Testing for Serial Correlation, Spatial Autocorrelation and Random Effects

This paper considers a spatial panel data regression model with serial correlation on each spatial unit over time as well as spatial dependence between the spatial units at each point in time. In addition, the model allows for heterogeneity across the spatial units using random effects. The paper then derives several Lagrange Multiplier tests for this panel data regression model including a joint test for serial correlation, spatial autocorrelation and random effects. These tests draw upon two strands of earlier work. The first is the LM tests for the spatial error correlation model discussed in Anselin and Bera (1998) and in the panel data context by Baltagi, Song and Koh (2003). The second is the LM tests for the error component panel data model with serial correlation derived by Baltagi and Li (1995). Hence the joint LM test derived in this paper encompasses those derived in both strands of earlier works. In fact, in the context of our general model, the earlier LM tests become marginal LM tests that ignore either serial correlation over time or spatial error correlation. The paper then derives conditional LM and LR tests that do not ignore these correlations and contrast them with their marginal LM and LR counterparts. The small sample performance of these tests is investigated using Monte Carlo experiments. As expected, ignoring any correlation when it is significant can lead to misleading inferencepanel data, spatial correlation

The impact of sequential versus single anastomoses on flow characteristics and mid-term patency of saphenous vein grafts in coronary bypass grafting

ObjectiveTo assess the influence of bypass grafting technique on the flow characteristics and mid-term patency of saphenous vein coronary bypass grafts.MethodsIn the present study, 309 patients who underwent either sequential (group A, N = 84 grafts) or individual (group B, N = 244 grafts) saphenous vein coronary bypass grafting between February 2002 and September 2007 were investigated. Individual bypassing only was performed in 212 patients, and sequential bypassing only was performed in 78 patients. The remaining 19 patients received both. A total of 436 distal anastomoses were performed with 328 saphenous vein grafts. The intraoperative flow characteristics and the graft patency were assessed with the transit time flow meter and serial multi-detector computed tomography coronary angiograms, respectively.ResultsGroup A showed a higher mean flow compared with group B at 49.4 ± 27.4 mL/min versus 37.1 ± 20.1 mL/min, respectively (P = .001). The mean flow increased linearly as the number of anastomoses increased per graft (P < .001). Graft patency at 3 years was 93.3% ± 3.4% in group A and 86.5% ± 3.1% in group B (P = .048). After adjustment for baseline characteristics, group A showed a tendency for superior mid-term patency than group B (hazard ratio 0.362; 95% confidence interval, 0.129–1.017; P = .0538).ConclusionsSequential bypass grafts were associated with higher mean flows and superior mid-term patency compared with individual grafts. These findings suggest the more favorable results of sequential bypass grafting to be attributed to the enhanced flow hemodynamics

Surgical repair of descending thoracic and thoracoabdominal aortic aneurysm involving the distal arch: Open proximal anastomosis under deep hypothermia versus arch clamping technique

BackgroundSurgical repair of a descending thoracic and thoracoabdominal aortic aneurysm (DTA/TAAA) involving the distal arch is challenging and requires either deep hypothermic circulatory arrest (DHCA) or crossclamping of the distal arch. The aim of this study was to compare these 2 techniques in the treatment of DTA/TAAA involving the distal arch.MethodsFrom 1994 to 2012, 298 patients underwent open repair of DTA/TAAA through a left thoracotomy. One hundred seventy-four patients with distal arch involvement who were suitable for either DHCA (n = 81) or arch clamping (AC; n = 93), were analyzed. In-hospital outcomes were compared using propensity scores and inverse-probability-of-treatment weighting adjustment to reduce treatment selection bias.ResultsEarly mortality was 11.1% in the DHCA group and 8.6% in the AC group (P = .58). Major adverse outcomes included stroke in 16 patients (9.2%), low cardiac output syndrome in 15 (8.6%), paraplegia in 10 (5.7%), and multiorgan failure in 10 (5.7%). After adjustment, patients who underwent DHCA were at similar risk of death (odds ratio [OR], 1.14; P = .80) and permanent neurologic injury (OR, 0.95; P = .92) to those who underwent AC. Although prolonged ventilator support (>24 hours) was more frequent with DHCA than with AC (OR, 2.60; P = .003), DHCA showed a tendency to lower the risk of paraplegia (OR, 0.15; P = .057).ConclusionsCompared with AC, DHCA did not increase postoperative mortality and morbidity, except for prolonged ventilator support. However, DHCA may offer superior spinal cord protection to AC during repair of DTA/TAAA involving the distal arch

Cancer Statistics in Korea: Incidence, Mortality, Survival, and Prevalence in 2008

PURPOSE: This paper overviews the nationwide cancer statistics including incidence, mortality, survival and prevalence, and their trends in Korea based on the year 2008 cancer incidence data. MATERIALS AND METHODS: Incidence data from 1993 to 2008 were obtained from the Korea National Cancer Incidence Database, and the vital status was followed through December 31, 2009. Mortality data from 1983 to 2008 were obtained from the Korea National Statistics Office. Crude rates and age-standardized rates for incidence, mortality, prevalence and relative survival were calculated. RESULTS: There were 178,816 cancer cases and 68,912 cancer deaths observed during year 2008 and 724,663 10-year cancer prevalent cases as of January 1, 2009 in Korea. The incidence rate for all cancer combined showed an annual increase of 3.1% from 1999 to 2008. CONCLUSION: With significantly increasing cancer incidence, Korea faces a large cancer burden and efficient cancer control programs are essential.ope

Titanium Plate Fixation for a Dehisced Sternum Following Coronary Artery Bypass Grafting: A Case Report

Sternal dehiscence is one of the most troublesome complications following cardiac surgery. Treatment failure and consequent lethal results are very common, even with all the efforts to resolve sternal dehiscence such as removal of infectious tissue, muscle flap interposition, and sternal rewiring. We report on a case of sternal osteomyelitis following coronary artery bypass grafting that was successfully treated with wide sternal resection, titanium plate fixation, and pectoralis muscle flap interposition