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Horne RS, Harrewijn I, Hunt CE. Physiology during sleep in preterm infants: Implications for increased risk for the sudden infant death syndrome. Sleep Med Rev 2024; 78:101990. [PMID: 39116607 DOI: 10.1016/j.smrv.2024.101990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 07/14/2024] [Accepted: 07/26/2024] [Indexed: 08/10/2024]
Abstract
Approximately 15 million babies are born preterm (<37 weeks of completed gestation) worldwide annually. Although neonatal and perinatal medicine have contributed to the increased survival rate of preterm newborn infants, premature infants are at increased risk of mortality in the first years of life. Infants born preterm are at four times the risk of Sudden Infant Death Syndrome (SIDS) compared to infants born at term. SIDS is believed to be multifactorial in origin. The Triple Risk hypothesis has been proposed to explain this. The model suggests that when a vulnerable infant, such as one born preterm, is at a critical but unstable developmental period in homeostatic control, death may occur if exposed to an exogenous stressor, such as being placed prone for sleep. The highest risk period is at ages 2-4 months, with 90 % of deaths occurring before 6 months. The final pathway to SIDS is widely believed to involve some combination of immature cardiorespiratory control and a failure of arousal from sleep. This review will focus on the physiological factors which increase the risk for SIDS in preterm infants and how these factors may be identified and potentially lead to effective preventative strategies.
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Affiliation(s)
| | | | - Carl E Hunt
- Uniformed Services University, Bethesda, MD, USA
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Berger J, Zaidi M, Halferty I, Kudchadkar S. Sleep in the Hospitalized Child: A Contemporary Review. Chest 2021; 160:1064-1074. [PMID: 33895129 DOI: 10.1016/j.chest.2021.04.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Revised: 04/13/2021] [Accepted: 04/17/2021] [Indexed: 11/17/2022] Open
Abstract
Acute illness and hospitalization introduce several risk factors for sleep disruption in children that can negatively affect recovery and healing and potentially compromise long-term cognition and executive function. The hospital setting is not optimized for pediatric sleep promotion, and many of the pharmacologic interventions intended to promote sleep in the hospital actually may have deleterious effects on sleep quality and quantity. To date, evidence to support pharmacologic sleep promotion in the pediatric inpatient setting is sparse. Therefore, nonpharmacologic interventions to optimize sleep-wake patterns are of highest yield in a vulnerable population of patients undergoing active neurocognitive development. In this review, we briefly examine what is known about healthy sleep in children and describe risk factors for sleep disturbances, available sleep measurement tools, and potential interventions for sleep promotion in the pediatric inpatient setting.
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Affiliation(s)
- Jessica Berger
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, MD
| | - Munfarid Zaidi
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, MD
| | | | - Sapna Kudchadkar
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, MD; Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD; Department of Physical Medicine and Rehabilitation, Johns Hopkins School of Medicine, Baltimore, MD.
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3
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Cardiovascular autonomic dysfunction in sudden infant death syndrome. Clin Auton Res 2018; 28:535-543. [PMID: 29299712 DOI: 10.1007/s10286-017-0490-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 12/12/2017] [Indexed: 10/18/2022]
Abstract
A failure of cardiorespiratory control mechanisms, together with an impaired arousal response from sleep, are believed to play an important role in the final event of sudden infant death syndrome (SIDS). The 'triple risk model' describes SIDS as an event that results from the intersection of three overlapping factors: (1) a vulnerable infant, (2) a critical developmental period in homeostatic control and (3) an exogenous stressor. In an attempt to understand how the triple risk hypothesis is related to infant cardiorespiratory physiology, many researchers have examined how the known risk and protective factors for SIDS alter infant cardiovascular control during sleep. This review discusses the association between the three components of the triple risk hypothesis and major risk factors for SIDS, such as prone sleeping, maternal smoking, together with three "protective" factors, and cardiovascular control during sleep in infants, and discusses their potential involvement in SIDS.
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Schneebaum Sender N, Govindan RB, Whitehead MT, Massaro AN, Metzler M, Wang J, Cheng YI, du Plessis AJ. Cerebral modulation of the autonomic nervous system in term infants. J Perinatol 2017; 37:558-562. [PMID: 28079874 DOI: 10.1038/jp.2016.248] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 11/02/2016] [Accepted: 11/22/2016] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Central topography of autonomic nervous system (ANS) function has yet to be fully deciphered. In adults it has been shown to lateralize sympathetic and parasympathetic influence predominantly to the right and left cerebral hemispheres, respectively. We examined functional topography of central ANS in newborn subjects utilizing spectral analysis of heart rate variability (HRV), an established measure of ANS function. STUDY DESIGN We studied newborns with hypoxic-ischemic encephalopathy participating in a prospective study undergoing a therapeutic hypothermia protocol.We included subjects with continuous heart rate data over the first 3 h of normothermia (post rewarming) and brain magnetic resonance imaging, which was reviewed and scored according to a 4 region scheme. HRV was evaluated by spectral analysis in the low-frequency (0.05 to 0.25 Hz) and high-frequency (0.3 to 1 Hz) ranges. The relationship between injured brain regions and HRV was studied using multiple regressions. RESULTS Forty eight newborns were included. When examined in isolation, right hemisphere injury had a significant negative effect on HRV (-0.088; 95% CI: -0.225,-0.008). The combination of posterior fossa region injury with right hemispheric injury or left hemispheric injury demonstrated significant positive (0.299; 95% CI: 0.065, 0.518) and negative (-0.475; 95% CI: -0.852, -0.128) influences on HRV, respectively. The association between brain injury location and HRV in the high-frequency range did not reach significance. CONCLUSION Our data support the notion that lateralized cerebral modulation of the ANS, specifically of its sympathetic component, is present in the term newborn, and suggest complex modulation of these tracts by components of the posterior fossa.
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Affiliation(s)
- N Schneebaum Sender
- Department of Fetal and Transitional Medicine, Fetal Medicine Institute, Children's National Health System, Washington, DC, USA
| | - R B Govindan
- Department of Fetal and Transitional Medicine, Fetal Medicine Institute, Children's National Health System, Washington, DC, USA
| | - M T Whitehead
- Department of Radiology, Children's National Health System, Washington, DC, USA
| | - A N Massaro
- Division of Neonatology and Division of Fetal and Transitional Medicine, Children's National Health Systems Pediatrics, The George Washington University School of Medicine, Washington, DC, USA
| | - M Metzler
- Department of Fetal and Transitional Medicine, Fetal Medicine Institute, Children's National Health System, Washington, DC, USA
| | - J Wang
- Division of Biostatistics and Study Methodology, Center for Translational Science, Children's Research Institute, Children's National Health System, Washington, DC, USA
| | - Y I Cheng
- Division of Biostatistics and Study Methodology, Center for Translational Science, Children's Research Institute, Children's National Health System, Washington, DC, USA
| | - A J du Plessis
- Department of Fetal and Transitional Medicine, Fetal Medicine Institute, Children's National Health System, Washington, DC, USA
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Fyfe KL, Odoi A, Yiallourou SR, Wong FY, Walker AM, Horne RS. Preterm Infants Exhibit Greater Variability in Cerebrovascular Control than Term Infants. Sleep 2015; 38:1411-21. [PMID: 25669192 PMCID: PMC4531409 DOI: 10.5665/sleep.4980] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 01/10/2015] [Indexed: 11/03/2022] Open
Abstract
STUDY OBJECTIVES Sudden infant death syndrome (SIDS) remains an important cause of infant death, particularly among infants born preterm. Prone sleeping is the major risk factor for SIDS and this has recently been shown to alter cerebrovascular control in term infants. As preterm infants are at greater risk for SIDS than those born at term, we hypothesized that their cerebrovascular control in the prone position would be reduced compared to term infants. PATIENTS OR PARTICIPANTS There were 35 preterm (mean gestation 31.2 ± 0.4 w) and 17 term (mean gestation 40.1 ± 0.3 w) infants. DESIGN Infants underwent daytime polysomnography at 2-4 w, 2-3 mo, and 5-6 mo postterm age. Infants slept both prone and supine and were presented with cardiovascular challenges in the form of 15° head-up tilts (HUT). MEASUREMENTS AND RESULTS Cerebral tissue oxygenation index (TOI) was recorded using near-infrared spectroscopy (NIRO-200 spectrophotometer, Hamamatsu Photonics KK, Japan) and mean arterial pressure (MAP) was recorded using a Finometer cuff (Finapres Medical Systems, Amsterdam, The Netherlands). In the prone position TOI increased following the HUT (P < 0.05), whereas no change was seen in the supine position. The overall pattern of response was similar in both groups, but more variable in preterm than term infants (P < 0.05). CONCLUSIONS Cerebrovascular control differs between the prone and supine positions in preterm infants. Although overall the responses to head-up tilts were similar between term and preterm infants, greater variability of responses in preterm infants suggests persisting immaturity of their cerebrovascular control in the first year of life, which may contribute to their increased risk of sudden infant death syndrome.
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Affiliation(s)
- Karinna L. Fyfe
- The Ritchie Centre, Hudson Institute of Medical Research and Monash University, Melbourne, Victoria, Australia
- Department of Paediatrics, Monash University, Melbourne, Victoria, Australia
| | - Alexsandria Odoi
- The Ritchie Centre, Hudson Institute of Medical Research and Monash University, Melbourne, Victoria, Australia
| | - Stephanie R. Yiallourou
- The Ritchie Centre, Hudson Institute of Medical Research and Monash University, Melbourne, Victoria, Australia
- Department of Paediatrics, Monash University, Melbourne, Victoria, Australia
| | - Flora Y. Wong
- The Ritchie Centre, Hudson Institute of Medical Research and Monash University, Melbourne, Victoria, Australia
- Department of Paediatrics, Monash University, Melbourne, Victoria, Australia
- Monash Newborn, Monash Medical Centre, Melbourne, Victoria, Australia
| | - Adrian M. Walker
- The Ritchie Centre, Hudson Institute of Medical Research and Monash University, Melbourne, Victoria, Australia
| | - Rosemary S.C. Horne
- The Ritchie Centre, Hudson Institute of Medical Research and Monash University, Melbourne, Victoria, Australia
- Department of Paediatrics, Monash University, Melbourne, Victoria, Australia
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Fyfe KL, Yiallourou SR, Wong FY, Odoi A, Walker AM, Horne RSC. Gestational age at birth affects maturation of baroreflex control. J Pediatr 2015; 166:559-65. [PMID: 25556016 DOI: 10.1016/j.jpeds.2014.11.026] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 09/29/2014] [Accepted: 11/11/2014] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To assess the effect of prone sleeping, the major risk factor for sudden infant death syndrome, in the control of blood pressure (BP) in preterm infants born across a range of gestational ages. STUDY DESIGN Daytime polysomnography was performed at 2-4 weeks, 2-3 months, and 5-6 months postterm age. The participants were 21 very preterm (mean gestation 29.4 ± 0.3 weeks), 14 preterm (mean gestation 33.1 ± 0.3 weeks), and 17 term (mean gestation 40.1 ± 0.3 weeks). BP was measured via a Finometer cuff (Finapres Medical Systems, Amsterdam, The Netherlands) placed around the wrist. Data were recorded both supine and prone. Baroreflex sensitivity (BRS) was calculated via cross-spectral analysis of spontaneous fluctuations in BP. RESULTS BRS was lower in the prone position in very preterm infants at 2-4 weeks in active sleep (P < .05). Maturation of BRS was delayed in very preterm compared with both preterm and term infants. CONCLUSIONS Maturation of BRS after term-equivalent age is altered in very preterm infants. Reduced BRS may result in an impaired ability of very preterm infants to respond to cardiovascular stress during infancy and may predispose them to cardiovascular disease later in life.
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Affiliation(s)
- Karinna L Fyfe
- The Ritchie Centre, Monash Institute of Medical Research and Prince Henry's Institute and Monash University, Melbourne, Victoria, Australia; The Department of Paediatrics, Monash University, Melbourne, Victoria, Australia
| | - Stephanie R Yiallourou
- The Ritchie Centre, Monash Institute of Medical Research and Prince Henry's Institute and Monash University, Melbourne, Victoria, Australia; The Department of Paediatrics, Monash University, Melbourne, Victoria, Australia
| | - Flora Y Wong
- The Ritchie Centre, Monash Institute of Medical Research and Prince Henry's Institute and Monash University, Melbourne, Victoria, Australia; The Department of Paediatrics, Monash University, Melbourne, Victoria, Australia; Monash Newborn, Monash Health, Melbourne, Victoria, Australia
| | - Alexsandria Odoi
- The Ritchie Centre, Monash Institute of Medical Research and Prince Henry's Institute and Monash University, Melbourne, Victoria, Australia
| | - Adrian M Walker
- The Ritchie Centre, Monash Institute of Medical Research and Prince Henry's Institute and Monash University, Melbourne, Victoria, Australia
| | - Rosemary S C Horne
- The Ritchie Centre, Monash Institute of Medical Research and Prince Henry's Institute and Monash University, Melbourne, Victoria, Australia; The Department of Paediatrics, Monash University, Melbourne, Victoria, Australia.
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7
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Wong F, Yiallourou SR, Odoi A, Browne P, Walker AM, Horne RSC. Cerebrovascular control is altered in healthy term infants when they sleep prone. Sleep 2013; 36:1911-8. [PMID: 24293766 PMCID: PMC3825441 DOI: 10.5665/sleep.3228] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
STUDY OBJECTIVES Sudden infant death syndrome (SIDS) is a leading cause of infant death, and prone sleeping is the major risk factor. Prone sleeping impairs arousal from sleep and cardiovascular control in infants at 2-3 months, coinciding with the highest risk period for SIDS. We hypothesized that prone sleeping would also alter cerebrovascular control, and aimed to test this hypothesis by examining responses of cerebral oxygenation to head-up tilts (HUTs) over the first 6 months after birth. STUDY DESIGN AND PARTICIPANTS Seventeen healthy full-term infants were studied at 2-4 weeks, 2-3 months, and 5-6 months of age using daytime polysomnography, with the additional measurements of blood pressure (BP, Finometer™, Finometer Medical Systems, The Netherlands) and cerebral tissue oxygenation index (TOI, NIRO 200, Hamamatsu Photonics KK, Japan). HUTs were performed in active sleep (AS) and quiet sleep (QS) in both prone and supine positions. RESULTS When infants slept in the prone position, a sustained increase in TOI (P < 0.05) occurred following HUTs, except in QS at 2-3 months when TOI was unchanged. BP was either unchanged or fell below baseline during the sustained TOI increase, signifying cerebro-vasodilatation. In contrast, when infants slept supine, TOI did not change after HUTs, except in QS at 2-3 and 5-6 months when TOI dropped below baseline (P < 0.05). CONCLUSIONS When infants slept in the prone position, cerebral arterial vasodilation and increased cerebral oxygenation occurred during head-up tilts, possibly as a protection against cerebral hypoxia. Absence of the vasodilatory response during quiet sleep at 2-3 months possibly underpins the decreased arousability from sleep and increased risk for sudden infant death syndrome at this age.
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Affiliation(s)
- Flora Wong
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
- Monash Newborn, Monash Medical Centre, Melbourne, Victoria, Australia
- Department of Paediatrics, Monash University, Melbourne, Victoria, Australia
| | - Stephanie R. Yiallourou
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
| | - Alexsandria Odoi
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
| | - Pamela Browne
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
| | - Adrian M. Walker
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
| | - Rosemary S. C. Horne
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
- Department of Paediatrics, Monash University, Melbourne, Victoria, Australia
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The development of cardiovascular and cerebral vascular control in preterm infants. Sleep Med Rev 2013; 18:299-310. [PMID: 23907095 DOI: 10.1016/j.smrv.2013.06.002] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 06/20/2013] [Accepted: 06/25/2013] [Indexed: 11/21/2022]
Abstract
Over the past three decades there has been a steady increase in the incidence of preterm birth. The worldwide rate of preterm birth is estimated to be 9.6% of all births, a total of almost 13 million births annually. Preterm birth is associated with a range of adverse cardiovascular and central nervous system outcomes, which may be attributed to altered development of these systems following preterm birth. Preterm birth has a considerable impact on cardiovascular parameters with preterm infants displaying higher heart rates and reduced blood pressure when compared to term born infants at matched ages. Furthermore, premature infants have altered autonomic control of cardiovascular parameters which manifests as abnormalities in heart rate variability and baroreflex mediated control of heart rate and blood pressure. As a result, systemic cardiovascular parameters can be unstable following preterm birth which may place stress on the neonatal brain. The brain of a preterm infant is particularly vulnerable to these fluctuations due to immature cerebral haemodynamics. Preterm infants, particularly those who are very preterm or unwell, display fluctuating pressure-passivity between systemic blood pressure and cerebral blood flow representing a considerably increased risk of cerebral haemorrhage or hypoxia. This is further compounded by immaturity of cerebral blood flow-metabolism coupling, which means increased metabolic demand cannot adequately be met by increased cerebral blood flow. It has been suggested that adverse long-term outcomes following preterm birth may occur as a result of exposure to physiological stress either in-utero or early in infancy.
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The development of autonomic cardiovascular control is altered by preterm birth. Early Hum Dev 2013; 89:145-52. [PMID: 23058299 DOI: 10.1016/j.earlhumdev.2012.09.009] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 09/11/2012] [Accepted: 09/14/2012] [Indexed: 11/23/2022]
Abstract
OBJECTIVES Autonomic dysfunction, either sympathetic or parasympathetic, may explain the increased incidence of Sudden Infant Death Syndrome (SIDS) among preterm infants, as well as their subsequent heightened risk of hypertension in adulthood. As little is known about the development of autonomic function in preterm infants, we contrasted autonomic cardiovascular control across the first 6months after term-corrected age (CA) in preterm and term infants. STUDY DESIGN Preterm (n=25) and age matched term infants (n=31) were studied at 2-4weeks, 2-3months and 5-6months CA using daytime polysomnography. Blood pressure and heart rate were measured during quiet (QS) and active (AS) sleep. Autonomic control was assessed using spectral indices of blood pressure and heart rate variability (BPV and HRV) in ranges of low frequency (LF, reflecting sympathetic+parasympathetic activity), high frequency (HF, respiratory-mediated changes+parasympathetic activity), and LF/HF ratio (sympatho-vagal balance). RESULTS In preterm infants, HF HRV increased, LF/HF HRV decreased and LF BPV decreased with age (p<0.05); these changes were most evident in AS. Compared to term infants, preterm infants in QS exhibited lower LF, HF and total HRV at 5-6months; higher HF BPV at all ages; and lower LF BPV at 2-4weeks (p<0.05). CONCLUSIONS With maturation, in preterm infants, parasympathetic modulation of the heart increases while sympathetic modulation of blood pressure decreases. Compared to term infants, preterm infants exhibit lesser parasympathetic modulation of the heart along with greater respiratory-mediated changes and lower sympathetic modulation of blood pressure. Impaired autonomic control in preterm infants may increase their risk of cardiovascular dysfunction later in life.
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Acute cardiovascular responses in preterm infants at 34-39 weeks of gestational age. Early Hum Dev 2012; 88:871-7. [PMID: 22831637 DOI: 10.1016/j.earlhumdev.2012.07.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 05/17/2012] [Accepted: 07/02/2012] [Indexed: 11/21/2022]
Abstract
BACKGROUND Premature infants demonstrate immature physiological control mechanisms; however their acute cardiovascular control has not yet been widely studied. AIM The aim of this study was to analyze heart rate (HR) and blood pressure (BP) control in preterm infants. SUBJECTS Twenty preterm infants with a mean gestational age of 31 ± 2.4 (26-34) weeks at birth were evaluated at a gestational age of 36 ± 1.5 (34-39) weeks. Results were compared to twenty, healthy, full-term, control infants studied at the age of 12 ± 3 weeks. OUTCOME MEASURES HR and BP responses to 45° head-up tilt and side motion tests during non-rapid eye movement sleep were analyzed. In addition, HR responses to spontaneous arousals from non-rapid eye movement sleep were evaluated. RESULTS Preterm infants showed significantly smaller initial HR and BP responses compared with controls in head-up tilt (HR p=0.0005, systolic BP p=0.02, diastolic BP p=0.01) and side motion tests (HR p=0.002, systolic BP p<0.0001, diastolic BP p<0.0001). Furthermore, in tilt tests, preterm infants presented with greater intersubject variability in BP responses than controls (systolic BP p=0.009, diastolic BP p=0005). Preterm HR responses to spontaneous arousals were similar to controls. CONCLUSIONS This study indicates immature vestibulo-mediated cardiovascular control in preterm infants compared with term infants. This is seen as attenuated BP responses to side motion test and more labile acute BP control to postural challenge.
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Yiallourou SR, Sands SA, Walker AM, Horne RS. Maturation of heart rate and blood pressure variability during sleep in term-born infants. Sleep 2012; 35:177-86. [PMID: 22294807 PMCID: PMC3250356 DOI: 10.5665/sleep.1616] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
STUDY OBJECTIVES Abnormal blood pressure control is implicated in the sudden infant death syndrome (SIDS). However, no data exist on normal development of blood pressure control during infancy. This study assessed maturation of autonomic control of blood pressure and heart rate during sleep within the first 6 months of life. PARTICIPANTS Term infants (n = 31) were studied longitudinally at 2-4 weeks, 2-3 months, and 5-6 months postnatal age. INTERVENTIONS Infants underwent daytime polysomnography at each age studied. Blood pressure and heart rate were recorded during quiet (QS) and active (AS) sleep in undisturbed baseline and head-up tilt conditions. MEASUREMENTS AND RESULTS Autonomic control was assessed using spectral indices of blood pressure and heart rate variability (BPV and HRV) in ranges of low frequency (LF, reflecting sympathetic + parasympathetic activity) and high frequency (HF, parasympathetic activity), total power (LF+HF), and LF/HF ratio (sympathovagal balance). With increasing postnatal age and predominantly during QS, HRV-LF, HRV-HF, and HRV total power increased, while HRV-LF/HF decreased. BPV-LF/HF also decreased with postnatal age. All changes were evident in both baseline and head-up tilt conditions. BPV-LF and BPV total power during tilts were markedly reduced in QS versus AS at each age. CONCLUSIONS In sleeping infants, sympathetic vascular modulation of the circulation decreases with age, while parasympathetic control of heart rate is strengthened. These normative data will aid in the early identification of conditions where autonomic function is impaired, such as in SIDS.
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Affiliation(s)
- Stephanie R. Yiallourou
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
| | - Scott A. Sands
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
- Division of Sleep Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston MA
| | - Adrian M. Walker
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
| | - Rosemary S.C. Horne
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
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12
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Witcombe NB, Yiallourou SR, Sands SA, Walker AM, Horne RSC. Preterm birth alters the maturation of baroreflex sensitivity in sleeping infants. Pediatrics 2012; 129:e89-96. [PMID: 22157139 DOI: 10.1542/peds.2011-1504] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE Impaired blood pressure (BP) control may underpin the increased incidence of the sudden infant death syndrome (SIDS) in preterm infants. This study aimed to examine the effects of preterm birth, postnatal age, and sleep state on BP control by measuring baroreflex sensitivity (BRS) across the first 6 months of term-corrected age (CA), when SIDS risk is greatest. METHODS Preterm (n = 25) and term (n = 31) infants were studied longitudinally at 2 to 4 weeks, 2 to 3 months, and 5 to 6 months CA using daytime polysomnography. BP was recorded during quiet (QS) and active (AS) sleep using a photoplethysmographic cuff placed around the infant's wrist (Finometer [FMS, Finapres Medical Systems, Amsterdam, Netherlands]). BRS (milliseconds/mm Hg) was assessed in 1- to 2-minute epochs using cross-spectral analysis. RESULTS In preterm infants, postnatal age had no significant effect on BRS within either QS or AS. This was in contrast to the maturational increase in QS observed in term infants. Compared with term infants, BRS of preterm infants was 38% higher at 2 to 4 weeks CA and 29% lower at 5 to 6 months CA during QS (P <.05). Comparing sleep states, BRS of preterm infants was 26% lower in QS compared with AS at 2 to 3 months CA (P <.05). CONCLUSIONS Preterm birth impairs the normal maturational increase in BRS, resulting in a substantial reduction in BRS at 5 to 6 months CA during QS. Lower BRS during QS compared with AS at 2 to 3 months CA may place preterm infants at an increased risk for cardiovascular instability at this age of peak incidence of SIDS.
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Affiliation(s)
- Nicole B Witcombe
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
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13
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Stark MJ, Hodyl NA, Wright IMR, Clifton V. The influence of sex and antenatal betamethasone exposure on vasoconstrictors and the preterm microvasculature. J Matern Fetal Neonatal Med 2011; 24:1215-20. [PMID: 21500977 DOI: 10.3109/14767058.2011.569618] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Dysregulated vascular resistance contributes to hypotension following preterm birth with sex-specific differences in microvascular function conferring a male disadvantage. We hypothesized that glucocorticoid mediated, sex-specific differences in the endogenous catecholamine norepinephrine and endothelially derived endothelin-1 (ET-1) contribute to microvascular dysfunction in preterm neonates in the immediate newborn period. METHODS Umbilical and plasma ET-1 and normetanephrine, in 24 h urine samples, were determined at 24, 72, and 120 h of age in 24-34 week infants (n = 60). Microvascular blood flow was determined by laser Doppler flowmetry. RESULTS In infants born within 72 h of antenatal glucocorticoid exposure, normetanephrine was higher in females than males (p = 0.048). Normetanephrine was inversely correlated with both microvascular blood flow at 24 h (p = 0.025) and CRIB II (p = 0.001). While umbilical arterial ET-1 was higher in females delivered <72 h after antenatal betamethasone (p = 0.006), plasma ET-1 did not correlate with microvascular blood flow or illness severity. Only sex and normetanephrine contributed significantly to both microvascular blood flow and endothelium dependant vasodilatation. CONCLUSIONS These data support glucocorticoid mediated, sex-specific differences in mediators of vascular tone that may contribute to the impaired mechanisms compromising successful hemodynamic adaption to neonatal life and resulting in excess male morbidity and mortality.
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Affiliation(s)
- Michael J Stark
- School of Paediatrics and Reproductive Health, The Robinson Institute, University of Adelaide, Adelaide, SA 5005, Australia.
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Wong FY, Witcombe NB, Yiallourou SR, Yorkston S, Dymowski AR, Krishnan L, Walker AM, Horne RSC. Cerebral oxygenation is depressed during sleep in healthy term infants when they sleep prone. Pediatrics 2011; 127:e558-65. [PMID: 21357341 DOI: 10.1542/peds.2010-2724] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE Prone sleeping is a major risk factor for the sudden infant death syndrome and is associated with lower blood pressure and impaired arousability from sleep, both of which may be signs of cerebral hypoxia. However, the impact of sleep position on cerebral oxygenation during infancy remains unknown. We assessed the effects of sleeping position, sleep state, and postnatal age on cerebral oxygenation by measuring tissue oxygenation index (TOI) during the first 6 months of infancy. SUBJECTS AND METHODS Seventeen healthy term infants (8 girls and 9 boys) were recruited as study participants. Infants were studied at ages 2 to 4 weeks, 2 to 3 months, and 5 to 6 months by use of daytime polysomnography, with additional measurements of blood pressure (Finometer, FMS Finometer Medical Systems, Amsterdam, Netherlands) and tissue oxygenation index (TOI) (NIRO 200 spectrophotometer, Hamamatsu Photonics KK, Tokyo, Japan). RESULTS In infants who slept in the prone position, TOI was lower in both quiet sleep (QS) and active sleep (AS) at age 2 to 4 weeks and in QS at age 2 to 3 months (P < .05). TOI was lower in AS compared with QS in infants aged 2 to 4 weeks (P < .05). When the infants reached 5 to 6 months of age, TOI was greater in AS (P < .05), as there was a profound decrease in TOI during QS (P < .05) over this period. No relationship was identified between blood pressure and TOI at any age. CONCLUSIONS In healthy infants cerebral oxygenation is reduced during sleep in the prone position. This reduction may underpin the reduced arousability from sleep exhibited by healthy infants who sleep prone, a finding that provides new insight into potential risks of prone sleeping and mechanisms of sudden infant death syndrome.
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Affiliation(s)
- Flora Y Wong
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Clayton, Victoria, Australia
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Horne RSC, Witcombe NB, Yiallourou SR, Scaillet S, Thiriez G, Franco P. Cardiovascular control during sleep in infants: Implications for Sudden Infant Death Syndrome. Sleep Med 2010; 11:615-21. [PMID: 20609624 DOI: 10.1016/j.sleep.2009.10.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Revised: 10/22/2009] [Accepted: 10/22/2009] [Indexed: 10/19/2022]
Abstract
In infants the cardiorespiratory system undergoes significant functional maturation after birth and these changes are sleep-state dependent. Given the immaturity of these systems it is not surprising that infants are at risk of cardiorespiratory instability, especially during sleep. A failure of cardiovascular control mechanisms in particular is believed to play a role in the final event of Sudden Infant Death Syndrome (SIDS). The "triple risk model" describes SIDS as an event that results from the intersection of three overlapping factors: (1) a vulnerable infant, (2) a critical development period in homeostatic control, and (3) an exogenous stressor. This review summarises normal development of cardiovascular control during sleep in infants and describes the association of impaired cardiovascular control with the three overlapping factors proposed to be involved in SIDS pathogenesis.
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Affiliation(s)
- Rosemary S C Horne
- Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Monash University, Melbourne, Australia.
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Yiallourou SR, Sands SA, Walker AM, Horne RSC. Postnatal development of baroreflex sensitivity in infancy. J Physiol 2010; 588:2193-203. [PMID: 20421281 DOI: 10.1113/jphysiol.2010.187070] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Baroreflex sensitivity (BRS) using spontaneous sequence analysis in the time domain is not fully applicable in infancy, as the time delay for heart period to change (heart period delay, HPD) after an arterial pressure change is unknown. We estimated and compared HPD and BRS in the frequency (BRS(sp), HPD(sp)) and time domains (BRS(seq), HPD(seq)) from systolic blood pressure (SBP) and heart period fluctuations. Continuous SBP, using photoplethysmography, and heart period measurements were performed on 30 term infants at 2-4 weeks, 2-3 months and 5-6 months postnatal age. Cross-spectral analysis between SBP and heart period fluctuations was used to estimate BRS(sp) and HPD(sp). Spontaneous sequence analysis was used to estimate BRS using a fixed beat delay of 1-12 beats (BRS(seq)) or a variable delay identified by a novel method accounting for epoch-epoch variability in HPD (BRS(seqvar)). HPD(sp) averaged 3.4 s (approximately 7 beats); BRS(sp) averaged 11.4 ms mmHg(1). BRS(seq) and BRS(seqvar) were consistently lower than BRS(sp) (P < 0.05), but the three BRS estimates were strongly correlated using a HPD of approximately 5-6 beats. BRS(seqvar) resulted in the average estimate (8.9 ms mmHg(1)) closest to BRS(sp) and overall had the strongest correlation with BRS(sp) (R(2) = 0.61; P < 0.001). All three BRS estimates increased progressively with postnatal age, with BRS(sp) averaging 6.4, 10.5 and 16.0 ms mmHg(1) at 2-4 weeks, 2-3 months and 5-6 months, respectively (P < 0.05). Accounting for the HPD of infancy provides estimates of BRS in the time domain that closely parallel spectral estimates, and provides a novel analytical tool to assess normal development and dysfunction of the baroreflex in infants.
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Affiliation(s)
- Stephanie R Yiallourou
- The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia
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