Episodic bradycardia in preterm infants.

Abstract

To analyse factors likely to precipitate bradycardia, 27 preterm infants born at 32 weeks' gestation or less were studied on 89 occasions. Polygraphic recordings of electrocardiography, oxygen saturation, and respiratory effort were made. Subsequently, upper airway flow was measured by a mask and pressure transducer.In 605 episodes detected during initial recordings, time of onset of bradycardia correlated positively with apnoea duration, with bradycardia often occurring as respiratory effort resumed. Airway closure occurred in 88% of apnoeas associated with bradycardia during flow measurements, and was significantly more common than in apnoea without bradycardia (64/). We suggest that bradycardia is most commonly a reflex response to the resumption of respiratory effort against a closed upper airway as apnoea is terminated, and that this reflex is potentiated by hypoxaemia.

Non-sinus bradyarrhythmias in very low birth weight infants

“…8 Yet, classical clinical studies on apnea and bradycardia have not reported non-sinus bradyarrhythmias. [1][2][3] The reason for the discrepancy is unclear. Short recording time as well as the difference in methodology presumably account for this difference.…”

“…None of the major studies on apnea and bradycardia in preterm infants [1][2][3] have reported the occurrence of non-sinus bradyarrhythmias, although the occurrence of supraventricular escape rhythm during transient episodes of bradycardia has been documented. 4 Consequently, this observation has received very little attention among neonatologists and other physicians caring for very low birth weight (VLBW) infants.…”

The Relationship between Bradycardia, Apnea, and Hypoxemia in Preterm Infants

“…In 1986, HendersonSmart et al (8) recorded Sao2 during episodes of apnea and bradycardia in five preterm infants, using an ear oximeter with an electronic response time of 0.1 s. They reported that the interval between the onset of apnea and the onset of the fall in Sao2 was shorter than that between the onset of apnea and the onset of bradycardia and concluded that the bradycardias occurred as a response to a fall in Sao2. This conclusion, however, was recently challenged by Upton et al (9), who warned, appropriately, against infemng a cause-and-effect relationship from observations on the temporal relationship between hypoxemia and bradycardia. Unfortunately, these latter authors used a pulse oximeter that averaged the Sao2 readings over 6 s, making it difficult to comment on the temporal relationship between hypoxemia and bradycardia.…”

The Emergence and Development of Physiological Regulatory Systems of Newborn Infants in a Neonatal Intensive Care Unit

“…The adaptation to extra-uterine life is a slow and difficult process for these babies because of their prematurity. At this critical period, hypothermia, apnoea, respiratory distress, and cardiac instabilities such as bradycardia and hypotension are common features in these newborn babies (Bhatt et al, 2010;Di Fiore et al,2001;Dransfield et al, 1983;Tirosh et al, 2010;Trevisanuto et al, 2005;Upton, et al, 1992), and the resulting hypoxia may lead to brain damage and cardiac arrest if the medical support of a special incubator equipped with a ventilator and systemic monitoring is not provided a as a "primary life support system". Therefore, the continuous monitoring of heartbeat, respiration, oxygen saturation, blood pressure and temperature has been integrated into the neonatal intensive care unit (NICU) as a mandatory tool to support the fragile clinical conditions of these infants.…”

“…The LF to HF ratio reflects the sympathovagal balances. Reports regarding the relevance of HRV to cardiac-health-related events that contribute to the ANS in the foetus, such as asphyxia (Bocking, 2003), foetal distress (Karin et al, 1993); in infants, such as respiratory distress, apnoea, sepsis, bradycardia (Bennet & Gunn, 2009;Frasch et al, 2009;Li et al, 2005;Logier et al, 2008 ;Sampson et al, 1980), and hypotension (Di Fiore et al, 2001;Dransfield et al, 1983;Fairchild & O'Shea, 2010;Frasch et al, 2009;Upton et al, 1992;Wennergren et al, 1986); and adults, such as stroke and myocardial events (Faber, 1996;Sosnowski et al, 2002), are numerous and well-documented. In foetuses and preterm infants, the ANS is highly dependent on the SNS while the PNS is immature (Chatow et al, 1995), and the role of the PNS increases with the increase in gestational age (Van Leeuwen et al, 2003).…”