Daniel L. Davenport

The obesity paradox: body mass index and outcomes in patients undergoing nonbariatric general surgery.

Objective:We sought to examine the effect of body mass index (BMI) on 30-day morbidity and mortality in a large cohort of patients undergoing nonbariatric general surgery. Summary Background Data:Obesity has long been considered a risk factor for poor outcomes from a variety of surgical procedures, yet recent studies of critically and chronically ill patients suggest that overweight and obese patients may paradoxically have better outcomes than “normal” weight patients. Methods:A prospective, multi-institutional, risk-adjusted cohort study of 118,707 patients undergoing nonbariatric general surgery who were included in the National Surgical Quality Improvement Program Participant Use database in 2005 and 2006 was performed. Outcomes and risk variables were compared across NIH-defined BMI class using analysis of variance, Bonferroni multiple comparisons of means tests, and multivariable logistic regression. Results:After adjusting for all significant perioperative risk factors, the risk of death according to BMI exhibited a reverse J-shaped relationship, with the highest rates in the underweight and morbidly obese extremes and the lowest rates in the overweight and moderately obese. Overweight (odds ratio, 0.85; 95% CI, 0.75–0.99) and moderately obese (odds ratio, 0.73; 95% CI, 0.57–0.94) patients had a significantly lower risk of death than normal weight patients. There was a progressive increase in the likelihood of a complication with increasing BMI class, almost entirely due to increasing rates of wound infection. Conclusions:Overweight and moderately obese patients undergoing nonbariatric general surgery have paradoxically “lower” crude and adjusted risks of mortality compared with patients at a “normal” weight. This finding is in contrast to observations from the general population, confirming the existence of an “obesity paradox” in this patient population.

Meta-analysis of endovascular vs open repair for traumatic descending thoracic aortic rupture

OBJECTIVES Traumatic thoracic aortic injuries are associated with high mortality and morbidity. These patients often have multiple injuries, and delayed aortic repair is frequently used. Endoluminal grafts offer an alternative to open surgical repair. We performed a meta-analysis of comparative studies evaluating endovascular vs open repair of these injuries. METHODS A systematic search of studies reporting treatment of traumatic aortic injury was performed using the following databases: Medline/PubMed, CINAHL, Proquest, Up to Date, Database of Abstracts of Reviews of Effects (DARE), ClinicalTrials.gov, the Cochrane Central Register of Controlled Trials and the Cochrane Database of Systematic Reviews. Search terms were thoracic aortic trauma, traumatic thoracic aortic injury, traumatic aortic rupture, stent graft repair, and endovascular repair. Outcomes analyzed were procedure-related mortality, overall 30-day mortality, and paraplegia/paraparesis rate using odds ratios (OR) and 95% confidence intervals (CI). Publication bias was investigated using funnel plots. Assessment of homogeneity was performed using the Q test; statistical heterogeneity was considered present at P < .05. Weighted averages of age, interval to repair, and injury severity score were compared with the Welch t test; P < .05 was considered statistically significant. RESULTS Seventeen retrospective cohort studies from 2003 to 2007 were included. All were nonrandomized; no prospective randomized trials were found. These studies reported on 589 patients; 369 were treated with open repair, and 220 underwent thoracic stent graft placement. There was no significant difference in age (mean 38.8 years for both) or interval to repair (mean 1.5 days for endoluminal repair; 1 day for open repair). Injury severity score was higher for patients undergoing endoluminal repair (mean, 42.4 vs 37.4 for open repair, P < .001). Procedure-related mortality was significantly lower with endoluminal repair (OR, 0.31; 95% CI, 0.15-0.66; P = .002). Overall 30-day mortality was also lower after endoluminal repair (OR, 0.44; 95% CI, 0.25-0.78; P = .005). Sixteen studies reported data for postoperative paraplegia; 215 patients were treated with endograft placement and 333 with open repair. The risk of postoperative paraplegia was significantly less with endoluminal repair (OR, 0.32; 95% CI, 0.1-0.93; P = .037). The Q test did not indicate significant heterogeneity for the outcomes of interest; publication bias was limited. CONCLUSIONS Meta-analysis of retrospective cohort studies indicates that endovascular treatment of descending thoracic aortic trauma is an alternative to open repair and is associated with lower postoperative mortality and ischemic spinal cord complication rates.

National Surgical Quality Improvement Program (NSQIP) Risk Factors Can Be Used to Validate American Society of Anesthesiologists Physical Status Classification (ASA PS) Levels

Objective:The purpose of this study was to determine the relationship between the American Society of Anesthesiologists’ Physical Status (ASA PS) classifications and the other National Surgical Quality Improvement Program (NSQIP) preoperative risk factors. Background:The ASA PS has been shown to predict morbidity and mortality in surgical patients but is inconsistently applied and clinically imprecise. It is desirable to have a method for validating ASA PS classification levels. Methods:The NSQIP preoperative risk factors, including ASA PS, were recorded from a random sample of 5878 surgical patients on 6 services between October 1, 2001 and September 30, 2003 at the University of Kentucky Medical Center. Mortality, morbidity, costs, and length of stay were obtained and compared across ASA PS levels. The ability of 1) ASA PS alone, 2) the other NSQIP risk factors, and, 3) all factors combined to predict outcomes was analyzed. A model using the other NSQIP risk factors was developed to predict ASA PS. Results:ASA PS alone was a strong predictor of outcomes (P < 0.01). However, the other NSQIP risk factors were better predictors as a group. There was significant interdependence between the ASA PS and the other NSQIP risk factors. Predictions of ASA PS using the other factors showed strong agreement with the anesthesiologists’ assignments. Conclusions:The NSQIP risk factors other than ASA PS can and should be used to validate ASA PS classifications.

General surgical operative duration is associated with increased risk-adjusted infectious complication rates and length of hospital stay.

BACKGROUND Studies of specific procedures have shown increases in infectious complications with operative duration. We hypothesized that operative duration is independently associated with increased risk-adjusted infectious complication (IC) rates in a broad range of general surgical procedures. STUDY DESIGN We queried the American College of Surgeons National Surgical Quality Improvement Program database for general surgical operations performed from 2005 to 2007. ICs (wound infection, sepsis, urinary tract infection, and/or pneumonia) and length of hospital stay (LOS) were evaluated versus operative duration (OD, ie, incision to closure). Multivariable regression adjusted for 38 patient risk variables, operation type and complexity, wound class and intraoperative transfusion. We also analyzed isolated laparoscopic cholecystectomies in patients of American Society of Anesthesiologists class 1 or 2, without intraoperative transfusion and with a clean or clean-contaminated wound class. RESULTS In 299,359 operations performed at 173 hospitals, unadjusted IC rates increased linearly with OD at a rate of close to 2.5% per half hour (chi-square test for linear trend, p < 0.001). After adjustment, IC risk increased for each half hour of OD relative to cases lasting <or=1 hour, almost doubling at 2.1 to 2.5 hours (odds ratio = 1.92; 95% CI, 1.82 to 2.03; p < 0.001). In isolated laparoscopic cholecystectomy, IC rates increased linearly with OD (n = 17,018, chi-square test for linear trend, p < 0.001) with rates for 1.1 to 1.5 hour cases (1.4%) doubling those lasting <or=0.5 hour (0.7%). Across all procedures, adjusted LOS increased geometrically with operative duration at a rate of about 6% per half hour (coefficient for natural log transformed LOS = 0.059 per half hour; 95% CI, 0.058 to 0.060; p < 0.001). CONCLUSIONS Operative duration is independently associated with increased ICs and LOS after adjustment for procedure and patient risk factors.

Preoperative risk factors and surgical complexity are more predictive of costs than postoperative complications: a case study using the National Surgical Quality Improvement Program (NSQIP) database.

Objective:This single-center study tested the hypothesis that preoperative risk factors and surgical complexity predict more variation in hospital costs than complications. Background:Complications after surgical operations have been shown to significantly increase hospital cost. The impact on complication-related costs of preoperative risk factors is less well known. Methods:The National Surgical Quality Improvement Program (NSQIP) preoperative risk factors, surgical complexity, and outcomes, along with hospital costs, were analyzed for a random sample of 5875 patients on 6 surgical services. Operation complexity was assessed by work RVUs (Centers for Medicare and Medicaid Services Resource Based Relative Value Scale). The difference in mean hospital costs associated with all variables was analyzed. Multiple linear regression was used to determine the cost variation associated with all variables separately and combined. Results:Fifty-one of 60 preoperative risk factors, work RVUs, and 22 of 29 postoperative complications were associated with higher variable direct costs (P < 0.05). Linear regressions showed that risk factors predicted 33% (P < 0.001) of cost variation, work RVUs predicted 23% (P < 0.001), and complications predicted 20% (P < 0.001). Risk factors and work RVUs together predicted 49% of cost variation (P < 0.001) or 16% more than risk factors alone. Adding complications to this combined model modestly increased prediction of costs by 4% for a total of 53% (P < 0.001). Conclusion:Preoperative risk factors and surgical complexity are more effective predictors of hospital costs than complications. Preoperative intervention to reduce risk could lead to significant cost savings. Payers and regulatory agencies should risk-adjust hospital cost assessments using clinical information that integrates costs, preoperative risk, complexity of operation, and outcomes.

Endovascular versus open repair for descending thoracic aortic rupture: institutional experience and meta-analysis

Rupture of thoracic aneurysm, acute type B dissection, blunt thoracic trauma, and penetrating aortic ulcer can present with a similar clinical profile of thoracic aortic rupture. We report a meta-analysis of comparative studies evaluating endoluminal graft versus open repair of these lesions as well as the early experience from our institution. We searched the following databases for reports of endovascular versus open repair of acute descending thoracic aortic rupture: Medline/PubMed, OVID, EMBASE, CINAHL, ClinicalTrials.gov, the Cochrane central register of controlled trials and the Cochrane database of systematic reviews. We used the random-effects model to calculate the odds ratio (OR) and 95% confidence intervals (CI) for mortality, paraplegia/paraparesis and stroke rates. Also, the medical records of the patients treated in our institution with this technique from 2000 to 2008 were reviewed. Demographics, comorbidities and operative procedure information were retrieved. Outcomes examined were mortality, paraplegia and stroke. Meta-analysis indicates that endoluminal graft repair is accompanied by lower procedure related mortality (OR 0.46, 95% CI 0.26-0.78, p=0.005) and paraplegia rates (OR 0.23, 95% CI 0.08-0.65, p=0.005), as compared to open repair. There was no difference in stroke rate between the two methods (OR 0.86, 95% CI 0.26-2.8, p=0.8). We have treated 13 patients with endoluminal stent-grafts. No conversion to open repair was necessary. Stroke rate was 15%, no patient died as a result of the stent-graft placement, one patient died as a result of massive head injury (overall 30-day mortality: 7.5%). There were no spinal cord ischemic complications. Our experience and meta-analysis indicate that thoracic endograft repair has low mortality and spinal cord complication rates for treatment of acute thoracic aortic rupture. If this method proves to be durable, it could replace open repair as the treatment of choice for these critically ill patients.

Assessing Surgical Quality Using Administrative and Clinical Data Sets: A Direct Comparison of the University HealthSystem Consortium Clinical Database and the National Surgical Quality Improvement Program Data Set

The use of “clinical” versus “administrative” data sets for health care quality assessment continues to be debated. This study directly compares the University HealthSystem Consortium Clinical Database (UHC CDB) and the National Surgical Quality Improvement Program (NSQIP) in terms of their assessment of complications and death for 26 322 surgery patients using analyses of variance, correlation, and multivariable logistic regression. The NSQIP had more variables with significant correlation with outcomes. The NSQIP was better at predicting death (c-index 0.94 vs 0.90, P < .05) and complications (c-index 0.78 vs 0.76, P = .07), especially for higher risk patients. The UHC CDB missed and misclassified several major complications. The data sets are similar in their explanatory power relative to outcomes, but the clinical data set is better, particularly at identifying higher risk patients and specific complications. It should prove more useful for initiating and monitoring clinical process improvements because of more clinically relevant variables. (Am J Med Qual 2009;24:395-402)

Gender and 30-day outcome in patients undergoing endovascular aneurysm repair (EVAR): An analysis using the ACS NSQIP dataset

PURPOSE Prior studies have demonstrated higher in-hospital mortality in women undergoing open abdominal aortic aneurysm repair. The current study evaluates the relationship between gender and 30-day outcomes for endovascular aneurysm repair (EVAR) in a multicenter, contemporary patient population. METHODS Patients in the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) participant use file that underwent EVAR of abdominal aortic aneurysm (AAA) from 2005 to 2007 were identified by CPT codes. Outcomes analyzed were 30-day mortality, morbidity (one or more of 21 complications defined by the ACS NSQIP protocol), length of hospital stay, and six complication subgroups. Preoperative risk factors, intraoperative variables, and outcomes were compared across genders using chi(2) (binary and categorical variables) and t tests (continuous variables). The relationship of gender to outcomes was further evaluated using multivariate logistic regressions to adjust for pre- and intraoperative risk variables. RESULTS In 3662 EVAR patients, 647 (17.7%) were women and 3015 (82.3%) men with mean ages of 75.1 +/- 9.0 and 73.7 +/- 8.5 years (P < .001). Tube graft (360, 9.8%); bifurcated, one docking limb (1624, 44.3%); bifurcated, two docking limbs (1294, 35.3%); unibody (218, 5.9%); and aorto-uni-iliac/femoral (166, 4.4%) repairs were performed. Tube and aorto-uni-iliac/femoral grafts were more common in women (21.4% vs 12.8%, P < .001) than men, as were femoral/femoral crossovers (3.9% vs 1.8%, P = .011) and iliac or brachial exposures (2.8% vs 1.0%, P = .009). Overall morbidity and mortality were 11.9% and 2.1%, respectively. Mortality in women was significantly higher (3.4% vs 2.1%, P = .014), as was morbidity (17.8% vs 10.6%, P < .001). Of thirteen independent preoperative risk factors for mortality or morbidity, women had a higher incidence in five: emergent operation, functional dependence, recent weight loss, underweight status or morbid obesity, and severe chronic obstructive pulmonary disease (COPD). After adjustment for these variables, the odds ratio (OR) for mortality in women vs men was 1.52 (95% confidence interval [CI] 0.85-2.69, P = .157); OR for morbidity was 1.65 (95% CI 1.28-2.14, P < .001). Female gender was also found to be an independent risk factor for length of stay (Beta 0.7 days, 95% CI 0.2-1.2, P = .006), infectious complications (OR 1.49, 95% CI 1.10-2.03, P = .011), wound complications (OR 1.80, 95% CI 1.12-2.90, P = .015) and postoperative transfusion (OR 2.92, 95% CI 1.39-6.13, P = .002). CONCLUSIONS Mortality and morbidity were higher in women than men undergoing EVAR. Multivariate analysis showed that the increased risk of mortality was related to women presenting more emergently, more debilitated (recent weight loss and functional dependence), and requiring iliac or brachial exposure. After adjustment for multiple preoperative and operative factors, women remained at significantly higher risk for the development of a broad range of complications and increased length of stay.

Blood transfusion is associated with increased morbidity and mortality after lower extremity revascularization

BACKGROUND Little is known about the significance of blood transfusion in patients with peripheral arterial disease. We queried the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database to examine the effect of intraoperative blood transfusion on the morbidity and mortality in patients who underwent lower extremity revascularization. METHODS We analyzed data from the participant use data file containing vascular surgical cases submitted to the ACS NSQIP in 2005, 2006, and 2007 by 173 hospitals. Current procedural terminology codes were used to select lower extremity procedures that were grouped into venous graft, prosthetic graft, or thromboendarterectomy. Thirty-day outcomes analyzed were (1) mortality, (2) composite morbidity, (3) graft/prosthesis failure, (4) return to the operating room within 30 days, (5) wound occurrences, (6) sepsis or septic shock, (7) pulmonary occurrences, and (8) renal insufficiency or failure. Intraoperative transfusion of packed red blood cells was categorized as none, 1 to 2 units, and 3 or more units. Outcome rates were compared between the transfused and nontransfused groups using the chi(2) test and multivariable regression adjusting for transfusion propensity, comorbid and procedural risk. RESULTS A total of 8799 patients underwent lower extremity revascularization between 2005 and 2007. Mean age was 66.8 +/- 12.0 years and 5569 (63.3%) were male. Transfusion rates ranged from 14.5% in thromboendarterectomy patients to 27.1% in prosthetic bypass patients (P < .05). After adjustment for transfusion propensity and patient and procedural risks, transfusion of 1 or 2 units remained significantly predictive of mortality, composite morbidity, sepsis/shock, pulmonary occurrences, and return to the operating room. The adjusted odds ratios for 30-day mortality ranged from 1.92 (95% confidence interval [CI] 1.36-2.70) for 1 to 2 units to 2.48 (95% CI 1.55-3.98) for 3 or more units. CONCLUSION In a large number of patients undergoing lower extremity revascularization, we have found that there is a higher risk of postoperative mortality, pulmonary, and infectious complications after receiving intraoperative blood transfusion. Additional studies are necessary to better define transfusion triggers that balance the risk/benefit ratio for blood transfusion.

Thirty-day NSQIP database outcomes of open versus endoluminal repair of ruptured abdominal aortic aneurysms

BACKGROUND The mortality of ruptured abdominal aortic aneurysm (rAAA) has decreased 3.5% per decade in the last 50 years to a current rate of 40%-50%. Reports have indicated that endovascular repair (EVAR) is feasible for rAAA and may offer potential benefits over open repair. We examined the National Surgical Quality Improvement Program (NSQIP) database to compare 30-day multicenter outcomes for EVAR vs open rAAA repair. METHODS Patients that underwent rAAA repair in the NSQIP database from 2005 to 2007 were identified through a combination of Current Procedural Terminology (CPT) codes and International Classification of Diseases-Ninth Revision (ICD-9) diagnoses. Preoperative comorbidities, operative duration and transfusion, and 30 day outcomes were evaluated using t tests or Chi-squared tests depending on the variable. A separate multivariable regression was performed for each outcome adjusting for all independently predictive preoperative and intraoperative risk factors. RESULTS A total of 427 patients were identified and 76.8% of patients underwent open repair. The open repair groups exhibited lower albumin levels and higher percentage of patients with preoperative hematocrit (Hct) <38% and need for preoperative ventilation. The requirement for preoperative blood transfusion was similar. Patients undergoing open repair had much higher intraoperative transfusion requirements (11.8 +/- 8.9 vs 4.2 +/- 6.0 red blood cell units, P < .001). After adjustment for preoperative mortality risk factors, the mortality risk was higher for open repair versus EVAR (odds ratio 1.67, 95% confidence interval [CI] 0.91-3.05, P = .096) but did not reach significance. After similar adjustment the composite morbidity odds ratio for open repair versus EVAR was 1.82 (95% CI 1.11-2.99, P = .018) and the pulmonary adverse events odds ratio was 1.99 (95% CI 1.22-3.25, P = .006). Risks for the other outcomes were not significant. CONCLUSIONS Composite 30-day morbidity risk is lower after EVAR vs open repair of rAAA. Open repair is associated with increased transfusion requirements. Performance of EVAR in rAAA patients with favorable anatomy could potentially result in improved outcome as compared with open repair.