RESUMEN
As the comparative pathophysiology of perinatal infection in the fetus and newborn is uncertain, this study contrasted the cerebral effects of endotoxemia in conscious fetal sheep and newborn lambs. Responses to intravenous bacterial endotoxin (lipopolysaccharide, LPS) or normal saline were studied on three consecutive days in fetal sheep (LPS 1 µg/kg, n = 5; normal saline n = 5) and newborn lambs (LPS 2 µg/kg, n = 10; normal saline n = 5). Cerebro-vascular function was assessed by monitoring cerebral blood flow (CBF) and cerebral vascular resistance (CVR) over 12 h each day, and inflammatory responses were assessed by plasma TNF alpha (TNF-α), nitrate and nitrite concentrations. Brain injury was quantified by counting both resting and active macrophages in the caudate nucleus and periventricular white matter (PVWM). An acute cerebral vasoconstriction (within 1 h of LPS injection) occurred in both the fetus (ΔCVR +53%) and newborn (ΔCVR +63%); subsequently prolonged cerebral vasodilatation occurred in the fetus (ΔCVR -33%) in association with double plasma nitrate/nitrite concentrations, but not in the newborn. Abundant infiltration of activated macrophages was observed in both CN and PVWM at each age, with the extent being 2-3 times greater in the fetus (P < 0.001). In conclusion, while the fetus and newborn experience a similar acute disruption of the cerebral circulation after LPS, the fetus suffers a more prolonged circulatory disruption, a greater infiltration of activated macrophages, and an exaggerated susceptibility to brain injury.
Asunto(s)
Encéfalo/embriología , Encefalitis/fisiopatología , Enfermedades Fetales/fisiopatología , Lipopolisacáridos/toxicidad , Animales , Encéfalo/crecimiento & desarrollo , Encéfalo/fisiopatología , Circulación Cerebrovascular , Encefalitis/etiología , Femenino , Enfermedades Fetales/etiología , Macrófagos/patología , Masculino , Nitratos/sangre , Nitritos/sangre , Ovinos , Factor de Necrosis Tumoral alfa/sangre , Vasoconstricción , VasodilataciónRESUMEN
STUDY OBJECTIVE: Preterm birth delays maturation of autonomic cardiovascular control, reflected in reduced heart rate variability (HRV) in preterm compared to term infants at term-equivalent age. It has been suggested that immature cardiovascular control contributes to the increased risk for the sudden infant death syndrome (SIDS) in preterm infants. However, the effects of prone sleeping, the major SIDS risk factor, and of gestational age (GA) at birth on HRV have not been assessed in preterm infants beyond term-equivalent age. SUBJECTS AND METHODS: Very preterm (n = 21; mean GA 29.4 ± 0.3 weeks), preterm (n = 14; mean GA 33.5 ± 0.3 weeks), and term (n = 17; mean GA 40.1 ± 0.3 weeks) infants were recruited and underwent daytime polysomnography at 2-4 weeks, 2-3 months, and 5-6 months post-term corrected age (CA). Infants slept both supine and prone. HRV was assessed in the low frequency (LF) and high frequency (HF) ranges. RESULTS: There was no effect of prone sleeping on HRV parameters in either preterm group. In term infants LF/HF was significantly elevated in the prone position in AS at 2-4 weeks (P < 0.05). HF HRV was significantly reduced (P < 0.05) and LF/HF increased (P < 0.05) in very preterm compared to both preterm and term infants at 2-3 months CA. CONCLUSION: Prone sleeping did not significantly impact on heart rate variability (HRV) in preterm infants. However, reduced maturation of high frequency HRV in very preterm infants resulted in significantly altered sympathovagal balance at 2-3 months corrected age, the age of peak sudden infant death syndrome (SIDS) risk. This may contribute to the increased risk of SIDS in infants born at earlier gestational age.
Asunto(s)
Edad Gestacional , Frecuencia Cardíaca/fisiología , Recien Nacido Prematuro/fisiología , Parto/fisiología , Sistema Nervioso Autónomo/fisiología , Femenino , Humanos , Lactante , Recién Nacido , Masculino , Polisomnografía , Posición Prona/fisiología , Factores de Riesgo , Sueño/fisiología , Muerte Súbita del Lactante , Posición Supina/fisiología , Sistema Nervioso Simpático/fisiología , Nacimiento a Término/fisiología , Nervio Vago/fisiologíaRESUMEN
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.
Asunto(s)
Trastornos Cerebrovasculares/complicaciones , Trastornos Cerebrovasculares/fisiopatología , Recien Nacido Prematuro/fisiología , Muerte Súbita del Lactante/etiología , Femenino , Inclinación de Cabeza , Humanos , Lactante , Recién Nacido , Masculino , Polisomnografía , Posición Prona , Factores de Riesgo , Sueño/fisiología , Posición SupinaRESUMEN
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.
Asunto(s)
Barorreflejo/fisiología , Recién Nacido de Bajo Peso , Enfermedades del Prematuro/fisiopatología , Recien Nacido Prematuro , Sueño/fisiología , Muerte Súbita del Lactante/etiología , Femenino , Edad Gestacional , Humanos , Incidencia , Lactante , Recién Nacido , Masculino , Polisomnografía , Posición Prona , Factores de Riesgo , Muerte Súbita del Lactante/epidemiología , Victoria/epidemiologíaRESUMEN
BACKGROUND AND OBJECTIVE: Prone sleeping is a major risk factor for sudden infant death syndrome (SIDS) and preterm infants are at significantly increased risk. In term infants, prone sleeping is associated with reduced mean arterial pressure (MAP) and cerebral tissue oxygenation index (TOI). However, little is known about the effects of sleeping position on TOI and MAP in preterm infants. We aimed to examine TOI and MAP in preterm infants after term-equivalent age, during the period of greatest SIDS risk. METHODS: Thirty-five preterm and 17 term infants underwent daytime polysomnography, including measurement of TOI (NIRO-200 spectrophotometer, Hamamatsu Photonics KK, Japan) and MAP (Finapress Medical Systems, Amsterdam, Netherlands) at 2 to 4 weeks, 2 to 3 months, and 5 to 6 months postterm age. Infants slept prone and supine in active and quiet sleep. The effects of sleep state and position were determined by using 2-way repeated measures analysis of variance and of preterm birth by using 2-way analysis of variance. RESULTS: In preterm infants, TOI was significantly lower when prone compared with supine in both sleep states at all ages (P < .05). Notably, TOI was significantly lower in preterm compared with term infants at 2 to 4 weeks, in both positions (P < .05), and at 2 to 3 months when prone (P < .001), in both sleep states. MAP was also lower in preterm infants in the prone position at 2 to 3 months (P < .01). CONCLUSIONS: Cerebral oxygenation is reduced in the prone position in preterm infants and is lower compared with age-matched term infants, predominantly in the prone position when MAP is also reduced. This may contribute to their increased SIDS risk.
Asunto(s)
Corteza Cerebral/metabolismo , Recien Nacido Prematuro/metabolismo , Consumo de Oxígeno/fisiología , Posición Prona/fisiología , Muerte Súbita del Lactante/etiología , Muerte Súbita del Lactante/prevención & control , Presión Sanguínea/fisiología , Femenino , Frecuencia Cardíaca/fisiología , Humanos , Lactante , Recién Nacido , Masculino , Polisomnografía/métodos , Muerte Súbita del Lactante/diagnóstico , Posición Supina/fisiologíaRESUMEN
AIM: Dopamine is used as an inotropic medication in preterm infants. The preterm human blood brain barrier (BBB) is permeable to intravascular dopamine, and the impact of exogenous dopamine on the preterm brain remains unknown. The preterm lamb model may be suitable for studying the cerebral impact of dopamine therapy whether its BBB permeability is similar to preterm human infants. We aimed to examine BBB permeability to exogenous dopamine in the preterm lamb, by measuring dopamine levels in the cerebrospinal fluid (CSF). METHODS: Nine preterm foetal lambs (125-130 days, term = 147 days) were given either dopamine at 10 µg/kg/min (dopamine, n = 4) or saline (control, n = 5). CSF, and plasma samples were taken for dopamine assay. RESULTS: The median (range) baseline CSF dopamine level for the combined control and dopamine groups (n = 9) was 0.10(0.03-0.16) ng/mL, and baseline plasma dopamine was 0.30(0.13-0.84) ng/mL. The dopamine lambs showed increase in CSF dopamine to 3.91(1.87-11.35) ng/mL with plasma dopamine increased to 14.2 (9.1-57.9) ng/mL. No change was found in the control lambs. CONCLUSION: In the preterm lamb, the BBB permeability and pharmacokinetics to dopamine infusion are similar to findings in the preterm human infant, supporting applicability of the preterm lamb model for studying effects of dopamine infusion in the preterm human brain.
Asunto(s)
Barrera Hematoencefálica , Dopaminérgicos/farmacocinética , Dopamina/farmacocinética , Animales , Animales Recién Nacidos , Dopamina/líquido cefalorraquídeo , Dopaminérgicos/administración & dosificación , Infusiones Intravenosas , OvinosRESUMEN
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.
Asunto(s)
Circulación Cerebrovascular/fisiología , Posición Prona/fisiología , Sueño/fisiología , Presión Sanguínea , Química Encefálica , Femenino , Humanos , Lactante , Masculino , Oxígeno/análisis , Polisomnografía , Posición Supina/fisiologíaRESUMEN
OBJECTIVE: Sleep disordered breathing (SDB) in adults has been associated with a loss of nocturnal dipping in blood pressure (BP) and heart rate, however, there have been limited studies in children. We measured BP non-invasively and continuously overnight in 105 children aged 7-12 with a range of severities of SDB and 36 non-snoring controls to examine nocturnal dipping profiles. STUDY DESIGN: Children with SDB were divided into three severity groups according to their obstructive apnea hypopnea index. Nocturnal dipping profiles across sleep stages were described both as a proportion of children exhibiting a ≥10% fall in systolic arterial pressure (SAP) and heart rate (HR) from wake to sleep and according to SAP sleep/SAP wake ratio as extreme dippers (ratio ≤ 0.8), dippers (ratio < 0.8 and ≤0.9), non-dippers (ratio < 0.9 and ≤1.0), and reverse dippers (ratio > 1.0). RESULTS: The mean fall in BP between wake and NREM 1/2, SWS, and REM sleep was not different between the groups and there were no differences between the dipping profiles of children in each group. CONCLUSIONS: SDB did not alter nocturnal dipping patterns of BP and HR compared to controls, a finding which may suggest that these young children have not been exposed to the effects of SDB long enough or that SDB severity was not great enough to affect nocturnal dipping profiles. However, further studies are required to determine if the elevated BP previously reported in this group of children will have long-term effects on the cardiovascular system.
Asunto(s)
Presión Sanguínea , Síndromes de la Apnea del Sueño/fisiopatología , Adolescente , Niño , Femenino , Humanos , Masculino , Índice de Severidad de la EnfermedadRESUMEN
BACKGROUND: Obstructive sleep apnea (OSA) in adults has been associated with hypertension, low baroreflex sensitivity (BRS), a delayed heart rate response to changing blood pressure (heart period delay [HPD]), and increased blood pressure variability (BPV). Poor BRS may contribute to hypertension by impairing the control of blood pressure (BP), with increased BPV and HPD. Although children with OSA have elevated BP, there are scant data on BRS, BPV, or HPD in this group. METHODS: 105 children ages 7-12 years referred for assessment of OSA and 36 nonsnoring controls were studied. Overnight polysomnography (PSG) was performed with continuous BP monitoring. Subjects were assigned to groups according to their obstructive apnea-hypopnea index (OAHI): primary snoring (PS) (OAHI ≤1event/h), mild OSA (OAHI>1- ≤5events/h) and moderate/severe (MS) OSA (OAHI>5events/h). BRS and HPD were calculated using cross spectral analysis and BPV using power spectral analysis. RESULTS: Subjects with OSA had significantly lower BRS (p<.05 for both) and a longer HPD (PS and MS OSA, p<.01; mild OSA, p<.05) response to spontaneous BP changes compared with controls. In all frequencies of BPV, the MS group had higher power compared with the control and PS groups (low frequency [LF], p<.05; high frequency [HF], p<.001). CONCLUSIONS: Our study demonstrates reduced BRS, longer HPD, and increased BPV in subjects with OSA compared to controls. This finding suggests that children with OSA have altered baroreflex function. Longitudinal studies are required to ascertain if this dampening of the normal baroreflex response can be reversed with treatment.
Asunto(s)
Presión Sanguínea/fisiología , Hipertensión/complicaciones , Hipertensión/fisiopatología , Apnea Obstructiva del Sueño/complicaciones , Apnea Obstructiva del Sueño/fisiopatología , Fases del Sueño/fisiología , Sistema Nervioso Autónomo/fisiología , Barorreflejo/fisiología , Niño , Femenino , Frecuencia Cardíaca/fisiología , Humanos , Masculino , Polisomnografía , Índice de Severidad de la Enfermedad , Ronquido/complicaciones , Ronquido/fisiopatologíaRESUMEN
PURPOSE: Sleep disordered breathing (SDB) has adverse effects on cardiovascular health in adults, partly due to changes in autonomic activity. However, there have been limited studies in children. We analysed the impact of SDB and sleep stage on autonomic control of heart rate in 7-12-year-old children, utilizing spectral heart rate variability (HRV) as a measure of autonomic activity. METHODS: Eighty children underwent overnight polysomnography. Subjects were grouped according to their obstructive apnoea-hypopnoea index (OAHI): controls, OAHI ≤1 event/h and no history of snoring; primary snorers (PS) OAHI ≤1, Mild (OAHI 1-5) and moderate/severe (MS) OAHI >5. HRV was analysed during Wake, nonrapid eye movement (NREM) 1&2, slow wave sleep (SWS) and REM. RESULTS: Compared with controls, total power, low (LF) and high frequency (HF) power were reduced in all SDB severities during REM. LF/HF ratio was less in MS SDB (median = 0.34; range, 0.20-0.49; p < 0.05) versus controls (0.38; 0.26-0.55; p < 0.05) and PS (0.39; 0.23-0.57; p < 0.05) during SWS. In all groups, total power, LF and HF power were highest during NREM 1&2 while LF/HF ratio was lowest during SWS. Blood pressure was elevated in SDB in all sleep states. CONCLUSIONS: HRV was altered in 7-12-year-old children with SDB, which may signify an overall depression of autonomic tone, perhaps a consequence of their elevated blood pressure during sleep coupled with repeated exposure to SDB event-related cardiovascular disturbance. Further research is warranted to elucidate the long-term effects on the cardiovascular system of subjects exhibiting impaired HRV and elevated BP in childhood.
Asunto(s)
Enfermedades del Sistema Nervioso Autónomo/fisiopatología , Presión Sanguínea/fisiología , Electrocardiografía , Frecuencia Cardíaca/fisiología , Corazón/inervación , Polisomnografía , Procesamiento de Señales Asistido por Computador , Apnea Obstructiva del Sueño/fisiopatología , Sistema Nervioso Autónomo/fisiopatología , Enfermedades del Sistema Nervioso Autónomo/diagnóstico , Corteza Cerebral/fisiopatología , Niño , Femenino , Humanos , Masculino , Valores de Referencia , Apnea Obstructiva del Sueño/diagnósticoRESUMEN
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.
Asunto(s)
Sistema Nervioso Autónomo/fisiología , Fenómenos Fisiológicos Cardiovasculares , Nacimiento Prematuro/fisiopatología , Factores de Edad , Análisis de Varianza , Presión Sanguínea , Frecuencia Cardíaca , Humanos , Recién Nacido , Recien Nacido Prematuro , Polisomnografía , Factores de Riesgo , VictoriaRESUMEN
BACKGROUND: Allergy and respiratory viral infection may contribute to the pathogenesis of sleep disordered breathing (SDB) through promoting adenotonsillar growth. We investigated the seasonal variation of SDB in children by analysing the change in the obstructive apnoea hypopnoea index (OAHI) throughout the year. PARTICIPANTS: 257 3-12-year-old children referred for assessment of SDB underwent overnight polysomnography (PSG). RESULTS: Mean seasonal OAHI was significantly higher in winter (5.1±0.8 events/h) and spring (4.6±0.9 events/h) compared with autumn (2.4±0.8 events/h; p<0.01 and p<0.05, respectively) and summer (2.0±0.5 events/h; p<0.05 for both). There were no differences in OAHI between summer and the other seasons or between winter and spring. CONCLUSIONS: We identified more severe obstructive sleep apnoea in clinically referred children during winter and spring and suggest that inflammation from respiratory viruses may contribute to adenotonsillar hypertrophy, worsening airway obstruction. Clinicians should take season into account when interpreting PSG results.
Asunto(s)
Apnea Obstructiva del Sueño/fisiopatología , Niño , Preescolar , Femenino , Humanos , Masculino , Polisomnografía , Estaciones del Año , Índice de Severidad de la EnfermedadRESUMEN
STUDY OBJECTIVES: Sleep disordered breathing (SDB) occurs at an increased incidence in children with Down Syndrome (DS) compared to the general pediatric population. We hypothesized that, compared with typically developing (TD) children with SDB, children with DS have a reduced cardiovascular response with delayed reoxygenation after obstructive respiratory events, and reduced sympathetic drive, providing a potential explanation for their increased risk of pulmonary hypertension. DESIGN: Beat-by-beat heart rate (HR) was analyzed over the course of obstructive events (pre, early, late, post-event) and compared between groups. Also compared were the time for oxygen resaturation post-event and overnight urinary catecholamines. SETTING: Pediatric sleep laboratory. PATIENTS: Sixty-four children aged 2-17 y referred for investigation of SDB (32 DS; 32 TD) matched for age and obstructive apnea/hypopnea index. MEASUREMENT AND RESULTS: Children underwent overnight polysomnography with overnight urine collection. Compared to TD children, those with DS had significantly reduced HR changes post-event during NREM (DS: 21.4% ± 1.8%, TD: 26.6% ± 1.6%, change from late to post-event, P < 0.05). The time to resaturation post-event was significantly increased in the DS group (P < 0.05 for both NREM and REM sleep). Children with DS had significantly reduced overnight urinary noradrenaline (P < 0.01), adrenaline (P < 0.05) and dopamine levels (P < 0.01) compared with TD children. CONCLUSION: Children with DS and SDB exhibit a compromised acute cardio-respiratory response and dampened sympathetic response to SDB compared with TD children with SDB. These data may reflect autonomic dysfunction in children with DS that may place them at increased risk for cardiovascular complications such as pulmonary hypertension.
Asunto(s)
Sistema Cardiovascular/fisiopatología , Síndrome de Down/complicaciones , Síndrome de Down/fisiopatología , Síndromes de la Apnea del Sueño/etiología , Síndromes de la Apnea del Sueño/fisiopatología , Sistema Nervioso Simpático/fisiopatología , Adolescente , Biomarcadores/metabolismo , Biomarcadores/orina , Sistema Cardiovascular/metabolismo , Catecolaminas/orina , Niño , Preescolar , Dopamina/orina , Síndrome de Down/metabolismo , Electroencefalografía/métodos , Electromiografía/métodos , Epinefrina/orina , Femenino , Frecuencia Cardíaca , Humanos , Masculino , Norepinefrina/orina , Oxígeno/metabolismo , Polisomnografía/métodos , Síndromes de la Apnea del Sueño/metabolismo , Sistema Nervioso Simpático/metabolismoRESUMEN
OBJECTIVES: The significance of blood pressure variability (BPV) for cerebral oxygenation in extremely preterm infants has not been explored, though BPV may well be associated with end organ injury. We hypothesized that increased BPV in sick preterm infants, by exceeding the cerebral autoregulatory capacity, is associated with cerebral oxygenation changes which closely follow the blood pressure fluctuations. We assessed the autoregulatory capacity in the early postnatal period, by determining the correlation between BPV (mmHg(2)) and coherence of mean arterial blood pressure (MABP mmHg) and cerebral oxygenation (tissue oxygenation index, TOI %). STUDY DESIGN: Thirty-two preterm infants of mean gestational age of 26.3 (± 1.5) weeks were studied on the first 3 postnatal days. Spectral analysis (Coherence and transfer-function gain analysis) was used to calculate coherence of MABP and TOI; BPV was quantified using power spectral density of MABP. RESULTS: Overall, maximum Coherence showed a trend for positive correlation with BPV (n = 32, p = 0.06). Infants identified as clinically unstable with documented brain injury (n = 7) had high Coherence values at low BPV. Separate analysis of stable infants (excluding the 7 critically ill infants) revealed a significant association between maximum Coherence and BPV (n = 25, p = 0.006). CONCLUSIONS: Fluctuation in cerebral oxygenation is closely associated with increased BPV in preterm infants undergoing intensive care. Moreover, in the critically sick preterm infant, blood pressure-dependent variations in cerebral oxygenation occur even with relatively lower BPV, suggesting they have severely impaired autoregulation, and placing them at greater vulnerability to cerebral injury arising from blood pressure fluctuations.
Asunto(s)
Presión Sanguínea , Encéfalo/patología , Recien Nacido Prematuro/fisiología , Oxígeno/metabolismo , Presión Arterial , Circulación Cerebrovascular , Femenino , Edad Gestacional , Humanos , Recien Nacido Extremadamente Prematuro , Recién Nacido , Masculino , Modelos Estadísticos , Consumo de Oxígeno , PerfusiónRESUMEN
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.
Asunto(s)
Sistema Nervioso Autónomo/fisiología , Presión Sanguínea/fisiología , Desarrollo Infantil/fisiología , Frecuencia Cardíaca/fisiología , Recién Nacido/fisiología , Sueño/fisiología , Factores de Edad , Electrocardiografía/métodos , Electrocardiografía/estadística & datos numéricos , Electroencefalografía/métodos , Electroencefalografía/estadística & datos numéricos , Electromiografía/métodos , Electromiografía/estadística & datos numéricos , Femenino , Estudios de Seguimiento , Humanos , Lactante , Estudios Longitudinales , Masculino , Polisomnografía/métodos , Polisomnografía/estadística & datos numéricos , Valores de ReferenciaRESUMEN
PURPOSE: This study compared electroencephalogram (EEG) spectral analysis with standard visual scoring to assess the validity of clinical classification of arousals at respiratory event termination in children with obstructive sleep apnoea (OSA). METHODS: Twenty children (six M/14 F) aged 7-12 years, diagnosed with moderate to severe OSA participated in this study. Overnight polysomnography was performed, and sleep stages and arousals visually scored using clinical paediatric measures. The EEG was spectrally analysed in six 5-s epochs across respiratory events, namely two consecutive 5-s epochs pre-event onset and a 5s epoch post-event onset, 5-s before event termination, and two contiguous 5-s epochs post-event termination. EEG spectral power distribution was compared across respiratory events visually categorised as full cortical arousals, subcortical activations, or non-arousals using specialised software (Sleep Research System 5.0). RESULTS: There was no difference in power spectra between events in REM and NREM sleep and these were combined. There was a statistically significant fall from pre-arousal baseline values in delta and theta spectral power at respiratory event terminations associated with cortical arousals only. No change in power was detected at respiratory event terminations associated with subcortical activations or non-arousals. CONCLUSIONS: The lack of significant EEG spectral power changes at respiratory event terminations not associated with visually identified cortical arousals indicates undetected micro-arousals are not present. The results support the validity of clinical classifications of arousals at respiratory event termination.
Asunto(s)
Electroencefalografía , Análisis de Fourier , Polisomnografía , Procesamiento de Señales Asistido por Computador , Apnea Obstructiva del Sueño/diagnóstico , Nivel de Alerta/fisiología , Corteza Cerebral/fisiopatología , Niño , Femenino , Humanos , Masculino , Reproducibilidad de los Resultados , Apnea Obstructiva del Sueño/fisiopatología , Programas InformáticosRESUMEN
Treatment of subclinical seizures in newborn HIE remains a contentious issue, especially in light of potential adverse effects of aggressive use of anticonvulsants. We report on the association of subclinical seizures with changes in cerebral oxygenation in an infant with HIE. Our results show that subclinical seizures of longer durations and with associated autonomic disturbance (increased blood pressure) are more likely to be associated with fluctuation in cerebral oxygenation, with some seizures resulting in cerebral hypoxia. Future studies should aim to delineate the effects of subclinical seizure and anticonvulsant treatment on cerebral oxygenation, and their relationships to developmental outcome. Level of cerebral oxygenation may play a role in refining anti-convulsant treatment and management of subclinical seizures in newborns.
Asunto(s)
Encéfalo/irrigación sanguínea , Encéfalo/fisiopatología , Epilepsias Parciales/etiología , Epilepsias Parciales/fisiopatología , Hipoxia-Isquemia Encefálica/complicaciones , Hipoxia-Isquemia Encefálica/fisiopatología , Presión Sanguínea/fisiología , Encéfalo/patología , Electroencefalografía , Epilepsias Parciales/patología , Humanos , Hipoxia-Isquemia Encefálica/patología , Recién Nacido , Masculino , Espectroscopía Infrarroja CortaRESUMEN
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.
Asunto(s)
Barorreflejo , Nacimiento Prematuro , Sueño/fisiología , Presión Sanguínea , Femenino , Humanos , Lactante , Recién Nacido , Recien Nacido Prematuro/fisiología , Masculino , Polisomnografía , Muerte Súbita del Lactante/etiologíaRESUMEN
BACKGROUND: Parents consistently report working memory deficits in children with sleep-disordered breathing (SDB); however, results from objective testing measures are inconsistent. This study aims to examine and compare working memory performance in children with various degrees of severity of SDB using both parent report and objective testing. METHODS: Subjects included 127 children aged 7-12 years (mean age 9.6 ± 1.6 y: 71 M/56 F). Overnight polysomnography classified subjects into four groups: control (N=34); primary snoring (PS: N=55), mild obstructive sleep apnoea (mild OSA: N=22) and moderate to severe OSA (MS OSA: N=16). The Behaviour Rating Inventory of Executive Function (BRIEF) was used as the parent reported measure of working memory. A computerised task involving immediate recognition of playing cards (CogHealth) was used as the objective measure. RESULTS: Results of the BRIEF revealed working memory deficits at all severities of SDB compared to controls. Results of CogHealth revealed no difference between SDB groups and controls; however, mild OSA performed significantly worse than PS. Comparison of the two measures revealed that parents of controls reported less deficits, and parents of PS reported more deficits, than were found on the objective measure of working memory. CONCLUSIONS: This study showed that parents of children with less severe SDB have a tendency to overestimate the level of working memory deficit in their children, possibly as a reflection of behaviour. This suggests that observation of deficits in working memory may be largely dependent on the assessment method and children with SDB may not be as impaired as previously thought.
Asunto(s)
Trastornos de la Memoria/diagnóstico , Trastornos de la Memoria/fisiopatología , Memoria a Corto Plazo/fisiología , Pruebas Neuropsicológicas/normas , Polisomnografía/normas , Síndromes de la Apnea del Sueño/fisiopatología , Niño , Conducta Infantil/fisiología , Función Ejecutiva/fisiología , Femenino , Humanos , Masculino , Trastornos de la Memoria/psicología , Padres/psicología , Reproducibilidad de los Resultados , Síndromes de la Apnea del Sueño/psicologíaRESUMEN
OBJECTIVE: Sleep-disordered breathing (SDB) in adults has been associated with elevated blood pressure (BP); however, the effects of severity of SDB on BP in children are uncertain. We addressed this issue by measuring BP noninvasively and continuously during sleep in children with a range of severities of SDB and in a group of nonsnoring control children. METHODS: A total of 105 children referred for assessment of SDB and 36 nonsnoring controls were studied. Routine polysomnography (PSG) was performed with continuous BP monitoring. Children were assigned to groups according to obstructive apnea/hypopnea index (OAHI). BP data were categorized as quiet awake (recorded before sleep onset), non-rapid eye movement sleep 1 and 2 combined, slow-wave sleep, and rapid eye movement sleep. RESULTS: BP during awake before sleep onset and during overnight sleep was elevated by 10 to 15 mm Hg in the 3 SDB groups compared with the control group; this finding was independent of SDB severity. BP during stable sleep (with respiratory events and movements excluded) was also elevated in the children with OSA compared with the control group. BP was elevated in rapid eye movement sleep compared with the non-rapid eye movement sleep, and heart rate was higher during wake state than in all sleep states. CONCLUSIONS: We recorded BP continuously overnight and found that SDB, regardless of the severity, was associated with increased BP during sleep and wake compared with nonsnoring control children. These findings highlight the importance of considering the cardiovascular effects of SDB of any severity in children, and the need to review current clinical management that focuses primarily on more severe SDB.