Machine Learning Approaches to Define Candidates for Ambulatory Single Level Laminectomy Surgery

STUDY DESIGN

retrospective cohort study.

OBJECTIVES

To test and compare 2 machine learning algorithms to define characteristics associated with candidates for ambulatory same day laminectomy surgery.

METHODS

The American College of Surgeons National Surgical Quality Improvement Program database was queried for patients who underwent single level laminectomy in 2017 and 2018. The main outcome was ambulatory same day discharge. Study variables of interest included demographic information, comorbidities, preoperative laboratory values, and intra-operative information. Two machine learning predictive modeling algorithms, artificial neural network (ANN) and random forest, were trained to predict same day discharge. The quality of models was evaluated with area under the curve (AUC), accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) measures.

RESULTS

Among 35,644 patients, 13,230 (37.1%) were discharged on the day of surgery. Both ANN and RF demonstrated a satisfactory model quality in terms of AUC (0.77 and 0.77), accuracy (0.69 and 0.70), sensitivity (0.83 and 0.58), specificity (0.55 and 0.80), PPV (0.77 and 0.69), and NPV (0.64 and 0.70). Both models highlighted several important predictive variables, including age, duration of operation, body mass index and preoperative laboratory values including, hematocrit, platelets, white blood cells, and alkaline phosphatase.

CONCLUSION

Machine learning approaches provide a promising tool to identify candidates for ambulatory laminectomy surgery. Both machine learning algorithms highlighted the as yet unrecognized importance of preoperative laboratory testing on patient pathway design.

The Use of Critical Care Services After Orthopedic Surgery at a High-Volume Orthopedic Medical Center: A Retrospective Study

Background: With an aging population, orthopedics has become one of the largest and fastest growing surgical fields. However, data on the use of critical care services (CCS) in patients undergoing orthopedic procedures remain sparse. Purpose: We sought to elucidate the prevalence and characteristics of patients requiring CCS and intermediate levels of care after orthopedic surgeries at a high-volume orthopedic medical center. Methods: We retrospectively reviewed inpatient electronic medical record data (2016-2020) at a high-volume orthopedic hospital. Patients who required CCS and intermediate levels of care, including step-down unit (SDU) and telemetry services, were identified. We described characteristics related to patients, procedures, and outcomes, including type of advanced services required and surgery type. Results: Of the 50,387 patients who underwent orthopedic inpatient surgery, 1.6% required CCS and 21.6% were admitted to an SDU. Additionally, 482 (1.0%) patients required postoperative mechanical ventilation and 3602 (7.1%) patients required continuous positive airway pressure therapy. Spine surgery patients were the most likely to require any form of advanced care (45.7%). Conclusions: This retrospective review found that approximately one-fourth of orthopedic surgery patients were admitted to units that provided critical and intermediate levels of care. These results may prove useful to hospitals in estimating needs and allocating resources for advanced and critical care services after orthopedic surgery.

Tramadol prescribed at discharge is associated with lower odds of chronic opioid use after elective total joint arthroplasty

INTRODUCTION

We aimed to study the association between tramadol prescribed at discharge (after elective total hip and knee arthroplasty (THA/TKA) surgery) and chronic opioid use postoperatively.

METHODS

This retrospective cohort study queried the Truven MarketScan database and identified patients who underwent an elective THA/TKA surgery between 2016 and 2018 and were prescribed opioids at discharge (n=81 049). Multivariable analysis was conducted to study the association between tramadol prescription at discharge and chronic opioid use, with additional analysis adjusting for the amount of opioids prescribed in oral morphine equivalents. Chronic opioid use was defined as filling ≥10 opioid prescriptions or prescriptions for ≥120 pills within the period from 90 days to 1 year after surgery.

RESULTS

Overall, tramadol was prescribed at discharge in 11.0% of all THA/TKA cases. Of those, 26.9% and 73.1% received tramadol only or tramadol with another opioid, respectively. Chronic opioid use was observed in 5.4% of cases. After adjustment for relevant covariates, prescription of tramadol combined with another opioid at discharge was associated with lower odds of chronic opioid use comparing to prescription of other opioids (OR 0.69 CI 0.61 to 0.78).

DISCUSSION

Among patients undergoing elective THA/TKA surgery and discharged with a prescription of opioids, we found that prescription of tramadol combined with another opioid was associated with lower odds of chronic opioid use. This finding must be considered in the context of the tramadol's pharmacology, as well-described genetic differences in metabolism that can make it ineffective in many patients, while for patients with ultrarapid metabolism can cause drug-drug interactions and adverse events, including feelings of high and seizures.

Machine learning approaches in predicting ambulatory same day discharge patients after total hip arthroplasty

BACKGROUND

With continuing financial and regulatory pressures, practice of ambulatory total hip arthroplasty is increasing. However, studies focusing on selection of optimal candidates are burdened by limitations related to traditional statistical approaches. Hereby we aimed to apply machine learning algorithm to identify characteristics associated with optimal candidates.

METHODS

This retrospective cohort study included elective total hip arthroplasty (n=63 859) recorded in National Surgical Quality Improvement Program dataset from 2017 to 2018. The main outcome was length of stay. A total of 40 candidate variables were considered. We applied machine learning algorithms (multivariable logistic regression, artificial neural networks, and random forest models) to predict length of stay=0 day. Models' accuracies and area under the curve were calculated.

RESULTS

Applying machine learning models to compare length of stay=0 day to length of stay=1-3 days cases, we found area under the curve of 0.715, 0.762, and 0.804, accuracy of 0.65, 0.73, and 0.81 for logistic regression, artificial neural networks, and random forest model, respectively. Regarding the most important predictive features, anesthesia type, body mass index, age, ethnicity, white blood cell count, sodium level, and alkaline phosphatase were highlighted in machine learning models.

CONCLUSIONS

Machine learning algorithm exhibited acceptable model quality and accuracy. Machine learning algorithms highlighted the as yet unrecognized impact of laboratory testing on future patient ambulatory pathway assignment.

Differential Perioperative Outcomes in Patients With Obstructive Sleep Apnea, Obesity, or a Combination of Both Undergoing Open Colectomy: A Population-Based Observational Study

BACKGROUND

An increasing body of evidence demonstrates an association between obstructive sleep apnea (OSA) and adverse perioperative outcomes. However, large-scale data on open colectomies are lacking. Moreover, the interaction of obesity with OSA is unknown. This study examines the impact of OSA, obesity, or a combination of both, on perioperative complications in patients undergoing open colectomy. We hypothesized that while both obesity and OSA individually increase the likelihood for perioperative complications, the overlap of the 2 conditions is associated with the highest risk.

METHODS

Patients undergoing open colectomies were identified using the national Premier Healthcare claims-based Database (2006-2016; n = 340,047). Multilevel multivariable models and relative excess risk due to interaction (RERI) analysis quantified the impact of OSA, obesity, or both on length and cost of hospitalization, respiratory and cardiac complications, intensive care unit (ICU) admission, mechanical ventilation, and inhospital mortality.

RESULTS

Nine thousand twenty-eight (2.7%) patients had both OSA and obesity diagnoses; 10,137 (3.0%) had OSA without obesity; and 33,692 (9.9%) had obesity without OSA. Although there were overlapping confidence intervals in the binary outcomes, the risk increase was found highest for OSA with obesity, intermediate for obesity without OSA, and lowest for OSA without obesity. The strongest effects were seen for respiratory complications: odds ratio (OR), 2.41 (2.28-2.56), OR, 1.40 (1.31-1.49), and OR, 1.50 (1.45-1.56), for OSA with obesity, OSA without obesity, and obesity without OSA, respectively (all P < .0001). RERI analysis revealed a supraadditive effect of 0.51 (95% confidence interval [CI], 0.34-0.68) for respiratory complications, 0.11 (-0.04 to 0.26) for cardiac complications, 0.30 (0.14-0.45) for ICU utilization, 0.34 (0.21-0.47) for mechanical ventilation utilization, and 0.26 (0.15-0.37) for mortality in patients with both OSA and obesity, compared to the sum of the conditions' individual risks. Inhospital mortality was significantly higher in patients with both OSA and obesity (OR [CI], 1.21 [1.07-1.38]) but not in the other groups.

CONCLUSIONS

Both OSA and obesity are individually associated with adverse perioperative outcomes, with a supraadditive effect if both OSA and obesity are present. Interventions, screening, and perioperative precautionary measures should be tailored to the respective risk profile. Moreover, both conditions appear to be underreported compared to the general population, highlighting the need for stringent perioperative screening, documentation, and reporting.

The Impact of Immunization and Use of Oseltamivir on Influenza-Related Hospitalizations: A Population-Based Study

Background

As the COVID-19 pandemic continues into flu season, it is critical to minimize hospitalizations to maximize capacity and preserve critical care resources. We sought to identify risk factors for influenza-related hospitalization, specifically the role of immunization and oseltamivir prescriptions.

Methods

Patients with influenza diagnoses were identified from the MarketScan database (2014-2018). Primary risk factors of interest were an influenza vaccination within 6 months prior to infection and oseltamivir prescriptions (filled on the day diagnosis, the following day, or 2-5 days). A multivariable logistic regression model was run to identify risk factors for influenza-related hospitalizations within 30 days of diagnosis.

Results

Among 2 395 498 influenza infections, 0.27% were hospitalized. Of those prescribed oseltamivir the day of diagnosis, 0.13% were later hospitalized, compared to 0.67% among those who filled prescriptions the following day and 11.8% when filled within 2 to 5 days. Upon adjustment, oseltamivir prescriptions filled on the day of diagnosis were associated with significantly decreased odds of hospitalization (OR 0.51 CI 0.48-0.55). Prescriptions filled within 1 to 5 days of diagnosis were associated with significantly increased odds of hospitalization (1 day OR 2.01 CI 1.81-2.24; 2-5 days OR 34.1 CI 31.7-36.6). Flu vaccination was associated with a lower odds for hospitalization (OR 0.84 CI 0.74-0.95).

Conclusions

We recommend oseltamivir be prescribed to patients when they first present with influenza-like symptoms to reduce the burden on the healthcare system. We also identified reduced odds of hospitalization associated with influenza vaccination, which is already well established, but particularly important this coming flu season.

Hip fracture characteristics and outcomes during COVID-19: a large retrospective national database review

Background

The COVID-19 pandemic has impacted healthcare in various vulnerable patient subpopulations. However, data are lacking on the impact of COVID-19 on hip fractures, seen mainly in older patients. Using national claims data, we aimed to describe the epidemiology during the first COVID-19 wave in the USA.

Methods

We compared patients admitted for hip fractures during March and April of 2020 with those admitted in 2019 in terms of patient and healthcare characteristics, COVID-19 diagnosis, and outcomes. An additional comparison was made between COVID-19-positive and -negative patients. Outcomes included length of hospital stay (LOS), admission to an ICU, ICU LOS, use of mechanical ventilation, 30-day readmission, discharge disposition, and a composite variable of postoperative complications.

Results

Overall, 16 068 hip fractures were observed in 2019 compared with 7498 in 2020. Patients with hip fractures in 2020 (compared with 2019) experienced earlier hospital discharge and were less likely to be admitted to ICU, but more likely to be admitted to home. Amongst 83 patients with hip fractures with concomitant COVID-19 diagnosis, we specifically observed more non-surgical treatments, almost doubled LOS, a more than 10-fold increased mortality rate, and higher complication rates compared with COVID-19-negative patients.

Conclusions

The COVID-19 pandemic significantly impacted not only volume of hip fractures, but also patterns in care and outcomes. These results may inform policymakers in future outbreaks and how this may affect vulnerable patient populations, such as those experiencing a hip fracture.

Association between sex and perioperative opioid prescribing for total joint arthroplasty: a retrospective population-based study

BACKGROUND

Scarce data exist on differential opioid prescribing between men and women in the pre-, peri-, and postoperative phases of care among patients undergoing total hip/knee arthroplasty (THA/TKA).

METHODS

In this retrospective population-based study, Truven Health MarketScan claims data were used to establish differences between men and women in (1) opioid prescribing in the year before THA/TKA surgery, (2) the amount of opioids prescribed at discharge, and (3) chronic opioid prescribing (3-12 months after surgery). Multivariable regression models measured odds ratios (OR) with 95% confidence intervals (95% CI).

RESULTS

Among 29 038 THAs (42% men) and 48 523 TKAs (52% men) men (compared with women) were less likely to receive an opioid prescription in the year before surgery (54% vs 60%, and 54% vs 60% for THA and TKA, respectively); P<0.001. However, in multivariable analyses male sex was associated with higher total opioid dosages prescribed at discharge after THA (OR=1.04; 95% CI 1.03, 1.06) and TKA (OR=1.05; 95% CI 1.04, 1.06); both P<0.001. Chronic opioid prescribing was found in 10% of the cohort (THA: n=2333; TKA: n=5365). Here, men demonstrated lower odds of persistent opioid prescribing specifically after THA (OR=0.90; 95% CI 0.82, 0.99) but not TKA (OR=0.96; 95% CI 0.90, 1.02); P=0.026 and P=0.207, respectively.

CONCLUSIONS

We found sex-based differences in opioid prescribing across all phases of care for THA/TKA. The results highlight temporal opportunities for targeted interventions to improve outcomes after total joint arthroplasty, particularly for women, and to decrease chronic opioid prescribing.

Tranexamic Acid Administration is Associated With a Decreased Odds of Prosthetic Joint Infection Following Primary Total Hip and Primary Total Knee Arthroplasty: A National Database Analysis

BACKGROUND

Tranexamic acid (TXA) for the reduction of blood loss in orthopedic surgery is coming into greater adoption. Because TXA administration lowers the incidence of blood transfusion and of hematoma formation, risk factors for infection, we asked whether TXA use might be associated with a lower incidence of periprosthetic joint infection (PJI) following orthopedic surgery.

METHODS

We queried the Premier Healthcare database for ICD-9 codes corresponding to elective inpatient primary total hip replacement (THR) or total knee replacement (TKR) from 2012 to 2016, TXA administration on the day of surgery, and PJI during the hospital stay or within 90 days. We performed a multilevel multivariable logistic regression (SAS version 9.4. SAS Institute, Cary, NC) to determine if TXA administration or other covariates were a significant predictor of infection.

RESULTS

Among 914,990 total joint arthroplasty patients, 46.0% received TXA on the day of surgery. 0.13% developed PJI within 90 days. After adjusting for patient and hospital-related covariates, TXA use was associated with significantly lower odds of PJI within 90 days of surgery (OR 0.49 [0.69, 0.91]).

CONCLUSION

Administration of TXA on the day of surgery in total knee and total hip arthroplasty was associated with a statistically significant decreased odds of PJI in the first 90 days. We therefore conclude that TXA might play an important role in our attempts to decrease PJI after joint arthroplasty. The exact mechanisms and ideal dosage by which TXA can contribute to such a reduction need further study.

Persistent opioid use after surgical treatment of paediatric fracture

BACKGROUND

The opioid epidemic is one of the most pressing public health crises in the USA. With fractures being amongst the most common reasons for a child to require surgical intervention and receive post-surgical pain management, characterisation of opioid prescription patterns and risk factors is critical. We hypothesised that the numbers of paediatric patients receiving opioids, or who developed persistent opioid use, are significant, and a number of risk factors for persistent opioid use could be identified.

METHODS

We conducted a retrospective population-based cohort study. National claims data from the Truven Health Analytics® MarketScan database were used to (i) characterise opioid prescription patterns and (ii) describe the epidemiology and risk factors for single use and persistent use of opioids amongst paediatric patients who underwent surgical intervention for fracture treatment.

RESULTS

Amongst 303 335 patients, 21.5% received at least one opioid prescription within 6 months after surgery, and 1671 (0.6%) developed persistent opioid use. Risk factors for persistent opioid use include older age; female sex; lower extremity trauma; surgeries involving the spine, rib cage, or head; closed fracture treatment; earlier surgery years; previous use of opioid; and higher comorbidity burden.

CONCLUSIONS

Amongst a cohort of paediatric patients who underwent surgical fracture treatment, 21.5% filled at least one opioid prescription, and 0.6% (N=1671) filled at least one more opioid prescription between 3 and 6 months after surgery. Understanding risk factors related to persistent opioid use can help clinicians devise strategies to counter the development of persistent opioid use for paediatric patients.

Trends in Comorbidities and Complications Among Patients Undergoing Hip Fracture Repair

BACKGROUND

Hip fracture patients represent various perioperative challenges related to their significant comorbidity burden and the high incidence of morbidity and mortality. As population trend data remain rare, we aimed to investigate nationwide trends in the United States in patient demographics and outcomes in patients after hip fracture repair surgery.

METHODS

After Institutional Review Board (IRB) approval (IRB#2012-050), data covering hip fracture repair surgeries were extracted from the Premier Healthcare Database (2006-2016). Patient demographics, comorbidities, and complications, as well as anesthesia and surgical details, were analyzed over time. Cochran-Armitage trend tests and simple linear regression assessed significance of (linear) trends.

RESULTS

Among N = 507,274 hip fracture cases, we observed significant increases in the incidence in preexisting comorbid conditions, particularly the proportion of patients with >3 comorbid conditions (33.9% to 43.4%, respectively; P < .0001). The greatest increase for individual comorbidities was seen for sleep apnea, drug abuse, weight loss, and obesity. Regarding complications, increased rates over time were seen for acute renal failure (from 6.9 to 11.1 per 1000 inpatient days; P < .0001), while significant decreasing trends for mortality, pneumonia, hemorrhage/hematoma, and acute myocardial infarction were recorded. In addition, decreasing trends were observed for the use of neuraxial anesthesia either used as sole anesthetic or combined with general anesthesia (7.3% to 3.6% and 6.3% to 3.4%, respectively; P < .0001). Significantly more patients (31.9% vs 41.3%; P < .0001) were operated on in small rather than medium- and large-sized hospitals.

CONCLUSIONS

From 2006 to 2016, the overall comorbidity burden increased among patients undergoing hip fracture repair surgery. Throughout this same time period, incidence of postoperative complications either remained constant or declined with the only significant increase observed in acute renal failure. Moreover, use of regional anesthesia decreased over time. This more comorbid patient population represents an increasing burden on the health care system; however, existing preventative measures appear to be effective in minimizing complication rates. Although, given the proposed benefits of regional anesthesia, decreased utilization may be of concern.

Bilateral Total Knee Arthroplasty and In-Hospital Opioid Dispension: A Population-Based Study

BACKGROUND

There is paucity of data regarding opioid dispension in patients undergoing bilateral total knee arthroplasty (BTKA). Our aim is to compare in-hospital opioid dispension between BTKA and unilateral TKA (UTKA) and to identify other factors associated with opioid dispension in the BTKA and UTKA cohorts.

METHODS

Patients receiving elective TKA from 2006 to 2016 were retrospectively extracted from the Premier Healthcare Database. The effect of interest was bilateral TKA. Our primary outcome was in-hospital opioid dispension in oral morphine equivalents. Univariable statistics between study variables and TKA type were obtained. A multilevel logistic regression model was run for the outcome of high opioid dispension.

RESULTS

A total of 1,029,120 patients were included. Among these, 14,469 (1.4%) underwent a BTKA. Within the 10-year period studied, there was a decrease in opioid dispension in both groups. Logistic regression analysis showed that patients treated with BTKA had 1.68 times higher odds for high opioid dispension compared to UTKA patients (odds ratio = 1.68; 95.5% confidence interval = 1.62, 1.75; P < .0001). White race, longer length of stay, Charlson/Deyo index, type of insurance, rural location, general anesthesia, peripheral nerve block use, and patient-controlled analgesia were also associated with high opioid dispension. Conversely, a more recent year of surgery, female gender, older age, and administration of nonsteroidal anti-inflammatory drugs and cyclooxygenase-2 inhibitors were associated with lower odds for high opioid dispension.

CONCLUSION

BTKA patients have increased odds for higher in-hospital opioid dispension compared to UTKA recipients. Utilization and prescribing habits should be examined to determine the optimal approach to opioid prescription in BTKA patients compared to UTKA.

The Utilization of Regional Anesthesia Among Pediatric Patients: A Retrospective Study

BACKGROUND

The use of regional anesthesia (RA) in pediatric patients remains understudied, although evidence suggests benefits over general anesthesia.

QUESTIONS/PURPOSES

We sought to identify factors associated with RA use in patients under the age of 21 years undergoing ambulatory orthopedic surgery.

METHODS

Patients under the age of 21 who underwent anterior cruciate ligament (ACL) repair or reconstruction, knee arthroscopy (KA), or shoulder arthroscopy (SA) were identified from the NY Statewide Planning and Research Cooperative System (SPARCS) database (2005-2015). Frequencies of RA use (defined by femoral nerve block, spinal, epidural, caudal, or brachial plexus anesthesia) were calculated. Multivariable regression analysis identified patient- and healthcare system-related factors associated with the use of RA. Odds ratios (OR) and 95% confidence intervals (CI) were reported.

RESULTS

We identified 87,273 patients who underwent the procedures of interest (ACL n = 28,226; SA n = 18,155; KA n = 40,892). In our primary analysis, 14.4% (n = 1404) had RA as their primary anesthetic; this percentage increased for patients who had ACL or KA. When adjusting for covariates, Hispanic ethnicity (OR 0.78; CI 0.65-0.94) and Medicaid insurance (OR 0.75; CI 0.65-0.87) were associated with decreased odds for the provision of RA. Further, we identified increasing age (OR 1.10; CI 1.08-1.11), ACL versus SA (OR 1.91; CI 1.74-2.10), and sports injuries (OR 1.20; CI 1.10-1.31) as factors associated with increased odds of RA use.

CONCLUSION

In this analysis, RA was used in a minority of patients under the age of 21 undergoing ambulatory orthopedic surgery. Older age was associated with increased use while Hispanic ethnicity and lower socioeconomic status were associated with lower use.

Return to Normal: Prioritizing Elective Surgeries With Low Resource Utilization

Supplemental Digital Content is available in the text.

Modifiable Analgesia-/Anesthesia-Related Factors and Risk of Severe Gastrointestinal Complications After Lower Extremity Total Joint Arthroplasty: A Nationwide Analysis

BACKGROUND

Severe gastrointestinal (GI) complications after elective hip and knee arthroplasty (THA/TKA) are rare. Some of them can be life-threatening and/or require emergency abdominal surgery. We studied the epidemiology of severe GI complications after THA/TKA and associations with anesthesia- and/or analgesia-related factors.

METHODS

We included 591,865 THA and 1,139,616 TKA cases (Premier Healthcare claims database; 2006-2016). Main outcomes were GI complications and related emergency surgeries within 30 days after THA/TKA. Anesthesia- and analgesia-related factors were anesthesia type (neuraxial, general), use of peripheral nerve block, patient-controlled analgesia, nonopioid analgesics (acetaminophen, gabapentin/pregabalin, nonsteroidal anti-inflammatory drugs, cyclooxygenase-2 inhibitors, ketamine), and opioids (in oral morphine equivalents, categorized into low, medium, and high use based on the interquartile range). Mixed-effects models measured associations between anesthesia- and analgesia-related factors and outcomes, which were reported using odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Among THA patients, GI complications were observed in 1.03% (n = 6103), with 0.08% (n = 450) requiring emergency surgery; this was 0.79% (n = 8971) and 0.05% (n = 540), respectively, for TKA patients. After adjustment for relevant covariates (including opioid use), almost all anesthesia-/analgesia-related factors were associated with significantly decreased odds of GI complications, specifically use of cyclooxygenase-2 inhibitors (OR 0.72 CI 0.67-0.76/OR 0.82 CI 0.78-0.86), nonsteroidal anti-inflammatory drugs (OR 0.81 CI 0.77-0.85/OR 0.90 CI 0.86-0.94), and peripheral nerve blocks (OR 0.77 CI 0.69-0.87/OR 0.91 CI 0.85-0.97); all for THA and TKA, respectively (all P < .01).

CONCLUSION

Rare, but devastating, acute GI complications (requiring surgery) after THA/TKA may be positively impacted by a variety of modifiable anesthesia-/analgesia-related interventions.

Increased Use of Intra-Articular Steroid Injection to Treat Osteoarthritis is Associated With Chronic Opioid Dependence After Later Total Knee Arthroplasty But Not Total Hip Arthroplasty

BACKGROUND

Intra-articular (IA) injections of corticosteroid (CO) and hyaluronic acid (HA) are commonly used for osteoarthritis. The efficacy of these interventions is controversial. Furthermore, research regarding the potential association of IA injection with later postoperative pain trajectories is lacking.

METHODS

We performed analysis on Truven Health MarketScan database (2012-2016) in total hip arthroplasty (THA) and total knee arthroplasty (TKA). Trends over time were assessed. Multivariable logistic regression analyses were executed to evaluate the impact of IA injections on postoperative chronic opioid use.

RESULTS

Preoperative CO and HA injections decreased throughout the study period in both THA and TKA. Preoperative CO and HA injections, regardless of frequency, had no significant impact on the odds of THA patients becoming chronic opioid users postoperatively. TKA patients who had 1 CO injection in the year before surgery experienced lower odds of postoperative chronic opioid use (odds ratio [OR], 0.89; 95% confidence interval [95% CI], 0.82-0.97), whereas patients who had 2 or more CO injections experienced significantly greater odds (OR, 1.14; 95% CI, 1.04-1.24). TKA patients who received 2 or more HA injections before surgery had significantly lower odds of chronic opioid use (OR, 0.90; 95% CI, 0.81-0.99).

CONCLUSION

The utilization of IA injections in patients with hip and knee osteoarthritis appears to be decreasing over time. TKA patients who received 2 or more preoperative CO injections experienced greater odds of chronic opioid utilization, whereas TKA patients with 2 or more HA injections in the year before surgery had decreased odds of chronic opioid use.

Tranexamic acid administration during total joint arthroplasty surgery is not associated with an increased risk of perioperative seizures: a national database analysis

Background

Tranexamic acid (TXA) has been used extensively to minimize blood loss in cardiac surgery and more recently in orthopedic surgery. Despite a generally good safety profile, an increased risk of seizures has been observed in patients with cardiac disease. However, this issue has not been adequately addressed in the orthopedic literature.

Methods

After institutional review board approval, we queried a large national database to identify patients who had undergone total hip and total knee arthroplasties (2012–2016). Patients were divided based on their exposure to TXA and history of seizures. The main outcome of interest was a perioperative seizure. We conducted univariable comparisons and a multivariable regression analysis to elucidate a potential independent association between TXA administration and seizures in the perioperative period (with or without a history of seizures).

Results

TXA was used overall in 45.9% (n=4 21 890) of joint arthroplasty recipients (n=9 18 918), with more frequent use over time. Utilization rates did not differ between those with and without a history of seizures; 42.2% (3487/8252) of patients with a seizure history received TXA. Rates of perioperative seizure were low and did not differ between those who did and did not receive TXA (0.01% vs 0.02%, p=0.11); when subgrouping patients by history of seizures, we found no difference in incidence of perioperative seizures between groups (0.06% vs 0.02%, p=0.39). Our adjusted analysis further confirmed these results.

Conclusion

Despite increasing TXA utilization in total joint arthroplasty, we found an overall low seizure incidence. TXA use was not associated with elevated odds of perioperative seizure, even in patients with history of seizure.

Cost of Care for Patients With Pre-Existing Comorbidities Undergoing Total Joint Arthroplasty: A Retrospective Cohort Study Evaluating Disease-Specific Perioperative Care

BACKGROUND

Investigations suggest a relationship between increased resource utilization with disease burden and advanced age. However, it remains unknown the degree increased resource utilization is associated with pre-existing conditions, before complications occur.

METHODS

This retrospective study identified total hip/knee arthroplasty cases in the Premier Database from 2006 to 2016 (N = 1,613,744), with hospitalization cost as the primary outcome. With a variable combining the conditions and complication, generalized linear models measured associations between condition/complication interaction groups and hospitalization cost. Estimates of percent cost increase by variable were obtained.

RESULTS

Across all conditions, an increase in cost ranging from 0.38% to 4.28% was found in the absence of a complication. The "Condition = No, Complication = Yes" group was associated with a range of 11.50%-12.40% increase in average hospitalization cost, and the range was 14.43%-30.85% for the "Condition = Yes, Complication = Yes" group.

CONCLUSION

We found that having a high-risk condition without a complication accounted only for a modest hospitalization cost increase.

Anaesthesia provider volume and perioperative outcomes in total joint arthroplasty surgery

BACKGROUND

While increased surgical-provider volume has been associated with improved outcomes, research regarding volume-outcome relationships within high-volume institutions and the role of anaesthesiologists is limited. Further, the effect of anaesthesia-care-team composition remains understudied. This analysis aimed to identify the impact of anaesthesiologist and surgeon volume on adverse events after total joint arthroplasties.

METHODS

We retrospectively identified 40 437 patients who underwent total joint arthroplasties at a high-volume institution from 2005 to 2014. The main effects of interest were anaesthesiologist and surgeon volume and experience along with anaesthesia-care-team composition. Multivariable logistic regression models were used to evaluate three outcomes: any complication, cardiopulmonary complication, and length of stay (>5 days). Odds ratios (ORs) and 99.75% confidence intervals (CIs) were reported.

RESULTS

Across all three models, anaesthesiologist volume and experience, and anaesthesia-care-team composition were not significant predictors. Surgeon annual case volume >50 was associated with significantly reduced odds of any complication (annual case volume: 50-149; OR: 0.80; CI: 0.66-0.98) and prolonged length of stay (OR: 0.69; CI: 0.60-0.80). Surgeon experience >20 yr was associated with significantly reduced odds of prolonged length of stay (OR: 0.85; CI: 0.75-0.95).

CONCLUSIONS

Anaesthesiologist volume and experience, and anaesthesia-care-team composition did not impact the odds of an adverse outcome, although a higher surgeon volume was associated with decreased odds of complications and prolonged length of stay. Further study is necessary to determine if these findings can be extrapolated to less specialised, lower volume surgical settings.

Relating gastric scintigraphy and symptoms to motility capsule transit and pressure findings in suspected gastroparesis

BACKGROUND

Wireless motility capsule (WMC) findings are incompletely defined in suspected gastroparesis. We aimed to characterize regional WMC transit and contractility in relation to scintigraphy, etiology, and symptoms in patients undergoing gastric emptying testing.

METHODS

A total of 209 patients with gastroparesis symptoms at NIDDK Gastroparesis Consortium centers underwent gastric scintigraphy and WMCs on separate days to measure regional transit and contractility. Validated questionnaires quantified symptoms.

KEY RESULTS

Solid scintigraphy and liquid scintigraphy were delayed in 68.8% and 34.8% of patients; WMC gastric emptying times (GET) were delayed in 40.3% and showed 52.8% agreement with scintigraphy; 15.5% and 33.5% had delayed small bowel (SBTT) and colon transit (CTT) times. Transit was delayed in ≥2 regions in 23.3%. Rapid transit was rarely observed. Diabetics had slower GET but more rapid SBTT versus idiopathics (P ≤ .02). GET delays related to greater scintigraphic retention, slower SBTT, and fewer gastric contractions (P ≤ .04). Overall gastroparesis symptoms and nausea/vomiting, early satiety/fullness, bloating/distention, and upper abdominal pain subscores showed no relation to WMC transit. Upper and lower abdominal pain scores (P ≤ .03) were greater with increased colon contractions. Constipation correlated with slower CTT and higher colon contractions (P = .03). Diarrhea scores were higher with delayed SBTT and CTT (P ≤ .04).

CONCLUSIONS & INFERENCES

Wireless motility capsules define gastric emptying delays similar but not identical to scintigraphy that are more severe in diabetics and relate to reduced gastric contractility. Extragastric transit delays occur in >40% with suspected gastroparesis. Gastroparesis symptoms show little association with WMC profiles, although lower symptoms relate to small bowel or colon abnormalities.

A laser driven pulsed X-ray backscatter technique for enhanced penetrative imaging

X-ray backscatter imaging can be used for a wide range of imaging applications, in particular for industrial inspection and portal security. Currently, the application of this imaging technique to the detection of landmines is limited due to the surrounding sand or soil strongly attenuating the 10s to 100s of keV X-rays required for backscatter imaging. Here, we introduce a new approach involving a 140 MeV short-pulse (< 100 fs) electron beam generated by laser wakefield acceleration to probe the sample, which produces Bremsstrahlung X-rays within the sample enabling greater depths to be imaged. A variety of detector and scintillator configurations are examined, with the best time response seen from an absorptive coated BaF2 scintillator with a bandpass filter to remove the slow scintillation emission components. An X-ray backscatter image of an array of different density and atomic number items is demonstrated. The use of a compact laser wakefield accelerator to generate the electron source, combined with the rapid development of more compact, efficient and higher repetition rate high power laser systems will make this system feasible for applications in the field. Content includes material subject to Dstl (c) Crown copyright (2014). Licensed under the terms of the Open Government Licence except where otherwise stated. To view this licence, visit http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: psi@ nationalarchives.gsi.gov.uk.

Energy transport in short-pulse-laser-heated targets measured using extreme ultraviolet laser backlighting

The accurate characterization of thermal electron transport and the determination of heating by suprathermal electrons in laser driven solid targets are both issues of great importance to the current experiments being performed at the National Ignition Facility, which aims to achieve thermonuclear fusion ignition using lasers. Ionization, induced by electronic heat conduction, can cause the opacity of a material to drop significantly once bound-free photoionization is no longer energetically possible. We show that this drop in opacity enables measurements of the transmission of extreme ultraviolet (EUV) laser pulses at 13.9 nm to act as a signature of the heating of thin (50 nm) iron layers with a 50-nm thick parylene-N (CH) overlay irradiated by 35-fs pulses at irradiance 3×10(16) Wcm(-2). Comparing EUV transmission measurements at different times after irradiation to fluid code simulations shows that the target is instantaneously heated by hot electrons (with approximately 10% of the laser energy), followed by thermal conduction with a flux limiter of ≈0.05.

Upregulated c-myc expression in multiple myeloma by internal ribosome entry results from increased interactions with and expression of PTB-1 and YB-1

The 5' untranslated region of the proto-oncogene c-myc contains an internal ribosome entry segment (IRES) and c-myc translation can therefore be initiated by internal ribosome entry as well as by cap-dependent mechanisms. It has been shown previously that in patients with multiple myeloma (MM) and in MM-derived cell lines there is a C to T mutation in the c-myc IRES that increases IRES activity and the corresponding synthesis of c-myc protein although it is not fully understood how this occurs. Our data show that two recently identified c-myc IRES trans-acting factors, Y-box binding protein 1 (YB-1) and polypyrimidine tract-binding protein 1 (PTB-1), bind more strongly (approximately 3.5- and 2-fold respectively) to the mutated version of the c-myc IRES and in vitro these proteins exert their effect synergistically to stimulate IRES activity of the mutant IRES 4.5-fold more than the wild-type version. Importantly, we show that there is a strong correlation between the expression of PTB-1, YB-1 and c-myc in MM-derived cell lines, suggesting that by reducing either PTB-1 or YB-1 protein levels it is possible to decrease c-myc expression and inhibit cell proliferation of MM-derived cell lines.

Utilization of okara, a byproduct from soymilk production, through the development of soy-based snack food

This study was conducted to develop a new soy-based food product that could utilize okara (a byproduct from soymilk production) and maximize the health benefits of okara for the consumer. A Japanese commercial okara snack product was used as a standard reference. Two types of dried okara powder, a commercially dried okara powder with 7.7% moisture content made from regular (lipoxygenase-present) soybeans and a partially dried okara with 44.3% moisture content made from lipoxygenase-free (LOX-null) soybeans, were used in this study. Commercial low saturated soybean oil and commercial low linolenic acid soybean oil were also used in the same formulation to compare and find the best formulation for a baked or deep-fat-fried soy-based food product. Two descriptive analysis studies were performed with a minimum of 15 trained panelists. Instrumental analyses with a Hunter Lab system and a TA.XT2i texture analyzer and chemical analysis were performed to compare with the sensory results. All the results were statistically analyzed. The baked product made from commercial low saturated soybean oil and the partially dried LOX-null okara powder gave the closest flavor, texture, and appearance to the reference standard. The final product contained 11.4% protein and 7.4% dietary fiber, which were, respectively, 1.5 and 2.0 times higher than the reference. The calcium content was also 4.3 times higher than the reference. The objectives of this study were achieved by developing a new soy-based snack food, which has more health benefits with an enjoyable flavor and texture than the existing commercial product.

Utilization of soybeans and their components through the development of textured soy protein foods

Textured soy protein (TSP), an extruded and fibrous-structured product, is mainly used as meat analog or extender. Meat alternatives are third in sales in the U.S. soy food marketplace. A primary problem that limits the incorporation of more TSP into products is the undesirable "beany" flavor. The objective of this study was to develop the best formulation of TSP and vegetable-based flavors to produce consumer acceptable "chicken" or "shrimp" flavored TSP using heat application processes. Four different types of commercial TSP (containing an average of 51% protein) strip-shaped extruded with a narrow die (STRIP-N) or with a wider die (STRIP-W), shred-shaped (SHRED) strips, and 1-cm crouton-shaped bits (BITs) were used. The TSPs were baked or deep-fat fried after soaking in 5 different commercial vegetable-based powered, liquid, or oil-based flavors ranged from 0% to 22.3% concentrations. Four descriptive analyses with a minimum of 14 trained panelists were utilized to evaluate the attributes of the finished TSP. Proximate, color, and texture analyses were performed on each TSP product. All treatments were statistically analyzed. Both instrumental and sensory tests demonstrated that BIT had a significantly higher crispness than other TSP. The powder type of chicken flavor used for a consumer panel had a more intense flavor than others with the optimum hydration time, 15 min. A consumer test with 125 people was performed with the highest chicken flavored (22.3%) fried and baked BIT. Overall, 66% of the total consumers preferred the fried BIT to the baked BIT, and 31% preferred the baked BIT.

Changes of soybean quality during storage as related to soymilk and tofu making

Soybeans are stored and transported under various humidity and temperature conditions. Soymilk and tofu are two of the most important foods made from whole soybeans. The objective of this study was to investigate the influence of storage conditions on soybean quality as related to soymilk and tofu-making properties. Soybeans of 3 different genotypes (Proto, IA2032, and Vinton 81) were stored in varying conditions: temperature ranging from 4 to 50 degrees C, relative humidity from 55% to 80%, initial moisture content from 6% to 14%, and storage time up to 15 mo depending upon storage conditions. The effects of different storage conditions on soybean color, solids and protein extractability, soymilk pH, tofu yield, tofu solids and protein contents, tofu color, and texture were investigated. While no significant changes occurred for the soybeans stored at 4 degrees C, the soybeans stored at high temperatures (30 to 50 degrees C) exhibited significant quality loss (P < 0.05). The degradation of soybean lightness (Hunter L), color difference (Delta E), and solid extractability exhibited a linear relationship with time. Soak weight decreased at high temperature and relative humidity, but increased at mild storage conditions. Several combinations of storage conditions at temperatures exceeding 30 degrees C produced a drastic loss in tofu yield. Storage also affected the tofu making process by reducing optimum mixing time to produce the highest tofu yield. Varietal difference in soybean storability was observed. The results provided useful information for the soybean processing industry to store soybeans using the optimal storage conditions and to estimate soybean quality after storage.

Growth of synthetic stromatolites and wrinkle structures in the absence of microbes - implications for the early fossil record

Stromatolites and wrinkle structures are often taken to be an important indicator for early life. While both may be shaped by microbial mat growth, this can be open to doubt, so that the contribution of abiotic processes in their construction always needs to be established (Grotzinger & Knoll, 1999). We here report laboratory spray deposition experiments that can generate stromatolites and wrinkle structures in the absence of microbes. These minicolumnar and sometimes branched stromatolites are produced artificially by the aggregation of a synthetic colloid in a turbulent flow regime. They self-organize at the relatively low particle concentrations found in the outer parts of a spray beam. This contrasts with adjacent stratiform deposits that are produced by high rates of colloid deposition and relatively low sediment viscosities found in the centre of a spray beam. These stratiform laminae become subsequently wrinkled during hardening of the colloid. These results support numerical models that together suggest that physicochemical processes are capable of generating laminated sedimentary structures without the direct participation of biology. Geological environments where comparable abiogenic stromatolites and wrinkle structures may be found include: splash-zone silica sinters, desert varnish crusts and early Archean cherts formed from silica gel precursors.

Acute demyelinating encephalomyelitis (ADEM) in a patient with HIV infection

A case of acute demyelinating encephalomyelitis (ADEM) in a patient with HIV infection is reported. Although the diagnosis of ADEM is based on clinical and radiological findings, the potential for full recovery, with appropriate treatment, is highlighted by this case. A concise review of the subject is given in the discussion.

Different regional effects of voluntary exercise on the mechanical and electrical properties of rat ventricular myocytes

Short-term (6 weeks) voluntary wheel running exercise in young female rats that were in an active growth phase resulted in whole-heart hypertrophy and myocyte concentric hypertrophy, when compared to sedentary controls. The cross-sectional area of ventricular myocytes from trained rats was significantly greater than for those isolated from sedentary rats, with the greatest change in morphology seen in sub-endocardial cells. There was no statistically significant effect of training on cell shortening in the absence of external mechanical loading, in [Ca2+](i) transients, or in myofilament Ca2+ sensitivity (assessed during re-lengthening following tetanic stimulation). Under the external mechanical load of carbon fibres, absolute force developed in myocytes from trained rats was significantly greater than in those from sedentary rats. This suggests that increased myocyte cross-sectional area is a major contractile adaptation to exercise in this model. Training did not alter the passive mechanical properties of myocytes or the relative distribution of titin isomers, which was exclusively of the short, N2B form. However, training did increase the steepness of the active tension-sarcomere length relationship, suggesting an exercise-induced modulation of the Frank-Starling mechanism. This effect would be expected to enhance cardiac contractility. Training lengthened the action potential duration of sub-epicardial myocytes, reducing the transmural gradient in action potential duration. This observation may be important in understanding the cellular causes of T-wave abnormalities found in the electrocardiograms of some athletes. Our study shows that voluntary exercise modulates the morphological, mechanical and electrical properties of cardiac myocytes, and that this modulation is dependent upon the regional origin of the myocytes.

Urinary biomarkers for assessing dietary exposure to caffeine

The feasibility of using metabolites specific to caffeine as urinary biomarkers to be employed in the estimation of dietary caffeine intake is reported. The influence of inter-individual differences in the metabolism of caffeine and the effect of volunteer phenotype on the interpretation of potential biomarkers has been investigated using urinary caffeine metabolite data. This method of phenotype determination accurately reflected the rate constant for the cytochrome P4501A2 (CYP1A2)-catalysed 3-demethylation of caffeine in vivo. Three studies with up to 20 human volunteers demonstrated that a 24-h urine collection after a caffeine dose allows quantification of the metabolites excreted; that the ratios of selected metabolites used to classify the volunteers into fast, intermediate or slow caffeine metabolizers by CYP1A2 phenotype gave a similar result (2:7:3, slow:intermediate:fast) to that found in the general population (1:7:2); and that three metabolites, 1,7-dimethylxanthine, 1,7-dimethyluric acid and 1-methylxanthine, could be studied further as potential biomarkers for caffeine dietary intake.

CT colonography without cathartic preparation: feasibility study

PURPOSE

To evaluate methods for contrast material labeling of stool in the unprepared colon for computed tomographic (CT) colonography and to determine their sensitivity for polyp detection.

MATERIALS AND METHODS

Fifty-six patients with suspected or known polyps were assigned to five groups. Two to seven doses of 225 mL of dilute contrast material were orally administered during 24 or 48 hours. Transverse CT images were assessed for effectiveness of stool labeling. Colonoscopy was performed in all patients and was the standard. Two radiologists blinded to prior imaging and colonoscopic results assessed polyp detection.

RESULTS

For each group, average stool labeling scores and ranges were as follows: 24 hour two dose, 16% and 8%-21%; 24 hour five dose, 53% and 27%-66%; 48 hour four dose, 38% and 22%-48%; 48 hour six dose, 68% and 54%-77%; and 48 hour seven dose, 88% and 75%-98%. Sensitivity for the two radiologists for the identification of patients with polyps 1 cm or larger for each group was as follows: 24 hour two dose, 50% and 67%; 24 hour five dose, 100% and 100%; 48 hour four dose, 58% and 75%; 48 hour six dose, 56% and 67%; and 48 hour seven dose, 100% and 80%.

CONCLUSION

Ingestion of contrast material adequately labels stool for lesion identification; a 48-hour lead time and multiple doses of contrast material are required. Sensitivity for polyp detection in patients with adequate stool labeling approaches the sensitivity for polyp detection in prepared colons.

Mouse models for the Wolf-Hirschhorn deletion syndrome

Wolf-Hirschhorn syndrome (WHS) is a deletion syndrome caused by segmental haploidy of chromosome 4p16.3. Its hallmark features include a 'Greek warrior helmet' facial appearance, mental retardation, various midline defects and seizures. The WHS critical region (WHSCR) lies between the Huntington's disease gene, HD, and FGFR3. In mice, the homologs of these genes map to chromosome 5 in a region of conserved synteny with human 4p16.3. To derive mouse models of WHS and map genes responsible for subphenotypes of the syndrome, five mouse lines bearing radiation-induced deletions spanning the WHSCR syntenic region were generated and characterized. Similar to WHS patients, these animals were growth-retarded, were susceptible to seizures and showed midline (palate closure, tail kinks), craniofacial and ocular anomalies (colobomas, corneal opacities). Other phenotypes included cerebellar hypoplasia and a shortened cerebral cortex. Expression of WHS-like traits was variable and influenced by strain background and deletion size. These mice represent the first animal models for WHS. This collection of nested chromosomal deletions will be useful for mapping and identifying loci responsible for the various subphenotypes of WHS, and provides a paradigm for the dissection of other deletion syndromes using the mouse.

IL-2Ralpha-Directed monoclonal antibodies provide effective therapy in a murine model of adult T-cell leukemia by a mechanism other than blockade of IL-2/IL-2Ralpha interaction

Adult T-cell leukemia (ATL) develops in a small proportion of human T-cell lymphotrophic virus-I infected individuals. The leukemia consists of an overabundance of activated T cells, which are characterized by the expression of CD25, or IL-2Ralpha, on their cell surface. Presently, there is not an accepted curative therapy for ATL. We developed an in vivo model of ATL in non-obese diabetic/severe combined immunodeficient (NOD/ SCID) mice by introducing cells from an ATL patient (MET-1) into the mice. The leukemic cells proliferated in these mice that lack functional T, B, and natural killer (NK) cells. The MET-1 leukemic cells could be monitored by measurements of both serum soluble Tac (IL-2Ralpha) and soluble human beta2-microglobulin (beta2mu) by ELISA. The disease progressed to death in the mice after approximately 4-6 weeks. The mice developed grossly enlarged spleens and a leukemia involving ATL cells that retained the phenotype and the T-cell receptor rearrangement and human T-cell lymphotrophic virus-I integration pattern of the patient's ATL leukemia cells. This model is of value for testing the efficacy of novel therapeutic agents for ATL. The administration of humanized anti-Tac (HAT), murine anti-Tac (MAT), and 7G7/B6, all of which target IL-2Ralpha, significantly delayed the progression of the leukemia and prolonged the survival of the tumor-bearing mice. In particular, HAT induced complete remissions in 4 of 19 mice and partial remissions in the remainder. It appears that the antibodies act by a mechanism that had not been anticipated. The prevailing view is that antibodies to the IL-2Ralpha receptor have their effective action by blocking the interaction of IL-2 with its growth factor receptor, thereby inducing cytokine deprivation apoptosis. However, although both HAT and MAT block the binding of IL-2 to IL-2Ralpha of the high affinity receptor, the 7G7/B6 monoclonal antibody binds to a different epitope on the IL-2Ralpha receptor, one that is not involved in IL-2 binding. This suggested that the antibodies provide an effective therapy by a mechanism other than induction of cytokine deprivation. In accord with this view, the MET-1 cells obtained from the spleens of leukemic mice did not produce IL-2, nor did they express IL-2 mRNA as assessed by reverse transcription-PCR. Another possible conventional mechanism of action involves complement-mediated killing. However, although MAT and 7G7/B6 fix rabbit complement, HAT does not do so. Furthermore, in the presence of NOD/SCID mouse serum, there was no complement-mediated lysis of MET-1 cells. In addition, the antibodies did not manifest antibody-dependent cellular cytotoxicity with NOD/SCID splenocytes that virtually lack NK cells as the effector cells as assessed in an in vitro chromium-release assay. However, in contrast to the efficacy of intact HAT, the F(ab')2 version of this antibody was not effective in prolonging the survival of mice injected with MET-1 ATL cells. In conclusion, in our murine model of ATL, monoclonal antibodies, HAT, MAT, and 7G7/B6, appear to delay progression of the leukemia by a mechanism of action that is different from the accepted mechanism of IL-2 deprivation leading to cell death. We consider two alternatives: the first, antibody-dependent cellular cytotoxicity mediated by FcRI- or FcRIII-expressing cells other than NK cells, such as monocytes or polymorphonuclear leukocytes. The second alternative we consider involves direct induction of apoptosis by the anti-IL-2R antibodies in vivo. It has been shown that the IL-2R is a critical element in the peripheral self-tolerance T-cell suicide mechanism involved in the phenomenon of activation-induced cell death.

Optimization of CT colonography technique: prospective trial in 180 patients

PURPOSE

To assess the added benefits of prone positioning in addition to supine positioning and oral iodinated contrast medium for help in the detection of colonic polyps at computed tomographic (CT) colonography.

MATERIALS AND METHODS

CT colonography was performed in prone and supine positions in 180 patients with polyps or risk factors for colonic neoplasia. Patients were randomly assigned to receive a standard bowel preparation or a standard preparation plus oral iodinated contrast medium. One radiologist interpreted supine images alone, and another analyzed supine and prone images. All patients subsequently underwent colonoscopy.

RESULTS

At colonoscopy, 121 large (> or =1-cm-diameter) polyps and 142 smaller (0.5-0.9-cm) polyps were identified. Prone positioning resulted in increased sensitivity for identification of patients with large (> or =1-cm) polyps (increase from 70% to 85%, P: =.004) and of patients with polyps 0.5 cm or larger (increase from 75% to 88%, P: <.005), with no change in specificity. Use of oral contrast medium did not significantly improve polyp detection even in the subset of patients in whom colonic fluid attenuation was markedly increased.

CONCLUSION

Acquisition and review of supine and prone CT colonographic images significantly improves the ability to identify patients with polyps 0.5 cm in diameter or larger. Administration of oral iodinated contrast medium does not significantly improve polyp detection.

Identification of SIV env-specific CTL in the jejunal mucosa in vaginally exposed, seronegative rhesus macaques (Macaca mulatta)

We previously reported major histocompatibility complex Class I-restricted cytotoxic T lymphocytes (CTL) in jejunal lamina propria (LP) of monkeys following colonic exposure to subinfectious SIV doses. Those monkeys with strong mucosal CTL responses specific for simian immunodeficiency virus (SIV) envelope (env) were protected from later colonic challenge with a heterologous pathogenic virus dose. Here, env-specific CTL were similarly induced in jejunal LP in five of eight non-progesterone treated macaques that were vaginally exposed to SIV, but not infected. Subsequent vaginal challenge following progesterone treatment produced systemic infection. The only two monkeys that had jejunal env-specific CTL detectable post-challenge developed significantly lower plasma virus loads, and had delayed disease progression. Either vaginal or colonic exposure to subinfectious SIV doses can induce CTL detectable in jejunal LP. The association of such CTL with protection or delayed disease upon challenge suggests that successful vaccine protection against SIV/HIV may require CTL responses in the mucosa.

Interdigitated deletion complexes on mouse chromosome 5 induced by irradiation of embryonic stem cells

Chromosome deletions have several applications in the genetic analysis of complex organisms. They can be used as reagents in region-directed mutagenesis, for mapping of simple or complex traits, or to identify biological consequences of segmental haploidy, the latter being relevant to human contiguous gene syndromes and imprinting. We have generated three deletion complexes in ES (Embryonic Stem) cells that collectively span approximately 40 cM of proximal mouse chromosome 5. The deletion complexes were produced by irradiation of F(1) hybrid ES cells containing herpes simplex virus thymidine kinase genes (tk) integrated at the Dpp6, Hdh (Huntington disease locus), or Gabrb1 loci, followed by selection for tk-deficient clones. Deletions centered at the adjacent Hdh and Dpp6 loci ranged up to approximately 20 cM or more in length and overlapped in an interdigitated fashion. However, the interval between Hdh and Gabrb1 appeared to contain a locus haploinsufficient for ES cell viability, thereby preventing deletions of either complex from overlapping. In some cases, the deletions resolved the order of markers that were previously genetically inseparable. A subset of the ES cell-bearing deletions was injected into blastocysts to generate germline chimeras and establish lines of mice segregating the deletion chromosomes. At least 11 of the 26 lines injected were capable of producing germline chimeras. In general, those that failed to undergo germline transmission bore deletions larger than the germline-competent clones, suggesting that certain regions of chromosome 5 contain haploinsufficient developmental genes, and/or that overall embryonic viability is cumulatively decreased as more genes are rendered hemizygous. Mice bearing deletions presumably spanning the semidominant hammertoe locus (Hm) had no phenotype, suggesting that the classic allele is a dominant, gain-of-function mutation. Overlapping deletion complexes generated in the fashion described in this report will be useful as multipurpose genetic tools and in systematic functional mapping of the mouse genome.

Analysis of annatto (Bixa orellana) food coloring formulations. 2. Determination of aromatic hydrocarbon thermal degradation products by gas chromatography

Twenty samples of commercial annatto formulations have been analyzed for m-xylene and toluene using ambient alkaline hydrolysis, followed by solvent extraction and capillary gas chromatography. Fifteen of the samples contained <5 mg/kg toluene, four samples contained between 5 and 10 mg/kg toluene, and one sample contained 12 mg/kg toluene. The amounts found of m-xylene were 200 mg/kg (one sample), 160 mg/kg (one sample), between 30 and 88 mg/kg (four samples), between 7 and 25 mg/kg (seven samples), and <5 mg/kg (seven samples). Bixin-in-oil formulations contained the highest m-xylene concentrations and also gave the largest increase in headspace m-xylene concentration when heated in closed systems. The results are evidence for the thermal degradation of annatto during source extraction and processing, resulting in contamination by internal generation of both bixin and norbixin types with aromatic hydrocarbons. Two samples of norbixin of known production history (i. e., thermal versus nonthermal processes) were analyzed specifically to identify possible differences in their degradation component profiles. They were found to differ significantly in m-xylene content, which is consistent with their respective production histories.