Hemodynamic Responses to Cardio-respiratory Events in Preterm Infants
Condition: Apnea of Prematurity; Preterm Birth; Patent Ductus Arteriosus; Hypoxia, Brain; Cardiac Output, Low; Bradycardia Neonatal; Hypoxia Neonatal
MeSH terms: Hypoxia, Brain; Premature Birth; Bradycardia; Ductus Arteriosus, Patent; Cardiac Output, Low; Hypoxia
Study type: Observational

Summary: 
      Intermittent episodes of hypoxemia and/or bradycardia, also defined as cardio-respiratory
      events (CRE) are very frequent in preterm infants and may result in transient hypoxia and
      hypoperfusion of target organs, with possible clinical implications. The hemodynamic
      instability that characterizes the first 72 hours of life, also called as transitional
      period, place preterm infants at high risk of complications and may contribute to enhance
      fluctuations in end-organ perfusion and oxygenation induced by CRE. In this study we aimed to
      explore cardiovascular and cerebrovascular changes determined by different CRE types in
      preterm infants during the transitional period.
    

Detailed description: 
      Intermittent episodes of hypoxemia and/or bradycardia, also defined as cardio-respiratory
      events (CRE) are very frequent in preterm infants and may result in transient hypoxia and
      hypoperfusion of target organs, with possible clinical implications. The hemodynamic
      instability that characterizes the first 72 hours of life, also called as transitional
      period, place preterm infants at high risk of complications and may contribute to enhance
      fluctuations in end-organ perfusion and oxygenation induced by CRE. Moreover, during this
      period, several clinical variables (e.g., antenatal steroid administration, gestational age
      [GA], patent ductus arteriosus [PDA], respiratory support etc.) may contribute to modulate
      the hemodynamic fluctuations in response to CRE.

      Hence, this study aims:

        -  to explore changes in the main cardiovascular and cerebrovascular parameters elicited by
           different CRE types

        -  to evaluate whether different antenatal, perinatal and postnatal factors may influence
           the observed cardiovascular and cerebrovascular responses to CRE.

      Infants born at S. Orsola-Malpighi Hospital are consecutively enrolled in this observational,
      prospective study if fulfilling the following eligibility criteria: gestational age (GA) <32
      weeks' gestation, birth weight <1500 g, 0-12 hours of life, written informed consent obtained
      from the parents/legal guardians of each infant.

      As routinely performed in infants with the eligible characteristics, the enrolled infants
      undergo a simultaneous, continuous and non-invasive monitoring of

        -  peripheral oxygen saturation (SpO2) and heart rate (HR) using a pulse oximeter

        -  cerebral tissue oxygenation index (cTOI) and cerebral total hemoglobin index (cTHI),
           which represents a proxy of cerebral blood flow, using near infrared spectroscopy.
           Cerebral fraction of oxygen extraction (cFTOE) is also calculated as follows:
           (SpO2-cTOI)/SpO2.

        -  cardiovascular parameters (cardiac output [CO], stroke volume [SV], cardiac
           contractility index [ICON], systemic vascular resistance [SVR]) using electrical
           cardiometry.

      In the enrolled infants, each monitoring device is connected via a RS232 cable to a laptop
      running ICM+® (https://icmplus.neurosurg.cam.ac.uk/, Cambridge Enterprise, UK), a software
      tool that allows a real-time synchronized multi-parametric data collection, which recorded
      the above mentioned parameters continuously, from the time of enrollment up to 72 hours of
      life.

      Cardiorespiratory event types are classified on the basis of SpO2 and HR values as follows:

        -  isolated desaturation (ID): SpO2 <85% and classified into mild (SpO2 80-84%), moderate
           (SpO2 70-79%) and severe (SpO2 <70%).

        -  isolated bradycardia (IB): any HR drop <100 bpm or >30% from baseline values, calculated
           daily over the first 72 hours of life

        -  desaturation and bradycardia occurring within a 60-sec time window: combined events
           (DB).

      The following antenatal and neonatal data are tracked down on a specific case report form:
      GA, antenatal steroids (complete course vs. incomplete course or not given) evidence of
      reversed end-diastolic flow at antenatal umbilical Doppler (uREDF) (present vs. absent);
      ventilatory status over the first 72 hours of life (continuous positive airway pressure
      [CPAP] vs. nasal cannulas or self-ventilating in air [SVIA]); surfactant administration;
      development of IVH over the first 72 hours of life.

      A screening echocardiogram is routinely performed at the time of enrollment and repeated 6-12
      hourly in the presence of a patent ductus arteriosus (PDA) or 12-24 hourly if there is no
      evidence of PDA. Based on echocardiographic features, the ductal status is classified as
      follows: no evidence of PDA (noPDA), restrictive PDA (rPDA; restrictive shunt pattern and
      left atrium to aortic root ratio [LA:Ao] ratio <1.5), hemodynamically significant PDA (hsPDA;
      pulsatile shunt pattern, LA:Ao ratio ≥1.5 or presence of reversed end-diastolic flow either
      in the descending aorta or in the anterior cerebral artery).

      For statistical analysis, percentage changes of cardiovascular (CO, ICON, SVR) and
      cerebrovascular (cTOI, cTHI, cFTOE) parameters will be compared between different CRE types
      (ID, DB and IB) using Kruskal-Wallis test. Generalized estimating equation (GEE) models will
      be used to analyze the concomitant effect of clinical variables (e.g., GA, uREDF, antenatal
      steroids, ductal and ventilatory status etc.) on the percentage changes of the study
      parameters. IBM SPSS, version 25.0, will be used for statistical analysis. The significance
      level is set at p<0.05.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Preterm infants on spontaneous breathing during the transitional period (0-72 hours of
        life).
      
Keywords: preterm infants; hypoxic episodes; non-invasive cardiac output monitoring; near infrared spectroscopy; cardiac output; cerebral oxygenation; bradycardia; cardiorespiratory events