Silvia Martini1, Luigi Corvaglia1, Giulia Frabboni1, Paola Rucci2, Silvia Galletti1, Anna Giulia Cimatti1, Giacomo Faldella1, Topun Austin3
1 Neonatal Intensive Care Unit, St. Orsola-Malpighi University Hospital, Bologna, Italy
2 Department of Biomedical and Neuromotor Sciences, Division of Hygiene and Biostatistics, University of Bologna, Italy
3 Neonatal Intensive Care Unit, Cambridge University Hospitals, Cambridge, UK
Cardio-respiratory events (CRE), defined as intermittent episodes of hypoxemia and/or bradycardia, are particularly common among preterm infants. It has been previously shown that CRE result in transient brain hypoxia and hypoperfusion and may represent a possible risk factor for neurodevelopmental impairment and retinopathy of prematurity. The high cardio-respiratory instability typically seen in preterm infants during the first 72 hours of life may influence CRE occurrence, with possible clinical implications. This study aimed to characterize CRE features in this transitional period and to evaluate whether specific neonatal and clinical characteristics are associated with different CRE types.
Newborn infants with gestational age (GA) <32 weeks or birth weight (BW) <1500 g were enrolled. Congenital malformations and mechanical ventilation were exclusion criteria. During the first 72 hours, heart rate (HR) and peripheral oxygen saturation (SpO2) were continuously recorded, and an echocardiogram was performed 12- to 24-hourly to assess the status of the ductus arteriosus. CRE ≥10 sec were clustered into isolated desaturation (ID, SpO2<85%), isolated bradycardia (IB, HR<100 bpm or <70% baseline), combined desaturation and bradycardia (DB, occurrence of the two events within a 60-sec window). According to their duration and SpO2 and/or HR nadir values, CRE were also classified as mild (SpO2 80-84% and HR 80-100 bpm and duration <60 sec), moderate (SpO2 70-79% or HR 80-60 bpm or duration 61-120 sec) or severe (SpO2 <70% or HR <60 bpm or duration >120 sec). A generalized estimating equation (GEE) was used to examine the impact of relevant variables on CRE type and severity. Significance level was set at p<0.05. No funds were perceived for the present study. The study protocol was approved by the Ethics Committee of St. Orsola-Malpighi Hospital (Bologna, Italy).
A total of 897 events from 24 neonates (mean GA 30±2 weeks) were recorded and analysed; of these, ID were 549 (61.2%), IB 132 (14.7%) and DB 216 (24.1%). For the latter events, in most cases bradycardia preceded desaturation onset (n=73, 33.8%) or nadir (n=87, 40.3%); a nadir concomitance was observed in 49 events (22.7%), whereas bradycardia followed desaturation only in 7 events (3.2%).
Compared with other CRE types, ID were more likely in the presence of a hemodynamically significant PDA (B 1.06 [95% confidence interval 0.21-1.91], p=0.01), whereas IB were less common (B -0.80 [-1.40; -0.19], p=0.01). DB were significantly higher in infants <30 weeks’ gestation (B 1.42 [0.73-2.11], p<0.01) and in continuous positive airway pressure (CPAP) support (B 1.93 [0.29-3.59], p=0.02). No effect of antenatal Doppler status, antenatal steroids or surfactant administration on CRE type was observed.
As for CRE severity, 362 out of 897 events (40.4%) were mild, 350 (39%) moderate and 185 (20.6%) severe. Event severity differed significantly in relation to the type of CRE, being highest for DB (B 0.94 [0.55-1.33], p<0.01) and lowest for IB (B -1.41 [-1.87; -0.95], p<0.01). A protective effect towards severe events was observed for complete antenatal steroids administration (B -0.54 [-0.96; -0.12], p=0.01), CPAP (B -0.75 [-1.47; -0.36], p=0.04) and nasal cannulas (B -0.99 [-1.86; -0.13], p=0.02), whereas these events were more likely in infants who required surfactant administration (B 1.22 [0.62-1.82], p<0.01).
Neonatal Society Meeting Clare College Cambridge June 27-28th 2019 29
Preterm infants who do not require invasive ventilation have different types of CRE during the first 72 hours of life. The significant association observed between the CRE type and specific neonatal characteristics suggest different underlying physiological mechanisms. Moreover, during the transitional period, one out of 5 CRE has severe clinical features; if desaturation and bradycardia occur simultaneously, this likelihood rises significantly, whereas antenatal steroids administration and non-invasive respiratory support are associated with lowered risk, with possible clinical implications.
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