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Numerical solutions of eight differential equations in uid dynamics are obtained by the nite-difference method with uniform unidimensional grids and with six types of numerical approximations. The main purpose of this work is to calculate uncertainties of numerical solutions using the Richardson error estimator and another estimator which is introduced in this work. These estimators are examined for reliability and accuracy of the uncertainty for the situation in which the size of the grid elements is small. In this case, as is shown in this work, two values of uncertainty can be found that bound the discretization error.

Introduction We investigated the clinical course and outcomes of patients submitted to cardiovascular surgery in Brazil and who had developed symptoms/signs of coronavirus disease 2019 (COVID-19) in the perioperative period. Methods A retrospective multicenter study including 104 patients who were allocated in three groups according to time of positive real time reverse transcriptase-polymerase chain reaction (RT-PCR) for the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2): group 1, patients who underwent cardiac surgery > 10 days after positive RT-PCR; group 2, patients with a positive RT-PCR within 10 days before or after surgery; group 3, patients who presented positive RT-PCR > 10 days after surgery. The primary outcome was mortality and secondary outcomes were postoperative complications, intensive care unit (ICU) length of stay, and postoperative days of hospitalization. Results The three groups were similar with respect to age, the European System of Cardiac Operative Risk Evaluation score, and comorbidities, except hypertension. Postoperative complications and death were significantly higher in groups 2 and 3 than in group 1, and no significant difference between groups 2 and 3 was seen. Group 2 showed a high prevalence of surgery performed as an urgent procedure. Although no significant differences were observed in ICU length of stay, total postoperative hospitalization time was significantly higher in group 3 than in groups 1 and 2. Conclusion COVID-19 affecting the postoperative period of patients who underwent cardiovascular surgery is associated with a higher rate of morbidity and mortality. Delaying procedures in RT-PCR-positive patients may help reduce risks of perioperative complications and death.

Objective To analyze data related to surgical treatment in patients with congenital heart defects (CHD) and Down syndrome (DS) based on information from International Quality Improvement Collaborative Database for Congenital Heart Disease (IQIC). Methods Between July 1, 2010 and December 31, 2017, 139 patients with CHD and DS underwent surgery at Hospital de Base and Hospital da Criança e Maternidade de São José do Rio Preto (FUNFARME)/Faculdade de Medicina de São José do Rio Preto - SP (FAMERP). A quantitative, observational and cross-sectional study was performed in which the pre, intra and postoperative data were analyzed in an IQIC database. The data included gender, age, prematurity, weight, preoperative procedures, diagnosis, associated cardiac and non-cardiac anomalies, Risk Adjustment for Congenital Heart Surgery (RACHS-1), type of surgery, cardiopulmonary bypass (CPB), perfusion time, aortic clamping time and CPB temperature, bacterial sepsis, surgical site infection and other infections, length of stay in intensive care unit (ICU), length of hospital stay and in-hospital mortality. Results The most prevalent procedures were complete atrioventricular septal defect repair (58 - 39.45%), followed by closure of ventricular septal defect (36 - 24.49%). The RACHS-1 categories 1, 2, 3 and 4 were distributed as 22 (15%); 49 (33.3%); 72 (49%) and 4 (2.7%), respectively. There were no procedures classified as categories 5 or 6. Bacterial sepsis occurred in 10.2% of cases, surgical site infection in 6.1%, other infections in 14.3%. The median length of ICU stay was 5 days and the median length of hospital stay was 11 days. In-hospital mortality was 6.8%. Conclusion Surgical treatment in patients with CHD and DS usually does not require highly complex surgical procedures, but are affected by infectious complications, resulting in a longer ICU and hospital length of stay with considerable mortality.