Post-operative alarm signs in the rapid response system and hospital mortality after non-cardiac surgery.

BACKGROUND: A variety of rapid response systems (RRSs) based on the systematic assessment of vital signs and laboratory tests have been developed to reduce hospital mortality through the early detection of alarm signs, while deterioration may still be reversible. This study aimed to determine the association between alarm signs and post-operative hospital mortality during post-operative days (POD) 0-3 in patients undergoing non-cardiac surgery. METHODS: This retrospective observational study used data from the registry of a single tertiary academic hospital. The study population included patients who were ≥18 years old, admitted between 1 January 2013 and 30 June 2018 for non-cardiac surgery, and subsequently transferred to the general ward. RESULTS: A total of 116 329 patients were included in the analysis. Among them, 10 099 patients (8.7%) showed positive alarm criteria and triggered the RRS in the post-operative ward during POD 0-3. In the multivariate logistic regression model, PaO2 <55 mm Hg, SpO2 <90%, and total CO2 <15 mmol/L were associated with a 3.57-, 3.46-, and 12.53-fold increase in post-operative hospital mortality, respectively. Moreover, when compared to the no alarm signs group, patients with 1, 2, 3, and ≥4 alarm signs showed a 2.79-, 2.76-, 6.54-, and 20.02-fold increase in hospital mortality, respectively. CONCLUSION: Increased post-operative hospital mortality was found to be associated with alarm signs detected by the RRS during POD 0-3. The post-operative alarm signs detected by the RRS may therefore be useful in determining high-risk patients who require medical interventions in the surgical ward.

A rapid response system reduces the incidence of in-hospital postoperative cardiopulmonary arrest: a retrospective study.

PURPOSE: Rapid response systems (RRSs) have been introduced into hospitals to help reduce the incidence of sudden cardiopulmonary arrest (CPA). This study evaluated whether an RRS reduces the incidence of in-hospital postoperative CPA. METHODS: This retrospective before-and-after analysis evaluated data collected from electronic medical records during a pre-intervention (January 2008 to September 2012) and post-intervention (implementation of an RRS) interval (October 2012 to December 2016) at a single tertiary care institution. The primary outcome was a change in the rate of CPA in surgical patients recovering in a general ward. A Poisson regression analysis adjusted for the Charlson Comorbidity Index (CCI) was used to compare CPA rates during these two intervals. RESULTS: Of the 207,054 surgical procedures performed during the study period, mean (95% confidence interval [CI]) CPA events per 10,000 cases of 7.46 (5.72 to 9.19) and 5.19 (3.85 to 6.52) were recorded before and after RRS intervention, respectively (relative risk [RR], 0.73; 97.5% CI, 0.48 to 1.13; P = 0.103). Cardiopulmonary arrest incidence was reduced during RRS operational hours of 07:00-22:00 Monday-Friday and 07:00-12:00 Saturday (RR, 0.56; 97.5% CI, 0.31 to 1.02; P = 0.027) but was unchanged when the RRS was not operational (RR, 0.86; 97.5% CI, 0.52 to 1.40; P = 0.534). The CCI-adjusted RR of CPA after RRS implementation was lower than before RRS intervention (0.63; 97.5% CI, 0.41 to 0.98; P = 0.018) but this reduction was still only apparent during RRS operational hours (RR, 0.48; 97.5% CI, 0.27 to 0.89; P = 0.008 vs RR, 0.85; 97.5% CI, 0.45 to 1.58; P = 0.55). CONCLUSION: Implementation of an RRS reduced the incidence of postoperative CPA in patients recovering in a general ward. Furthermore, this reduction was observed only during RRS operational hours.

Characterization of biofilm structure and its effect on membrane permeability in MBR for dye wastewater treatment.

Two membrane bioreactors were operated at aerobic (DO=6.0mg/L) and anoxic (DO<0.3mg/L) conditions for the treatment of synthetic dye wastewater to determine the effect of dissolved oxygen on membrane filterability. The rate of membrane fouling for the anoxic MBR was five times faster than that for the aerobic MBR. Differences in the nature of the biofilm that was formed on the membrane surface as the result of different DO level was the main factor in the different fouling rates. The biofilm structure was characterized using digital image analysis techniques. Biofilm images were obtained using confocal laser scanning microscopy (CLSM) at various operation points. Structural parameters were then computed from these images using an image analysis software (ISA-2). The structural parameters indicated that the anoxic biofilm was thinner than the aerobic biofilm but the anoxic biofilm was spread out on the membrane surface more uniformly and densely, resulting in the higher membrane fouling. Based on the extracellular polymeric substances (EPS) visualization and quantification, it was also found that EPS, key membrane foulants were spread out more uniformly in the anoxic biofilm in spite of lower amount of EPS compared to that in the aerobic biofilm.