A nomogram predicts early neurological deterioration after mechanical thrombectomy in patients with ischemic stroke

IntroductionEarly neurological deterioration (END) is common in acute ischemic stroke and is directly associated with poor outcome after stroke. Our aim is to develop and validate a nomogram to predict the risk of END after mechanical thrombectomy (MT) in acute ischemic stroke patients with anterior circulation large-vessel occlusion.MethodsWe conducted a real-world, multi-center study in patients with stroke treated with mechanical thrombectomy. END was defined as a worsening by 2 or more NIHSS points within 72-hour after stroke onset compared to admission. Multivariable logistic regression was used to determine the independent predictors of END, and the discrimination of the scale was assessed using the C-index. Calibration curves were constructed to evaluate the calibration of the nomogram, and decision curves were used to describe the benefits of using the nomogram.ResultsA total of 1007 patients were included in our study. Multivariate logistic regression analysis found age, admission systolic blood pressure, initial NIHSS scores, history of hyperlipemia, and location of occlusion were independent predictors of END. We developed a nomogram that included these 6 factors, and it revealed a prognostic accuracy with a C-index of 0.678 in the derivation group and 0.650 in the validation group. The calibration curves showed that the nomogram provided a good fit to the data, and the decision curves demonstrated a large net benefit.DiscussionOur study established and validated a nomogram to stratify the risk of END before mechanical embolectomy and identify high-risk patients, who should be more cautious when making clinical decisions

Flexible Power Regulation and Limitation of Voltage Source Inverters under Unbalanced Grid Faults

This paper develops a flexible power regulation and limitation strategy of voltage source inverters (VSIs) under unbalanced grid faults. When the classical power theory is used under unbalanced grid faults, the power oscillations and current distortions are inevitable. In the proposed strategy, the extended power theory is introduced to compute the power feedbacks together with the classical power theory. Based on the combination of the classical and extended power theory, the proposed strategy can achieve the sinusoidal current provision and the flexible regulation between three common targets, i.e., constant active power, balanced current, and constant reactive power. Meanwhile, the proposed strategy is associated with a power limiter, which is capable to keep the currents under the pre-defined threshold and to compute the maximum apparent power for better utilization of the inverter capacity. With this power limiter, the rated inverter capacity is fully used for both the active and reactive power provisions under unbalanced grid faults. Using the proposed power regulation and limitation, the VSI can avoid overcurrent tripping and flexibly regulate its power under unbalanced grid faults. All the conclusions are verified by the real-time hardware-in-loop tests

Improved active power control of virtual synchronous generator for enhancing transient stability

Abstract Virtual synchronous generators (VSGs) are widely used as grid‐forming control converters in the inverter‐dominated power system. Similar to synchronous generators (SGs), there would also be transient instability of VSGs under certain conditions. In this paper, the transient dynamics of VSGs during gird faults are fully investigated based on the large‐signal model. It is revealed that the significant deteriorative of active power control loop (APCL) is the main factor on the transient stability of VSGs. Thus, for enhancing transient stability during grid faults, an integrator‐based feedback loop is introduced for APCL. Then, an enhanced active power control of VSGs is presented with transient stability enhancement during grid faults. Moreover, the impacts of different integral parameters on the transient stability of VSGs are studied. Finally, the validity of the transient stability enhancement of VSGs is demonstrated by the hardware‐in‐loop (HIL) results

Table_1_A nomogram predicts early neurological deterioration after mechanical thrombectomy in patients with ischemic stroke.docx

IntroductionEarly neurological deterioration (END) is common in acute ischemic stroke and is directly associated with poor outcome after stroke. Our aim is to develop and validate a nomogram to predict the risk of END after mechanical thrombectomy (MT) in acute ischemic stroke patients with anterior circulation large-vessel occlusion.MethodsWe conducted a real-world, multi-center study in patients with stroke treated with mechanical thrombectomy. END was defined as a worsening by 2 or more NIHSS points within 72-hour after stroke onset compared to admission. Multivariable logistic regression was used to determine the independent predictors of END, and the discrimination of the scale was assessed using the C-index. Calibration curves were constructed to evaluate the calibration of the nomogram, and decision curves were used to describe the benefits of using the nomogram.ResultsA total of 1007 patients were included in our study. Multivariate logistic regression analysis found age, admission systolic blood pressure, initial NIHSS scores, history of hyperlipemia, and location of occlusion were independent predictors of END. We developed a nomogram that included these 6 factors, and it revealed a prognostic accuracy with a C-index of 0.678 in the derivation group and 0.650 in the validation group. The calibration curves showed that the nomogram provided a good fit to the data, and the decision curves demonstrated a large net benefit.DiscussionOur study established and validated a nomogram to stratify the risk of END before mechanical embolectomy and identify high-risk patients, who should be more cautious when making clinical decisions.</p

Pancreatic surgery outcomes: multicentre prospective snapshot study in 67 countries

Background: Pancreatic surgery remains associated with high morbidity rates. Although postoperative mortality appears to have improved with specialization, the outcomes reported in the literature reflect the activity of highly specialized centres. The aim of this study was to evaluate the outcomes following pancreatic surgery worldwide.Methods: This was an international, prospective, multicentre, cross-sectional snapshot study of consecutive patients undergoing pancreatic operations worldwide in a 3-month interval in 2021. The primary outcome was postoperative mortality within 90 days of surgery. Multivariable logistic regression was used to explore relationships with Human Development Index (HDI) and other parameters.Results: A total of 4223 patients from 67 countries were analysed. A complication of any severity was detected in 68.7 percent of patients (2901 of 4223). Major complication rates (Clavien-Dindo grade at least IIIa) were 24, 18, and 27 percent, and mortality rates were 10, 5, and 5 per cent in low-to-middle-, high-, and very high-HDI countries respectively. The 90-day postoperative mortality rate was 5.4 per cent (229 of 4223) overall, but was significantly higher in the low-to-middle-HDI group (adjusted OR 2.88, 95 per cent c.i. 1.80 to 4.48). The overall failure-to-rescue rate was 21 percent; however, it was 41 per cent in low-to-middle-compared with 19 per cent in very high-HDI countries.Conclusion: Excess mortality in low-to-middle-HDI countries could be attributable to failure to rescue of patients from severe complications. The authors call for a collaborative response from international and regional associations of pancreatic surgeons to address management related to death from postoperative complications to tackle the global disparities in the outcomes of pancreatic surgery (NCT04652271; ISRCTN95140761)