Abstract Objective: To analyze the impact of vacuum-assisted venous drainage (VAVD) on arterial pump flow in a simulated pediatric cardiopulmonary bypass circuit utilizing a centrifugal pump (CP) with an external arterial filter. Methods: The simulation circuit consisted of a Quadrox-I Pediatric oxygenator, a Rotaflow CP (Maquet Cardiopulmonary AG, Rastatt, Germany), and a custom pediatric tubing set primed with Lactated Ringer's solution and packed red blood cells. Venous line pressure, reservoir pressure, and arterial flow were measured with VAVD turned off to record baseline values. Four other conditions were tested with progressively higher vacuum pressures (-20, -40, -60, and -80 mmHg) applied to the baseline cardiotomy pressure. An arterial filter was placed into the circuit and arterial flow was measured with the purge line in both open and closed positions. These trials were repeated at set arterial flow rates of 1500, 2000, and 2500 mL/min. Results: The use of progressively higher vacuum caused a reduction in effective arterial flow from 1490±0.00 to 590±0.00, from 2020±0.01 to 1220±0.00, and from 2490±0.0 to 1830±0.01 mL/min. Effective forward flow decreased with increased levels of VAVD. Conclusion: The use of VAVD reduces arterial flow when a CP is used as the main arterial pump. The reduction in the forward arterial flow increases as the vacuum level increases. The loss of forward flow is further reduced when the arterial filter purge line is kept in the recommended open position. An independent flow probe is essential to monitor pump flow during cardiopulmonary bypass.

RESUMO INTRODUÇÃO: O sucesso das infecções por Acinetobacter baumannii pode ser atribuído a seus vários fatores de virulência e a mecanismos de resistência a antimicrobianos. OBJETIVO: Avaliar a presença e a correlação entre diferentes fatores de resistência e virulência em amostras clínicas de A. baumannii. MÉTODOS: Estudo conduzido em um hospital universitário em Belo Horizonte, Minas Gerais, Brasil. A confirmação do complexo Acinetobacter baumannii-calcoaceticus foi realizada pela detecção do gene blaOXA-51, por meio da reação em cadeia da polimerase (PCR), assim como a pesquisa dos genes: blaOXA-23, 24, 58, 143, blaVIM-1, csuE, ompA e ISAba1. Os antimicrobianos e a expressão das metalobetalactamases (MβL) foram avaliados pelo E-test®; e a diversidade genética, por enterobacterial repetitive intergenic consensus (ERIC)-PCR. A formação de biofilme foi classificada em quatro categorias de acordo com a média da densidade ótica obtida. RESULTADOS: Do total de amostras, 98, 4% (61/62) foram resistentes ao meropenem; 71%, a ceftazidime; e 61, 3%, a ampicilina-sulbactam; enquanto 98, 4% foram sensíveis a polimixina B; e 48, 4%, a tigeciclina. A produção de MβL foi detectada em 95, 2% das amostras. O gene blaOXA-51 foi detectado em todas as amostras testadas; blaVIM-1, em 83, 9%; e ISAba1, em 90, 3%. Por outro lado, os genes csuE e ompA estiveram presentes em 43, 5% e 53, 2% das amostras, respectivamente. CONCLUSÃO: Houve uma possível correlação entre as amostras resistentes a gentamicina e aquelas positivas para o gene ompA. O gene csuE correlacionou-se positivamente com ISAba1.

ABSTRACT INTRODUCTION: The success of Acinetobacter baumannii infections can be attributed to its various virulence factors and antimicrobial resistance mechanisms. OBJECTIVE: To evaluate the presence and correlation between different resistance and virulence factors in clinical A. baumannii strains. METHODS: Study conducted at a University Hospital in Belo Horizonte, Minas Gerais, Brazil. The confirmation of Acinetobacter baumannii-calcoaceticus complex was performed by detecting the blaOXA-51 gene through the polymerase chain reaction (PCR), as well as the search for genes: blaOXA-23, 24, 58, 143, blaVIM-1, csuE, ompA and ISAba1. Antimicrobials and metallo-betalactamase (MβL) expression were evaluated by E-test®; and genetic diversity, by enterobacterial repetitive intergenic consensus (ERIC)-PCR. Biofilm formation was classified into four categories according to the mean optical density obtained. RESULTS: 98.4% (61/62) of the strains were resistant to meropenem; 71%, to ceftazidime; and 61.3%, to ampicillin-sulbactam; while 98.4% were sensitive to polymyxin B; and 48.4%, to tigecycline. The production of MβL was detected in 95.2% of the strains. The blaOXA-51 gene was detected in all strains tested; blaVIM-1, in 83.9%; and ISAba1, in 90.3%. On the other hand, the csuE and ompA genes were present in 43.5% and 53.2% of the strains, respectively. CONCLUSION: There was a possible correlation between gentamicin resistant samples and those that were positive for the ompA gene. The csuE gene correlated positively with ISAba1.