Low-Complexity Tracking Control of Unknown Strict-Feedback Systems With Quantitative Performance Guarantees.

This article is concerned with the prescribed performance tracking control problem for the strict-feedback systems with unknown nonlinearities and unmatched disturbances. The challenge lies in the realization of a complete performance specification for trajectory tracking in the sense of quantitatively regulating the peak value, overshoot, settling time, and accuracy while ensuring that the initial condition holds naturally. To this end, an error transformation, equipped with a shifting function, is introduced and incorporated with a new-type barrier function. Then, a class of performance functions is exploited to quantify the settling times and steady-state bounds of the intermediate errors. Moreover, to improve the flexibility of formulating performance specifications for the tracking error, a pair of asymmetric performance boundaries are further designed. With their combination, a novel robust prescribed performance control (PPC) approach is proposed in this article. It not only achieves the quantitative performance guarantees but also preserves the unique simplicity of PPC, evading the needs for function approximation, parameter identification, disturbance estimation, derivative calculation, or command filtering. The above theoretical findings are confirmed via three simulation studies.

Mortality risk factors in patients receiving ECPR after cardiac arrest: Development and validation of a clinical prognostic prediction model.

BACKGROUND: Previous studies have shown an increasing trend of extracorporeal cardiopulmonary resuscitation (ECPR) use in patients with cardiac arrest (CA). Although ECPR have been found to reduce mortality in patients with CA compared with conventional cardiopulmonary resuscitation (CCPR), the mortality remains high. This study was designed to identify the potential mortality risk factors for ECPR patients for further optimization of patient management and treatment selection. METHODS: We conducted a prospective, multicentre study collecting 990 CA patients undergoing ECPR in 61 hospitals in China from January 2017 to May 2022 in CSECLS registry database. A clinical prediction model was developed using cox regression and validated with external data. RESULTS: The data of 351 patients meeting the inclusion criteria before October 2021 was used to develop a prediction model and that of 68 patients after October 2021 for validation. Of the 351 patients with CA treated with ECPR, 227 (64.8%) patients died before hospital discharge. Multivariate analysis suggested that a medical history of cerebrovascular diseases, pulseless electrical activity (PEA)/asystole and higher Lactate (Lac) were risk factors for mortality while aged 45-60, higher pH and intra-aortic balloon pump (IABP) during ECPR have protective effects. Internal validation by bootstrap resampling was subsequently used to evaluate the stability of the model, showing moderate discrimination, especially in the early stage following ECPR, with a C statistic of 0.70 and adequate calibration with GOF chi-square = 10.4 (p = 0.50) for the entire cohort. Fair discrimination with c statistic of 0.65 and good calibration (GOF chi-square = 6.1, p = 0.809) in the external validation cohort demonstrating the model's ability to predict in-hospital death across a wide range of probabilities. CONCLUSION: Risk factors have been identified among ECPR patients including a history of cerebrovascular diseases, higher Lac and presence of PEA or asystole. While factor such as age 45-60, higher pH and use of IABP have been found protective against in-hospital mortality. These factors can be used for risk prediction, thereby improving the management and treatment selection of patients for this resource-intensive therapy.

Adaptive fuzzy prescribed time tracking control for nonlinear systems with input saturation.

This article investigates the adaptive fuzzy prescribed time tracking control problem for a class of strict-feedback systems simultaneously considering the user-defined asymmetric tracking performance, input saturation, and external disturbances. From the perspective of ensuring the reliability for control implementation, a saturation-based fixed-time funnel boundary is constructed by embedding the modification signals related to input saturation errors into a funnel function, which is capable of automatically enlarging or recovering itself when input saturation occurs or disappears, thereby reducing the risk of system singularity. Subsequently, by constructing a fixed-time tracking performance function, any known bounded tracking error is recast into a new variable with a zero initial value. With such a treatment, funnel boundaries are no longer redeveloped for different initial tracking errors, and meanwhile the behavior of the tracking error is pre-specified as needed over a finite time interval. Also, auxiliary systems are devised to generate the aforesaid modification signals, while compensating for the adverse impact resulting from input saturation. Remarkably, by feat of the backstepping design based on the fuzzy approximation, it is proven that the tracking error converges to a user-defined region within a prescribed time (known as the practically prescribed time tracking), which is achieved without the fractional power feedback of system states. Finally, two simulation examples are presented to confirm the feasibility and effectiveness of the developed approach.

Impact of renal complications on outcome in adult patients with acute fulminant myocarditis receiving venoarterial extracorporeal membrane oxygenation: an analysis of nationwide CSECLS database in China.

BACKGROUND: Limited data are available on renal complications in patients with acute fulminant myocarditis (AFM) receiving venoarterial extracorporeal membrane oxygenation (VA-ECMO) support in China. To evaluate the impact of renal complications on outcomes in adult patients with AFM supported with VA-ECMO. METHODS: Data were extracted from Chinese Society of ExtraCorporeal Life Support (CSECLS) Registry database. Adult patients who were diagnosed with AFM receiving VA-ECMO support in the database were included. The primary outcome was 30-day mortality in patients with AFM supported with VA-ECMO. Logistic regression model was used to examine the impact of renal complications on 30-day mortality by adjusting confounders. RESULTS: A total of 202 patients were included. The median age was 38 years (IQR 29-48) and males (n = 103) represented 51.0% of the total accounted patients. The median ECMO duration was 142.9 h (IQR 112.1-188.8 h). 178 (88.1%) patients weaned from ECMO and 156 (71.9%) patients survived. 94(46.5%) patients developed renal complications while on ECMO course. Patients with renal complications had higher 30-day mortality (40.7% (37 of 94) vs 8.3% (9 of 108), P < 0.001) compared with those without. The development of renal complications was related to a 3.12-fold increase risk of 30-day mortality (adjusted OR 3.120, 95%CI 1.002-6.577, P = 0.049). Increasing age (adjusted OR1.025, 95% CI 1.008-1.298, P = 0.040) and higher SOFA score (adjusted OR 1.162, 95%CI 1.012-1.334, P = 0.034) were independent risk factors of renal complications. CONCLUSIONS: Our findings demonstrated that patients with AFM receiving VA-ECMO at high risk of developing renal complications. Advancing age and higher SOFA score was associated with increased risk of developing renal complications. The onset of renal complications was significantly associated with 30-day mortality.

Impact of Nosocomial Infection on in-Hospital Mortality Rate in Adult Patients Under Venoarterial Extracorporeal Membrane Oxygenation After Cardiac Surgery.

Objective: There was no consensus on the impact of nosocomial infection on In-hospital mortality rate in patients receiving ECMO. This study aimed to investigate the impact of nosocomial infection (NI) on In-hospital mortality rate in adult patients receiving venoarterial extracorporeal membrane oxygenation (VA-ECMO) after cardiac surgery. Materials and Methods: This retrospective study included 503 adult patients who underwent VA-ECMO after cardiac surgery. The impact of time-dependent NIs on In-hospital mortality rate within 28 days of ECMO initiation was investigated using a Cox regression model. The cumulative incidence function for death was compared between patients with NIs and those without NIs using a competing risk model. Results: Within 28 days after ECMO initiation, 206 (41.0%) patients developed NIs, and 220 (43.7%) patients died. The prevalence rates of NIs were 27.8% and 20.3% during and after ECMO therapy, respectively. The incidence rates of NIs during and after ECMO therapy were 49‰ and 25‰, respectively. Time-dependent NI was an independent risk factor for predicting death (hazard ratio = 1.05, 95% confidence interval = 1.00-1.11). The cumulative incidence of death in patients with NI was significantly higher than that in patients without NI at each time point within 28 days of ECMO initiation. (Z = 5.816, P = 0.0159). Conclusion: NI was a common complication in adult patients who received VA-ECMO after cardiac surgery, and time-dependent NI was an independent risk factor for predicting mortality in these patients. Using a competing risk model, we confirmed that NIs increased the risk of In-hospital mortality rate in these patients.

Clinical outcome and risk factors for acute fulminant myocarditis supported by venoarterial extracorporeal membrane oxygenation: An analysis of nationwide CSECLS database in China.

BACKGROUND: To assess the outcomes and risk factors for adult patients with acute fulminant myocarditis (AFM) supported with venoarterial extracorporeal membrane oxygenation (VA ECMO) in China mainland. METHODS: Data were extracted from Chinese Society of ExtraCorporeal Life Support (CSECLS) Registry database. Data from adult patients who were diagnosed with AFM and needed VA ECMO in the database were retrospectively analyzed. The primary outcome was 90-day mortality after ECMO initiation in patients with AFM supported with VA ECMO. Cox proportional hazard regression model was used to examine the risk factors associated with 90-day mortality. RESULTS: Among 221 patients enrolled and followed up to 90 days, 186 (84.2%) patients weaned from ECMO and 159 (71.9%) patients survived and discharged home. The median age was 38 years (IQR 29-49) and males (n = 115) represented 52.0% of the total accounted patients. The median ECMO duration was 134 h (IQR 96-177 h). The main adverse event during ECMO course was bleeding (16.3%), followed by infection (15.4%). In the multivariate Cox model analysis, cardiac arrest prior to ECMO initiation (adjusted HR 2.529; 95%CI: 1.341-4.767, p = 0.004), lower pH value (adjusted HR 0.016; 95%CI: 0.010-0.059, p < 0.001) and higher lactate concentration at 24 h after ECMO initiation (adjusted HR 1.146; 95%CI: 1.075-1.221, p < 0.001) were associated with 90-day mortality. CONCLUSIONS: 71.9% patients with AFM (clinical diagnosed) supported with VA ECMO survived. Cardiac arrest prior to ECMO, lower pH and higher lactate concentration at 24 h after ECMO initiation were correlated with 90-day mortality of AFM patients supported with VA ECMO.

A nomogram to predict nosocomial infection in patients on venoarterial extracorporeal membrane oxygenation after cardiac surgery.

INTRODUCTION: After cardiac surgery, patients on venoarterial extracorporeal membrane oxygenation (VA-ECMO) have a higher risk of nosocomial infection in the intensive care unit (ICU). We aimed to establish an intuitive nomogram to predict the probability of nosocomial infection in patients on VA-ECMO after cardiac surgery. METHODS: We included patients on VA-ECMO after cardiac surgery between January 2011 and December 2020 at a single center. We developed a nomogram based on independent predictors identified using univariate and multivariate logistic regression analyses. We selected the optimal model and assessed its performance through internal validation and decision-curve analyses. RESULTS: Overall, 503 patients were included; 363 and 140 patients were randomly divided into development and validation sets, respectively. Independent predictors derived from the development set to predict nosocomial infection included older age, white blood cell (WBC) count abnormality, ECMO environment in the ICU, and mechanical ventilation (MV) duration, which were entered into the model to create the nomogram. The model showed good discrimination, with areas under the curve (95% confidence interval) of 0.743 (0.692-0.794) in the development set and 0.732 (0.643-0.820) in the validation set. The optimal cutoff probability of the model was 0.457 in the development set (sensitivity, 0.683; specificity, 0.719). The model showed qualified calibration in both the development and validation sets (Hosmer-Lemeshow test, p > .05). The threshold probabilities ranged from 0.20 to 0.70. CONCLUSIONS: For adult patients receiving VA-ECMO treatment after cardiac surgery, a nomogram-monitoring tool could be used in clinical practice to identify patients with high-risk nosocomial infections and provide an early warning.

Risk factors and outcomes for patients with bleeding complications receiving extracorporeal membrane oxygenation: An analysis of the Chinese Extracorporeal Life Support Registry.

OBJECTIVE: Bleeding is a severe complication of patients supported with extracorporeal membrane oxygenation (ECMO). This study aimed to analyze the occurrence, risk factors, and clinical outcomes of patients on ECMO with bleeding complications. METHODS: ECMO cases reported to the multicenter ECMO registry database of the Chinese Society of Extracorporeal Life Support (CSECLS) from January 2017 to December 2020 were enrolled. General information, ECMO indications, application, complications, and patient outcomes were collected and analyzed. RESULTS: A total of 6541 ECMO patients from 112 centers were enrolled. Overall, 1185 patients (18.1%) presented with one of the following bleeding complications, including 82 cases (1.3%) with severe bleeding during ECMO catheterization, 462 cases (7.1%) with bleeding at the ECMO cannulation site, 200 cases (3.5%) with bleeding at the surgical site, 180 cases (2.8%) with cerebral hemorrhage, 99 cases (1.5%) with pulmonary hemorrhage, 200 cases (3.5%) with gastrointestinal hemorrhage, 82 cases (1.3%) with ECMO withdrawal, and 118 (1.8%) deaths due to severe bleeding. Extracorporeal cardiopulmonary resuscitation (ECPR) patients had the highest incidence of bleeding complications (22.4%), followed by those on circulatory support (18.7%) and respiratory support (15.4%) (p < 0.001). Multivariate analysis showed that pediatric patients (odds ratio [OR] 1.509, p < 0.001), patients receiving renal replacement therapy (OR 1.932, p < 0.001), and patients receiving central ECMO cannulation (OR 3.023, p < 0.001) were independent risk factors for all bleeding complications, while peripheral cannulation (OR 0.712, p < 0.001) was an independent protective factor. Patients with any bleeding complication had significantly higher in-hospital mortality than patients without (61.9% vs. 46.3%, p < 0.001). CONCLUSION: Up to 18.1% of ECMO patients in the CSECLS registry experienced bleeding complications, which was associated with higher in-hospital mortality, especially in patients who received ECPR, patients on circulatory support, and pediatric patients, which should arouse the attention of clinicians.

Dynamic and Hybrid Configurations for Extracorporeal Membrane Oxygenation: An Analysis of the Chinese Extracorporeal Life Support Registry.

Dynamic or hybrid configurations for extracorporeal membrane oxygenation (ECMO) are needed when patient physiology or clinical conditions change. Dynamic configurations included configurations converting from veno-arterial (V-A) ECMO or veno-venous (V-V) ECMO to other forms. Hybrid configurations included venous-arteriovenous (V-AV) and venovenous-arterial (VV-A) ECMO. This study retrospectively analyzed a total of 3,814 ECMO cases (3,102 adult cases) reported to the Chinese Society of Extracorporeal Life Support from January 1, 2017 to December 31, 2019. Eight-three adult patients had dynamic or hybrid ECMO configurations, whose primary diagnoses included cardiogenic shock (33.7%), cardiac arrest (6.0%), acute respiratory failure (39.8%), septic shock (9.6%), multiple trauma (3.6%), pulmonary hypertension (3.6%), and others (3.6%). Configuration changes occurred in 37 patients with the initial configuration of VA (20 to VV, 13 to V-AV, and 4 to VV-A) and 27 with the initial configuration of VV (7 to VA, and 20 to V-AV). A total of 46 (55.4%) patients received hybrid configurations of V-AV and 10 (12.0%) received VV-A. Patients with the initial configuration of VV who converted to other configurations had higher in-hospital mortality (74.1%) than other initial configurations (VA 45.9%, V-AV 76.9%, VV-A 66.7%, P = 0.021). We concluded that dynamic or hybrid ECMO configurations were used in various underlying diseases, in which V-AV was most commonly used. Patients receiving VV ECMO for respiratory support initially, who then converted to other configurations for both respiratory and circulatory support, had significantly worst outcomes among the groups studied. The initial configuration should be selected carefully after thorough assessment of patient condition.

Risk factors of acute renal injury and in-hospital mortality in adult patients with postcardiotomy cardiogenic shock requiring veno-arterial extracorporeal membrane oxygenation: utility of MELD-XI score.

BACKGROUND: The suitability of model for end-stage liver disease excluding international normalized ratio (MELD-XI) score to predict the incidence of acute kidney injury (AKI) and in-hospital mortality in adult patients with postcardiotomy cardiogenic shock (PCS) requiring venoarterial extracorporeal membrane oxygenation (VA ECMO) remains uncertain. This study was performed to explore whether the MELD-XI score has the association with the incidence of AKI and in-hospital mortality in these patients. METHODS: Adult patients with PCS requiring VA ECMO from January 2012 to December 2017 were enrolled and first classified into AKI group (n = 151) versus no-AKI group (n = 132), then classified into survival group (n = 143) versus no-survival group (n = 140). Multivariate logistic regressions were performed to identify factors independently associated with AKI and mortality. Baseline data were defined as the first measurement available. RESULTS: Of 283 patients, the incidence of AKI was 53.36%. The in-hospital mortality rates were 63.58% and 33.33% in patients with and without AKI (p < 0.0001). Baseline MELD-XI score, baseline serum total bilirubin (T-Bil), baseline blood urea nitrogen (BUN), baseline left ventricular ejection fraction (LVEF), sequential organ failure assessment (SOFA) score, and lactate level at ECMO initiation were shown to be associated with the AKI. Vasoactive-inotropic score (VIS) and SOFA score at ECMO initiation as well as renal failure requiring renal replacement therapy (RRT) were shown to be associated with in-hospital mortality. CONCLUSIONS: The baseline MELD-XI score, baseline BUN, baseline T-Bil, baseline LVEF, SOFA score and lactate at the initiation of ECMO were associated with AKI. AKI, SOFA score, and VIS at the initiation of ECMO were associated with in-hospital mortality, whereas MELD-XI score was not found to be associated with in-hospital mortality. A specific MELD-XI score as a threshold, as well as its sensitivity and specificity, needs to be confirmed in further studies.

Risk factors of in-hospital mortality in adult postcardiotomy cardiogenic shock patients successfully weaned from venoarterial extracorporeal membrane oxygenation.

OBJECTIVE: Mortality of adult postcardiotomy cardiogenic shock patients after successfully weaned from venoarterial extracorporeal membrane oxygenation remains high. The objective of this study is to identify the risk factors associated with mortality after successfully weaning from venoarterial extracorporeal membrane oxygenation in adult postcardiotomy cardiogenic shock patients. METHODS: All consecutive patients who were successfully weaned from venoarterial extracorporeal membrane oxygenation between January 2011 and December 2016 at the Beijing Anzhen Hospital were analyzed retrospectively. Multivariate logistic regression was performed to identify risk factors associated with in-hospital mortality after successfully weaning from venoarterial extracorporeal membrane oxygenation. RESULTS: In total, 212 (58.4%) of 363 postcardiotomy cardiogenic shock patients were successfully weaned from venoarterial extracorporeal membrane oxygenation. The non-survivors had a longer duration of extracorporeal membrane oxygenation than the survivors (120.0 (98.0, 160.50) vs. 100.0 (77.0, 126.0), p = 0.000). Variables associated with mortality of patients successfully weaned from extracorporeal membrane oxygenation by univariable analysis were age, diabetes, vasoactive inotropic score pre-extracorporeal membrane oxygenation, vasoactive inotropic score at weaning, left ventricular ejection fraction at weaning, central venous pressure at weaning, sequential organ failure assessment score pre-extracorporeal membrane oxygenation, sequential organ failure assessment at weaning, survival after venoarterial ECMO pre-extracorporeal membrane oxygenation, and survival after venoarterial ECMO at weaning. In the multivariate analysis, sequential organ failure assessment score at weaning (odds ratio = 1.889, 95% confidence interval = 1.460-2.455, p < 0.001) was an independent risk factor for in-hospital mortality of patients successfully weaned from venoarterial extracorporeal membrane oxygenation. The cumulative 30-day survival rate in patients with a sequential organ failure assessment score < 7 was significantly (p < 0.001) higher than in patients with a sequential organ failure assessment score ⩾ 7 (87% vs. 56.7%, p < 0.001). CONCLUSION: Vasoactive inotropic score, left ventricular ejection fraction, central venous pressure, and sequential organ failure assessment score at weaning were associated with in-hospital mortality for postcardiotomy cardiogenic shock patients successfully weaned from venoarterial extracorporeal membrane oxygenation. Sequential organ failure assessment score might help clinicians to predict in-hospital mortality for patients successfully weaned from venoarterial extracorporeal membrane oxygenation.

Predicting mortality in patients undergoing VA-ECMO after coronary artery bypass grafting: the REMEMBER score.

BACKGROUND: Prediction scoring systems for coronary artery bypass grafting (CABG) patients on venoarterial extracorporeal membrane oxygenation (VA-ECMO) have not yet been reported. This study was designed to develop a predictive score for in-hospital mortality for cardiogenic shock patients who received VA-ECMO after isolated CABG. METHODS: Retrospective cohort study of consecutive CABG patients supported with VA-ECMO (n = 166) at the Beijing Anzhen Hospital between February 2004 and March 2017. RESULTS: One hundred and six patients (64%) could be weaned from VA-ECMO, and 74 patients (45%) survived to hospital discharge. On the basis of multivariable logistic regression analyses, the pRedicting mortality in patients undergoing veno-arterial Extracorporeal MEMBrane oxygenation after coronary artEry bypass gRafting (REMEMBER) score was created with six pre-ECMO parameters: older age, left main coronary artery disease, inotropic score > 75, CK-MB > 130 IU/L, serum creatinine > 150 umol/L, and platelet count < 100 × 109/L. Four risk classes, namely class I (REMEMBER score 0-13), class II (14-19), class III (20-25), and class IV (> 25) with their corresponding mortality (13%, 55%, 70%, and 94%, respectively), were identified. The area under the receiver operating characteristic curve 0.85(95% CI 0.79-0.91) for the REMEMBER score was better than those for the SOFA, SAVE, EuroSCORE, and ENCOURAGE scores in this population. CONCLUSIONS: The REMEMBER score might help clinicians at bedside to predict in-hospital mortality for patients receiving VA-ECMO after isolated CABG for refractory cardiogenic shock. Prospective studies are needed to externally validate this scoring system.

Mortality risk factors from converting off-pump coronary artery bypass to on-pump coronary artery bypass.

INTRODUCTION: A number of large-scale retrospective studies revealed that off-pump coronary artery bypass (OPCAB) was superior to on-pump coronary artery bypass (ONCAB). The aim of the study was to investigate risk factors for mortality when OPCAB is converted to ONCAB. METHODS: Patients who underwent OPCAB conversion to ONCAB at the Beijing Anzhen Hospital between January 2003 and January 2013 were assigned to the non-survivor and survivor groups. Background demographics, illness history and preoperative, intraoperative and postoperative variables were compared. RESULTS: Of the 247 cases, 15.4% of the patients died. Patients in the non-survivor group were older and more frequently had diabetes mellitus (DM), arrhythmia, myocardial infarction (MI) in the past 30 days (all p<0.05) and MI combined with mitral regurgitation (p<0.0001); they more frequently had bigger left ventricular end-diastolic dimension (p=0.0019), greater fall in blood pressure, ventricular fibrillation for longer periods, longer conversion time and bypass graft occlusion. All patients in the non-survivor group received intra-aortic balloon pump compared to 89.5% in the survivor group and extracorporeal membrane oxygenation was more common. Left main coronary artery disease (OR=4.431, 95%CI: 2.440-8.048, p<0.0001), blood pressure decline ⩽40 mmHg (OR=0.509, 95%CI: 0.447-0.580, p<0.0001) and time for conversion to ONCAB ⩾20 min were independently associated with mortality. Rates of postoperative complications, such as renal failure, cerebral infarction or hemorrhage, MI and redo sternotomy, were higher in the non-survivor group. CONCLUSIONS: Conversion from OPCAB to ONCAB is associated with high mortality. Risk factors include left main artery disease and duration of blood pressure decline >40 min.