Sehoon Park

Design and evaluation of mobile offloading system for web-centric devices

Increasingly, smartphones are becoming one of the most popular mobile devices in the personal computing environment. As the need for a variety of mobile applications increases, the target mobile platform is a primary concern for mobile application developers. To reduce design complexity for different platforms and enhance the compatibility of applications on various mobile OSes, a JavaScript-based web environment became a main target framework for smartphone applications. Two particular characteristics of a smartphone are restricted power supply and low-end hardware resources, compared to high-end servers. Computing-intensive and rich graphics-based applications in a smartphone may fully utilize the CPU and consume a large amount of the battery power accordingly.In this paper, we propose a platform-independent mobile offloading system, which is a delegated system for a web centric devices environment. Our offloading architecture uses a built-in proxy system that splits the original JavaScript-based application codes into the following two parts: a lightweight code for the mobile client and a computationally heavy code that runs on the server system. We adopt one of the web applications utilizing a combinatory search for our case study. Our evaluation shows that our mobile offloading system reduces the response time of the application running in the web browser and enables a high workload application to run on relatively low-end mobile devices. In addition, this method reduces power consumption of the device. Therefore, this web-based offloading architecture creates a new mobile computing environment and supports various OS platforms of mobile clients.

Impact of Electronic Acute Kidney Injury (AKI) Alerts With Automated Nephrologist Consultation on Detection and Severity of AKI: A Quality Improvement Study

BACKGROUND Several electronic alert systems for acute kidney injury (AKI) have been introduced. However, their clinical benefits require further investigation. STUDY DESIGN Before-and-after quality improvement study. SETTING & PARTICIPANTS A tertiary teaching hospital in Korea, which adopted an AKI alert system on June 1, 2014. Before and after launch of the alert system, 1,884 and 1,309 patients with AKI were included in the usual-care and alert groups, respectively. QUALITY IMPROVEMENT PLAN Implementation of an AKI alert system through which clinicians could generate automated consultations to the nephrology division for all hospitalized patients. OUTCOMES Primary outcomes included overlooked AKI events, defined as not measuring the follow-up creatinine value, and the consultation pattern of clinicians. Secondary outcomes were severe AKI events; AKI recovery, defined based on the creatinine-based criterion; and patient mortality. MEASUREMENTS ORs for events of overlooked AKI, early consultation, and severe AKI were calculated with logistic regression. AKI recovery rate and patient mortality were assessed using Cox regression. RESULTS After introduction of the alert system, the odds of overlooked AKI events were significantly lower (adjusted OR, 0.40; 95% CI, 0.30-0.52), and the odds of an early consultation with a nephrologist were greater (adjusted OR, 6.13; 95% CI, 4.80-7.82). The odds of a severe AKI event was reduced after implementation of the alerts (adjusted OR, 0.75; 95% CI, 0.64-0.89). Furthermore, the likelihood of AKI recovery was improved in the alert group (adjusted HR, 1.70; 95% CI, 1.53-1.88). Mortality was not affected by the AKI alert system (adjusted HR, 1.07; 95% CI, 0.68-1.68). LIMITATIONS Possible unreported differences between the alert and usual-care groups. CONCLUSIONS Implementation of the AKI alert system was associated with beneficial effects in terms of an improved rate of recovery from AKI. Therefore, widespread adoption of such systems could be considered in general hospitals.

PIOS: A platform-independent offloading system for a mobile web environment

Increasingly, smart phones are becoming one of the most popular mobile devices in personal computing environment. As the need for a variety of mobile applications is increasing, the target mobile platform is a primary concern for mobile application developers. To reduce design complexity for different platforms and enhance the compatibility of applications on various mobile OSes, a JavaScript-based web environment became a main target framework for smart phone applications. Computing-intensive and rich graphics-based applications in a smart phone may fully utilize the CPU, and consume a large amount of the battery power accordingly. In this paper, we propose PIOS, a platform-independent offloading system, which is a delegated system for a mobile web environment. Our evaluation shows that PIOS increases the response time of the application, and reduces power consumption of the device. Our web-based offloading architecture creates a new mobile computing environment.

Elevated baseline potassium level within reference range is associated with worse clinical outcomes in hospitalised patients

The clinical significance of elevated baseline serum potassium (K+) levels in hospitalised patients is rarely described. Hence, we performed a retrospective study assessing the significance of elevated K+ levels in a one-year admission cohort. Adult patients without hypokalaemia or end-stage renal disease were included. Adverse outcomes were all-cause mortality, hospital-acquired acute kidney injury, and events of arrhythmia. In total, 17,777 patients were included in the study cohort, and a significant difference (P < 0.001) was observed in mortality according to baseline serum K+ levels. The adjusted hazard ratios (HRs) and associated 95% confidence intervals (CIs) of all-cause mortality for K+ levels above the reference range of 3.6–4.0 mmol/L were as follows: 4.1–4.5 mmol/L, adjusted HR 1.075 (95% CI 0.981–1.180); 4.6–5.0 mmol/L, adjusted HR 1.261 (1.105–1.439); 5.1–5.5 mmol/L, adjusted HR 1.310 (1.009–1.700); >5.5 mmol/L, adjusted HR 2.119 (1.532–2.930). Moreover, the risks of in-hospital acute kidney injury and arrhythmia were higher in patients with serum K+ levels above 4.0 mmol/L and 5.5 mmol/L, respectively. In conclusion, increased serum K+ levels, including mild elevations may be related to worse prognosis. Close monitoring and prompt correction of underlying causes or hyperkalaemia itself is warranted for admitted patients.

Metabolic Acidosis and Long-Term Clinical Outcomes in Kidney Transplant Recipients

Metabolic acidosis (MA), indicated by low serum total CO2 (TCO2) concentration, is a risk factor for mortality and progressive renal dysfunction in CKD. However, the long-term effects of MA on kidney transplant recipients (KTRs) are unclear. We conducted a multicenter retrospective cohort study of 2318 adult KTRs, from January 1, 1997 to March 31, 2015, to evaluate the prevalence of MA and the relationships between TCO2 concentration and clinical outcomes. The prevalence of low TCO2 concentration (<22 mmol/L) began to increase in KTRs with eGFR<60 ml/min per 1.73 m2 and ranged from approximately 30% to 70% in KTRs with eGFR<30 ml/min per 1.73 m2 Multivariable Cox proportional hazards models revealed that low TCO2 concentration 3 months after transplant associated with increased risk of graft loss (hazard ratio [HR], 1.74%; 95% confidence interval [95% CI], 1.26 to 2.42) and death-censored graft failure (DCGF) (HR, 1.66; 95% CI, 1.14 to 2.42). Cox regression models using time-varying TCO2 concentration additionally demonstrated significant associations between low TCO2 concentration and graft loss (HR, 3.48; 95% CI, 2.47 to 4.90), mortality (HR, 3.16; 95% CI, 1.77 to 5.62), and DCGF (HR, 3.17; 95% CI, 2.12 to 4.73). Marginal structural Cox models adjusted for time-varying eGFR further verified significant hazards of low TCO2 concentration for graft loss, mortality, and DCGF. In conclusion, MA was frequent in KTRs despite relatively preserved renal function and may be a significant risk factor for graft failure and patient mortality, even after adjusting for eGFR.

SOME: Selective Offloading for a Mobile Computing Environment

As the popularity of mobile devices increase, more and more smart phones are being utilized as main computing devices in recent years. Applications for mobile devices have been widely developing even more prevalent than those for PCs. Most mobile applications also integrate with web browsers, with JavaScript serving as an important framework for web-based mobile applications. However, these applications require great amounts of computational power and energy. In addition, relatively low-end mobile devices that pose some limitations in supporting complicated web resource are widely used in developing countries. In this paper, we propose SOME architecture, which is an offloading system for mobile applications, in an effort to reduce the computational cost of mobile devices. We design and implement a delegated system that splits the original JavaScript-based application codes into two parts: a lightweight code for the client and a computationally heavy code to run on a server machine. In our evaluation, our system shows better performance in casual turn-based applications. Overall, the SOME architecture creates a new mobile computing environment that increases the total performance and overcomes resource limitation without platform dependence of mobile clients.

Midterm eGFR and Adverse Pregnancy Outcomes: The Clinical Significance of Gestational Hyperfiltration

BACKGROUND AND OBJECTIVES Although hemodynamic adaptation plays a crucial role in maintaining gestation, the clinical significance of midterm renal hyperfiltration (MRH) on pregnancy outcomes is unknown. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS This was an observational cohort study. Women with a singleton pregnancy and a serum creatinine measurement during their second trimester were followed at two university hospitals in Korea between 2001 and 2015. Those with substantial renal function impairment or who delivered during the second trimester were not considered. MRH was represented by the highest eGFR, which was calculated using the Chronic Kidney Disease Epidemiology Collaboration method. An adverse pregnancy event was defined by the composition of preterm birth (gestational age <37 weeks), low birth weight (<2.5 kg), and preeclampsia. RESULTS Data from 1931 pregnancies were included. The relationship between midterm eGFR and adverse pregnancy outcomes, which occurred in 538 mothers, was defined by a nonlinear U-shaped curve. The adjusted odds ratio and associated 95% confidence interval (95% CI) of an adverse pregnancy outcome for eGFR levels below and above the reference level of 120-150 ml/min per 1.73 m2 were 1.97 (95% CI, 1.34 to 2.89; P<0.001) for ≥150 ml/min per 1.73 m2; 1.57 (95% CI, 1.23 to 2.00; P<0.001) for 90-120 ml/min per 1.73 m2; and 4.93 (95% CI, 1.97 to 12.31; P<0.001) for 60-90 ml/min per 1.73 m2. Moreover, among mothers without baseline CKD, women with adverse pregnancy outcomes had less prominent MRH than those without (P<0.001). CONCLUSIONS We identified a unique U-shaped relationship between midterm eGFR and adverse pregnancy outcomes, and the optimal range of midterm eGFR levels was 120-150 ml/min per 1.73 m2. In those without evident functional renal impairment, the absence of prominent MRH might be a significant risk factor for poor pregnancy outcomes.

A case of gemcitabine-induced thrombotic microangiopathy in a urothelial tumor patient with a single kidney

Thrombotic microangiopathy (TMA) is a rare complication of gemcitabine treatment. A 55-year-old man with a history of urothelial cancer underwent right ureteronephrectomy and palliative chemotherapy. The patient presented with dyspnea, generalized edema with foamy urine, and new-onset hypertension with acute kidney injury (AKI). Although AKI with oliguria was evident, thrombocytopenia and hemolytic anemia were not overt. To determine the cause of rapidly progressive azotemia, kidney biopsy was performed despite a single kidney and revealed chronic TMA. Microangiopathic hemolytic anemia and thrombocytopenia developed after renal biopsy. Diagnosed as gemcitabine-induced TMA, gemcitabine cessation and active treatment including steroids, plasmapheresis, and rituximab were carried out, but the patient׳s condition progressed to a dialysis-dependent state. Gemcitabine-induced TMA is often difficult to diagnose because of its variable clinical course. Therefore, heightened awareness of this potentially lethal complication of gemcitabine is essential; renal biopsy may be helpful.

Elevated bilirubin levels are associated with a better renal prognosis and ameliorate kidney fibrosis.

Background Bilirubin has been reported to protect against kidney injury. However, further studies highlighting the beneficial effects of bilirubin on renal fibrosis and chronic renal function decline are necessary. Methods We assessed a prospective cohort with a reference range of total bilirubin levels. The primary outcome was a 30% reduction in the estimated glomerular filtration rate (eGFR) from baseline, and the secondary outcome was a doubling of the serum creatinine levels, halving of the eGFR and the initiation of dialysis. In addition, experiments with tubular epithelial cells and C57BL/6 mice were performed to investigate the protective effects of bilirubin on kidney fibrosis. Results As a result, 1,080 patients were included in the study cohort. The study group with relative hyperbilirubinemia (total bilirubin 0.8–1.2 mg/dL) showed a better prognosis in terms of the primary outcome (adjusted hazard ratio (HR) 0.33, 95% confidence interval (CI) 0.19–0.59, P < 0.001) and the secondary outcome (adjusted HR 0.20, 95% CI 0.05 to 0.71, P = 0.01) than that of the control group. Moreover, the bilirubin-treated mice showed less fibrosis in the unilateral ureteral obstruction (UUO) model (P < 0.05). In addition, bilirubin treatment decreased fibronectin expression in tubular epithelial cells in a dose-dependent manner (P < 0.05). Conclusions Mildly elevated serum bilirubin levels were associated with better renal prognosis, and bilirubin treatment induced a beneficial effect on renal fibrosis. Therefore, bilirubin could be a potential therapeutic target to delay fibrosis-related kidney disease progression.

Pregnancy in women with immunoglobulin A nephropathy: are obstetrical complications associated with renal prognosis?

Background Recent studies regarding immunoglobulin A nephropathy (IgAN) suggest no relationship between pregnancy and disease progression, although complicated pregnancies and impaired renal function are closely related. Methods This study used a propensity-score-matched cohort analysis. Among biopsy-confirmed IgAN women in three hospitals in Korea, those who experienced pregnancy after their diagnosis were included in the study group. Renal outcome was the composite of serum creatinine doubling, estimated glomerular filtration rate (eGFR) halving and events of end-stage renal disease. Pregnancies with preterm birth, low birth weight and pre-eclampsia were defined as complicated. Results Overall, 59 IgAN women who became pregnant after their diagnosis, and the same number of IgAN women who did not experience pregnancy were included in the control group. Although pregnancy itself did not worsen renal outcomes [adjusted hazard ratio (HR): 1.51; 95% confidence interval (CI) 0.57-4.01; P = 0.41], mothers with complicated pregnancies experienced worse renal prognosis, even after adjustment for baseline and pre-gestational characteristics (adjusted HR: 5.07; 95% CI 1.81-14.22; P = 0.002). Moreover, this relationship was only significant in mothers with decreased renal function (eGFR <60 mL/min/1.73 m2) (adjusted HR: 18.70; 95% CI 1.63-214.40; P = 0.02), baseline hypertension (adjusted HR: 4.17; 95% CI 1.13-15.33; P = 0.03) and overt proteinuria (≥1 g/day) (adjusted HR: 4.21; 95% CI 1.24-14.27; P = 0.02). In contrast, patients who experienced pregnancies without complications showed better renal outcomes than did those without post-biopsy pregnancy (P = 0.01). Conclusion Obstetric complications in patients with high renal risk, rather than pregnancy itself, are associated with renal progression of IgAN women.