[Fetal and pediatric cardiovascular physiology : Things you should know as an (pediatric) anesthesiologist]

Immediately after birth the physiology of the cardiovascular system of the neonate undergoes some significant changes. The first breaths in life and the inflation of the lungs lead to a considerable drop in pulmonary arterial resistance. This results in the closure of the foramen ovale and ductus arteriosus; however, during the first weeks of life a sharp rise in pulmonary vascular resistance caused by hypoxia, hypercapnia and excessive positive pressure ventilation can lead to the reopening of the ductus arteriosus. This may result in subsequent strain of the left heart. In order to anticipate the reopening of the ductus arteriosus, it is recommended to measure the saturation of peripheral oxygen not only preductal (right hand), but also postductal (feet).An excessive volume therapy should be avoided as the neonatal myocardium is hallmarked by low cardiac compliance, reduced contractility and reduced ventricular filling.Until now there is still no uniform definition of hypotension in pediatric patients. Blood pressure values that are measured in awake children or are derived from the 50% age percentile values can thus only be used as approximate values. In all cases it is mandatory to recognize and consistently treat hypotension during pediatric anesthesia in order to prevent postoperative organ damage, particularly of the brain.The transcranial measurement of cerebral regional oxygen saturation (c‑rSO₂) by means of near-infrared spectroscopy (NIRS) provides valuable information about regional tissue oxygenation of the brain. This enables conclusions about the state of the multifactorial cerebral perfusion to be drawn. In this way monitoring of the hypoxia sensitive cerebral tissue can be accomplished and should be used in premature infants and neonates. When measuring a baseline in awake patients, a 20% drop of c‑rSO₂ from this baseline should be challenged and treated if necessary.