A new Elixhauser-based comorbidity summary measure to predict in-hospital mortality.

BACKGROUND: Recently, van Walraven developed a weighted summary score (VW) based on the 30 comorbidities from the Elixhauser comorbidity system. One of the 30 comorbidities, cardiac arrhythmia, is currently excluded as a comorbidity indicator in administrative datasets such as the Nationwide Inpatient Sample (NIS), prompting us to examine the validity of the VW score and its use in the NIS. METHODS: Using data from the 2009 Maryland State Inpatient Database, we derived weighted summary scores to predict in-hospital mortality based on the full (30) and reduced (29) set of comorbidities and compared model performance of these and other comorbidity summaries in 2009 NIS data. RESULTS: Weights of our derived scores were not sensitive to the exclusion of cardiac arrhythmia. When applied to NIS data, models containing derived summary scores performed nearly identically (c statistics for 30 and 29 variable-derived summary scores: 0.804 and 0.802, respectively) to the model using all 29 comorbidity indicators (c=0.809), and slightly better than the VW score (c=0.793). Each of these models performed substantially better than those based on a simple count of Elixhauser comorbidities (c=0.745) or a categorized count (0, 1, 2, or ≥ 3 comorbidities; c=0.737). CONCLUSIONS: The VW score and our derived scores are valid in the NIS and are statistically superior to summaries using simple comorbidity counts. Researchers wishing to summarize the Elixhauser comorbidities with a single value should use the VW score or those derived in this study.

Lumbar microdiscectomy complication rates: a systematic review and meta-analysis.

OBJECT Lumbar microdiscectomy and its various minimally invasive surgical techniques are seeing increasing popularity, but a systematic review of their associated complications has yet to be performed. The authors sought to identify all prospective clinical studies reporting complications associated with lumbar open microdiscectomy, microendoscopic discectomy (MED), and percutaneous microdiscectomy. METHODS The authors conducted MEDLINE, Scopus, Web of Science, and Embase database searches for randomized controlled trials and prospective cohort studies reporting complications associated with open, microendoscopic, or percutaneous lumbar microdiscectomy. Studies with fewer than 10 patients and published before 1990 were excluded. Overall and interstudy median complication rates were calculated for each surgical technique. The authors also performed a meta-analysis of the reported complications to assess statistical significance across the various surgical techniques. RESULTS Of 9504 articles retrieved from the databases, 42 met inclusion criteria. Most studies screened were retrospective case series, limiting the number of studies that could be included. A total of 9 complication types were identified in the included studies, and these were analyzed across each of the surgical techniques. The rates of any complication across the included studies were 12.5%, 13.3%, and 10.8% for open, MED, and percutaneous microdiscectomy, respectively. New or worsening neurological deficit arose in 1.3%, 3.0%, and 1.6% of patients, while direct nerve root injury occurred at rates of 2.6%, 0.9%, and 1.1%, respectively. Hematoma was reported at rates of 0.5%, 1.2%, and 0.6%, respectively. Wound complications (infection, dehiscence, orseroma) occurred at rates of 2.1%, 1.2%, and 0.5%, respectively. The rates of recurrent disc complications were 4.4%, 3.1%, and 3.9%, while reoperation was indicated in 7.1%, 3.7%, and 10.2% of operations, respectively. Meta-analysis calculations revealed a statistically significant higher rate of intraoperative nerve root injury following percutaneous procedures relative to MED. No other significant differences were found. CONCLUSIONS This review highlights complication rates among various microdiscectomy techniques, which likely reflect real-world practice and conceptualization of complications among physicians. This investigation sets the framework for further discussions regarding microdiscectomy options and their associated complications during the informed consent process.

Effect of a randomized controlled trial on the surgical treatment of spinal metastasis, 2000 through 2010: a population-based cohort study.

BACKGROUND: The effect of randomized controlled trials (RCT) on clinical practice patterns and patient outcomes is understudied. A 2005 RCT by Patchell et al demonstrated benefit for surgical decompression in patients with spinal metastasis (SpM). We examined trends in spinal surgery for patients with SpM before and after publication of the Patchell RCT. METHODS: The Nationwide Inpatient Sample (NIS) was used to identify a 20% stratified sample of surgical SpM admissions to nonfederal United States hospitals from 2000 to 2004 and 2006 to 2010, excluding 2005 when the RCT was published. Propensity scores were generated and logistic regression analysis was performed to compare outcomes in pre- and post-RCT time periods. RESULTS: A total of 7404 surgical admissions were identified. The rate of spine surgery increased post-RCT from an average of 3.8% to 4.9% surgeries per metastatic admission per year (P = .03). Admissions in the post-RCT group were more likely to be non-Caucasian, lower income, Medicaid recipients, and have more medical comorbidities and a greater metastatic burden (P < .001). Logistic regression of the propensity-matched sample showed increased odds post-RCT for expensive hospital stay (2.9; 95% confidence interval [CI] = 2.6-3.4) and some complications, including neurologic (1.7; 95% CI = 1.1-2.8), venous thromboembolism (2.8; 95% CI = 1.9-4.2), and decubitis ulcers (15.4; 95% CI = 6.7-34.5). However, odds for in-hospital mortality decreased (0.6; 95% CI = 0.5-0.8). CONCLUSIONS: Surgery for SpM increased after publication of a positive RCT. A significantly greater proportion of patients with lower socioeconomic status, more comorbidities, and greater metastatic burden underwent surgery post-RCT. These patients experienced more postoperative complications and higher in-hospital charges but less in-hospital mortality.

Variations in cost calculations in spine surgery cost-effectiveness research.

OBJECT: Cost-effectiveness research in spine surgery has been a prominent focus over the last decade. However, there has yet to be a standardized method developed for calculation of costs in such studies. This lack of a standardized costing methodology may lead to conflicting conclusions on the cost-effectiveness of an intervention for a specific diagnosis. The primary objective of this study was to systematically review all cost-effectiveness studies published on spine surgery and compare and contrast various costing methodologies used. METHODS: The authors performed a systematic review of the cost-effectiveness literature related to spine surgery. All cost-effectiveness analyses pertaining to spine surgery were identified using the cost-effectiveness analysis registry database of the Tufts Medical Center Institute for Clinical Research and Health Policy, and the MEDLINE database. Each article was reviewed to determine the study subject, methodology, and results. Data were collected from each study, including costs, interventions, cost calculation method, perspective of cost calculation, and definitions of direct and indirect costs if available. RESULTS: Thirty-seven cost-effectiveness studies on spine surgery were included in the present study. Twenty-seven (73%) of the studies involved the lumbar spine and the remaining 10 (27%) involved the cervical spine. Of the 37 studies, 13 (35%) used Medicare reimbursements, 12 (32%) used a case-costing database, 3 (8%) used cost-to-charge ratios (CCRs), 2 (5%) used a combination of Medicare reimbursements and CCRs, 3 (8%) used the United Kingdom National Health Service reimbursement system, 2 (5%) used a Dutch reimbursement system, 1 (3%) used the United Kingdom Department of Health data, and 1 (3%) used the Tricare Military Reimbursement system. Nineteen (51%) studies completed their cost analysis from the societal perspective, 11 (30%) from the hospital perspective, and 7 (19%) from the payer perspective. Of those studies with a societal perspective, 14 (38%) reported actual indirect costs. CONCLUSIONS: Changes in cost have a direct impact on the value equation for concluding whether an intervention is cost-effective. It is essential to develop a standardized, accurate means of calculating costs. Comparability and transparency are essential, such that studies can be compared properly and policy makers can be appropriately informed when making decisions for our health care system based on the results of these studies.

Radio frequency identification (RFID) in health care: privacy and security concerns limiting adoption.

Radio frequency identification (RFID) technology has been implemented in a wide variety of industries. Health care is no exception. This article explores implementations and limitations of RFID in several health care domains: authentication, medication safety, patient tracking, and blood transfusion medicine. Each domain has seen increasing utilization of unique applications of RFID technology. Given the importance of protecting patient and data privacy, potential privacy and security concerns in each domain are discussed. Such concerns, some of which are inherent to existing RFID hardware and software technology, may limit ubiquitous adoption. In addition, an apparent lack of security standards within the RFID domain and specifically health care may also hinder the growth and utility of RFID within health care for the foreseeable future. Safeguarding the privacy of patient data may be the most important obstacle to overcome to allow the health care industry to take advantage of the numerous benefits RFID technology affords.

Regional and Institutional Practice Variations in Decompressive Spine Surgery for Patients with Penetrating Spinal Injury in the United States.

BACKGROUND: The surgical management of penetrating spinal injury (PSI) has been widely debated in the literature, and the benefit of decompressive surgery for neurological function remains controversial. No national guidelines exist for the PSI population, and surgical practice patterns are unknown. We studied regional and institutional trends in the surgical management of PSI in the United States from 1988 to 2011. METHODS: The National Inpatient Sample database was accessed to identify a 20% stratified sample of PSI admissions to US hospitals from 1988 to 2011. PSI patients were divided into surgical (SXPSI) and nonsurgical (NSXPSI) groups, and these groups were analyzed across several regional, institutional, and patient-related variables. RESULTS: A total of 6632 PSI admissions were identified between 1988 and 2011. Decreased age (P = 0.002) and male gender (P = 0.015) were significantly more common in SXPSI than NSXPSI. Surgical rates were higher in teaching hospitals (P < 0.001), large hospitals (P = 0.012), and non-Northeast region hospitals (P < 0.020). Surgical management was associated with decreased mortality, increased length of stay, and increased total hospital charges (P < 0.001). CONCLUSIONS: Decompressive surgery rates for PSI differ significantly across regions and institutions in the United States. Institutional bias, patient preferences, and regional practice patterns all influence decision-making in PSI. A lack of large outcome studies in PSI and the absence of national guidelines contribute to variation in practice patterns. Our study indicates the need for future studies to better describe outcomes in patients with PSI.

Dural arteriovenous fistulas masquerading as dural sinus thrombosis.

The authors report dural sinus thrombosis diagnosed in 2 patients based on noninvasive imaging results, which were revealed to be dural arteriovenous fistulas (DAVFs) diagnosed using digital subtraction (DS) angiography. The first patient was a 63-year-old man who presented with headaches. Magnetic resonance venography was performed and suggested dural sinus thrombosis of the left transverse sinus and jugular vein. He was administered warfarin anticoagulation therapy but then suffered multiple intracranial hemorrhages. A DS angiogram was requested for a possible dural sinus thrombectomy, but the DS angiogram revealed a DAVF. The patient underwent serial liquid embolization with complete obliteration of the DAVF. The second patient, an 11-year-old boy, also presented with headaches and was diagnosed with dural sinus thrombosis on MR imaging. A DS angiogram was also requested for a possible thrombectomy and revealed a DAVF. This patient underwent serial liquid embolization and eventual operative resection. These reports emphasize that different venous flow abnormalities can appear similar on noninvasive imaging and that proper diagnosis is critical to avoid contraindicated therapies.

Medical student involvement in website development.

BACKGROUND: The digital management of educational resources and information is becoming an important part of medical education. AIMS: At Vanderbilt University School of Medicine, two medical students sought to create a website for all medical students to act as each student's individual homepage. METHOD: Using widely available software and database technology, a highly customized Web portal, known as the VMS Portal, was created for medical students. Access to course material, evaluations, academic information, and community assets were customized for individual users. Modular features were added over the course of a year in response to student requests, monitoring of usage habits, and solicitation of direct student feedback. RESULTS: During the first 742 days of the VMS Portal's release, there were 209,460 student login sessions (282 average daily). Of 348 medical students surveyed (71% response rate), 84% agreed or strongly agreed that 'consolidated student resources made their lives easier' and 82% agreed or strongly agreed that their needs were represented by having medical students design and create the VMS Portal. CONCLUSION: In the VMS Portal project, medical students were uniquely positioned to help consolidate, integrate, and develop Web resources for peers. As other medical schools create and expand digital resources, the valuable input and perspective of medical students should be solicited.

Career guidance and the Web: bridging the gap between the AAMC careers in Medicine Web site and local career guidance programs.

BACKGROUND: Medical students face a difficult challenge choosing a specialty. The Web offers several advantages in guiding students in the decision-making process. DESCRIPTION: The Vanderbilt University School of Medicine created a school-specific Web site to complement the Association of American Medical College's Careers in Medicine program. The goals were: connecting students with institution-specific resources, providing students with information on specialty choices and residency preparation, and promoting an interactive Web-based tool. A student team developed the Web site over several months. The site incorporates tracking tools to assess usage. During the first 240 days of use, the Web site has had 3,782 sessions viewing 29,864 Web pages. Monthly usage has trended upward. CONCLUSIONS: Using the Web to provide school-specific career information can guide students in the difficult process of specialty selection. Future studies are required to assess the Web site's overall effectiveness and overall student satisfaction.

Prediction of hemodialysis sorbent cartridge urea nitrogen capacity and sodium release from in vitro tests.

In sorbent-based hemodialysis, factors limiting a treatment session are urea conversion capacity and sodium release from the cartridge. In vitro experiments were performed to model typical treatment scenarios using various dialyzers and 4 types of SORB sorbent cartridges. The experiments were continued to the point of column saturation with ammonium. The urea nitrogen removed and amount of sodium released in each trial were analyzed in a multi-variable regression against several variables: amount of zirconium phosphate (ZrP), dialysate flow rate (DFR), simulated blood flow rate (BFR), simulated patient whole-body fluid volume (V), initial simulated patient urea concentration (BUNi), dialyzer area permeability (KoA) product, initial dialysate sodium and bicarbonate (HCO3i) concentrations, initial simulated patient sodium (Nai), pH of ZrP, creatinine, breakthrough time, and average urea nitrogen concentration in dialysate. The urea nitrogen capacity (UNC) of various new SORB columns is positively related to ZrP, BFR, V, BUNi, and ZrP pH and negatively to DFR with an R2 adjusted=0.990. Two models are described for sodium release. The first model is related positively to DFR and V and negatively to ZrP, KoA product, and dialysate HCO3i with an R2 adjusted=0.584. The second model incorporates knowledge of initial simulated patient sodium (negative relationship) and urea levels (negative relationship) in addition to the parameters in the first model with an R2 adjusted=0.786. These mathematical models should allow for prediction of patient sodium profiles and the time of column urea saturation based on simple inputs relating to patient chemistries and the dialysis treatment.

Physicians' response to guided geriatric dosing: initial results from a randomized trial.

Guided dosing within a computerized provider order entry (CPOE) system is an effective method of individualizing therapy for patients. Physicians' responses to guided dosing decision support have not been extensively studied. As part of a randomized trial evaluating efficacy of dosing advice on reducing falls in the elderly, CPOE prompts to physicians for 88 drugs included tailored messages and guided dose lists with recommended initial doses and frequencies. The study captured all prescribing activity electronically. The primary outcome was the ratio between prescribed dose and recommended dose. Over 9 months, 778 providers entered 9111 study-related medication orders on 2981 patients. Physicians using guided orders chose recommended doses more often than controls(28.6% vs. 24.1%, p<0.001). Selected doses were significantly lower in the intervention group (median ratio of actual to recommended 2.5, interquartile range [1.0,4.0]) than the control group (median 3.0 interquartile range [1.5,5.0], p<0.001). While physicians selected the recommended dose less than a third of the time, guided geriatric dosing modestly improved compliance with guidelines.

Value in Single-level Lumbar Discectomy: Surgical Disposable Item Cost and Relationship to Patient-reported Outcomes.

STUDY DESIGN: This is a retrospective study. OBJECTIVE: Compare improvements in health status measures (HSMs) and surgical costs to determine whether use of more costly items has any relationship to clinical outcome and value in lumbar disc surgery. SUMMARY OF BACKGROUND DATA: Association between cost, outcomes, and value in spine surgery, including lumbar discectomy is poorly understood. Outcomes were calculated as difference in mean HSM scores between preoperative and postoperative timeframes. Prospective validated patient-reported HSMs studied were EuroQol quality of life index score (EQ-5D), Pain Disability Questionnaire (PDQ), and Patient Health Questionnaire (PHQ-9). Surgical costs consisted of disposable items and implants used in operating room. METHODS: We retrospectively identified all adult patients at Cleveland Clinic main campus between October 2009 and August 2013 who underwent lumbar discectomy (652) using administrative billing data, Current Procedural Terminology (CPT) code 63030. HSMs were obtained from Cleveland Clinic Knowledge Program Data Registry. RESULTS: In total, 67% of operations performed in the outpatient or ambulatory setting, 33% in the inpatient setting. Among 9 surgeons who performed >10 lumbar discectomies, there were 72.4 operations per surgeon, on average. Mean surgical costs of each surgeon differed (P<0.0001). In a multivariable regression, only the surgeon and surgery type (outpatient or inpatient) were statistically correlated with surgical costs (P<0.0001 and 0.046, respectively). Changes in EQ-5D, PDQ, and PHQ-9 were not correlated with surgical costs (P=0.76, 0.07, 0.76, respectively). In multivariable regression, only surgical cost was significantly correlated to mean difference in PDQ (P=0.030). More costly surgeries resulted in worse PDQ outcomes. CONCLUSIONS: Mean surgical costs varied statistically among 9 surgeons; costs were not shown to be positively correlated with patient outcomes. Performing an operation using more costly disposable supplies/implants does not seem to improve patient outcomes and should be considered when constructing preference cards and during an operation.

Dysphagia Rates after Anterior Cervical Diskectomy and Fusion: A Systematic Review and Meta-Analysis.

STUDY DESIGN: Systematic review and meta-analysis. OBJECTIVE: Anterior cervical diskectomy and fusion (ACDF) is an effective surgical option for patients with cervical radiculopathy, myelopathy, or deformity. Although ACDF is generally safe, dysphagia is a common complication. Despite its high incidence, prolonged postoperative dysphagia is poorly understood; its etiology remains relatively unknown, and its risk factors are widely debated. METHODS: We searched MEDLINE, Scopus, Web of Science, and Embase for studies reporting complications for cervical diskectomy with plating. We recorded dysphagia events from all included studies and calculated effect summary values, 95% confidence intervals (CIs), Q values, and I2 values. RESULTS: Of the 7,780 retrieved articles, 14 met inclusion criteria. The overall dysphagia rate was 8.5% (95% CI 5.7 to 11.3%). The rate of moderate or severe dysphagia was 4.4% (0.4 to 8.4%). Follow-up times of <12, 12 to 24, and >24 months reported rates of 19.9% (6.0 to 33.7%), 7.0% (5.2 to 8.7%), and 7.6% (1.4 to 13.8%), respectively. Studies utilizing the Bazaz Dysphagia Score resulted in an increase in dysphagia diagnosis relative to studies with no outlined criteria (19.8%, 5.9 to 33.7% and 6.9%, 3.7 to 10.0%, respectively), indicating that the criteria used for dysphagia identification are critical. There was no difference in dysphagia rate with the use of autograft versus allograft. CONCLUSIONS: This review represents a comprehensive estimation of the actual incidence of dysphagia across a heterogeneous group of surgeons, patients, and criteria. The classification scheme for dysphagia varied significantly within the literature. To ensure its diagnosis and identification, we recommend the use of a standardized, well-outlined method for dysphagia diagnosis.

Propensity-matched Analysis of Outcomes and Hospital Charges for Anterior Versus Posterior Cervical Fusion for Cervical Spondylotic Myelopathy.

STUDY DESIGN: Retrospective analysis of data from the Nationwide Inpatient Sample, a nationally representative, all-payer database of inpatient diagnoses and procedures in the United States. OBJECTIVE: The objective of this study is to compare anterior cervical fusion (ACF) to posterior cervical fusion (PCF) in the treatment of cervical spondylotic myelopathy (CSM). SUMMARY OF BACKGROUND DATA: Previous studies used retrospective single-institution level data to quantify outcomes for CSM patients fusion. It is unclear whether ACF or PCF is superior with regards to charges or outcomes for the treatment of CSM. MATERIALS AND METHODS: We used Nationwide Inpatient Sample data to compare ACF to PCF in the management of CSM. All patients 18 years or older with a diagnosis of CSM between 1998 and 2011 were included. ACF patients were matched to PCF patients using propensity scores based on patient characteristics (number of levels fused, spine alignment, comorbidities), hospital characteristics, and patient demographics. Multivariable regression was used to measure the effect of treatment assignment on in-hospital charges, length of hospital stay, in-hospital mortality, discharge disposition, and dysphagia diagnosis. RESULTS: From 1998 to 2011, we identified 109,728 hospitalizations with a CSM diagnosis. Of these patients, 45,629 (41.6%) underwent ACF and 14,439 (13.2%) underwent PCF. The PCF cohort incurred an average of $41,683 more in-hospital charges (P<0.001, inflation adjusted to 2011 dollars) and remained in hospital an average of 2.4 days longer (P<0.001) than the ACF cohort. The ACF cohort was just as likely to die in the hospital [odds ratio 0.91; 95% confidence interval (CI), 0.68-1.2], 3.0 times more likely to be discharged to home or self-care (95% CI, 2.9-3.2), and 2.5 times more likely to experience dysphagia (95% CI, 2.0-3.1) than the PCF cohort. CONCLUSIONS: In treating CSM, ACF led to lower hospital charges, shorter hospital stays, and an increased likelihood of being discharged to home relative to PCF.

Trends in Inpatient Vertebroplasty and Kyphoplasty Volume in the United States, 2005-2011: Assessing the Impact of Randomized Controlled Trials.

STUDY DESIGN: Retrospective analysis of the Nationwide Inpatient Sample, 2005-2011. OBJECTIVE: To identify trends in procedural volume and rates in the time period surrounding publication of randomized controlled trials (RCTs) that examined the utility of vertebroplasty and kyphoplasty. SUMMARY OF BACKGROUND DATA: Vertebroplasty and kyphoplasty are frequently performed for vertebral compression fractures. Several RCTs have been published with conflicting outcomes regarding pain and quality of life compared with nonsurgical management and sham procedures. Four RCTs with discordant results were published in 2009. MATERIALS AND METHODS: The Nationwide Inpatient Sample provided longitudinal, retrospective data on United States' inpatients between 2005 and 2011. Inclusion was determined by a principal or secondary International Classification of Diseases, Ninth Revision, Clinical Modification code of 81.65 (percutaneous vertebroplasty) or 81.66 (percutaneous vertebral augmentation; "kyphoplasty"). No diagnoses were excluded. Years were stratified as "pre" (2005-2008) and "post" (2010-2011) in relation to the 4 RCTs published in 2009. Patient, hospital, and admission characteristics were compared using Pearson χ test. RESULTS: The estimated annual inpatient procedures performed decreased from 54,833 to 39,832 in the pre and post periods, respectively. The procedural rate for fractures decreased from 20.1% to 14.7% (P<0.0001). Patient and hospital demographics did not change considerably between the time periods. In the post period, weekend admissions increased (34.2% vs. 12.4%, P<0.0001), elective admissions decreased (21.4% vs. 40.0%, P<0.0001), routine discharge decreased (33.0% vs. 52.1%, P<0.0001), and encounters with ≥3 Elixhauser comorbidities increased (54.5% vs. 39.1%, P<0.0001). CONCLUSIONS: The absolute rate of inpatient vertebroplasty and kyphoplasty procedures for fractures decreased 5% in the period (2010-2011) following the publication of 4 RCTs in 2009. The proportion of elective admissions and routine discharges decreased, possibly indicating a population with greater disease severity. Although our analysis cannot demonstrate a cause-and-effect relationship, the decreased inpatient volume and procedural rates surrounding the publication of sentinel negative RCTs is clearly observed.

Insurance status and reportable quality metrics in the cervical spine fusion population.

BACKGROUND CONTEXT: The incidence of adverse care quality events among patients undergoing cervical fusion surgery is unknown using the definition of care quality employed by the Centers for Medicare and Medicaid Services (CMS). The effect of insurance status on the incidence of these adverse quality events is also unknown. PURPOSE: This study determined the incidence of hospital-acquired conditions (HAC) and patient safety indicators (PSI) in patients with cervical spine fusion and analyzed the association between primary payer status and these adverse events. STUDY DESIGN: This is a retrospective cohort design. PATIENT SAMPLE: All patients in the Nationwide Inpatient Sample (NIS) aged 18 and older who underwent cervical spine fusion from 1998 to 2011 were included. OUTCOME MEASURES: Incidence of HAC and PSI from 1998 to 2011 served as outcome variables. METHODS: We queried the NIS for all hospitalizations that included a cervical fusion during the inpatient episode from 1998 to 2011. All comparisons were made between privately insured patients and Medicaid or self-pay patients because Medicare enrollment is confounded with age. Incidence of nontraumatic HAC and PSI was determined using publicly available lists of International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis codes. We built logistic regression models to determine the effect of primary payer status on PSI and nontraumatic HAC. RESULTS: We identified 419,424 hospitalizations with cervical fusion performed during an inpatient episode. The estimated national incidences of nontraumatic HAC and PSI were 0.35% and 1.6%, respectively. After adjusting for patient demographics and hospital characteristics, Medicaid or self-pay patients had significantly greater odds of experiencing one or more HAC (odds ratio [OR] 1.51 95% conflict of interest [CI] 1.23-1.84) or PSI (OR 1.52 95% CI 1.37-1.70) than the privately insured cohort. CONCLUSIONS: Among patients undergoing inpatient cervical fusion, primary payer status predicts PSI and HAC (both indicators of adverse health-care quality used to determine hospital reimbursement by CMS). As the US health-care system transitions to a value-based payment model, the cause of these disparities must be studied to improve the quality of care delivered to vulnerable patient populations.

Design and implementation of a web-based, database-driven histology atlas: technology at work.

At Vanderbilt University, the "Human Cell and Tissue Biology" course is a required lecture and laboratory course with 2 full-time instructors and 106 students. To address demands placed on faculty for individual attention, an interactive Web-based histology atlas was developed and implemented in January 2005. This atlas was specifically designed to complement the existing laboratory manual and to transform the manual into an interactive educational tool whereby students could view high-resolution images of histological specimens online. By utilizing a computer scripting language, interactive highlighting of histological structures was accomplished through the implementation of a simple mouse-rollover function. This computer-aided instruction software allows students to preview histological structures of interest prior to entering the laboratory, to have additional faculty-directed contact hours during laboratory, and to review material efficiently. The conversion of the originally developed static application into a database-driven tool streamlined the development and modification of the atlas while facilitating the creation of advanced features. Six weeks after launching this interactive atlas, Vanderbilt medical students logged 1,200 hr of use. Through the cooperative efforts of faculty and students, the interactive atlas evolved to meet the educational demands of medical students owing to the development and implementation of a database structure. The functionality and educational value of the interactive atlas in facilitating self-learning was ultimately measured by positive student feedback and use.

Predictors of outcomes and hospital charges following atlantoaxial fusion.

BACKGROUND CONTEXT: Atlantoaxial fusion is used to correct atlantoaxial instability that is often secondary to traumatic fractures, Down syndrome, or rheumatoid arthritis. The effect of age and comorbidities on outcomes following atlantoaxial fusion is unknown. PURPOSE: This study aimed to better understand trends and predictors of outcomes and charges following atlantoaxial fusion and to identify confounding variables that should be included in future prospective studies. STUDY DESIGN: A retrospective analysis of data from the Nationwide Inpatient Sample (NIS), a nationally representative, all-payer database of inpatient diagnoses and procedures in the United States. PATIENT SAMPLE: We included all patients who underwent atlantoaxial fusion (International Classification of Disease, Ninth Revision, Clinical Modification code 81.01) between 1998 and 2011 who were 18 years or older at the time of admission. OUTCOME MEASURES: Outcome measures included in-hospital charges, hospital length of stay (LOS), in-hospital mortality, and discharge disposition. METHODS: Predictors of outcome following atlantoaxial fusion were assessed using a series of univariable analyses. Those predictors with a p-value of less than .2 were included in the final multivariable models. Independent predictors of outcome were those that were significant at an alpha level of 0.05 following inclusion in the final multivariable models. Logistic regression was used to determine predictors of in-hospital mortality and discharge disposition whereas linear regression was used to determine predictors of hospital charges and LOS. Discharge weights were used to produce generalizable results. RESULTS: From 1998 to 2011, there were 8,914 hospitalizations recorded wherein atlantoaxial fusion was performed during the inpatient hospital stay. Of these hospitalizations, 8,189 (91.9%) met inclusion criteria. Of the study sample, 62% was white, and the majority of patients were either insured by Medicare (47.2%) or had private health insurance (35.6%). The most common comorbidity as defined by the NIS and the Elixhauser comorbidity index was hypertension (43.2%). The in-hospital mortality rate for the study population was 2.7%, and the median LOS was 6.0 days. The median total charge (inflation adjusted) per hospitalization was $73,561. Of the patients, 48.9% were discharged to home. Significant predictors of in-hospital mortality included increased age, emergent or urgent admissions, weekend admissions, congestive heart failure, coagulopathy, depression, electrolyte disorder, metastatic cancer, neurologic disorder, paralysis, and non-bleeding peptic ulcer. Many of these variables were also found to be predictors of LOS, hospital charges, and discharge disposition. CONCLUSION: This study found that older patients and those with greater comorbidity burden had greater odds of postoperative mortality and were being discharged to another care facility, had longer hospital LOS, and incurred greater hospital charges following atlantoaxial fusion.

Predicting dialysate sodium composition in sorbent dialysis using single point and multiple-dilution conductivity measurement.

This research establishes the ability to predict the sodium composition in dialysate from a single conductivity measurement over the wide range of concentrations of chloride, bicarbonate, and acetate that occur during sorbent dialysis. The ranges explored in mEq/L were sodium 100-180, chloride 76-143, bicarbonate 16-31, and acetate 4-11. Through mathematical optimization using a pattern search method, a single point measurement technique was shown to predict the total sodium concentration within approximately +/- 4.2 mEq/L in solutions with varying relative concentrations of chloride, bicarbonate, and acetate. The data analysis showed that the total sodium concentration can be predicted within +/- 2.1 mEq/L in most cases. Another potential approach to determining sodium concentration, a multiple-dilution measurement method, was tested and is also described. It is based on the varying relationship of activity to concentration for each of the sodium-anion pairs. This technique has practical limitations because of interactions between the various ions in solution at normal concentrations of dialysis along with the complexities involved in creating high dilutions of dialysate for on-line assays during dialysis.

Thoracic range of motion, stability, and correlation to imaging-determined degeneration.

OBJECT The degenerative process of the spinal column results in instability followed by a progressive loss of segmental motion. Segmental degeneration is associated with intervertebral disc and facet changes, which can be quantified. Correlating this degeneration with clinical segmental motion has not been investigated in the thoracic spine. The authors sought to determine if imaging-determined degeneration would correlate with native range of motion (ROM) or the change in ROM after decompressive procedures, potentially guiding clinical decision making in the setting of spine trauma or following decompressive procedures in the thoracic spine. METHODS Multidirectional flexibility tests with image analysis were performed on thoracic cadaveric spines with intact ib cage. Specimens consisted of 19 fresh frozen human cadaveric spines, spanning C-7 to L-1. ROM was obtained for each specimen in axial rotation (AR), flexion-extension (FE), and lateral bending (LB) in the intact state and following laminectomy, unilateral facetectomy, and unilateral costotransversectomy performed at either T4-5 (in 9 specimens) or T8-9 (in 10 specimens). Image grading of segmental degeneration was performed utilizing 3D CT reconstructions. Imaging scores were obtained for disc space degeneration, which quantified osteophytes, narrowing, and endplate sclerosis, all contributing to the Lane disc summary score. Facet degeneration was quantified using the Weishaupt facet summary score, which included the scoring of facet osteophytes, narrowing, hypertrophy, subchondral erosions, and cysts. RESULTS The native ROM of specimens from T-1 to T-12 (n = 19) negatively correlated with age in AR (Pearson's r coefficient = -0.42, p = 0.070) and FE (r = -0.42, p = 0.076). When regional ROM (across 4 adjacent segments) was considered, the presence of disc osteophytes negatively correlated with FE (r = -0.69, p = 0.012), LB (r = -0.82, p = 0.001), and disc narrowing trended toward significance in AR (r = -0.49, p = 0.107). Facet characteristics, scored using multiple variables, showed minimal correlation to native ROM (r range from -0.45 to +0.19); however, facet degeneration scores at the surgical level revealed strong negative correlations with regional thoracic stability following decompressive procedures in AR and LB (Weishaupt facet summary score: r = -0.52 and r = -0.71; p = 0.084 and p = 0.010, respectively). Disc degeneration was not correlated (Lane disc summary score: r = -0.06, p = 0.861). CONCLUSIONS Advanced age was the most important determinant of decreasing native thoracic ROM, whereas imaging characteristics (T1-12) did not correlate with the native ROM of thoracic specimens with intact rib cages. Advanced facet degeneration at the surgical level did correlate to specimen stability following decompressive procedures, and is likely indicative of the terminal stages of segmental degeneration.