OptiscopeⓇ may have less stimulation on hemodynamic changes

인준용,Gyungserk Shim,Seunghyun Chung,Jeoung Hyuk Lee 대한마취통증의학회 2013 Korean Journal of Anesthesiology Vol.64 No.4

Survival analysis: Part I — analysis of time-to-event

인준용,이동규 대한마취통증의학회 2018 Korean Journal of Anesthesiology Vol.71 No.3

Length of time is a variable often encountered during data analysis. Survival analysis provides simple, intuitive results concerning time-to-event for events of interest, which are not confined to death. This review introduces methods of analyzing time-to-event. The Kaplan-Meier survival analysis, log-rank test, and Cox proportional hazards regression modeling method are described with examples of hypothetical data.

Discrimination of hemoglobin-effects on arterial-to-jugular bulb oxygen content differences according to arterial carbon dioxide tension

인준용 대한마취통증의학회 2008 Anesthesia and pain medicine Vol.3 No.4

Background: Arterial jugular bulb oxygen content differences (AJVDO2)can be related to cerebral blood flow and oxygen consumption. Plasma Hb has been reported to have both-sided effect on AJVDO2. Increased Hb increases oxygen content in artery and jugular bulb, and the net effect is to reduce AJVDO2. Moreover, increasing Hb raises blood viscosity, and could increase AJVDO2. This study was designed to discriminate the Hb-effects on AJVDO2 mathematically. Methods: Sixty adults were enrolled in this study. General anesthesia and mechanical ventilation were administered. A normocapnic and a subsequent hypocapnic state were achieved. Paired data including 1/AJVDO2, PaCO2, Hb, mean arterial pressure, temperature and anesthetic concentration were recorded during each state. Nonlinear mixed-effects model was applied to fit 1/AJVDO2 using PaCO2 and Hb as covariates. Results: The 1/AJVDO2 was well modeled by PaCO2 and Hb using a three-parameter logistic function: predicted 1/AJ DO2 = 0.38713/ 1 + e The increase in PaCO2 raised the 1/AJVDO2 sigmoidally (P < 0.0001) and its slope was affected by Hb (P = 0.0022). The transition point of the Hb-effect was PaCO2 = 31.20981 (SEM 1.519201). Intraclass correlation coefficient was estimated at 0.9973. Conclusions: Our finding suggests that the Hb-effect on 1/AJVDO2 is both-sided; the viscosity-effect is dominant at low levels of PaCO2 and effect of oxygen content is dominant at high levels of PaCO2.

Temporary solution for one lung ventilation with isolated bronchial blocker of UniventⓇ tube

인준용,박문기,한진영 대한마취통증의학회 2013 Korean Journal of Anesthesiology Vol.64 No.2

Introduction of a pilot study

인준용 대한마취통증의학회 2017 Korean Journal of Anesthesiology Vol.70 No.6

A pilot study asks whether something can be done, should the researchers proceed with it, and if so, how. However, a pilot study also has a specific design feature; it is conducted on a smaller scale than the main or full-scale study. In other words, the pilot study is important for improvement of the quality and efficiency of the main study. In addition, it is conducted in order to assess the safety of treatment or interventions and recruitment potentials, examine the randomization and blinding process, increase the researchers’ experience with the study methods or medicine and interventions, and provide estimates for sample size calculation. This review discusses with a focus on the misconceptions and the ethical aspect of a pilot study. Additionally how to interpret the results of a pilot study is also introduced in this review.

Survival analysis: part II – applied clinical data analysis

인준용,이동규 대한마취통증의학회 2019 Korean Journal of Anesthesiology Vol.72 No.5

As a follow-up to a previous article, this review provides several in-depth concepts regarding a survival analysis. Also, several codes for specific survival analysis are listed to enhance the understanding of such an analysis and to provide an applicable survival analysis method. A proportional hazard assumption is an important concept in survival analysis. Validation of this assumption is crucial for survival analysis. For this purpose, a graphical analysis method and a goodnessof- fit test are introduced along with detailed codes and examples. In the case of a violated proportional hazard assumption, the extended models of a Cox regression are required. Simplified concepts of a stratified Cox proportional hazard model and time-dependent Cox regression are also described. The source code for an actual analysis using an available statistical package with a detailed interpretation of the results can enable the realization of survival analysis with personal data. To enhance the statistical power of survival analysis, an evaluation of the basic assumptions and the interaction between variables and time is important. In doing so, survival analysis can provide reliable scientific results with a high level of confidence.

Tips for troublesome sample-size calculation

인준용,강현,김종해,김태균,안은진,이동규,이상석,박재홍 대한마취통증의학회 2020 Korean Journal of Anesthesiology Vol.73 No.2

Properly set sample size is one of the important factors for scientific and persuasive research. The sample size that can guarantee both clinically significant differences and adequate power in the phenomena of interest to the investigator, without causing excessive financial or medical considerations, will always be the object of concern. In this paper, we reviewed the essential factors for sample size calculation. We described the primary endpoints that are the main concern of the study and the basis for calculating sample size, the statistics used to analyze the primary endpoints, type I error and power, the effect size and the rationale. It also included a method of calculating the adjusted sample size considering the dropout rate inevitably occurring during the research. Finally, examples regarding sample size calculation that are appropriately and incorrectly described in the published papers are presented with explanations.

Randomization in clinical studies

인준용,임지연 대한마취통증의학회 2019 Korean Journal of Anesthesiology Vol.72 No.3

Randomized controlled trial is widely accepted as the best design for evaluating the efficacy of a new treatment because of the advantages of randomization (random allocation). Randomization eliminates accidental bias, including selection bias, and provides a base for allowing the use of probability theory. Despite its importance, randomization has not been properly understood. This article introduces the different randomization methods with examples: simple randomization; block randomization; adaptive randomization, including minimization; and response-adaptive randomization. Ethics related to randomization are also discussed. The study is helpful in understanding the basic concepts of randomization and how to use R software.

임신과 동반된 갈색세포종 환자의 마취 관리-증례보고-

인준용,김범석,김상호,이명애,곽호성 대한마취통증의학회 2005 Korean Journal of Anesthesiology Vol.49 No.4

Pheochromocytoma with pregnancy is very uncommon but it is associated with very high maternal and fetal morbidity and mortality. Antepartum diagnosis and proper management can prevent mother and fetus from potentially lethal outcome. Since pheochromocytoma produces and secretes catecholamines, hemodynamic instability can be brought. The aim of anesthetic management is the avoidance of drugs and episodes that will result in hypertensive crisis, and the selection of safe anesthetic measures and anesthetics to mother and fetus. We report a case of pheochromocytoma with pregnancy managed with combined anesthetic technique-epidural anesthesia for cesarean section and general anesthesia for resection of pheochromocytoma 3 weeks after cesarean section.

Statistical data presentation

인준용,이상석 대한마취통증의학회 2017 Korean Journal of Anesthesiology Vol.70 No.3

Data are usually collected in a raw format and thus the inherent information is difficult to understand. Therefore, raw data need to be summarized, processed, and analyzed. However, no matter how well manipulated, the information derived from the raw data should be presented in an effective format, otherwise, it would be a great loss for both authors and readers. In this article, the techniques of data and information presentation in textual, tabular, and graphical forms are introduced. Text is the principal method for explaining findings, outlining trends, and providing contextual information. A table is best suited for representing individual information and represents both quantitative and qualitative information. A graph is a very effective visual tool as it displays data at a glance, facilitates comparison, and can reveal trends and relationships within the data such as changes over time, frequency distribution, and correlation or relative share of a whole. Text, tables, and graphs for data and information presentation are very powerful communication tools. They can make an article easy to understand, attract and sustain the interest of readers, and efficiently present large amounts of complex information. Moreover, as journal editors and reviewers glance at these presentations before reading the whole article, their importance cannot be ignored.