independent risk factors for wound healing complications included log of operative time (OR 1.21; P < 0.001), tobacco use (OR 1.69; P < 0.001), and inpatient (versus outpatient) surgery (OR 1.40; P < 0.001).
Table 5 –
Generalized logistic regression model predicting the occurrence of wound healing complications and any adverse event across the cohort.
| Variables | Wound healing complication |
Any adverse event |
||||
|---|---|---|---|---|---|---|
| Odds ratio | Coefficient | P value | Odds ratio | Coefficient | P value | |
|
| ||||||
| (Intercept) | 0.000 | −11.541 | <0.001 | 0.000 | −9.053 | <0.001 |
| Log of BMI | 7.862 | 2.062 | <0.001 | 3.312 | 1.198 | <0.001 |
| Hypertension | 1.146 | 0.136 | <0.001 | 1.205 | 0.186 | <0.001 |
| Diabetes | 1.254 | 0.227 | <0.001 | 1.236 | 0.212 | <0.001 |
| Log of operation time | 1.206 | 0.187 | <0.001 | 1.438 | 0.363 | <0.001 |
| Tobacco use | 1.686 | 0.522 | <0.001 | 1.452 | 0.373 | <0.001 |
| Surgery class | ||||||
| Outpatient | REF | REF | ||||
| Inpatient | 1.400 | 0.336 | <0.001 | 1.909 | 0.647 | <0.001 |
| Age | 1.002 | 0.002 | 0.057 | 1.004 | 0.004 | <0.001 |
| Gender | ||||||
| Female | REF | REF | ||||
| Male | 0.978 | −0.022 | 0.813 | 1.295 | 0.258 | <0.001 |
| Race/Ethnicity | ||||||
| Caucasian | REF | REF | ||||
| Asian | 0.615 | −0.486 | <0.001 | 0.838 | −0.177 | 0.019 |
| Black/African American | 0.707 | −0.347 | <0.001 | 0.824 | −0.193 | <0.001 |
| Hispanic | 0.798 | −0.226 | 0.002 | 0.804 | −0.218 | <0.001 |
| Other | 0.645 | −0.438 | 0.057 | 0.921 | −0.082 | 0.570 |
Each model also controlled for individual CPT codes and missing race.
Independent predictors of adverse complications
A logistic regression model was then used to model the occurrence of adverse events, again adjusted by individual CPT codes. Similar to wound healing complications, log of BMI (OR 3.31; P < 0.001), HTN (OR 1.21; P < 0.001), and diabetes (OR 1.24; P < 0.001) were all independent risk factors for the incidence of any adverse event, with odds ratios all greater than one indicating that patients with multiple metabolic comorbidities (i.e., metabolically unhealthy obesity) have a higher cumulative risk of adverse events compared to those with obesity, diabetes, or hypertension alone. Other risk factors included log of operative time (OR 1.44; P < 0.001), tobacco use (OR 1.45; P < 0.001), inpatient surgery (OR 1.91; P < 0.001), age (OR 1.004; P < 0.001), and male gender (OR 1.30; P < 0.001).
Interaction between metabolic status, operative time, and wound complication risk
We then modeled adjusted probability of wound healing complications against operative time for patients with metabolically unhealthy obesity versus healthy patients adjusted by CPT code (Fig. 1), with higher incidence of wound healing complications for metabolically unhealthy patients across studied operative times. For patients with metabolically unhealthy obesity, probability of wound healing complications increased rapidly from 4.2% to 6.2% when the operation time increases from 30 to 240 min. An inflection point occurred around 240 min after which probability of wound healing complications still increased, but at a lower speed. Finally, we plotted probability of wound healing complications against the log of operative time for metabolically unhealthy patients (Fig. 2), finding that probability of wound healing complication and operation time is log-linear, which means that the risk of wound healing complication increases by the same amount each time when operation time doubles. The odds ratio of log of operation time is 1.206 (P < 0.001), meaning that if the log of operation time increases by one unit (such as operation time increases from 100 to 272 min), the probability of having wound healing complications increased by 20.6%.
Fig. 1 –
Adjusted probability of wound healing complications by operative time between patients with and without metabolically unhealthy obesity. Inflection points where a risk of increased occurrence of wound healing complications levels off are around 240 min for both cohorts.
Fig. 2 –
Adjusted probability of wound healing complications by log of operative time between patients with and without metabolically unhealthy obesity.
Discussion
In this analysis of 139,352 plastic surgery patients undergoing elective breast and body procedures, we compare wound healing complications and 30-d adverse events between patients with metabolically unhealthy versus healthy obesity. We find that obese patients with metabolic comorbidities have significantly higher incidence of 30-d adverse events and wound healing complications and that obesity, diabetes, and hypertension are additive risk factors for the occurrence of both wound healing complications and adverse events. By modeling the probability of wound healing complications by the operative time in the metabolically unhealthy obese population, we find that an accrued risk of wound healing complications increases logarithmically with operative time, with most risk incurred occurring within the first 4 h of surgery. Ultimately, as the population of patients with metabolic syndrome continues to grow nationally, we aim for these data to guide preoperative decision making regarding patient selection and staging of elective plastic surgery procedures within this population.
Metabolic syndrome has become a rapidly growing disease in the United States, now affecting more than one-third of adults nationally.26 Characterized by a cluster of comorbidities including visceral obesity, hypertension, dyslipidemia, and insulin resistance, patients with metabolic syndrome have been shown to have a higher risk of cardiovascular disease and earlier all-cause mortality.4–6 In turn, metabolic syndrome has been associated with worse surgical outcomes, including a higher risk of wound infections, all-cause mortality, and readmission in patients undergoing general surgery9,10,12,14,25,27 and orthopedic surgery.8,13
The association between obesity and wound healing problems has been well established in the plastic surgery literature, particularly in breast and body procedures. An increasing obesity class has been associated with a higher complication risk after reduction mammaplasty,17,28 breast reconstruction,16,18,29–32 abdominoplasty,33–35 brachioplasty,36,37 lower body lifts,38 and aesthetic surgery,21 with wound healing complications as the most common obesity-related complication reported. This literature has clinical implications for preoperative patient selection and counseling, with many plastic surgeons recommending BMI cutoffs of 30 to 35 kg/m2 prior to proceeding with elective breast and body procedures.22–24 Moreover, obesity has been found to have a synergistic effect with other comorbidities and treatment variables including tobacco use and radiation to further increase the complication risk among obese patients.39 However, despite these data and the growing incidence of metabolic syndrome nationally, whether a synergistic effect also exists between obesity and metabolic risk factors on a complication risk after plastic surgery procedures has not been studied.
In this study, we find that metabolically unhealthy obese patients have higher incidence of adverse events, wound healing complications, readmission, and longer overall length of stay after elective plastic surgery breast and body procedures than metabolically healthy obese patients. Moreover, obesity, diabetes, and hypertension were independent and cumulative risk factors for wound healing complications and adverse events, with obesity being the largest risk factor for wound healing complications across studied variables. Putting in the context of prior studies demonstrating similar trends of higher complications and healthcare utilization among metabolically unhealthy obese surgical patients,8–14,25,27 these data underscore the necessity of careful preoperative planning regarding patient selection in this population. Although preoperative optimization targeting certain BMI cutoffs has become the commonplace in elective plastic surgery, these data suggest that preoperative optimization strategies should perhaps extend efforts to improve glycemic and blood pressure control. In fact, prior studies in general surgery have developed quality improvement programs targeting preoperative glycemic control prior to elective surgery, finding that targeted glycemic control may improve postoperative outcomes including length of stay.40
In addition to preoperative optimization, our data emphasize the importance of reducing operative time by staging procedures or adopting time-saving measures in the metabolically unhealthy obese patient population. In our study, probability of wound healing complications increased logarithmically with increasing operative time among metabolically unhealthy obese patients. In this model, a risk of wound healing complication increased the most within the first 4 h of surgery, with an inflection point occurring around 240 min where a risk of additional wound healing risk incurred leveled out. In a study of 1753 plastic surgery cases, Hardy et al similarly demonstrated increasing morbidity with prolonged operative time, with a proposed cutoff of 3 h to reduce the risk of overall wound healing complications.41 Combined plastic surgery procedures, although safe in the appropriately selected candidate, have been shown to increase complication rates among high-risk patients with preexisting comorbidities including elevated BMI.15,36,42,43 Thus, in the context of these data, our study underscores the importance of staging procedures and adopting time-saving strategies to reduce the operative time to less than 4 h in metabolically unhealthy obese patients, to mitigate the sequelae of wound healing complications within this population.
Underlying the association between metabolic syndrome and worsened medical and surgical outcomes, especially wound healing complications, is abdominal obesity.3 An elevated waist circumference is an integral component of the definition of metabolic syndrome, with proinflammatory hypertrophied abdominal adipocytes promoting both insulin resistance and local inflammation.3 On a molecular level, obesity has been shown to decrease local vasculogenic progenitor cells, leading to decreased overall neovascularization and impaired wound healing.44 In plastic surgery, abdominal cross-sectional area, and particularly subcutaneous fat thickness, have been shown to be significant predictors of complications after sternal and abdominal wall reconstruction.45,46 Other studies have found that abdominal wall thickness predicts a risk of wound infection and dehiscence after general surgery procedures.47 This association may underlie the findings of this study, with metabolically unhealthy obese patients more likely to have an elevated abdominal circumference, with resulting impaired local vasculogenesis and reduced wound healing potential after surgery. Although the abdominal circumference is not available within the NSQIP dataset and BMI was used as a surrogate for this variable in this study, future directions include more granular studies on how metabolic syndrome and measurements of abdominal obesity interact to affect incidence of wound healing complications after plastic surgery.
This study has limitations with implications for its interpretation. First, we were unable to define true metabolic syndrome based on established criteria3 given the confines of the NSQIP dataset, which does not contain data on dyslipidemia or abdominal circumference. We used BMI as a surrogate for elevated abdominal circumference for the purpose of this study but recognized this as a limitation of our study design. In addition, we were unable to account for how different medications taken by certain metabolic groups may influence wound healing and complications. Our patient population is likely representative of selection bias because many patients with BMI extremes or with uncontrolled metabolic syndrome may have already been selected against, and the population of patients seeking elective plastic surgery is generally younger and healthier compared to other surgical patient populations. As with all NSQIP and large national database studies, our data are subject to the limitations inherent to a retrospective entry and the possibility of coding errors. Despite these limitations, our study is one of the first to report the implications of metabolically unhealthy obesity on outcomes after elective plastic surgery procedures and to model the interaction between the operative time and wound complication risk within this population. We aim for this study to serve as a foundation for future studies on the intersection between metabolism, abdominal circumference, and obesity and resulting implications on wound healing complications in plastic surgery.
Conclusion
Obese patients with metabolic comorbidities have significantly higher incidence of 30-d adverse events and wound healing complications after elective plastic surgery breast and body procedures compared to obese patients without metabolic comorbidities. Obesity, diabetes, and hypertension are independent and additive risk factors for the occurrence of both wound healing complications and adverse events. Among metabolically unhealthy obese patients, a risk of wound healing complications increases logarithmically with operative time, with most risk incurred within 4 h of surgery. Ultimately, as the population of patients with metabolic syndrome continues to grow nationally, we aim for these data to guide preoperative decision making regarding patient selection, preoperative optimization, and staging of elective plastic surgery procedures within this population.
Supplementary Material
Footnotes
Supplementary Material
Supplementary data related to this article can be found at https://doi.org/10.1016/j.jss.2022.03.017.
Disclosure
None of the authors have a relevant financial disclosure.
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