Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub. 2020; 164:XX. 1 Ultrasound cardiac output monitoring in mechanically ventilated children Jiri Fremuth, Jiri Kobr, Lumir Sasek, Katerina Pizingerova, Jana Zamboryova, Josef Sykora Aim. To non-invasively identify the hemodynamic changes in critically ill children during the first 48 h following initia- tion of mechanical ventilation by the ultrasound cardiac output monitor (USCOM) method and compare the data in children with pulmonary and non-pulmonary pathology. Materials and Methods. This was a prospective observational study to evaluate the influence of mechanical ventila- tion on hemodynamic changes and to describe hemodynamic profiles of mechanically ventilated children. A total of 56 children with respiratory failure were included in the present study. Ventilated patients are divided into two groups. Group A (n=36) includes patients with pulmonary pathology. Group B (n=20) consists of patients with extra pulmonary etiology of respiratory failure. Hemodynamic parameters (cardiac index and systemic vascular resistance index) were evaluated using ultrasound cardiac output monitoring (USCOM 1A) immediately following initiation of mechanical ventilation and again at 6, 12, and 48 h. Pharmacological circulatory support (inotropes, vasopressors, levosimendan and phosphodiesterase III inhibitors) was individually and continuously modified based on real-time hemodynamic parameters and optimal fluid balance. Results. No significant differences in hemodynamic profiles were found between Group A and Group B. Conclusion. The protective strategy of mechanical ventilation was not associated with significant differences in he- modynamic profiles between children ventilated for pulmonary and non-pulmonary pathologies. Clinical Significance. Hemodynamically unstable children ventilated for pulmonary pathology with the protective strategy of mechanical ventilation had a greater requirement for inotropic and combined inotropic and vasoactive circulatory support than children ventilated for non-pulmonary causes of respiratory failure. Key words: hemodynamics, ultrasound cardiac output monitor, mechanical ventilation, children, case-control study Received: March 24, 2020; Revised: September 15, 2020; Accepted: October 6, 2020; Available online: October 21, 2020 https://doi.org/10.5507/bp.2020.048 © 2020 The Authors; https://creativecommons.org/licenses/by/4.0/ Department of Pediatrics - PICU, Faculty of Medicine in Pilsen, Charles University in Prague, Czech Republic Corresponding author: Jiri Kobr, e-mail: Jikobr93@gmail.com INTRODUCTION Circulatory failure in critically ill children is most often caused by a low circulatory volume and low myo- cardial contractility or a decrease in systemic vascular resistance. Treatment aims to optimize oxygen delivery to peripheral tissues according to the current needs of the child by supporting blood circulation and ventilation. Cardiac output is determined by the heart rate and stroke volume, and blood pressure by cardiac output and system- ic vascular resistance. Current and reliable hemodynamic evaluation is necessary for effective treatment, and he- modynamic monitoring helps physicians to identify early pathophysiological changes and choose an appropriate treatment strategy 1,2 . Published studies have clearly shown that a clinical estimation of hemodynamic parameters, such as cardiac index and systemic vascular resistance, does not correspond to invasively measured results in critically ill pediatric or adult patients 3,4 . The interval from first presentation to cardiac output measurement using invasive techniques typically exceeds the 60-minute period recommended by the American College of Critical Care Medicine guidelines for fluid resuscitation and selection of first- and second-line vasoactive and inotropic drugs 1 . It should be noted that previously published studies have only documented changes in hemodynamics in septic children 5 , and the initial treatment strategy for critically ill, hemodynamically unstable pediatric patients is often based on fluid administration 6 . Following initial resuscita- tion of fluid-responsive pediatric patients, the fluid, vaso- active, and inotropic therapies should be selected based on the profile obtained from hemodynamic monitoring. From a clinical point of view, there has been increas- ing interest in, and preference for, the use of semi- or non-invasive techniques to measure cardiac output; and an ultrasound cardiac output monitor (USCOM 1A) has recently become available for use in clinical practice. Conventional mechanical ventilation with permanent positive pressure induces cardiopulmonary interactions and reduces myocardial performance 7,8 ; however, clinical studies considering these interactions are almost nonexis- tent in the pediatric population, even though understand- ing these interaction patterns is essential for the treatment of critically ill children. Patients ventilated for pulmonary pathology often require higher inspiratory pressures to achieve the desired tidal volume, and cardiopulmonary interactions in these groups of children are more pro- nounced 9,10 .