Kristina D. Simmons

The rise in metastasectomy across cancer types over the past decade

Although studies of metastasectomy have been limited primarily to institutional experiences, reports of favorable long‐term outcomes have generated increasing interest. In the current study, the authors attempted to define the national practice patterns in metastasectomy for 4 common malignancies with varying responsiveness to systemic therapy.

Fast, scalable, Bayesian spike identification for multi-electrode arrays.

We present an algorithm to identify individual neural spikes observed on high-density multi-electrode arrays (MEAs). Our method can distinguish large numbers of distinct neural units, even when spikes overlap, and accounts for intrinsic variability of spikes from each unit. As MEAs grow larger, it is important to find spike-identification methods that are scalable, that is, the computational cost of spike fitting should scale well with the number of units observed. Our algorithm accomplishes this goal, and is fast, because it exploits the spatial locality of each unit and the basic biophysics of extracellular signal propagation. Human interaction plays a key role in our method; but effort is minimized and streamlined via a graphical interface. We illustrate our method on data from guinea pig retinal ganglion cells and document its performance on simulated data consisting of spikes added to experimentally measured background noise. We present several tests demonstrating that the algorithm is highly accurate: it exhibits low error rates on fits to synthetic data, low refractory violation rates, good receptive field coverage, and consistency across users.

High Accuracy Decoding of Dynamical Motion from a Large Retinal Population

Motion tracking is a challenge the visual system has to solve by reading out the retinal population. It is still unclear how the information from different neurons can be combined together to estimate the position of an object. Here we recorded a large population of ganglion cells in a dense patch of salamander and guinea pig retinas while displaying a bar moving diffusively. We show that the bar’s position can be reconstructed from retinal activity with a precision in the hyperacuity regime using a linear decoder acting on 100+ cells. We then took advantage of this unprecedented precision to explore the spatial structure of the retina’s population code. The classical view would have suggested that the firing rates of the cells form a moving hill of activity tracking the bar’s position. Instead, we found that most ganglion cells in the salamander fired sparsely and idiosyncratically, so that their neural image did not track the bar. Furthermore, ganglion cell activity spanned an area much larger than predicted by their receptive fields, with cells coding for motion far in their surround. As a result, population redundancy was high, and we could find multiple, disjoint subsets of neurons that encoded the trajectory with high precision. This organization allows for diverse collections of ganglion cells to represent high-accuracy motion information in a form easily read out by downstream neural circuits.

Bariatric Centers of Excellence: Effect of Centralization on Access to Care

BACKGROUND In 2006, the Centers for Medicare and Medicaid Services restricted coverage for bariatric procedures to designated high-volume Centers of Excellence. The effect of centralization of elective surgical procedures on the ability of patients to access surgery has not been studied previously. STUDY DESIGN Inpatient claims data from 2008 to 2011 from 2 high-volume surgical states were used. All patients older than 18 years undergoing a bariatric surgical procedure were included. The number of bariatric procedures and characteristics of patients undergoing bariatric surgery were examined in each year. Nonparametric tests for trend were performed to analyze time trends. Difference-in-difference analyses were performed to assess the rate of bariatric surgery in underserved Medicare patients compared with underserved patients with other payers. RESULTS The percentage of procedures performed at Centers of Excellence increased from 60.5% in 2008 to 73.1% in 2011 (p < 0.01). The proportion of Medicare patients receiving surgery at a Center of Excellence increased from 77.7% in 2008 to 88.1% in 2011 (p < 0.01). The proportion of bariatric surgery patients from underserved groups increased over time except among those residing in rural areas, for whom there was no change. Among patients from underserved populations, only black Medicare patients experienced an increase in bariatric surgery use when compared with non-Medicare patients. The travel distance for Medicare patients consistently exceeded travel distance for non-Medicare patients. However, travel distance for Medicare patients decreased slightly during the study period. CONCLUSIONS Despite the longer travel distance required for Medicare patients, centralization of bariatric surgery to Centers of Excellence did not result in impaired access to care. In fact, in this study, an improvement in access to bariatric surgery was seen and persisted among some underserved populations.

Blood Transfusion in Major Abdominal Surgery for Malignant Tumors: A Trend Analysis Using the National Surgical Quality Improvement Program

IMPORTANCE Blood transfusion can be a lifesaving treatment for the surgical patient, yet transfusion-related immunomodulation may underlie the association of allogeneic transfusion with increased perioperative morbidity and possibly poorer long-term oncologic outcomes. OBJECTIVE To evaluate trends in transfusion rates for major abdominal oncologic resections to assess changes in recent clinical practice (given the accumulating evidence of the deleterious effects of blood transfusion). DESIGN, SETTING, AND PARTICIPANTS Retrospective review of a population-based registry of all hospitals participating in the American College of Surgeons National Surgical Quality Improvement Project (2005-2013 Participant Use Data Files), which was queried for patients who underwent major resection of a pancreatic, hepatic, or gastric malignant tumor. Data analysis was performed from July to August 2015. MAIN OUTCOME AND MEASURES The primary outcome was the transfusion of any quantity of packed red blood cells. Transfusion rates were calculated for the perioperative period, which was defined as the time from the start of surgery to 72 hours after surgery. Secondary outcomes included wound infection, myocardial infarction, and renal insufficiency, and the rates of these complications were calculated as well. Trend analysis was performed for each year of data to evaluate for changes over the study period. RESULTS A total of 19 680 patients (median age, 65.0 years [interquartile range, 57.0-73.0 years]) were identified, of whom 5900 (30.0%) received a blood transfusion (of 13 657 patients who underwent a pancreatic resection, 4074 required transfusion [29.8%]; of 1605 patients who underwent a gastric resection, 378 required transfusion [23.6%]; and of 4418 patients who underwent a hepatic resection, 1448 required transfusion [32.8%]). There was a significant trend toward decreasing rates of transfusion during the study period (z = -7.89, P < .001), which corresponded to an absolute 6.1% decrease in the rate of transfusion of packed red blood cells from 2005 to 2013 (ie, from 32.8% to 26.7%). There was no significant change in the rates of postoperative wound infection or renal insufficiency during this time period, but there was an increased rate of perioperative myocardial infarction during the study period (0.33% absolute increase; z = 3.15, P = .002). CONCLUSIONS AND RELEVANCE Over 9 years of contemporary practice, a trend of less perioperative blood transfusions for oncologic abdominal surgery was observed. Further studies are needed to assess whether these trends reflect changes in operative techniques, hospital cohorts, or transfusion thresholds.

Using Patient Outcomes to Evaluate General Surgery Residency Program Performance.

IMPORTANCE To evaluate and financially reward general surgery residency programs based on performance, performance must first be defined and measureable. OBJECTIVE To assess general surgery residency program performance using the objective clinical outcomes of patients operated on by program graduates. DESIGN, SETTING, AND PARTICIPANTS A retrospective cohort study was conducted of discharge records from 349 New York and Florida hospitals between January 1, 2008, and December 31, 2011. The records comprised 230,769 patients undergoing 1 of 24 general surgical procedures performed by 454 surgeons from 73 general surgery residency programs. Analysis was conducted from June 4, 2014, to June 16, 2015. MAIN OUTCOMES AND MEASURES In-hospital death; development of 1 or more postoperative complications before discharge; prolonged length of stay, defined as length of stay greater than the 75th percentile when compared with patients undergoing the same procedure type at the same hospital; and failure to rescue, defined as in-hospital death after the development of 1 or more postoperative complications. RESULTS Patients operated on by surgeons trained in residency programs that were ranked in the top tertile were significantly less likely to experience an adverse event than were patients operated on by surgeons trained in residency programs that were ranked in the bottom tertile. Adjusted adverse event rates for patients operated on by surgeons trained in programs that were ranked in the top tertile and those who were operated on by surgeons trained in programs that were ranked in the bottom tertile were, respectively, 0.483% vs 0.476% for death, 9.68% vs 10.79% for complications, 16.76% vs 17.60% for prolonged length of stay, and 2.68% vs 2.98% for failure to rescue (all P < .001). The differences remained significant in procedure-specific subset analyses. The rankings were significantly correlated among some but not all outcome measures. The magnitude of the effect of the residency program on the outcomes achieved by the graduates decreased with increasing years of practice. Within the analyses of surgeons within 20, 10, and 5 years of practice, the relative difference in adjusted adverse event rates across the individual models between the top and bottom tertiles ranged from 1.5% to 12.3% (20 years), 9.1% to 33.8% (10 years), and 8.0% to 44.4% (5 years). CONCLUSIONS AND RELEVANCE Objective data were successfully used to rank the clinical outcomes achieved by graduates of general surgery residency programs. Program rankings differed by the outcome measured. The magnitude of differences across programs was small. Careful consideration must be used when identifying potential targets for payment-for-performance initiatives in graduate medical education.

Variation in the Utilization of Minimally Invasive Surgical Operations.

Objective: The goal of this study was to examine regional variation in use of minimally invasive surgical (MIS) operations. Summary Background Data: Regional variation exists in performance of surgical operations. Variation in the use of MIS has not been studied. Methods: Five operations that are performed open or MIS were selected: cholecystectomy, appendectomy, colectomy, antireflux, and bariatric. A 3-state database from 2008 to 2011 was used; states were divided into hospital service areas (HSAs). For each operation, the percentage of MIS operations was calculated. HSAs with less than 50% or more than 150% of the MIS average were considered outliers. Population demographics, geography, and hospital and physician presence were compared between HSAs. Rates of performance by patient disease and the presence of MIS surgeons were also investigated. Results: MIS cholecystectomy was performed with low variation; MIS appendectomy, antireflux, and bariatric operations with medium variation; and MIS colectomy with high variation. With the exception of MIS colectomy, there were no differences in the patient demographics, geography, or disease types treated with an MIS approach between HSAs with low-, non-, or high utilization of MIS. There is no correlation between the number of MIS surgeons and the percentage of procedures performed MIS. Conclusions: Variation in utilization of MIS exists and differs by operation. Patient demographics, patient disease, and the ability to access care are associated only with variation in use of MIS for colectomy. For all other operations studied, these factors do not explain variation in MIS use. Further investigation is warranted to identify and eliminate causes of variation.

Variation in the use of minimally invasive bariatric surgery

BACKGROUND Obesity is a significant public health problem in the United States. Despite the known benefits of bariatric surgery, most patients eligible for bariatric surgery do not receive it. Access to minimally invasive bariatric surgery (MIS), the surgical gold standard, may be a limitation. OBJECTIVES We investigated geographic variation in the utilization of laparoscopy for bariatric surgical procedures. METHODS We utilized a unique 3-state inpatient database. Adult patients receiving initial bariatric surgery were included. Patients were divided into hospital service areas (HSAs). Rates of MIS utilization in each HSA were calculated. HSAs were divided into quintiles of utilization. Patient and hospital characteristics were compared across quintiles. RESULTS Over the 5-year study period, 127,008 patients received bariatric surgery. MIS technology was available in all HSAs. MIS was performed in 88.4% of procedures and was performed in 70.6% of patients in the lowest quintile compared with 97.0% in the highest (P<.01). The use of laparoscopy across quintiles varied significantly by rural hospital status: All 7 rural hospitals were located in the lowest quintile of utilization. CONCLUSION Variation in the performance of MIS bariatric surgical procedures exists. These differences can likely be attributed to physician preference or patient population. Obesity rates are elevated in rural areas. The implementation of MIS bariatric surgery programs in rural areas may improve the treatment of obesity and downstream co-morbidities in these populations.

Comparing International and United States Undergraduate Medical Education and Surgical Outcomes Using a Refined Balance Matching Methodology.

Objective: The aim of this study is to compare surgical outcomes of international medical graduates (IMGs) and United States medical graduates (USMGs). Summary of Background Data: IMGs represent 15% of practicing surgeons in the United States (US), and their training pathways often differ substantially from USMGs. To date, differences in the clinical outcomes between the 2 cohorts have not been examined. Methods: Using a unique dataset linking AMA Physician Masterfile data with hospital discharge claims from Florida and New York (2008–2011), patients who underwent 1 of 32 general surgical operations were stratified by IMG and USMG surgeon status. Mortality, complications, and prolonged length of stay were compared between IMG and USMG surgeon status using optimal sparse network matching with balance. Results: We identified 972,718 operations performed by 4581 surgeons (72% USMG, 28% IMG). IMG and USMG surgeons differed significantly in demographic (age, gender) and baseline training (years of training, university affiliation of training hospital) characteristics. USMG surgeons performed complex procedures (13.7% vs 11.1%, P < 0.01) and practiced in urban settings (79.4% vs 75.6%, P < 0.01) more frequently, while IMG surgeons performed a higher volume of studied operations (50.7 ± 5.1 vs 57.8 ± 8.4, P < 0.01). In the matched cohort analysis of 396,810 patients treated by IMG and USMG surgeons, rates of mortality (USMG: 2.2%, IMG: 2.1%; P < 0.001), complications (USMG: 14.5%, IMG: 14.3%; P = 0.032), and prolonged length of stay (pLOS) (USMG: 22.7%, IMG: 22.8%; P = 0.352) were clinically equivalent. Conclusion: Despite considerable differences in educational background, surgical training characteristics, and practice patterns, IMG and USMG-surgeons deliver equivalent surgical care to the patients whom they treat.

A risk prediction model for mortality in the moribund general surgical patient.

INTRODUCTION Surgeons struggle to counsel families on the role of surgery and likelihood of survival in the moribund patient. We sought to develop a risk prediction model for postoperative inpatient death for the moribund surgical candidate. MATERIALS AND METHODS Using 2007-2012 American College of Surgeons National Surgical Quality Improvement Program data, we identified American Society of Anesthesiologists class 5 (moribund) patients. The sample was randomly divided into development and validation cohorts. In the development cohort, preoperative patient characteristics were evaluated. The primary outcome measure was in-hospital mortality. Factors significant in univariate analysis were entered into a multivariable model; points were assigned based on β coefficients. A scoring system was generated to predict inpatient mortality. Models were developed separately for operations performed within and after 24 hours of admission, and tested on the validation cohort. RESULTS A total of 3120 patients were included. In-hospital mortality was 50.6%. In multivariable analysis, patient characteristics associated with in-hospital mortality were age, functional status, recent dialysis, recent myocardial infarction, ventilator dependence, body mass index, and procedure type. The scoring system generated from this model accurately predicted in-hospital mortality for patients undergoing surgery within and after 24 hours. CONCLUSION A simple risk prediction model using readily available preoperative patient characteristics accurately predicts postoperative mortality in the moribund surgical patient. This scoring system can assist in decision making.