Quantification of Brain and Kidney Perfusion Before, During, and After Hypothermia Treatment in Neonates With Perinatal Asphyxia Using Contrast-enhanced Ultrasound

Inclusion Criteria: * Fulfillment of the inclusion criteria for hypothermia treatment according to the AWMF guideline * Severe acidosis (pH ≤7.0 or a base deficit ≥16 mmol/l) in umbilical cord blood or a blood sample from the first hour of life, and * clinical signs of moderate or severe encephalopathy (severity grade 2 or 3 according to Sarnat \& Sarnat), and * postnatal age ≤6h, and * gestational age ≥36 weeks' gestation * Consent of the parents/legal guardians * Time 1 (before the start of hypothermia treatment) * Informing the parents/legal guardians present on site despite an emotionally stressful situation with high individual benefit for the patient * If only one parent is present and able to provide information, their consent is sufficient - the second parent is informed repeatedly when they regain the ability to provide information * Information adapted to the emergency situation, addressing the personal situation and comprehensible presentation of the plan * Time 2 (during hypothermia treatment) --\>Offer of a further informative discussion/repeated explanation with the parents/legal representatives before the second measurement in order to answer any questions that may have arisen * Suitable acoustic window * Availability of the qualified examiner Exclusion Criteria: * Lack of consent of at least one parent * Pre-existing brain malformations * Absence of the competent examiner