Choongrak Kim

The effects of anesthetics on chronic pain after breast cancer surgery.

BACKGROUND:The incidence and predictive factors for chronic pain after breast cancer surgery have been widely studied. Because it negatively affects patients’ daily lives, methods to prevent and reduce chronic pain and its severity should be developed. Our previous study showed that propofol anesthesia has an antihyperalgesic effect under remifentanil-induced hyperalgesia and reduced acute pain compared with sevoflurane anesthesia. In this study, we investigated the hypothesis that propofol would prevent the development and severity of chronic pain after breast cancer surgery, as in acute pain. METHODS:A retrospective study was conducted with 175 women (n = 86 in the propofol group and n = 89 in the sevoflurane group) aged 20 to 65 years who underwent breast cancer surgery between March 2007 and December 2008. Patients were followed up by telephone in July 2011. Analysis included incidence, severity, and duration of chronic pain between propofol and sevoflurane groups. Severity was categorized into mild, moderate, and severe pain. Duration of chronic pain was also divided into 3 categories by 1-year time interval. Risk factors associated with the incidence and severity of chronic pain after breast cancer surgery were also identified. RESULTS:Chronic pain after breast cancer surgery was more likely to occur in the sevoflurane group compared with the propofol group (95% confidence interval [CI] 1.146–1.809, P = 0.007). Among patients with chronic pain, neither the severity (95% CI 0.516–7.419) nor duration (95% CI 0.106–1.007) differed between patients receiving sevoflurane and propofol. Younger age (95% CI 0.907–0.992, P = 0.021), axillary lymph node dissection (95% CI 1.204–1.898, P = 0.003), 24-hour postoperative morphine consumption (95% CI 1.004–1.116, P = 0.036), and sevoflurane (95% CI 1.146–1.809, P = 0.007) were predictive factors for the development of chronic pain. Higher 24-hour postoperative morphine consumption (95% CI 1.001–1.379, P = 0.049) increased the severity of chronic pain. CONCLUSIONS:This study showed that propofol anesthesia was associated with a lower incidence of chronic pain after breast cancer surgery than sevoflurane anesthesia. However, propofol did not have a significant effect on severity and duration of chronic pain. Further prospective studies are needed to confirm the validity of these provocative findings.

Instrumentation, control and automation in wastewater - From London 1973 to Narbonne 2013

Key developments of instrumentation, control and automation (ICA) applications in wastewater systems during the past 40 years are highlighted in this paper. From the first ICA conference in 1973 through to today there has been a tremendous increase in the understanding of the processes, instrumentation, computer systems and control theory. However, many developments have not been addressed here, such as sewer control, drinking water treatment and water distribution control. It is hoped that this review can stimulate new attempts to more effectively apply control and automation in water systems in the coming years.

Cook's distance in spline smoothing

We present a version of Cooks distance that is applicable to groups of observations in spline smoothing and can be used for outlier detection when masking is present. We express them as functions of the basic diagnostic building blocks: residuals and leverage values. An example based on a real data set is given to illustrate the methods.

Reference values for cook's distance

Cooks distance (Cook, 1977) is often used to assess the influence of single observations or sets of observations in the linear regression model, and it is available, at least for single observatio...

Cook's distance in local polynomial regression

In fitting parametric or nonparametric regression models, one or a few observations may have undue effects on estimators. These influential observations are precisely detected by the well-known influence measure, Cooks distance. In this paper, we introduce a type of Cooks distance for one or a set of observations in local polynomial regression. Using the local property we simplify the Cooks distance in a numerical sense. In fact, it turned out that the simplified Cooks distance behaves quite well as far as detecting influential observations is concerned. We express Cooks distance in terms of the local residuals and the local leverages, and express the simplified version of Cooks distance in terms of the ordinary residuals and leverages. We suggest a way of obtaining reference values for Cooks distances. We also consider influential observations on the bandwidth estimator. As an illustrative example, a real data set is analyzed.

Correspondence analysis approach for finding allele associations in population genetic study

In population genetic study, one of the first analyses is to explore the relationships among the frequencies of alleles within or between loci. Hardy-Weinberg equilibrium is tested for two alleles of a single locus, and the linkage disequilibrium is tested for an allele from each of two loci. Although the equilibrium plays an important role and often serves as a basis for genetic inference, research on the graphical representation of this information is rare. In this study, we consider correspondence analysis and biplot approaches as tools for finding associations between alleles. We also propose the supplementary data method to compare allele frequencies of several populations from different studies. These approaches provide the graphical representation which makes it easy to interpret the patterns of disequilibrium and to compare the allele frequencies between populations. These proposed methods are illustrated with numerical examples.

Smoothing techniques via the bezier curve

Although the Bezier curve is very popular in the area of computational graphics it has rarely been used by statisticians. In this paper we develop methods and techniques for use of the Bezier curve in estimation of density and regression function. Also, asymptotic mean integrated square error for both estimators are derived. Comparisons with kernel estimator are conducted using simulation.

C-arm assessment of cervical pedicle screw: screw coaxial fluoroscopy and oblique view.

Study Design. Oblique view and screw coaxial fluoroscopy were used to assess cervical pedicle screw position in human cadaveric spine, results of which were compared with those of direct visual inspection by an anatomist. Objectives. To determine whether clinicians can detect misplaced cervical pedicle screws with accurate sensitivity and specificity using conventional C-arm equipment. Summary of Background Data. In the cervical region, pedicle screws have not been used so popularly as in lumbar or in thoracic regions. The reasons are related to the risk of inserting screw in small pedicle. So far, no method has been studied to assess the position of cervical pedicle screw during the operation. Methods. Ten human cadavers were prepared for this study. Headed and nonheaded pedicle screws were inserted bilaterally from C3–C7. Using C-arm oblique and screw coaxial fluoroscopy, the depth of penetration was recorded in 2-dimension scale (superoinferior and mediolateral direction) by 6 different observers. The vertebrae were all harvested, and the penetration depth was recorded by an anatomist under direct visualization. The accuracy of C-arm measurements was analyzed. The results of nonheaded and headed screws also were compared. Results. A total of 98 pedicle screw positions were finally enrolled into the study. The oblique view can verify screw position with the sensitivity of 86.1% and specificity of 64.5%. Coaxial fluoroscopy had a sensitivity of 89.8% and a specificity of 56.9% in superoinferior direction. Mediolaterally coaxial fluoroscopy had a sensitivity of 70.0% and a specificity of 51.3%. Conclusion. C-arm assessment of pedicle position has acceptable accuracy. With C-arm swing motion of the coaxial fluoroscopy, headed screws were also inspected without any difference as nonheaded screws. Measurements for superoinferior direction showed better sensitivity than those for mediolateral direction, which are supposed to be related to be elliptical shape and thin lateral margin of cervical pedicle.

A note on Box-Cox transformation diagnostics

With the Box–Cox transformation, one or a few responses can greatly influence the transformation parameter estimate. To detect influential observations, several diagnostics have been suggested. We highlight the importance of multiple case deletion, especially when the masking effect is present, and derive an analytic expression for Tsai and Wus diagnostic.

Non-parametric hazard function estimation using the Kaplan–Meier estimator

Estimation of the hazard function when the data are censored is an important problem in medical research. In this article, we propose a simple non-parametric estimator of the hazard function. Its asymptotic properties are derived, and numerical comparisons with other existing estimators are made. The proposed estimator is shown to be at least as good as the other estimators from both the theoretical and the numerical points of view.