Fluid Status After Cardiac Surgery Assessed by Bioelectrical Impedance Vector Analysis and the Effects of Extracorporeal Circulation.

OBJECTIVE: Hydration status after cardiac surgery can be difficult to assess, often requiring invasive measurements. Bioelectrical impedance vector analysis (BIVA) is based on patterns of resistance (R) and reactance (Xc), corrected by height, and has been used in various clinical scenarios to determine body composition and monitor its changes over time. The purpose of the present study was to apply this method in cardiac surgery patients to assess the variation in hydration status and to compare its changes according to the use of extracorporeal circulation. DESIGN: Single-center, observational, prospective study including patients older than 18 years undergoing elective or urgent cardiac surgery. SETTING: Intensive cardiac care unit of a tertiary center in a metropolitan area. PARTICIPANTS: The study comprised 76 patients with a median age of 60 years and mostly undergoing coronary artery bypass grafting (CABG) (n = 47 [61.8%]) with extracorporeal circulation (n = 54 [73%]). INTERVENTIONS: Bioimpedance was measured with a standard tetrapolar single-frequency bioimpedance meter using a standardized procedure and plotted in an R-Xc graph. MEASUREMENTS AND MAIN RESULTS: The study demonstrated an increase in total body water immediately after surgery that was sustained until producing hyperhydration 24 hours later. Off-pump CABG was associated with a normal hydration status after surgery, whereas on-pump CABG produced a significant increase in total body water. CONCLUSIONS: Fluid status assessment with BIVA in cardiac surgery showed an increase in total body water up to 24 hours after surgery. Off-pump surgery prevented overhydration, which partially could explain the reduction in some of the postoperative complications. BIVA could serve as a useful method for monitoring fluid status in the setting of goal-directed therapy to assist in maintaining euvolemia in cardiac surgical patients.

Relación entre la grasa corporal y la morbimortalidad en cirugía cardíaca / Relationship Between Body Fat and Morbidity and Mortality in Cardiac Surgery

RESUMEN Introducción: Existe un efecto potencialmente protector de la obesidad cuando coexiste con la enfermedad cardiovascular, conocido como "paradoja de la obesidad". Es posible que se deba a que las medidas antropométricas no sean un marcador fidedigno de la grasa corporal. En este estudio, proponemos estimar la grasa corporal con métodos no invasivos y estudiar su relación con la morbimortalidad en cirugía cardíaca. Métodos: Llevamos a cabo un estudio prospectivo y observacional en pacientes adultos sometidos a cirugía cardíaca. Analizamos variables demográficas, antropométricas y clínicas junto con la estimación de la composición corporal a través de la impedancia bioeléctrica, para relacionarlas con los días de internación y eventos adversos luego de la cirugía cardíaca. Resultados: En el análisis de 98 pacientes, encontramos una relación directa entre el porcentaje de grasa corporal y los días de internación, independiente de la edad, el sexo, el índice de masa corporal y el riesgo prequirúrgico (coeficiente de 0,27, p: 0,021). Además, los pacientes que presentaron mediastinitis tuvieron una grasa corporal significativamente mayor (31,55 ± 0,64% contra 27,13 ± 7,9%, p <0,001), y los pacientes que fallecieron presentaron una tendencia a presentar más masa grasa (36,05 ± 3,19% contra 27,20 ± 7,82%, p: 0,08). Conclusiones: La mayor cantidad de grasa corporal estimada por análisis de impedancia bioeléctrica se relacionó con una mayor morbilidad en la cirugía cardíaca. A pesar de que esto es biológicamente plausible, sería necesario llevar a cabo estudios de mayor tamaño para poder esclarecer definitivamente la "paradoja del índice de masa corporal".

ABSTRACT Introduction: There is a potentially protective effect of obesity when it coexists with cardiovascular disease, known as the "obesity paradox." It could be explained by the fact that anthropometric measurements are not a reliable marker of body fat. In this study we propose to estimate body fat with a non-invasive method and study its relationship with morbidity and mortality in cardiac surgery. Methods: We conducted a prospective and observational study in adult patients undergoing cardiac surgery. We analyzed demographic, anthropometric and clinical variables along with the estimation of body composition using bioelectric impedance, to study their association to hospitalization days and adverse events after cardiac surgery. Results: In the analysis of 98 patients, we found a direct relationship between the percentage of body fat and the length of hospital stay, independent of age, sex, body mass index (BMI) and surgical risk (coefficient of 0.27, p = 0.021). In addition, patients who had mediastinitis showed a significantly higher body fat (31.55 ± 0.64% versus 27.13 ± 7.9%, p <0.001), and patients who died had a tendency to have more fat mass (36.05 ± 3.19% versus 27.20 ± 7.82%, p = 0.08). Conclusion: Increased body fat as assessed with BIA was related to morbidity in cardiac surgery. Although this is biologically plausible, it would be necessary to carry out larger studies in order to definitively establish the "BMI paradox".