Higher body mass index deteriorates postoperative outcomes of pancreaticoduodenectomy.

BACKGROUND: Previous studies presented controversies in impact of body mass index (BMI) on perioperative complications in pancreatectomy, and mainly focused on Western population. This study aimed to explore the impact of BMI on perioperative outcomes in Chinese patients undergoing pancreaticoduodenectomy. METHODS: Seven hundred and seven adult patients undergoing open pancreaticoduodenectomy between January 2005 and December 2016 at Ruijin Hospital were studied retrospectively and categorized as obese (BMI ≥25 kg/m2), overweight (BMI ≥23 kg/m2 and <25 kg/m2), or normal weight (BMI ≥18.5 kg/m2 and <23 kg/m2). Associations of these BMI groups with perioperative outcomes were evaluated. RESULTS: The overweight and obese groups experienced higher risk of clinically related postoperative pancreatic fistula (CR-POPF) (7.6% vs. 9.9% vs. 17.6%, P = 0.002) and re-operation (1.1% vs. 2.5%  vs. 5.1%, P = 0.017), and longer systemic inflammation response syndrome (SIRS) duration [2 (1-9) d vs. 2 (1-7) d vs. 3 (1-10) d, P = 0.003] and postoperative hospital stay [19 (2-84) d vs. 19 (7-158) d vs. 23 (8-121) d, P = 0.023] than the normal weight group did. The multiple logistic regression models showed obese as an independent risk factor for CR-POPF (P = 0.013). The multiple linear regression analysis confirmed BMI as a predictor for prolonged postoperative hospital stay (P = 0.005). CONCLUSIONS: Higher BMI results in higher morbidity of Chinese patients undergoing open pancreaticoduodenectomy. Pancreaticoduodenectomy is still a safe surgery procedure for overweight and obese patients, with intensive perioperative management.

An innovative modeling approach using Qual2K and HEC-RAS integration to assess the impact of tidal effect on River Water quality simulation.

Water quality modeling has been shown to be a useful tool in strategic water quality management. The present study combines the Qual2K model with the HEC-RAS model to assess the water quality of a tidal river in northern Taiwan. The contaminant loadings of biochemical oxygen demand (BOD), ammonia nitrogen (NH(3)-N), total phosphorus (TP), and sediment oxygen demand (SOD) are utilized in the Qual2K simulation. The HEC-RAS model is used to: (i) estimate the hydraulic constants for atmospheric re-aeration constant calculation; and (ii) calculate the water level profile variation to account for concentration changes as a result of tidal effect. The results show that HEC-RAS-assisted Qual2K simulations taking tidal effect into consideration produce water quality indices that, in general, agree with the monitoring data of the river. Comparisons of simulations with different combinations of contaminant loadings demonstrate that BOD is the most import contaminant. Streeter-Phelps simulation (in combination with HEC-RAS) is also performed for comparison, and the results show excellent agreement with the observed data. This paper is the first report of the innovative use of a combination of the HEC-RAS model and the Qual2K model (or Streeter-Phelps equation) to simulate water quality in a tidal river. The combination is shown to provide an alternative for water quality simulation of a tidal river when available dynamic-monitoring data are insufficient to assess the tidal effect of the river.

Influence of biological oxygen demand degradation patterns on water-quality modeling for rivers running through urban areas.

Water-quality modeling has been used as a support tool for water-resources management. The Streeter-Phelps (SP) equation is one often-used algorithm in river water-quality simulation because of its simplicity and ease in use. To characterize the river dissolved oxygen (DO) sag profile, it only considers that the first-order biological oxygen demand (BOD) degradation and atmospheric reaeration are the sink and source in a river, respectively. In the river water-quality calculation, the assumption may not always provide satisfactory simulation due to an inappropriate description of BOD degradation. In the study, various patterns of BOD degradation were combined with the oxygen reaeration to simulate the DO sag profile in a river. Different BOD degradation patterns used include the first-order decay, mixed second-order decay, and oxygen-inhibition decay. The results shows that the oxygen-inhibition SP equation calculates higher BOD and DO concentration, while the mixed second SP equation calculates the least among the three tested models. In river-water calculation of Keelung River, the SP and oxygen-inhibition SP equations calculate similar BOD and DO concentrations, and the mixed second SP equation calculates the least BOD and DO concentration. The pollution loading of BOD and atmospheric reaeration constant are the two important factors that have significant impacts on aqueous DO concentration. In the field application, it is suggested that the mixed second SP equation be employed in water-quality simulation when the monitoring data exhibits a faster trend in BOD decay. The oxygen-inhibition SP equation may calculate the water quality more accurately when BOD decay is slower.