Surgery Start Time Research Articles

Food and Drug Administration warning on anesthesia and brain development: implications for obstetric and fetal surgery

There has been growing concern about the detrimental effects of certain anesthetic agents on the developing brain. Preclinical studies in small animal models as well as nonhuman primates suggested loss or death of brain cells and consequent impaired neurocognitive function following anesthetic exposure in neonates and late gestation fetuses. Human studies in this area are limited and currently inconclusive. On Dec. 14, 2016, the US Food and Drug Administration issued a warning regarding impaired brain development in children following exposure to certain anesthetic agents used for general anesthesia, namely the inhalational anesthetics isoflurane, sevoflurane, and desflurane, and the intravenous agents propofol and midazolam, in the third trimester of pregnancy. Furthermore, this warning recommends that health care professionals should balance the benefits of appropriate anesthesia in young children and pregnant women against potential risks, especially for procedures that may last >3 hours or if multiple procedures are required in children <3 years old. The objective of this article is to highlight how the Food and Drug Administration warning may impact the anesthetic and surgical management of the obstetric patient. Neuraxial anesthesia (epidural or spinal anesthesia) is more commonly administered for cesarean delivery than general anesthesia. The short duration of fetal exposure to general anesthesia during cesarean delivery has not been associated with learning disabilities. However, the fetus can also be exposed to both intravenous and inhalation anesthetics during nonobstetric or fetal surgery in the second and third trimester; this exposure is typically longer than that for cesarean delivery. Very few studies address the effect of anesthetic exposure on the fetus in the second trimester when most nonobstetric and fetal surgical procedures are performed. It is also unclear how the plasticity of the fetal brain at this stage of development will modulate the consequences of anesthetic exposure. Strategies that may circumvent possible untoward long-term neurologic effects of anesthesia in the baby include: (1) use of nonimplicated (nongamma-aminobutyric acid agonist) agents for sedation such as opioids (remifentanil, fentanyl) or the alpha-2 agonist, dexmedetomidine, when appropriate; (2) minimizing the duration of exposure to inhalational anesthetics for fetal, obstetric, and nonobstetric procedures in the pregnant patient, as much as possible within safe limits; and (3) commencing surgery promptly and limiting the interval between induction of anesthesia and surgery start time will help decrease patient exposure to inhalational agents. While the Food and Drug Administration warning was based on duration and repetitive nature of exposure rather than concentration of inhalational agents, intravenous tocolytics can be considered for intraoperative use, to provide uterine relaxation for fetal surgery, in lieu of high concentrations of inhalational anesthetic agents. Practitioners should consider the type of anesthesia that will be administered and the potential risks when scheduling patients for nonobstetric and fetal surgery.

Integrating Optimal Heterogeneous Sensor Deployment and Operation Strategies for Dynamic Origin-Destination Demand Estimation.

Most existing network sensor location problem (NSLP) models are designed to identify the number of sensors with fixed costs and installation locations, and sensors are assumed to be installed permanently. However, sometimes sensors are carried by individuals to collect traffic data measurements manually at fixed locations. Hence, their duration of operation for which traffic data measurements are collected is limited, and their costs are not fixed as they are correlated with the duration of operation. This paper proposes a NSLP model that integrates optimal heterogeneous sensor deployment and operation strategies for the dynamic O-D demand estimates under budget constraints. The deployment strategy consists of the numbers of link and node sensors and their installation locations. The operation strategy includes sensors’ start time and duration of operation, which has not been addressed in previous studies. An algorithm is developed to solve the proposed model. Numerical experiments performed on a network from a part of Chennai, India show that the proposed model can identify the optimal heterogeneous sensor deployment and operation strategies with the maximum dynamic O-D demand estimation accuracy.

Assessment of emergency general surgery care based on formally developed quality indicators

Emergency general surgery outcomes vary widely across the United States. The utilization of quality indicators can reduce variation and assist providers in administering care aligned with established recommendations. Previous quality indicators have not focused on emergency general surgery patients. We identified indicators of high-quality emergency general surgery care and assessed patient- and hospital-level compliance with these indicators. We utilized a modified Delphi technique (RAND Appropriateness Methodology) to develop quality indicators. Through 2 rankings, an expert panel ranked potential quality indicators for validity. We then examined historic compliance with select quality indicators after 4 nonelective procedures (cholecystectomy, appendectomy, colectomy, small bowel resection) at 4 academic centers. Of 25 indicators rated as valid, 13 addressed patient-level quality and 12 addressed hospital-level quality. Adherence with 18 indicators was assessed. Compliance with performing a cholecystectomy for acute cholecystitis within 72hours of symptom onset ranged from 45% to 76%. Compliance with surgery start times within 3hours from the decision to operate for uncontained perforated viscus ranged from 20% to 100%. Compliance with exploration of patients with small bowel obstructions with ischemia/impending perforation within 3hours of the decision to operate was 0% to 88%. For 3 quality indicators (auditing 30-day unplanned readmissions/operations for patients previously managed nonoperatively, monitoring time to source control for intra-abdominal infections, and having protocols for bypass/transfer), none of the hospitals were compliant. Developing indicators for providers to assess their performance provides a foundation for specific initiatives. Adherence to quality indicators may improve the quality of emergency general surgery care provided for which current outcomes are potentially modifiable.

Translating the 2-dimensional mammogram into a 3-dimensional breast: Identifying factors that influence the movement of pre-operatively placed wire.

Pre-operative measurements from the skin to a wire-localized breast lesion can differ from operating room measurements. This study was designed to measure the discrepancies and study factors that may contribute to wire movement. Prospective data were collected on patients who underwent wire localization lumpectomy. Clip and hook location, breast size, density, and direction of wire placement were the main focus of the analysis. Wire movement was more likely with longer distance from skin to hook or clip, larger breast size (especially if "fatty"), longer time between wire placement and surgery start time, and medial wire placement in larger breast. Age, body mass index, presence of mass, malignant diagnosis, tumor grade, and clip distance to the chest wall were not associated with wire movement. A longer distance from skin to hook correlated with larger specimen volume. Translation of the lesion location from a 2-dimensional mammogram into 3-dimensional breasts is sometimes discrepant because of movement of the localizing wire. Breast size, distance of skin to clip or hook, and wire exit site in larger breasts have a significant impact on wire movement. This information may guide the surgeon's skin incision and extent of excision.

Time to Operating Room for Cholecystitis Decreases with a Mature Emergency General Surgery Service

Emergency general surgery (EGS) services are designed to increase the availability of timely, high-quality care to patients with urgent surgical problems. One of the most commonly performed operations on such services is cholecystectomy. Improved outcomes have recently been described in early cholecystectomy for cholecystitis. We hypothesized that, as our EGS service matured, time from imaging to operating room (OR) for cholecystectomy would decrease. At an academic referral center, we identified patients undergoing inpatient cholecystectomy for acute cholecystitis during three time periods: before the formation of an EGS service from 2005 to 2007, during the first years of the service from 2008 to 2010, and five years after its development from 2013 to 2014. Charts were reviewed for patient demographics, operative events, and findings. The time of radiologic diagnosis and operation start time were recorded, and time between diagnosis and operation was calculated. A total of 217 patients who met the study criteria were identified, 88 in 2005 to 2007, 84 in 2008 to 2010, and 45 in 2013 to 2014. Time from radiologic diagnosis to OR decreased over the study period, from a median of 48.4 hours in 2005 to 2007 to 32.4 hours in 2008 to 2010 during the early years of the EGS service. Time to OR further decreased to a median of 16.6 hours during 2013 to 2014. The formation and maturation of an EGS service was associated with decreased time to OR after radiologic diagnosis of acute cholecystitis at this institution. This decrease in preoperative time may lead to lower costs and improved outcomes.

Effect of Surgery Start Time on Day of Discharge in Anterior Cervical Discectomy and Fusion Patients.

Retrospective cohort. To compare time to discharge for anterior cervical discectomy and fusions (ACDF) when performed as either a first case versus later surgical start times. ACDF is a commonly performed spinal procedure that typically has a short acute recovery period. With an increasing focus on reducing hospital costs and a shift toward outpatient surgical practices, early patient discharge has become a priority for hospitals and physicians alike. However, the impact of surgery start time on the ability for same-day discharge has not been explored in spine surgery. A surgical database of patients who underwent ACDF from 2013 to 2015 was reviewed. Patients were stratified into two cohorts: those whose surgery was the first of the day (early cohort), and those who underwent later surgeries. Baseline patient characteristics and perioperative variables were compared between cohorts using Student t test and χ test. Same-day discharge was tested for association with surgical start time using Poisson regression with robust error variance controlling for preoperative variables. A total of 106 patients, divided into early and late cohorts of 60 and 46 patients, respectively, were included in the analysis. There were no significant differences in pre- or perioperative characteristics between cohorts (). Same-day discharge was achieved in 36.8% (n = 39) of all ACDF patients. The later cohort was significantly more likely to require an overnight stay compared with the early cohort (RR = 1.61 ± 0.30; P = 0.010).(Table is included in full-text article.)CONCLUSION.: Patients undergoing ACDF later in the day are at a higher risk for staying overnight than those who have the first surgery of the day. These results may influence operative scheduling, as performing ACDFs early in the day may result in a greater likelihood of same-day discharge, eliminating the increased resource utilization associated with an overnight hospital stay. 4.

Operation Start Times and Postoperative Morbidity from Liver Resection: A Propensity Score Matching Analysis.

Surgeons are likely to get progressively fatigued and work less effectively during the course of a normal workday. We sought to examine the effects of surgery start times (morning vs. afternoon) and workload of the surgeons on morbidity of patients after partial liver resection (LR). A total of 155 pairs of the patients from 383 patients undergoing LR were generated by propensity score analysis (PSM) according to the start times of surgery: group M (morning surgery, 8a.m.-1p.m.) and group A (afternoon surgery, 1p.m.-6p.m.). Patients in group A were further divided depending on whether or not the surgeons had performed other surgeries earlier in the day and the exact duration of the other surgeries before the afternoon surgery (≤180 and >180min). The incidence and severity of postoperative complications were compared between different groups. By using PSM analysis, the patients in group M and group A were well matched in basic characteristics. The incidence and severity of the postoperative complications were similar between the two groups (all p>0.05). Whether the surgeons had performed other surgeries prior to the afternoon surgery seemed not affecting the postoperative outcome (all p>0.05). Moreover, the duration of other surgeries the surgeons had performed did not have significant influence on the outcome of patients undergoing afternoon surgery (all p>0.05). Surgery start times and workload of surgeons during working time did not measurably affect short-term outcomes of the patients. The negative findings might be a manifestation of professional judgment and self-regulation of the experienced physicians.

Intraoperative Care Transitions Are Not Associated with Postoperative Adverse Outcomes.

Whether anesthesia care transitions and provision of short breaks affect patient outcomes remains unclear. The authors determined the number of anesthesia handovers and breaks during each case for adults admitted between 2005 and 2014, along with age, sex, race, American Society of Anesthesiologists physical status, start time and duration of surgery, and diagnosis and procedure codes. The authors defined a collapsed composite of in-hospital mortality and major morbidities based on primary and secondary diagnoses. The relationship between the total number of anesthesia handovers during a case and the collapsed composite outcome was assessed with a multivariable logistic regression. The relationship between the total number of anesthesia handovers during a case and the components of the composite outcome was assessed using multivariate generalized estimating equation methods. Additionally, the authors analyzed major complications and/or death within 30 days of surgery based on the American College of Surgeons National Surgical Quality Improvement Program-defined events. A total of 140,754 anesthetics were identified for the primary analysis. The number of anesthesia handovers was not found to be associated (P = 0.19) with increased odds of postoperative mortality and serious complications, as measured by the collapsed composite, with odds ratio for a one unit increase in handovers of 0.957; 95% CI, 0.895 to 1.022, when controlled for potential confounding variables. A total of 8,404 anesthetics were identified for the NSQIP analysis (collapsed composite odds ratio, 0.868; 95% CI, 0.718 to 1.049 for handovers). In the analysis of intraoperative handovers, anesthesia care transitions were not associated with an increased risk of postoperative adverse outcomes.

Improving first case start times using Lean in an academic medical center

BackgroundLean is a process improvement strategy that can improve efficiency of the perioperative process. The purpose of this study was to identify etiologies of late surgery start times, implement Lean interventions, and analyze their effects. MethodsA retrospective review of all first-start surgery cases was performed. Lean was implemented in May 2015, and cases 7 months before and after implementation were analyzed. ResultsA total of 4,492 first-start cases were included; 2,181 were pre-Lean and 2,311 were post-Lean. The post-Lean group had significantly higher on-time starts than the pre-Lean group (69.0% vs 57.0%, P < .01). The most common delay etiology was surgeon-related for both groups. Delayed post-Lean cases were significantly less likely to be due to preoperative assessment (14.9% vs 9.9%, P < .01) and more likely due to patient-related (16.5% vs 22.3%, P < .01) or chaplain (1.8% vs 4.0%, P < .01) factors. Delayed starts occurred more often on snowy and cold days, and less often on didactic days (P < .01). ConclusionsModifying preoperative tasks using Lean methods can improve operating room efficiency and increase on-time starts.

Modifiable Factors Leading to Increased Length of Stay after Carotid Endarterectomy

Carotid endarterectomy (CEA) is a commonly performed vascular operation. Yet, postoperative length of stay (LOS) varies greatly even within institutions. In this study, the morbidity and mortality, as well as financial impact of increased LOS were reviewed to establish modifiable factors associated with prolonged hospital stay. The Society for Vascular Surgery Vascular Quality Initiative database was used to identify all patients undergoing primary CEA at a single institution between June 1, 2011 and November 28, 2014. Preoperative patient characteristics, intraoperative details, postoperative factors, long-term outcomes, and cost data were reviewed using an Institutional Review Board-approved prospectively collected database. Multivariate analysis was used to determine statistical difference between patients with LOS ≤1day and >1day. Complete 30-day variable and cost data were available for 219 patients with an average follow-up of 12months. Seventy-nine (36%) patients had an LOS>1day. Variables determined to be statistically significant predictors of prolonged LOS included preoperative creatinine (P=0.02) and severe congestive heart failure (P=0.05) with self-pay status (P=0.02) and preoperative beta-blocker therapy (P=0.04) being protective. Shunt placement (P=0.04), arterial re-exploration, and postoperative cardiac (P=0.001) or neurological (P=0.03) complications also resulted in prolonged hospitalization. Specific modifiable riskfactors that contributed to increased LOS included operative start time after noon (P=0.04), drain placement (P=0.05), prolonged operative time (101 vs. 125min, P=0.01), return to the operating room (P=0.01), and postoperative hypertension (P=0.02) or hypotension (P=0.04). Of note, there was no difference in LOS associated with technique (conventional versus eversion), patch use (P=0.49), protamine administration (P=0.60), electroencephalogram monitoring (P=0.45), measurement of stump pressure (P=0.63), Doppler (P=0.36), or duplex (P=0.92). Both hospital charges (P=0.0001) and costs (P=0.0001) were found to be significantly higher in patients with prolonged LOS, with no difference in physician charges (P=0.10). Increased LOS after CEA was associated with an increase in 12-month mortality (P=0.05). Increased LOS was associated with increased hospital charges, costs, as well as significant morbidity and midterm mortality following CEA. Furthermore, this study highlights several modifiable risk factors leading to increased LOS. Identified factors associated with increase LOS can serve as targets for improving care in vascular surgery.

Surgery Start Time Does Not Impact Outcome in Elective Cardiac Surgery

Determine if surgery start time impacts patient outcomes in elective cardiac surgery. This was a retrospective study. This study was based at a single academic institution. Patients undergoing elective cardiac surgery over a 3-year period were included. There were no interventions. The authors performed a retrospective study of patients undergoing elective cardiac surgery over a 3-year period. They divided their patient groups into those who had an anesthesia start time between 6:00 a.m. and 4:00 p.m. and those who had an anesthesia start time between 4:01 p.m. and 5:59 a.m. In the original sample and propensity-score-matched groups, the authors examined the effects of start time on morbidity, mortality, and several metrics of hospital length of stay. The start time of elective cardiac surgery did not have a statistically significant effect upon mortality, individual or composite morbidity, or hospital length of stay in either the original sample or the propensity-score-matched sample. The authors' results suggested that elective cardiac surgery may be performed late at night without adverse effects, although institutional support for this effort (such as 24-hour intensivist coverage to facilitate fast-track extubation) may have been integral to their findings.

Can Preoperative Risk Factors be used to Predict Unplanned Admission or Readmission Rates? A Study of Foot and Ankle Patients

Category: Other Introduction/Purpose: In the current health care climate, there is an increasing focus on cost savings and resource management. As such, there is an emphasis on decreasing length of stay and performing surgery on an outpatient basis. Consequently, some patients will have unanticipated intra-operative or post-operative adverse events that will necessitate an unplanned post-operative hospital admission or a readmission after discharge. These unplanned admissions or readmissions represent an increased burden on health care systems and can cause cancellation of other scheduled procedures. The purpose of this study is to investigate whether pre-operative patient risk factors or intra-operative events could predict unplanned admission or readmission following discharge in patients undergoing either elective or emergency foot and ankle surgery. Methods: Data was prospectively collected on a total of 889 patients. The patients were divided into two groups: patients without readmissions (N=791) and patients who had an unplanned admission or readmission (N=98). We also collected and analyzed the following variables: age, gender, BMI, diabetes, ASA class, surgery start time, length of surgery, regional vs. general anesthetic, elective vs. trauma surgery and type of procedure. Logistic regression models were used to identify risk factors that could independently predict unplanned admissions or readmissions to hospital following foot and ankle surgery. Results: Factors that could be used to independently predict readmission were length of surgery (p 0.0154, Odds Ratio 1.004) and trauma surgery (0.0167; 1.978). For every 1-hour increase in length of surgery, the odds of unplanned admission/readmission increase by 1.27 times. The odds of patients undergoing surgery for acute traumatic injuries getting readmitted are 1.978 times higher than for elective surgery patients. Conclusion: In conclusion, our study showed that pre-operative patient risk factors including BMI, diabetes, and ASA status were unable to predict whether patients would have an unplanned admission or readmission. The two factors that were able to predict whether patients would have an unplanned admission or readmission were length of the procedure and trauma surgery – both of which are not readily modifiable. Our results showed that in spite of institutional measures to ensure timely discharge, only 11% of patients required an unplanned admission or readmission.

Day of Surgery and Surgical Start Time Affect Hospital Length of Stay After Total Hip Arthroplasty

BackgroundThe United States spends $12 billion each year on ∼332,000 total hip arthroplasty (THA) procedures with the postoperative period accounting for ∼40% of costs. The purpose of this study was to evaluate the effect of surgical scheduling (day of week and start time) on clinical outcomes, hospital length of stay (LOS), and rate of nonhome discharge in THA patients. MethodsAnalysis of perioperative variables was performed for patients who underwent THA at an urban tertiary care teaching hospital from 2009 to 2014. ResultsA total of 580 THA patients were included for analysis. LOS was higher for the Thursday/Friday cohort compared to Monday/Tuesday (3.7 vs 3.4 days; P = .03). Patients who had a surgical start time after 2 PM had longer LOS compared to patients operated on before 2 PM (3.9 vs 3.5 days; P = .03). After controlling for patient comorbidities and THA surgical approach (direct anterior vs posterior), Thursday/Friday THAs were associated with a 3.27 times risk of extended LOS (>75th percentile LOS) compared to Monday/Tuesday THAs (P < .001). Additionally, case start before 2 PM was protective and associated with a 0.46 times odds of extended LOS (P = .01). LOS reduction opportunity for changing surgical start time to before 2 PM was 0.9 days for high-risk patients (American Society of Anesthesiology class 3/4 and/or liver disease) and 0.2 days for low-risk patients (American Society of Anesthesiology class 1/2). ConclusionPatients who underwent THA Thursday/Friday or had start times after 2 PM had significantly extended hospital LOS. Preoperative risk modification along with adjustments to surgical scheduling and/or perioperative staffing may reduce LOS and thus hospital expenditures for THA procedures.

Early endocrine attending surgeon presence increases operating room efficiency

BackgroundPreincision operating room (OR) preparation varies greatly. Cases requiring exacting preoperative setup may be more sensitive to inconsistent team members and trainees. Leadership and oversight by the surgeon may facilitate a timely start. The study hypothesized that early attending presence in the OR expedites surgery start time, improving efficiency, and decreasing cost. MethodsProspective data collection of endocrine surgery cases at an urban teaching hospital was performed. Time points recorded in minutes. Cost/min of OR time was $54. Patients classified as in the OR ≤10 min before attending arrival or >10 min before attending arrival. ResultsA total of 227 cases (166 thyroid, 54 parathyroid, 10 adrenal) were performed over 14 mo. Of the patients, 128 were in the OR ≤10 min before attending arrival, and 99 patients were >10 min (3 ± 3 min versus 35 ± 14 min, P < 0.01). The ≤10 min procedures started sooner after patient arrival in OR (40 ± 11 versus 63 ± 19, P < 0.01) which equated to $1202 of savings before incision. Although attending time in the OR before incision was equivalent between groups for adrenal and parathyroid, time to incision was shorter in the ≤10 min groups, saving $2416 ± 477 and $1458 ± 244, respectively (P < 0.01). Attending time in OR before thyroidectomy was 13 min longer in ≤10 min than >10 min (P < 0.01), but incisions were made 20 min sooner (P < 0.01) equating to $1076 ± 120 in savings. ConclusionsEarly attending presence in the OR shortens time to incision. For parathyroid and adrenal cases, this does not require additional surgeon time. In ORs without consistent teams, early attending presence in the OR improves efficiency and yields significant cost savings.

가스터빈 열병합발전소 성능저하 분석에 관한 연구

In this study, the degree of performance changes between the guaranteed performance and the performance after a certain operating start time is calculated by using the performance test of gas turbine CHP. The reason of the performance degradation will then be analysed. For some results of the CHP plant performance tests the comprehensive electric power output was 8,380 kW lower than the guaranteed performance, and the gas turbine's output was reduced to about 250 kW whenever ambient temperatures rose to <TEX>$1^{\circ}C$</TEX>. Also, causes of the performance degradation of gas turbines are ambient temperature rise, temperature aging and air compressor's efficiency drop.

Operative Start Time Does Not Affect Post-Operative Infection Risk.

Surgical care is delivered 24 h a day at most institutions. Alarmingly, some authors have found that certain operative start times are associated with greater morbidity and mortality rates. This effect has been noted in both the public and private sector. Although some of these differences may be related to process, they may also be caused by the human circadian rhythm and corresponding changes in host defenses. We hypothesized that the time of day of an operation would impact the frequency of certain post-operative outcomes significantly. Cases at a single tertiary-care center reported to the American College of Surgeons National Surgical Quality Improvement Program over a 10-year period were identified. Operative start times were divided into six-hour blocks, with 6 am to noon serving as the reference. Standard univariable techniques were applied. Multivariable logistic regression with mixed effects modeling then was used to determine the relation between operative start times and infectious outcomes, controlling for surgeon clustering. Statistical significance was set at p < 0.01. A total of 21,985 cases were identified, of which 2,764 (12.6%) were emergency procedures. Overall, 9.7% (n = 2,142) of patients experienced some post-operative infectious complication. Seventy percent of these infections (n = 1,506) were surgical site infections. On univariable analysis considering all cases, nighttime and evening operations had higher rates of post-operative infections than those in performed during the day (9.1% from 6 am to noon; 9.7% from noon to 6 pm; 14.8% from 6 pm to midnight; and 14.4% from midnight to 6 am; p < 0.001). On multivariable analysis, operative start time was not associated with the risk of post-operative infection, even when emergency cases were considered independently. Our data suggest that operative start times have no correlation with post-operative infectious complications. Further work is required to identify the source of the time-dependent outcome variability observed in previous studies.

Hybrid genetic algorithm and tabu search for finite capacity material requirement planning system in flexible flow shop with assembly operations

The finite capacity material requirement planning system (FCMRP) for industrial scale flexible flow shops is known to be strongly NP-hard. Due to very long computational time, the exact method can be inappropriate for this problem. In this paper, a new hybrid improvement algorithm for the FCMRP system in a flexible flow shop with assembly operations is proposed. The proposed algorithm is a hybrid of genetic algorithm (GA) and tabu search (TS) called HGATS. There are six primary steps in HGATS. In step 1, a production schedule is generated by variable lead-time MRP (VMRP). In step 2, dispatching and random rules are applied to generate initial sequences of orders. From step 3 to step 5, the sequences of orders are iteratively improved by characteristics of TS and GA. Finally, the start times of operations are optimally determined by linear programming. The results show that HGATS outperforms GA, TS and the existing algorithm. Furthermore, HGATS requires a practical computational time when applied to real industrial cases.

Fair Routing for Overlapped Cooperative Heterogeneous Wireless Sensor Networks

In recent years, as wireless sensor networks (WSNs) are widely diffused, multiple overlapping WSNs constructed on the same area become more common. In such a situation, their lifetime is expected to be extended by cooperative packet forwarding. Although some researchers have studied about cooperation in multiple WSNs, most of them do not consider the heterogeneity in the characteristics of each WSN such as battery capacity, operation start time, the number of nodes, nodes locations, energy consumption, packet size and/or data transmission timing, and so on. In a heterogeneous environment, naive lifetime improvement with cooperation may not be fair. In this paper, we propose a fair cooperative routing method for heterogeneous overlapped WSNs. It introduces an energy pool to maintain the total amount of energy consumption by cooperative forwarding. The energy pool plays a role of broker for fair cooperation. Finally, simulation results show the excellent performance of the proposed method.

MP22-12 THE RELATIONSHIP BETWEEN OPERATIVE TIMES AND COMPLICATION RATES IN PERCUTANEOUS NEPHROSTOLITHOTOMY PROCEDURES

You have accessJournal of UrologyStone Disease: Surgical Therapy I1 Apr 2016MP22-12 THE RELATIONSHIP BETWEEN OPERATIVE TIMES AND COMPLICATION RATES IN PERCUTANEOUS NEPHROSTOLITHOTOMY PROCEDURES Julie Stein, Kaitlan Cobb, John Michael DiBianco, and Patrick Mufarrij Julie SteinJulie Stein More articles by this author , Kaitlan CobbKaitlan Cobb More articles by this author , John Michael DiBiancoJohn Michael DiBianco More articles by this author , and Patrick MufarrijPatrick Mufarrij More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.700AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Prolonged operative time has long been associated with postoperative complications. Percutaneous nephrostolithotomy (PCNL) is a common approach for the treatment of complex stone disease, often requiring lengthy operative times and/or multiple surgical stages. Complications of PCNL, including hemorrhage, injury to adjacent organs/structures, and infection, have been reported to occur at higher rates in procedures that have had prolonged operative times. Additionally, some of these complications may limit the duration of PCNL procedures, thereby decreasing stone-free rates or requiring more surgical stages. We aimed to investigate the relationship between operative times and postoperative complications as classified by the Clavien-Dindo System of Surgical Complications. METHODS A retrospective review was performed on 66 patients who underwent PCNL by a single endourologist at George Washington University Hospital and Sibley Memorial Hospital in Washington, D.C. from October 2012 to December 2014. Data on basic patient demographics and characteristics, operative times, and complications were collected. Operative time was defined by surgery start time and stop time as recorded by the anesthesiologist. Complications were classified by the Clavien-Dindo system on a scale of 0 to 5. RESULTS Mean age of patients was 57.3 +/- 12.2 years. Overall complication rate was 14.9% with 0% Clavien I, 9.0% Clavien II, 0% Clavien III, 6.0% Clavien IV, and 0% Clavien V. Mean operative time was 232.0 +/- 72.7 minutes. A simple linear regression model revealed that operative time accounted for 6.1% of the variance in Clavien score (R2 = .061, p < 0.05). One-way Analysis of Variance (ANOVA) demonstrated that the presence of infection stones differed significantly between Clavien classes (F(2, 60) = 3.32, p = 0.043). Post-hoc analyses showed that infection stones were associated with a Clavien II complication (p = 0.05), but not with a Clavien IV complication (p > 0.05). CONCLUSIONS In our investigation, increased operative time of PCNL procedures was not associated with an increase in complications. The increase in mid-level complications observed in patients identified to have infection-based stones corroborates previous data on this particular group of stone patients. While, in general, it is advisable to minimize operative duration, this data does not suggest an increased complication risk with lengthier PCNL procedures. © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e257-e258 Advertisement Copyright & Permissions© 2016MetricsAuthor Information Julie Stein More articles by this author Kaitlan Cobb More articles by this author John Michael DiBianco More articles by this author Patrick Mufarrij More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Two machines flow shop with reentrance and exact time lag

This paper considers a reentrant flow shop with two machines and exact time lag L , in which each task may be processed in this order M 1 , M 2 , M 1 and there is an identical time lag between the completion time of the first operation and the start time of the second operation on the first machine. The objective is to minimize the total completion time. We prove the NP-hardness of a special case and we give some special subproblems that can be solved in polynomial time.