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Address for reprints: Brendon M. Stiles, MD, Department of Cardiothoracic Surgery, Division of Thoracic Surgery, Weill Cornell Medicine, New York-Presbyterian Hospital, Ste M404, 525 East 68th St, New York, NY 10021.
We sought to determine the rate of postoperative supraventricular tachycardia (POSVT) in patients undergoing pulmonary lobectomy, and its association with adverse outcomes.
Methods
Using the State Inpatient Database, from the Healthcare Cost and Utilization Project, we reviewed lobectomies performed (2009-2011) in California, Florida, and New York, to determine POSVT incidence. Patients were grouped by presence or absence of POSVT, with or without other complications. Stroke rates were analyzed independently from other complications. Multivariable regression analysis was used to determine factors associated with POSVT.
Results
Among 20,695 lobectomies performed, 2449 (11.8%) patients had POSVT, including 1116 (5.4%) with isolated POSVT and 1333 (6.4%) with POSVT with other complications. Clinical predictors of POSVT included age ≥75 years, male gender, white race, chronic obstructive pulmonary disease, congestive heart failure, thoracotomy surgical approach, and pulmonary complications. POSVT was associated with an increase of: stroke (odds ratio [OR] 1.74; 95% confidence interval [CI] 1.03-2.94); in-hospital death (OR 1.85; 95% CI 1.45-2.35); LOS (OR 1.33; 95% CI 1.29-1.37); and readmission (OR 1.29; 95% CI 1.04-1.60). The stroke rate was <1% in patients who had isolated POSVT, and 1.5% in patients with POSVT with other complications. Patients with isolated POSVT had increased readmission and LOS, and a marginal increase in stroke rate, compared with patients with an uncomplicated course.
Conclusions
POSVT is common in patients undergoing pulmonary lobectomy and is associated with adverse outcomes. Comparative studies are needed to determine whether strict adherence to recently published guidelines will decrease the rate of stroke, readmission, and death after POSVT in thoracic surgical patients.
Postoperative atrial arrhythmias are common after pulmonary lobectomy, and they are associated with stroke, death, increased length of stay, and readmission. Identifying at-risk patients will allow for tailored prophylaxis strategies.
Lower preoperative fluctuation of heart rate variability is an independent risk factor for postoperative atrial fibrillation in patients undergoing major pulmonary resection.
Modifiable preoperative risk factors include medical control of hypertension and congestive heart failure, tobacco and alcohol use, and the surgical approach used. Modifiable postoperative risk factors include fluid overload, hypoxia, and heart rate control.
Postoperative SVT is associated with increased morbidity, length of stay (LOS), and cost, in patients undergoing thoracic surgery.
The Society of Thoracic Surgeons practice guideline on the prophylaxis and management of atrial fibrillation associated with general thoracic surgery: executive summary.
recently published evidence-based guidelines for the prophylaxis and treatment of POSVT in patients undergoing general thoracic surgical procedures. In the AATS guidelines,
both open and thoracoscopic lobectomy were classified as high-risk procedures for POSVT, with an estimated incidence >15%. Thus, the guidelines recommended that these patients be monitored continuously for ≥48 to 72 hours, and that pharmacologic prophylaxis be considered. However, individual risk likely spans a spectrum from low to high risk.
To perform a broad investigation of POSVT after pulmonary lobectomy, we utilized the State Inpatient Databases from the Healthcare Cost and Utilization Project (SID-HCUP).
Agency for Healthcare Research and Quality. Healthcare Cost and Utilization Project. Available at: http://www.hcup-us.ahrq.gov/sidoverview.jsp. Accessed date January 5, 2016.
We anticipate that a better understanding of factors associated with POSVT in this large patient population will allow for better risk stratification of patients, for both POSVT and stroke after POSVT. For example, the influence of patient-based, versus perioperative, factors on the risk of POSVT is unknown. Additionally, the risk of isolated POSVT is largely unknown.
We therefore sought to compare the clinical outcomes of isolated POSVT with those of POSVT that is associated with other postoperative complications. Isolated POSVT has been suggested to have little independent association with adverse postoperative outcomes.
The objective of the current study is to generate hypotheses for clinical comparative studies, to evaluate whether adherence to AATS guidelines influences the rate of POSVT and associated complications.
Methods
Database and Study Population
We examined hospitalizations for adults (aged ≥18 years), using SID-HCUP discharge data from the period 2009 to 2011, from California, Florida, and New York. All study activities were approved by the Weill Cornell Medicine Institutional Review Board. The SID-HCUP is an all-payer inpatient database, containing discharges from nonfederal, nonpsychiatric community hospitals. This database has been described previously, but briefly the SID contains >100 clinical and nonclinical variables, such as principal and secondary diagnoses and procedures, admission and discharge status, patient demographics, LOS, and total charges.
Agency for Healthcare Research and Quality. Healthcare Cost and Utilization Project. Available at: http://www.hcup-us.ahrq.gov/sidoverview.jsp. Accessed date January 5, 2016.
To identify the difference between pre-existing diagnoses and complications occurring after hospital admission, a unique identifier corresponding to each diagnosis code was used. For analysis of uncomplicated versus complicated POSVT, the patient cohort was divided into 4 groups: (1) no POSVT or other complications; (2) only POSVT as a complication; (3) other complications but no POSVT; and (4) other complications and POSVT. For the purposes of segregating patients into the 4 groups, we excluded stroke as a complication, to determine any association of isolated POSVT with stroke. To determine variability in rates of POSVT in the patient cohort, based on surgical volume of the hospitals at which the lobectomy was performed, hospitals were divided into quartiles and analyzed. The quartiles were based on number of cumulative cases performed during the 3-year period.
Clinical Modification Codes
Codes from the International Classification of Diseases, ninth edition (ICD-9), were used to identify patients undergoing pulmonary lobectomy: open lobectomy (or other lobectomy of lung [32.49]; lobectomy of lung [32.4] while excluding reopening of thoracotomy [34.03]; thoracoscopic lobectomy [32.41]; transpleural thoracoscopy [34.21]; and robot-assisted procedure [17.4x]) or minimally invasive lobectomy (MIL) (thoracoscopic lobectomy [32.41 while excluding 32.4, 32.49, 34.03, and 17.4x] and robotic lobectomy [17.4x and 32.4, 32.41, or 32.49 while excluding 34.03 and 34.21]). Similarly, ICD-9M codes were used to identify patients with POSVT not present on admission: atrial fibrillation and flutter (427.3); atrial fibrillation (427.31); atrial flutter (427.32); and paroxysmal SVT (427.0). Each diagnosis was coded with a separate identifier denoting whether it was present on admission, allowing for discrimination between pre-existing diagnoses and those occurring after admission. Records indicating SVT upon admission were excluded from further analyses. Additionally, patients aged ≤17 years, and those with missing age or gender data, were excluded.
Covariates
Data were obtained for patient demographics (age, gender, race, state, and insurance status), LOS, comorbidities (with the indication of being present on admission), and in-hospital events that were not present on admission. The latter category includes supraventricular arrhythmia, myocardial infarction, deep venous thrombosis, pulmonary embolism, pneumonia, pulmonary collapse, empyema with or without fistula, mechanical ventilation, noninvasive ventilation, tracheostomy, sepsis/shock, urinary tract infection, accidental puncture or laceration complicating surgery, and bleeding complicating surgery. Postoperative in-hospital events included: stroke, acute respiratory insufficiency, acute pneumothorax, pulmonary edema, and wound infection. Baseline comorbidities were compared, using the modified Deyo index, which adapts, for administrative data, the Elixhauser Comorbidity Index, the commonly used Charlson Comorbidity Index for predicting the adjusted relative risk of 1-year mortality.
We analyzed patient baseline, demographic, clinical, and postoperative characteristics, using frequencies and proportions for categoric variables, and means, medians, and interquartile ranges for continuous variables. The differences in preoperative and postoperative characteristics between patients with versus without POSVT were evaluated using a 2-sample t test, the Pearson χ2 statistic, and Kruskal-Wallis analysis of variance, as appropriate.
Logistic regression was used to identify factors associated with new-onset POSVT. Factors of interest were identified a priori; these included baseline patient demographics, state, comorbidities from the Elixhauser Comorbidity Index, and postoperative pulmonary complications. Variables with P ≤ .05 in bivariate analyses were kept in the multivariable logistic regression model. To analyze the association of POSVT with outcomes, we constructed multivariable logistic regression models for postoperative stroke, in-hospital mortality, and 30-day readmission, and a multivariable linear regression model for log-transformed LOS.
Models were adjusted for statistically significant variables that had a bivariate association with each outcome (P < .05), from among patient demographics, chronic comorbidities, procedure type (open lobotomy and minimally invasive lobectomy), and postoperative pulmonary complications. Generalized estimating equations with exchangeable variance estimation were used to account for the clustering of outcome measures at the hospital level. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) of POSVT were calculated. SAS version 9.3 (SAS Institute Inc, Cary, NC) was used to perform all statistical analyses. All P values are 2-sided.
Results
From the time period studied (2009-2011), we identified a total of 23,043 pulmonary lobectomies, of which 20,695 records met the study criteria (SVT not present on admission, nonmissing age and gender, and age ≥18 years). A relatively equal distribution was found among California (n = 7226 [34.9%]); Florida (n = 7019 [33.9%]); and New York (n = 6450 [31.2%]). Most were performed as open lobectomies (n = 12,154 [58.7%]); (n = 8541 [41.3%]) were minimally invasive lobectomies, including 7611 (36.8%) performed using video-assisted thoracoscopic surgery, and 930 (4.5%) using robot-assisted thoracoscopic surgery.
Most patients (n = 11,335 [54.8%]) were women; and white (n = 15,921 [76.9%]). The median age for the cohort was 67 (interquartile range: 59-74) years. The median modified Charlson/Deyo index of this cohort was 3 (interquartile range: 2-4) years. Among comorbidities, 17,617 patients (85.1%) had a diagnosis of cancer, 8965 patients (43.3%) were noted to have chronic obstructive pulmonary disease, and 479 patients (2.3%) had congestive heart failure.
The overall complications rate was 39.7% in the open lobectomy group, and 31.5% in the minimally invasive lobectomy group; these were pulmonary complications in 36.5% and 29.3% of patients in these groups, respectively. Among these 20,695 patients undergoing pulmonary lobectomy, 2449 patients (11.8%) were documented as having new-onset POSVT. This total included 1116 (5.4%) patients who had POSVT as an isolated complication (excluding stroke), and 1333 (6.4%) patients who had POSVT with other complications. We compared patients with (n = 2449) versus without (n = 18,246) POSVT, to determine differences in baseline characteristics between the 2 cohorts. Table 1 displays the characteristics of patients undergoing pulmonary lobectomy, stratified by POSVT status.
Table 1Characteristics of patients undergoing pulmonary lobectomy with or without postoperative supraventricular tachycardia
Variable
No POSVT (n = 18,246)
POSVT (n = 2449)
P value
Age, median (Q1; Q3)
67 (59; 74)
72 (66; 78)
<.001
Male gender
8027 (44.0)
1333 (54.4)
<.001
White race
13,850 (75.9)
2071 (84.6)
<.001
Mean Charlson/Deyo index (95% CI)
3.43 (3.40; 3.47)
3.72 (3.62; 3.83)
<.001
Median Charlson/Deyo index (Q1; Q3)
3 (2; 3)
3 (2; 4)
<.001
Chronic obstructive pulmonary disease
7712 (42.3)
1253 (51.2)
<.001
Renal failure
863 (4.7)
184 (7.5)
<.001
Congestive heart failure
381 (2.1)
98 (4.0)
<.001
Valvular heart disease
532 (2.9)
167 (6.8)
<.001
Pulmonary circulation disorders
139 (0.8)
65 (2.7)
<.001
Peripheral vascular disorders
1161 (6.4)
223 (9.1)
<.001
Hypertension, uncomplicated
9226 (50.6)
1321 (53.9)
.002
Hypertension, complicated
900 (4.9)
198 (8.1)
<.001
Solid tumor without metastasis
15,343 (84.1)
2189 (89.4)
<.001
POSVT, Postoperative supraventricular tachycardia; Q, quartile; CI, confidence interval.
We next performed multivariable analysis to determine independent factors associated with new-onset POSVT after pulmonary lobectomy (Table 2). These included: demographic distinctions (increasing age, male gender, white race); comorbidities (higher Deyo index, hypertension, chronic obstructive pulmonary disease, congestive heart failure, valvular heart disease); and perioperative factors (open vs minimally invasive lobectomy, pulmonary complications).
Table 2Factors associated with postoperative supraventricular tachycardia among pulmonary lobectomy patients
Variable
OR (95% CI)
P value
Patient demographics
Male gender
1.44 (1.31, 1.59)
<.001
Age (y)
18-54
Referent
<.001
55-64
2.34 (1.84, 2.99)
<.001
65-74
4.18 (3.11, 5.62)
<.001
≥75
6.21 (4.56, 8.46)
<.001
Race
White
Referent
<.001
Black
0.61 (0.50, 0.74)
<.001
Hispanic
0.59 (0.49, 0.71)
<.001
Other
0.80 (0.66, 0.96)
.020
Comorbidities
Congestive heart failure
1.31 (1.04, 1.64)
.020
Valvular disease
1.79 (1.43, 2.24)
<.001
Pulmonary circulation disorders
2.58 (1.77, 3.78)
<.001
Chronic obstructive pulmonary disease
1.17 (1.07, 1.26)
<.001
Perioperative
Surgical approach: thoracotomy vs minimally invasive
1.21 (1.09, 1.34)
<.001
Pulmonary complications
1.95 (1.75, 2.18)
<.001
Data are from multivariable logistic regression analysis, excluding 274 patients (1.32%) with missing race variable. OR, Odds ratio; CI, confidence interval.
We further sought to examine whether POSVT was associated with outcome variables, in particular, in-hospital stroke, in-hospital mortality, LOS, and readmission. We performed a multivariable analysis for each outcome, adjusting for age, gender, race, comorbidities, and acute perioperative factors (Figure 1). An independent association was found of POSVT with increased risk for stroke (OR 1.74; 95% CI: 1.03-2.94); in-hospital mortality (OR 1.85; 95% CI: 1.45-2.35); LOS (OR 1.33; 95% CI: 1.29-1.37); and 30-day readmission (OR 1.29; 95% CI: 1.04-1.60).
Figure 1Association between postoperative supraventricular tachycardia and adverse outcomes after pulmonary lobectomy. Odds ratios (circles) and confidence intervals (bars) are presented for postoperative stroke (P = .04), in-hospital death (P < .001), length of stay (P < .001), and 30-day readmission (P = .02). Post-op, Postoperative.
We sought to further examine whether the context of POSVT in regard to other complications was important, particularly whether isolated POSVT is associated with adverse outcomes. The patient cohort was divided into 4 groups: (1) no POSVT or other complications; (2) only POSVT as a complication; (3) those with other complications but no POSVT; and (4) other complications in addition to POSVT (Table 3).
Table 3Clinical impact of isolated versus complicated postoperative supraventricular tachycardia
The Healthcare Cost and Utilization Project Data Use Agreement prohibits the reporting of fewer than 11 observations. Sample size and P values are masked to prevent identification.
The Healthcare Cost and Utilization Project Data Use Agreement prohibits the reporting of fewer than 11 observations. Sample size and P values are masked to prevent identification.
The Healthcare Cost and Utilization Project Data Use Agreement prohibits the reporting of fewer than 11 observations. Sample size and P values are masked to prevent identification.
The Healthcare Cost and Utilization Project Data Use Agreement prohibits the reporting of fewer than 11 observations. Sample size and P values are masked to prevent identification.
229 (3.7)
103 (7.7)
<.001
Median length of stay (Q1; Q3)
5 (4; 6)
6 (5; 8)
<.001
7 (5; 12)
10 (7; 16)
<.001
90-d readmission
1807 (16.6)
205 (20.3)
.003
1207 (22.2)
309 (27.2)
<.001
90-d readmission with stroke
69 (0.6)
14 (1.4)
.006
41 (0.8)
20 (1.8)
.001
Values are n (%), unless otherwise indicated. “Other” indicates other complications. SVT, Supraventricular tachycardia; Q, quartile.
∗ The Healthcare Cost and Utilization Project Data Use Agreement prohibits the reporting of fewer than 11 observations. Sample size and P values are masked to prevent identification.
For the purpose of the study, any complication, as determined from ICD-9 codes, was included. From the SID-HCUP database, the temporal sequence of complications cannot be identified. Patients without any other complications, except for stroke, had a lower overall rate of POSVT (n = 13,180 [8.5%]) than did patients with other complications (n = 7515 [17.7%]; P < .0001). A comparison of patients who had no complications, with those who did have isolated POSVT but no other complications, showed no difference for in-hospital mortality. Patients with isolated POSVT had significantly higher rates of postoperative stroke, longer LOS (6 vs 5 days), and higher rates of 90-day readmission (20.3% vs 16.6%).
However, isolated POSVT patients were older (median age: 72 vs 67 years; P < .001) and had more cumulative comorbidities (mean Charlson/Deyo index: 3.69 vs 3.42; P = .001). We therefore performed distinct multivariable analyses in this cohort, to determine whether POSVT had independent associations with stroke, mortality, or LOS. However, the number of events (n = 28) was not sufficient to determine an association with stroke. An independent association was found, of POSVT with prolonged LOS (OR 1.33; 95% CI: 1.29-1.37) and with 30-day readmission (OR 1.29; 95% CI: 1.04-1.60).
Patients with POSVT who had other complications did quite poorly, even compared with other patients who had complications but did not have POSVT. The POSVT patients had: higher rates of stroke (1.5% vs 0.8%, P = .009); higher in-hospital mortality (7.7% vs 3.7%, P < .001); longer median LOS (10 vs 7 days, P < .001); higher rates of 90-day readmission (27.2% vs 22.2%, P < .001); and higher rates of readmission with stroke (1.8% vs 0.8%, P = .001).
Discussion
Postoperative SVT has long been recognized as a common complication after thoracic surgical procedures and has been found to be associated with increased morbidity, mortality, LOS, and cost, in single-institutional studies
using the STS General Thoracic Surgery Database. We are not aware of previous studies using insurance databases to validate prospectively reported rates of POSVT and associated complications after noncardiac thoracic surgery. However, the SID-HCUP database has been used to determine rates of new-onset atrial fibrillation in patients hospitalized for severe sepsis, and to determine associated morbidity and mortality.
define demographic characteristics that are associated with higher rates of POSVT, and determine the association of POSVT with adverse outcomes, including stroke, in-hospital mortality, LOS, and readmission. We acknowledge that limitations of the data include lack of temporal descriptors, and absence of oncologic details and clinical details, such as pulmonary function, performance status, and medication use.
Although such limitations are inherent in using administrative databases, previous studies have demonstrated that reported rates of complications using claims data can approximate those reported in prospective databases.
suggested that clinical and administrative databases may be discordant; however, their rates of reported cardiovascular complications were within 2% of each other. Campbell and colleagues
reported that ICD-9–based reporting was actually more accurate than prospective data accrual for capturing new cardiac events. Further, although claims data may be less sensitive than prospective thoracic surgical databases for capturing episodes of new-onset POSVT, this decreased sensitivity may be an advantage if only medically significant episodes of POSVT are recorded by billing specialists.
Patients with clinically insignificant, untreated, short runs of atrial tachycardia, and those not captured by telemetry, would likely not have been coded as having POSVT. The rate at which such prospective, self-reported, surgical databases include these patients is unclear. In our study, the reported overall rate of complications was slightly higher than that reported from the STS database,
To attempt to homogenize our patient cohort from the SID-HCUP dataset in which cancer staging details are not available, we elected to focus only on patients undergoing pulmonary lobectomy, rather than including other lung resections, such as wedge resection, segmentectomy, or pneumonectomy. A well established finding is that the more extensive the lung resection, the higher the risk of POSVT.
The current study's focus on lobectomy alone should allow patient characteristics, rather than operation performed, to dominate association models. We found that patient characteristics associated with POSVT include age, male gender, white race, and history of valvular heart disease, congestive heart disease, pulmonary circulation disorders, and chronic obstructive pulmonary disease. The demographic associations with POSVT were all noted in the STS study, and in previous single-institution studies.
The effect of congestive heart failure and of chronic obstructive pulmonary disease were not apparent in the STS study, although evaluation of both of these variables suffered from the absence of certain data points in the STS database.
We believe that these 2 comorbidities are likely to increase the risk of POSVT.
The surgical approach chosen, open lobectomy versus minimally invasive lobectomy (either video- or robotic-assisted thoracoscopic surgery), seemed to affect the rate of POSVT as well (OR 1.18). The association of thoracotomy with increased POSVT has been demonstrated in propensity-matched studies from the STS
Given this contemporary study, which included a higher rate of minimally invasive surgery than previous studies, an effect seems likely.
These data make abundantly clear that the risk of POSVT in patients undergoing pulmonary lobectomy is variable. Although in the recently published guidelines from the AATS, all patients undergoing lobectomy were deemed to be at high risk (>15%) for postoperative atrial arrhythmias, we suggest that risk is best characterized by a spectrum that should be evaluated before considering monitoring and prevention strategies for individual patients.
Such a risk calculator could be used to stratify patients into groups, for prospective studies evaluating the intensity of monitoring of postoperative patients, and for studies evaluating prophylaxis against POSVT.
As noted in previous studies, the consequences of POSVT seem to be significant. As patients who develop POSVT are older and have more comorbidities, direct causal effects of POSVT on adverse outcomes are sometimes difficult to identify. We have no data on the timing or nature of stroke or other complications with regard to POSVT. However, in our multivariable model, adjusted for numerous potential confounding factors, POSVT was independently associated with stroke, in-hospital mortality, LOS, and readmission.
In particular, the consequences of POSVT when it occurs with other complications seem to be particularly dire, with a stroke rate of 1.5%, a median LOS of 10 days, and an in-hospital mortality rate of 7.7%. From the coding in the SID-HCUP database, determining whether POSVT preceded or followed other complications is not possible. Nonetheless, when patients develop POSVT and other complications, managing them in a carefully monitored setting seems appropriate, as well as giving consideration to anticoagulation, when safe to do so.
In contrast to those high-risk patients who have multiple complications, the impact of “uncomplicated” POSVT is less clear. Atrial arrhythmias have been suggested to be transient and relatively harmless in this setting.
We sought to evaluate this possibility by defining a group of patients who have uncomplicated POSVT.
We excluded stroke as a complication, to determine its association with POSVT. We selected patients who were documented as having no other postoperative complications other than atrial fibrillation, atrial flutter, or paroxysmal atrial tachycardia. Among our cohort, 5.4% of patients undergoing pulmonary lobectomy had uncomplicated POSVT. In this setting, POSVT did not increase in-hospital mortality. However, POSVT was still associated with an increase in the incidence of stroke, median LOS, and readmission. This finding suggests that even POSVT without complications makes care of these pulmonary lobectomy patients more complex and puts them at risk for adverse outcomes.
Limitations
We are left with the question of whether guidelines and evidence-based medicine can be used to reduce the rate of POSVT and associated adverse outcomes in patients undergoing pulmonary lobectomy. Unfortunately, the SID-HCUP database does not contain any information pertaining to medical prophylaxis or to management algorithms for POSVT, which is certainly a limitation of the study. Other limitations are lack of cancer staging information, lack of detailed comorbidity information, and unmeasured variability in postoperative monitoring for POSVT.
Additionally, ICD-9 codes lack detailed, standard clinical definitions that can be universally applied, and are thus open to coding interpretation. Nevertheless, we believe that such ambiguity of definitions is apparent in prospective databases with regard to POSVT. The administrative data used here, carefully evaluated to exclude preoperative diagnoses of SVT, are widely generalizable and not restricted to the outcomes of specialized, experienced centers. The overall rate of POSVT was remarkably similar to that reported for patients in the STS database study (11.8% vs 12.6%), in which 87.5% of patients underwent lobectomy.
Based on our findings, we believe that further studies are needed to evaluate the role of rate control, rhythm conversion, and anticoagulation in these patients, ideally in patients segregated into low- and high-risk cohorts. Among high-risk patients, POSVT may not be as preventable as we like to think, given its dependence on nonmodifiable demographic variables and clinical characteristics.
Conflict of Interest Statement
A.U.B., R.Z., and P.M.F. have a financial interest in the company Analytical Care. All other authors have nothing to disclose with regard to commercial support.
Lower preoperative fluctuation of heart rate variability is an independent risk factor for postoperative atrial fibrillation in patients undergoing major pulmonary resection.
The Society of Thoracic Surgeons practice guideline on the prophylaxis and management of atrial fibrillation associated with general thoracic surgery: executive summary.
Agency for Healthcare Research and Quality. Healthcare Cost and Utilization Project. Available at: http://www.hcup-us.ahrq.gov/sidoverview.jsp. Accessed date January 5, 2016.
Funding for this work was provided by the Center for Perioperative Outcomes, Department of Anesthesiology at Weill Cornell Medicine, NewYork-Presbyterian Hospital. Xian Wu, MPH, was partially supported by the following grant: Clinical and Translational Science Center at Weill Cornell Medicine (UL1-TR000457-06).
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