Complex effects of high-flow nasal cannula therapy on hemodynamics in the pediatric patient after cardiac surgery

BACKGROUND: The high-flow nasal cannula (HFNC) system has been widely used for children in various clinical settings. However, the physiological and clinical impact of HFNC therapy on the pediatric patient with respiratory distress after cardiac surgery has not been thoroughly investigated. MAIN BODY OF THE ABSTRACT: It seems logical to use HFNC as a primary therapy for post-extubation respiratory failure after congenital heart surgery, in which low cardiac output syndrome and upper airway obstruction are commonly encountered; the HFNC therapy alleviates the work of breathing and large negative swings of intrathoracic pressure, which in turn helps to decrease the systemic ventricular afterload. When applying HFNC to patients after congenital heart surgery, however, consideration must be given to its diverse effects on hemodynamics because of the complex respiratory and cardiac pathophysiology in these patients. The positive pressure generated by HFNC can exert different effects on pulmonary vascular resistance depending on the lung condition, while its impact on cardiac output may also differ depending on the cardiac physiology. The hemodynamic effects of HFNC may become even more complex in a patient with a single ventricle. To better assess its physiologic effects in patients after cardiac surgery, future studies could utilize various modalities including esophageal balloon catheters, electrical impedance tomography, and near-infrared spectroscopy. At the same time, studies should focus on specific types of cardiac pathophysiology or surgery when evaluating the effects of HFNC, since it may exert various effects, depending on the cardiac physiology or preoperative pulmonary hemodynamics. Lastly, the optimal flow rate at which the benefit of HFNC is maximized through favorable cardiopulmonary interactions should be determined in future studies. SHORT CONCLUSION: Further studies are needed to better understand the effect of HFNC in different cardiac and respiratory physiologies, given their complexity in pediatric patients after cardiac surgery.