Low cerebral blood flow: a risk factor in the neonate

The role of blood pressure variability indicators combined with cerebral blood flow parameters in predicting intraventricular hemorrhage in very low birth weight preterm infants

Background

Hemodynamic instability is the main factor responsible for the development of intraventricular hemorrhage (IVH) in premature newborns. Herein, we evaluated the predictive ability of blood pressure variability (BPV) and anterior cerebral artery (ACA) blood flow parameters in IVH in premature infants with gestational age (GA) ≤32 weeks and birth weight (BW) ≤ 1,500 g.

Methods

Preterm infants with GA ≤32 weeks and BW ≤ 1,500 g admitted to the neonatal intensive care unit (NICU) of the hospital affiliated to Yangzhou University from January 2020 to January 2023 were selected as the research subjects. All preterm infants were admitted within 1 h after birth, and systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial blood pressure (MABP) were monitored at 1-h intervals. The difference between maximum and minimum values (max-min), standard deviation (SD), coefficient of variation (CV), and successive variation (SV) were used as BPV indicators. On the 1st, 3rd, and 7th day after birth, transcranial ultrasound examination was performed to screen for the occurrence of IVH. On the 24 ± 1 h after birth, systolic velocity (Vs), diastolic velocity (Vd), and resistance index (RI) of the ACA were measured simultaneously. Preterm infants were divided into the IVH group and non-IVH group based on the results of transcranial ultrasound examination, and the correlation between BPV indicators, ACA blood flow parameters, and development of IVH was analyzed.

Results

A total of 92 premature infants were enrolled, including 49 in the IVH group and 43 in the non-IVH group. There was no statistically significant difference in baseline characteristics such as BW, GA, sex, and perinatal medical history between the two groups of preterm infants (P > 0.05). The SBP SD (OR: 1.480, 95%CI: 1.020-2.147) and ACA-RI (OR: 3.027, 95%CI: 2.769-3.591) were independent risk factors for IVH in premature newborns. The sensitivity and specificity of combined detection of SBP SD and ACA-RI in predicting IVH were 61.2% and 79.1%, respectively.

Conclusion

High BPV and ACA-RI are related to IVH in premature infants with GA ≤32 w and BW ≤1,500 g. Combined detection of SBP SD and ACA-RI has a certain predictive effect on early identification of IVH.

Changes in cerebral blood flow parameters among preterm 30-34 week neonates who are initiated on kangaroo mother care - A prospective analytical observational study

BACKGROUND

Kangaroo mother care (KMC) is recommended standard of care for preterm neonates. They are vulnerable for cerebral blood flow (CBF) fluctuations linked to intraventricular hemorrhage and periventricular leukomalacia, which have implications on neurodevelopment. This study was designed to document any change in CBF in middle cerebral artery (MCA) of stabilized preterm 30-34 weeks neonates who are initiated on KMC.

METHODS

We designed a prospective analytical observational study in a tertiary care neonatal unit. We enrolled 30-34 weeks preterm neonates eligible for KMC after their stabilization (n = 40). CBF was measured in supine position via right MCA Doppler through the temporal window before any KMC, after 2 h of 1st KMC session and following 24 h of 1st session. CBF was quantified in terms of pulsatility index (PI), Resistive Index (RI), peak systolic velocity (PSV), end-diastolic velocity (EDV), mean velocity (MV) and values were compared against the existing normative values.

RESULTS

Mean gestation of study population was 31.91 weeks with a mean birth weight of 1432.75 g. Median day of initiation of KMC was 7 days with mean duration of KMC on day 1 was 4.56 h. We could find statistically significant decrease in the values of PI and RI from 90th centile towards 50th centile of normative values with a mean difference of 0.22 (99 % CI 0.02-0.43, p 0.005) for PI and 0.05 (99 % CI 0.02-0.07, p = 0.000) for RI post the first session of KMC. Following 24 h of 1st KMC session, we could find a significant increase in values of PSV, EDV and MV comparing values of pre-initiation with day 2 pre-KMC but values of PI and RI were not significantly different.

CONCLUSION

CBF among 30-34 week preterm neonates tend to optimize after initiation of KMC.

Blood pressure extremes and severe IVH in preterm infants

BACKGROUND

The optimal upper and lower limits of blood pressure in preterm infants are not known. Exceeding these thresholds may contribute to intraventricular hemorrhage (IVH).

METHODS

Preterm infants born ≤30 weeks GA were identified. Infants had continuous measurement of mean arterial blood pressure (MABP) for 7 days and cranial ultrasound imaging. IVH was classified as severe IVH (grade 3/4), no severe IVH (no IVH; grade 1/2), or no IVH. Mean ± SEM MABP values from hours 1-168 were calculated and sorted into bins 2 mm Hg wide. The normalized proportion of each recording spent in each bin was then calculated. Candidate limits were identified by comparison of MABP distribution in those with severe IVH vs. those without severe IVH.

RESULTS

Eighty-five million measurements were made from 157 infants. Mean EGA was 25.2 weeks; mean BW was 749 g; 65/157 female; inotrope use in 59/157; grade 3/4 IVH in 29/157. Infants with severe IVH spent significantly more time with extreme MABP measurements (<23 mm Hg or >46 mm Hg) compared to those without severe IVH (12% vs. 8% of recording, p = 0.02).

CONCLUSIONS

Infants who developed severe IVH had substantially more unstable MABP and spent a significantly greater period of time with MABP outside of the optimal range.

Neonatal cerebrovascular autoregulation

Cerebrovascular pressure autoregulation is the physiologic mechanism that holds cerebral blood flow (CBF) relatively constant across changes in cerebral perfusion pressure (CPP). Cerebral vasoreactivity refers to the vasoconstriction and vasodilation that occur during fluctuations in arterial blood pressure (ABP) to maintain autoregulation. These are vital protective mechanisms of the brain. Impairments in pressure autoregulation increase the risk of brain injury and persistent neurologic disability. Autoregulation may be impaired during various neonatal disease states including prematurity, hypoxic-ischemic encephalopathy (HIE), intraventricular hemorrhage, congenital cardiac disease, and infants requiring extracorporeal membrane oxygenation (ECMO). Because infants are exquisitely sensitive to changes in cerebral blood flow (CBF), both hypoperfusion and hyperperfusion can cause significant neurologic injury. We will review neonatal pressure autoregulation and autoregulation monitoring techniques with a focus on brain protection. Current clinical therapies have failed to fully prevent permanent brain injuries in neonates. Adjuvant treatments that support and optimize autoregulation may improve neurologic outcomes.

Cerebral white matter blood flow and arterial blood pressure in preterm infants

It is generally assumed that one reason why white matter injury is common in preterm infants is the relatively poor vascular supply.

Cerebrovascular physiology in perinates with congenital hydrocephalus

PURPOSE

This study investigated changes in regional cerebral blood flow (rCBF), autoregulation (AR), and mean CO(2) reactivity (CO(2)r) in nine neonates, who underwent cerebrospinal fluid (CSF) diversion for congenital hydrocephalus.

METHODS

During shunt insertion, a thermal diffusion probe inserted adjacent to the ventricular catheter in the right parietal region recorded rCBF. Changes in rCBF, mean arterial pressure, intracranial pressure (ICP), and expired CO(2) tension were recorded before and after removing CSF.

RESULTS

Mean baseline rCBF for the entire group was 19.5 mL/100 g/min (range 8.4-44.8), with a mean ICP of 9.9 mmHg (range 4-20). Following CSF removal, the rCBF increased significantly in two patients. Three patients demonstrated AR throughout their studies; one infant showed AR after CSF removal. One infant without AR during shunt insertion showed an increase in rCBF and AR during a revision 5 months later. Baseline CO(2)r varied considerably but was greater than two in two patients and increased in three other children after CSF removal. Mean follow-up was 23.6 months. One child, with severe developmental delay, died. Death or severe delay was associated with the absence of AR and a negative CO(2)r in three children. Normal or mild developmental delay was associated with AR and a neutral or positive CO(2)r in five patients.

CONCLUSIONS

Baseline levels of rCBF were not associated with developmental prognosis. AR and a positive CO(2)r were necessary but insufficient factors for normal development. The absence of AR and a negative CO(2)r were associated with poor prognosis.

The role of systemic hemodynamic disturbances in prematurity-related brain injury

Premature infants who experience cerebrovascular injury frequently have acute and long-term neurologic complications. In this article, we explore the relationship between systemic hemodynamic insults and brain injury in this patient population and the mechanisms that might be at play.

Randomized trial of milrinone versus placebo for prevention of low systemic blood flow in very preterm infants

OBJECTIVE

To assess the effectiveness of early prophylactic milrinone versus placebo for prevention of low systemic blood flow in high-risk preterm infants.

STUDY DESIGN

Double-blind randomized placebo controlled trial of milrinone (loading dose 0.75 microg/kg/min for 3 hours then maintenance 0.2 microg/kg/min until 18 hours after birth) versus placebo. Infants born <30 weeks gestational age and <6 hours of age were eligible and were monitored with serial echocardiography, head ultrasound scanning, and continuous invasive blood pressure. Primary outcome was maintenance of superior vena cava (SVC) flow > or =45 mL/kg/min through the first 24 hours. The exit criterion was hypotension unresponsive to volume and inotropes.

RESULTS

Ninety infants were enrolled, equal proportions maintained SVC flow > or =45 mL/kg/min after treatment commenced. No significant difference was observed in SVC flow, right ventricular output, and blood pressure during the first 24 hours; or grades 3 to 4 periventricular/intraventricular hemorrhage and death. Heart rate was higher and constriction of the ductus was slower in the infants randomized to milrinone.

CONCLUSIONS

Milrinone did not prevent low systemic blood flow during the first 24 hours in very preterm infants, and no adverse effects were attributable to milrinone. Use of a preventative treatment with rescue model allowed comparison of an inotrope with placebo in this high-risk group of infants.

Dopamine versus dobutamine in very low birthweight infants: endocrine effects

OBJECTIVES

To compare the endocrine effects of dopamine and dobutamine in hypotensive very low birthweight (VLBW) infants.

DESIGN

Non-blinded randomised prospective trial.

SETTING

Level III neonatal intensive care unit.

PATIENTS

35 hypotensive VLBW infants who did not respond to volume loading, assigned to receive dopamine or dobutamine.

MEASUREMENTS

Haemodynamic variables and serum levels of thyroid stimulating hormone (TSH), total thyroxine (T(4)), prolactin (PRL) and growth hormone were assessed during the first 72 h of treatment and the first 72 h after stopping treatment.

RESULTS

Demographic and clinical data did not significantly differ between the two groups. Necessary cumulative and mean drug doses and maximum infusion required to normalise blood pressure were significantly higher in the dobutamine than in the dopamine group (p<0.01). Suppression of TSH, T(4) and PRL was observed in dopamine-treated newborns from 12 h of treatment onwards, whereas levels of growth hormone reduced significantly only at 12 h and 36 h of treatment (p<0.01). TSH, T(4) and PRL rebound was observed from the first day onwards after stopping dopamine. Dobutamine administration did not alter the profile of any of the hormones and no rebound was observed after stopping treatment.

CONCLUSION

Dopamine and dobutamine both increase the systemic blood pressure, though dopamine is more effective. Dopamine reduces serum levels of TSH, T(4) and PRL in VLBW infants but such suppression is quickly reversed after treatment is stopped. Further research is required to assess if short-term iatrogenic pituitary suppression has longer-term consequences.

Assessment and support of the preterm circulation

There are no clinical outcome data on which to base recommendations on how to assess and support the preterm circulation. Current standards are derived from an assumed proportionality between systemic and organ blood flow and mean blood pressure. Our study of central measures of systemic blood flow suggests preterm haemodynamics are more complex than this. Low systemic blood flow is common in the first 24 h after birth in very preterm babies and is not necessarily reflected by low blood pressure. The causes of this low systemic blood flow are complex but may relate to maladaptation to high extrauterine systemic (and sometimes pulmonary) vascular resistance. After day 1, hypotensive babies are more likely to have normal or high SBF reflecting vasodilatation. Empirically, inotropes that reduce afterload (such as dobutamine) may be more appropriate in the transitional period, while those with more vasoconstrictor actions (such as dopamine) may be more appropriate later on. Defining the haemodynamic in an individual baby needs both blood pressure and echocardiographic measures of systemic blood flow. Research in this area needs to move beyond just demonstrating changes in physiological variables to showing improvements in important clinical outcomes.

Management of hypotension and low systemic blood flow in the very low birth weight neonate during the first postnatal week

Systemic hypotension during the first postnatal week is associated with increased mortality and morbidity in the very low birth weight (VLBW) neonate. Hypotension is generally defined as blood pressure below the fifth percentile of the gestational- and postnatal-age dependent blood pressure norms. Recent studies indicate that in most VLBW neonates, cerebral blood flow autoregulation is indeed lost when blood pressure reaches the fifth percentile. Treatment of the circulatory compromise should address the primary pathogenic factor(s) of the condition (hypovolemia, myocardial compromise, failure of vasoregulation or a combination of factors). Recent findings also suggest that vasopressor resistance can be treated with a brief course of low-dose hydrocortisone. However, due to the short- and potential long-term side effects of early hydrocortisone treatment, its use should be restricted to neonates with vasopressor-resistant hypotension. Finally, concomitant administration of hydrocortisone with indomethacin should be avoided due to the increased incidence of gastrointestinal perforations.

Which inotrope for which baby?

While we know a lot about blood pressure (BP) responses to various inotropes and a bit about systemic and organ blood flow responses, we know almost nothing about how different inotropes affect clinical outcomes. Low systemic blood flow (SBF) is common in the first 24 h after birth in very preterm babies (and more mature babies with severe respiratory problems) and is not always reflected by low BP. The causes of this low SBF are complex but may relate to maladaptation to high extrauterine systemic (and sometimes pulmonary) vascular resistance. After day 1, hypotensive babies are more likely to have normal or high SBF reflecting vasodilatation. Empirically, inotropes that reduce afterload (such as dobutamine) may be more appropriate in the transitional period, while those with more vasoconstrictor actions (such as dopamine) may be more appropriate later on. Defining the haemodynamic in an individual baby needs both BP and echocardiographic measures of SBF. Research in this area needs to move beyond just demonstrating changes in physiological variables to showing improvements in important clinical outcomes.

Pediatric Perfusion MR Imaging Using Arterial Spin Labeling

Cerebral blood flow (CBF, cerebral perfusion) mirrors cerebral metabolic demand and neuronal function, and therefore, is a vital parameter in the evaluation of pediatric brain injury and recovery. Until recently, measurement of CBF involved intravenous bolus injection of contrast agents or nuclear medicine methods that were technically difficult or ethically problematic in pediatrics. The development of arterial spin label (ASL) perfusion MR imaging as a noninvasive method for measuring CBF allows for the increased ability to measure this vital physiologic parameter in any age group. This article presents the technical aspects of performing ASL perfusion MR imaging in pediatrics, and discusses its current use in clinical studies and its potential for influencing important management strategies in specific disease entities.

Low systemic blood flow and pathophysiology of the preterm transitional circulation

The transitional circulation of the preterm infant differs significantly from the term infant. The preterm infant is uniquely at risk of hypotension and low systemic blood flow states due to failure or delay in the normal transitional circulation processes. The maintenance of normal tissue oxygenation requires maintenance of systemic blood flow and normal blood oxygen levels. Reduction in either of these physiological parameters may result in organ damage, leading to complications such as intraventricular haemorrhage and longer term neurodevelopmental disability. The identification and ongoing monitoring of low systemic blood flow in the preterm infant is more challenging than in older children and some of the assessment techniques used in paediatric and adult intensive care settings do not apply to the neonatal setting. The presence of ductal and atrial shunts makes the measurement of cardiac output problematic in the preterm infant so other newer ways of measuring systemic blood flow need to be considered. The proper treatment of hypotensive and low cardiac output states in the preterm infant requires primarily an understanding of the underlying pathophysiology.

The ratio of flow velocities in the middle cerebral and internal carotid arteries for the prediction of cerebral palsy in term neonates

OBJECTIVE

This study evaluated whether the ratio of the mean flow velocities in the middle cerebral artery (MCA) and the internal carotid artery (ICA) of neonates in the first days of life can be used to identify future neurodevelopmental disabilities.

METHODS

We observed 127 term neonates without congenital malformations, chromosomal aberrations, intracranial hemorrhage, or early onset sepsis. The mean cerebral blood flow velocities were measured in the right and left ICAs and in the right and left MCAs with a Doppler flowmeter once from day 1 to day 3. The Vm ratio was defined as the mean velocity in the right and left MCAs/mean velocity in the right and left ICAs. Neurologic examinations were performed at 12 months of age in the outpatient follow-up clinic to detect cerebral palsy (CP), and the subjects were divided into 4 groups according to the diagnosis of hypoxic-ischemic encephalopathy (HIE) and neurologic prognosis: HIE- and normal neurologic function, HIE- and CP, HIE+ and normal neurologic function, and HIE+ and CP.

RESULTS

The Vm ratio in infants with the HIE- diagnosis and CP was significantly lower than that in infants with the HIE- diagnosis without CP (P < .05). There was no significant difference between the Vm ratios in infants with the HIE+ diagnosis without CP and infants with the HIE+ diagnosis and CP.

CONCLUSIONS

The Vm ratio might be a useful index in estimating neurologic outcome at birth, especially in neonates without the diagnosis of HIE.

Low superior vena cava flow and neurodevelopment at 3 years in very preterm infants

OBJECTIVES

Low superior vena cava (SVC) flow is common in the first hours after very preterm birth and has a strong association with subsequent periventricular/intraventricular hemorrhage. We report the neurodevelopmental outcome at 3 years of age of very preterm babies who had serial echocardiographic studies, including measures of SVC flow, during the first 48 hours after birth.

STUDY DESIGN

A prospective observational study was performed on a cohort of 126 babies (<30 weeks), 103 of whom survived to discharge. Neurodevelopmental follow-up data, which included abnormal developmental quotient, abnormal motor score, and cerebral palsy, were available for 93% of this cohort at 3 years of age. Relations between 3-year outcome and early hemodynamic measures and clinical parameters were explored.

RESULTS

After controlling for confounding variables, average SVC flow over the first 24 hours of life was significantly associated with the primary outcome of death or survival with any disability (P=.004) and with the secondary outcome of abnormal developmental quotient (P = .006). A greater number of low SVC flow readings during the first 24 hours was significantly related to death and adverse developmental outcome, but the individual lowest SVC flow was not, suggesting the importance of duration of low SVC flow. After adjustment, there was no significant association between average mean blood pressure over the first 24 hours and abnormal developmental outcome, whereas the proportion of mean blood pressure readings less than the gestational age showed a trend toward an association with death and any disability.

CONCLUSIONS

Low early postnatal blood flow to the upper body and brain may be one factor in the causal pathway of impaired preterm neurodevelopmental outcome.

Low cerebral blood flow resistance in nonventilated preterm infants predicts poor neurologic outcome

OBJECTIVES

To examine whether cerebral blood flow variables during the first critical day of life can predict the 1-yr neurologic outcome in ventilated and nonventilated preterm infants.

DESIGN

Prospective follow-up study.

SETTING

Neonatal intensive care unit of university central hospital.

PATIENTS

Forty-nine preterm infants <33 wks of gestation.

INTERVENTIONS

Doppler ultrasound investigations of the brain circulation, heart rate, and systemic blood pressure were performed in ventilated (n = 35) and nonventilated (n = 14) preterm infants during the first day of life. The neurologic development was evaluated using Griffith's subscales at 12 months of corrected age.

MEASUREMENTS AND MAIN RESULTS

Cerebral blood flow velocity measurements were obtained from the anterior cerebral artery and internal carotid artery. Cerebral blood flow, cerebral blood flow resistance, and cerebral perfusion pressure subsequently were derived. These derived cerebral perfusion variables were associated with the sum of Griffith's developmental scales (p <.02). However, the slopes of regression lines between cerebral blood flow or cerebral blood flow resistance and the sum of Griffith's psychomotor developmental scales tended to be different in the ventilated and nonventilated infants (p =.06, p =.003, respectively). The correlations between these variables and the sum of Griffith's psychomotor developmental scales were significant only in nonventilated preterm infants (r =.69, p =.007, and r = -.85, p =.001, respectively).

CONCLUSIONS

Our data suggest that lowered cerebral blood flow resistance reflecting lowered cerebral blood flow during early circulatory transition is associated with adverse outcome in nonventilated preterm infants, but no connection in ventilated infants was found.

Brain Imaging Studies of the Anatomical and Functional Consequences of Preterm Birth for Human Brain Development

Premature birth can have devastating effects on brain development and long-term functional outcome. Rates of psychiatric illness and learning difficulties are high, and intelligence on average is lower than population means. Brain imaging studies of infants born prematurely have demonstrated reduced volumes of parietal and sensorimotor cortical gray matter regions. Studies of school-aged children have demonstrated reduced volumes of these same regions, as well as in temporal and premotor regions, in both gray and white matter. The degrees of these anatomical abnormalities have been shown to correlate with cognitive outcome and with the degree of fetal immaturity at birth. Functional imaging studies have shown that these anatomical abnormalities are associated with severe disturbances in the organization and use of neural systems subserving language, particularly for school-aged children who have low verbal IQs. Animal models suggest that hypoxia-ischemia may be responsible at least in part for some of the anatomical and functional abnormalities. Increasing evidence suggests that a host of mediators for hypoxic-ischemic insults likely contribute to the disturbances in brain development in preterm infants, including increased apoptosis, free-radical formation, glutamatergic excitotoxicity, and alterations in the expression of a large number of genes that regulate brain maturation, particularly those involved in the development of postsynaptic neurons and the stabilization of synapses. The collaboration of both basic neuroscientists and clinical researchers is needed to understand how normal brain development is derailed by preterm birth and to develop effective prevention and early interventions for these often devastating conditions.

Blood pressure in the very low birth weight neonate

Few aspects of management of very low birth weight (VLBW; <1500 g) neonates have generated as much controversy as the assessment of blood pressure (BP) and need for treatment of perceived abnormalities of this physiologic variable. The approach to this problem may differ greatly among various institutions and even among clinicians within a given center. The purpose of this manuscript is to review available information regarding physiologic determinants and measurement of BP in VLBW neonates, normative data for BP, clinical factors that may affect BP in these at-risk neonates and studies in which presumed abnormalities of BP resulted in adverse clinical outcomes. Options for treatment of low BP in VLBW neonates also will be discussed.

Determinants of blood pressure in very low birth weight neonates: lack of effect of antenatal steroids

OBJECTIVES

To define the range of normal blood pressures (BP) for very low birth weight (VLBW;</=1500 g) neonates and to study perinatal variables affecting BP measurements after birth, including the effects of antenatal steroids.

STUDY DESIGN

Antenatal steroids were rarely administered at Parkland Memorial Hospital before May 1994, permitting us to establish a cohort of VLBW neonates exposed to antenatal steroids [n=70, 1166+/-253 (S.D.) g, and 28.7+/-2.1 weeks] who were matched with neonates delivered during the prior year (n=46, 1100+/-241 g, 28.9+/-1.8 weeks). Maternal and neonatal charts were abstracted for pertinent data, and neonatal BP measurements (determined directly when an arterial catheter was available or indirectly by the oscillometric method) were extracted every 3 h for the first 12 h and every 6 h until 72 h postnatal.

RESULTS

Antenatal steroids did not affect BP immediately after birth or for the subsequent 72 h postnatal. Therefore, data from all neonates </=1500 g were combined and the pattern of BP change over 72 h postnatal assessed. Systolic, diastolic and mean BP increased (P<0.001) 33%, 44% and 38%, respectively, during the first 72 h. Although neonates weighing </=1000 g and 1001-1500 g demonstrated gradual increases (P<0.001) in systolic, diastolic and mean BP by 72 h, values were consistently lower (P<0.01) in neonates </=1000 g. Of interest, only 11 neonates (9.5%) were treated for clinical hypotension.

CONCLUSIONS

In VLBW neonates antenatal steroids do not modify BP measurements either immediately after birth or the 30-40% rise occurring in the first 72 h postnatal. Further, BP is developmentally regulated and is gestationally and birth weight dependent. These data provide additional insight into assessing the need for treating hypotension.

Low superior vena cava flow and intraventricular haemorrhage in preterm infants

OBJECTIVES

To document the incidence, timing, degree, and associations of systemic hypoperfusion in the preterm infant and to explore the temporal relation between low systemic blood flow and the development of intraventricular haemorrhage (IVH).

STUDY DESIGN

126 babies born before 30 weeks' gestation (mean 27 weeks, mean body weight 991 g) were studied with Doppler echocardiography and cerebral ultrasound at 5, 12, 24, and 48 hours of age. Superior vena cava (SVC) flow was assessed by Doppler echocardiography as the primary measure of systemic blood flow returning from the upper body and brain. Other measures included colour Doppler diameters of ductal and atrial shunts, as well as Doppler assessment of shunt direction and velocity, and right and left ventricular outputs. Upper body vascular resistance was calculated from mean blood pressure and SVC flow.

RESULTS

SVC flow below the range recorded in well preterm babies was common in the first 24 hours (48 (38%) babies), becoming significantly less common by 48 hours (6 (5%) babies). These low flows were significantly associated with lower gestation, higher upper body vascular resistance, larger diameter ductal shunts, and higher mean airway pressure. Babies whose mothers had received antihypertensives had significantly higher SVC flow during the first 24 hours. Early IVH was already present in 9 babies at 5 hours of age. Normal SVC flows were seen in these babies except in 3 with IVH, which later extended, who all had SVC flow below the normal range at 5 and/or 12 hours. Eight of these 9 babies were delivered vaginally. Late IVH developed in 18 babies. 13 of 14 babies with grade 2 to 4 IVH had SVC flow below the normal range before development of an IVH. Two of 4 babies with grade 1 IVH also had SVC flow below the normal range before developing IVH, and the other 2 had SVC flow in the low normal range. In all, IVH was first seen after the SVC flow had improved, and the grade of IVH related significantly to the severity and duration of low SVC flow. The 9 babies who had SVC flow below the normal range and did not develop IVH or periventricular leucomalacia were considerably more mature (median gestation 28 v 25 weeks).

CONCLUSIONS

Low SVC flow may result from an immature myocardium struggling to adapt to increased extrauterine vascular resistances. Critically low flow occurs when this is compounded by high mean airway pressure and large ductal shunts out of the systemic circulation. Late IVH is strongly associated with these low flow states and occurs as perfusion improves.

Dopamine versus dobutamine for hypotensive preterm infants

BACKGROUND

Inotropes are widely used in preterm infants to treat systemic hypotension. The most commonly used drugs are dopamine and dobutamine. These agents have different modes of action which may result in different haemodynamic effects.

OBJECTIVES

To compare the effectiveness and safety of dopamine and dobutamine in the treatment of systemic hypotension in preterm infants.

SEARCH STRATEGY

The standard search method of the Cochrane Neonatal Review Group was used. Searches of electronic and other databases were performed. Previous reviews were searched for references to relevant trials and leading authors in the field were contacted for information about other published and unpublished studies.

SELECTION CRITERIA

Randomised controlled trials where short and/or long term effects of treatment with dopamine and dobutamine for the treatment of systemic arterial hypotension were compared were selected for this review. Trials studying newborn infants born before 37 completed weeks gestation and less than 28 days of age were eligible for inclusion. Systemic arterial hypotension was not defined specifically, but accepted as defined in individual studies. Studies were not limited by birthweight, lower gestational age threshold or by route or duration of administration of inotropic agents. Study quality and eligibility were assessed independently by each reviewer.

DATA COLLECTION AND ANALYSIS

The standard method of the Cochrane Collaboration described in the Cochrane Collaboration Handbook was used to perform this systematic review. Data extraction was performed independently by each reviewer, with differences being resolved by discussion. The following outcomes were determined: mortality in the neonatal period, long term neurodevelopmental outcome, radiological evidence of severe neurological injury, short term haemodynamic changes and incidence of adverse effects. The effect of interventions is expressed either as Relative Risk (RR), Risk Difference (RD) or as Weighted Mean Difference (WMD) with their 95% Confidence Interval (CI).

MAIN RESULTS

Four trials met the pre-defined criteria for inclusion in this review. There was no evidence of a significant difference between dopamine and dobutamine in terms of neonatal mortality (RD 0.02 95% CI -0.12 to 0.16), incidence of periventricular leukomalacia (RD -0.08, 95% CI -0.19 to 0.04), or severe periventricular haemorrhage (RD -0.02, 95% CI -0.13 to 0.09). Dopamine was more successful than dobutamine in treating systemic hypotension, with fewer infants having treatment failure (RD -0.29, 95% CI -0.42 to -0.17; NNT = 3.5, 95% CI 2.4 to 5.9). There was no evidence of a significant difference in change in left ventricular output when dopamine was compared with dobutamine (WMD -83 ml/kg/min, 95% CI -174 to 8 ml/kg/min). There was no evidence of a significant difference between the two agents with respect to the incidence of tachycardia (RD -0.06, 95% CI -0.25 to 0.14). None of the studies reported the incidence of adverse long term neurodevelopmental outcome.

REVIEWER'S CONCLUSIONS

Dopamine is more effective than dobutamine in the short term treatment of systemic hypotension in preterm infants. There was no evidence of an effect on the incidence of adverse neuroradiological sequelae (severe periventricular haemorrhage and/or periventricular leucomalacia), or on the incidence of tachycardia. However, in the absence of data confirming long term benefit and safety of dopamine compared to dobutamine, no firm recommendations can be made regarding the choice of drug to treat hypotension.

A comparison of pulse oximetry and near infrared spectroscopy (NIRS) in the detection of hypoxaemia occurring with pauses in nasal airflow in neonates

OBJECTIVE

The aim of this study was to compare the ability of NIRS and pulse oximetry to detect changes in cerebral oxygenation occurring in response to a pause in nasal airflow (PNA).

METHODS

Twenty-one recordings of cerebral oxygenation index by NIRS together with oxyhemoglobin saturation by pulse oximetry were measured on 17 preterm infants with a history of apnoea. Photoplethysmography was used to confirm the accuracy of the pulse oximetry data. PNA events were defined as pauses of greater than 4 seconds in a thermistor trace measuring nasal air flow.

RESULTS

Baseline variability in oxygenation index (Hbdiff) was found to be from -0.12 to +0.13 micromol 100 g brain(-1). A fall in Hbdiff or SpO2 was defined as a decrease of greater magnitude than 2 standard deviations from the baseline, i.e., -0.12 micromol 100 g brain(-1) and 3% respectively. In 68% of 468 PNA events a fall in oxyhemoglobin saturation (SpO2) was detected and in 56% a fall in Hbdiff was detected. In 20% of events there was no fall in cerebral oxygenation despite a fall in SpO2. In 8% of PNA episodes we recorded a fall in cerebral oxygenation but no fall in SpO2. When a fall in cerebral oxygenation was recorded, the fall was greater when the event was also associated with a fall in SpO2 (median (interquartile range (IQR)) 0.32 (0.21-0.69) vs. 0.25 (0.16-0.43) micromol 100 g brain(-1), p < 0.05). When all the PNA episodes were reviewed no close correlation was shown between the magnitude of change in cerebral oxygenation and the change in SpO2 for small changes in both indices. However, large falls (>1.5 micromol 100 g brain(-1)) in cerebral oxygenation were closely associated with large changes in SpO2.

CONCLUSIONS

We conclude that both techniques are sensitive to changes in oxygenation during PNA. Small changes in cerebral Hbdiff and arterial SpO2 do not always correlate for physiological reasons. A change in Hbdiff of >0.3 micromol 100 g brain(-1) is likely to be physiologically significant and is associated with a change in SpO2 of 12%.

Cerebral blood flow increases over the first three days of life in extremely preterm neonates

AIM

To measure changes in cerebral haemodynamics over the first three days of life in very preterm infants with normal brains.

METHODS

Eleven mechanically ventilated infants (median gestational age 26 weeks) without evidence of major abnormalities on cranial ultrasound examination were studied. Cerebral blood flow (CBF) and cerebral blood volume (CBV) were measured using near infrared spectroscopy at least twice over the first three days of life.

RESULTS

Cerebral blood flow increased significantly with time (p = 0.02; stepwise linear regression) and this was independent of mean arterial blood pressure, PaCO2, and haematocrit.

CONCLUSION

This change is likely to represent a normal adaptive response of the cerebral circulation to postnatal life.

Measurements of cerebral blood flow in post-asphyxiated newborns by color Doppler imaging (CDI)

Cerebral blood flow of 10 asphyxiated term newborns was continuously measured during the first 7 days of life and compared with that of 10 normal term infants by CDI. Frequency spectrum and blood flow variables in the anterior, middle and posterior cerebral arteries were studied. The results showed evidently lower systolic amplitude in patients than that in normal subjects. End diastolic amplitude was zero in part of vessels, and values of blood flow variables were all lower in day 1 of the life as compared with the control groups. Frequency spectrum recovered to normal patterns in 9 survived infants in day 2, but blood flow variables recovered to normal by day 7. Values of resistance index (RI) rose to 1 in some vessels of moderate hypoxic ischemic encephalopathy (HIE) infants and stayed at 1 in the severe HIE infants. It is concluded that low CBF plays a key role in brain damage of post-asphyxiated newborns and RI may be an important parameter in the evaluation prognosis.

Early ductal shunting and intraventricular haemorrhage in ventilated preterm infants

AIM

To establish if there is an association between early cardiovascular adaptation and intraventricular haemorrhage (IVH).

METHODS

One hundred and seventeen ventilated preterm infants (mean gestational age 27 weeks, mean birthweight 993 g) were studied echocardiographically within the first 36 hours. Measurements included right (RVO) and left ventricular outputs (LVO), ductus arteriosus (PDA) and atrial shunt diameter using colour Doppler and pulsed Doppler direction and velocity of both shunts. Clinical variables collected over the first 24 hours included use of antenatal steroids, respiratory severity, and mean blood pressure. Cerebral ultrasound scans were reported by a radiologist blinded to clinical and echocardiographic data.

RESULTS

Antenatal steroids (two doses) had been given to 73% of the 86 infants with no IVH compared with 48% of the 21 infants with grades 1 and 2 IVH, and just 10% of 10 babies with grades 3 and 4 (P < 0.05). Both groups with IVH had significantly larger PDA diameters than the group with no IVH. Infants with grades 3 and 4 IVH had significantly lower RVO than the other infants. These differences were more pronounced when only infants with definite late IVH were analysed. Logistic regression analysis showed lack of antenatal steroids and larger PDA diameters were significantly associated with any grade of IVH and lack of antenatal steroids; lower RVO was significantly associated with grades 3 and 4 IVH.

CONCLUSIONS

Larger early PDA shunts, lower RVO, and lack of antenatal steroids were significantly associated with IVH.

Relationship between blood pressure and cardiac output in preterm infants requiring mechanical ventilation

OBJECTIVE

To assess the contribution of cardiac output in determining the blood pressure of preterm infants and to identify other factors that may be important.

METHODS

Sixty-seven preterm infants requiring mechanical ventilation (median birth weight, 1015 gm: median gestational age, 28 weeks) underwent on echocardiographic study at on average age of 19 hours (range, 7 to 31 hours). Measurements taken included left ventricular ejection fraction, left and right ventricular outputs by means of pulsed Doppler and the diameter of both the ductal and atrial shunt jets with the use of color Doppler as a measure of the size of shunt. Simultaneous measurements of intraarterial blood pressures, mean airway pressure, and inspired fraction of oxygen were recorded.

RESULTS

After we allowed for the influence of ductal shunting, the correlation between the left ventricular output and mean arterial blood pressure was significant but weak (r = 0.38). There were infants with low blood pressures and normal cardiac outputs, and conversely there were infants with low cardiac outputs and normal blood pressure. The infants with a mean arterial blood pressure of less than 30 mm Hg had a significantly lower gestational age (27 vs 28 weeks), higher mean airway pressure (9.0 vs 7.0 cm H2O), larger ductal diameter (1.6 mm vs 0.7 mm) and a lower systemic vascular resistance (163 vs 184 mm Hg/L per minute per kilogram of body weight). Multilinear regression identified higher mean airway pressure and larger ductal diameter as significant negative influences on mean arterial blood pressure, with higher gestational age and higher left ventricular output as significant positive influences.

CONCLUSIONS

Normal blood pressure cannot necessarily be equated with normal systemic now. These data emphasize the importance of other influences, and in particular that of varying systemic vascular resistance, in the determination of blood pressure in preterm infants.

Limited role for nitric oxide in mediating cerebrovascular control of newborn piglets

AIMS

To investigate the effects of the nitric oxide (NO) synthase inhibitor L-nitro-arginine methyl ester (L-NAME) on cerebral blood flow, and its response to alterations in arterial carbon dioxide tension (CBF-CO2 reactivity).

METHODS

Cerebral blood flow was measured six times at varying arterial carbon dioxide tension (PaCO2) using the intravenous 133Xenon clearance technique in eight mechanically ventilated piglets of less than 24 hours postnatal age. After the third measurement L-NAME was administered as a bolus (20 mg/kg) and subsequently infused (10 mg/kg/hour).

RESULTS

PaCO2 ranged between 2.7-8.9 kPa. Cerebral blood flow decreased by 14.0% (95% confidence interval 1.9-27.4) after L-NAME. CBF-CO2 reactivity was 18.4% per kPa (95% CI 14.1-22.2) before L-NAME and 15.2%/kPa (95% CI 11.1-19.3) afterwards; the difference between the CBF-CO2 reactivities was 3.2%/kPa (95% CI -0.4-6.8): these were not significantly different.

CONCLUSIONS

Inhibition of nitric oxide synthesis reduces cerebral blood flow no more than a 0.5-1.0 kPa fall in PaCO2. Nitric oxide is not an important mediator of CBF-CO2 reactivity.

Bioenergetic recovery following ischemia in brain slices studied by 31P-NMR spectroscopy: differential age effect of depolarization mediated by endogenous nitric oxide

Proximate neurotoxic mechanisms during postischemic recovery may be influenced by stage of development and complicating factors such as cortical spreading depression or secondary brain insult. Using 31P nuclear magnetic resonance spectroscopy, we have monitored pH and cellular energy metabolites phosphocreatine (PCr) and ATP in the ex vivo rat cerebral cortex before, during, and after substrate and oxygen deprivation, which represents "in vitro ischemia." There were important developmental differences in resistance and response to an ischemic insult. Twenty-one-day-old (P21) rat cortical slices had no detectable beta-ATP or PCr at the end of a 20-min insult, while 7-day-old (P7) slices had 50 +/- 13.7% (mean +/- SD, n = 12) and 17 +/- 14.8% relative to preischemia levels, respectively. Postischemic depolarization resulted in age-dependent effects on PCr (p < 0.05): In the older tissue, depolarization significantly worsened the recovery of PCr, whereas in young tissue it ameliorated recovery. This amelioration could be prevented by inhibiting nitric oxide production with methylene blue (depolarization-methylene blue interaction, p < 0.05) and enhanced by administration of the nitric oxide donor glyceryl trinitrate (GTN; p < 0.01). However, in P21 tissue, GTN further exacerbated injury (age-GTN interaction, p < 0.01). Therefore, in this vascular-independent preparation, a neuronal or glial nitric oxide-dependent mechanism appears to confer improved postischemic bioenergetic recovery in the developing brain compared with the mature brain.

Effect of cerebral blood flow and cerebrovascular autoregulation on the distribution, type and extent of cerebral injury

Global cerebral blood flow (GCBF) is low in the human neonate compared to the adult. It is even lower in mechanically ventilated, preterm infants: 10-12 ml/100 g/minute, a level associated with brain infarction in adults. The reactivity, however, of global CBF to changes in cerebral metabolism, PaCO2, and arterial blood pressure is normal, except following severe birth asphyxia, or in mechanically ventilated preterm infants, who subsequently develop major germinal layer hemorrhage. The low level of cerebral blood flow (CBF) matches a low cerebral metabolism of glucose and a relatively small number of cortical synapses in the perinatal period. It has not been possible to define a threshold for GCBF below which electrical dysfunction or brain damage occurs (such as white matter and thalamic-basal ganglia necrosis). Three explanations for the lack of clear relation between GCBF and electrical brain activity of the preterm infant must be examined more closely: 1) low levels of CBF are adequate; 2) GCBF does not adequately reflect critically low perfusion of the white matter, and 3) acute white matter ischemia does not result in electrical silence. Two clinical patterns of brain damage following asphyxia may be explained by changes in the blood flow distribution induced by asphyxia: brainstem sparing and parasagittal cerebral injury. Hours to days after severe asphyxia, a state of marked global hyperperfusion may prevail. It is associated with poor neurological outcome and may be an entry point for trials of interventions aiming sat blocking the translation of asphyctic injury to cellular death and tissue damage.

A study of cerebral perfusion using single photon emission computed tomography in neonates with brain lesions

In this study we used a single photon emission computed tomography technique (SPECT) with radiolabelled 99mTcHMPAO to assess cerebral perfusion in newborn infants with documented cerebral lesions and to determine to what extent brain SPECT might be useful in the neonatal period. A total of 15 newborn infants with the following cerebral pathologies were enrolled: severe parietal bilateral periventricular leucomalacia (PVL, n = 6); moderate parietal bilateral PVL (n = 2); intraventricular haemorrhage grade II with unilateral parietal parenchymal extension (IHV + PE, n = 3); cerebral infarction (CI, n = 2) in the zone of middle cerebral artery; and post-haemorrhagic hydrocephalus (n = 2). Follow-up was available in all infants. Alterations in cerebral perfusion were seen in only 12 of 15 infants and at the location of severe PVL, PE and CI. We have noted that the regions of diminished perfusion extended beyond the apparent extent of cerebral pathology delineated by ultrasound or magnetic resonance imaging. Markedly diminished perfusion was seen in 1 infant with hydrocephalus, which recovered following placement of ventriculo-peritoneal shunt. Regarding outcome, SPECT data failed to provide additional information than that of neuroradiological investigations. We conclude that the use of SPECT, under these conditions, to assess alteration of cerebral perfusion in the neonatal period will not provide any additional information than that of neuroradiological investigations.

Effect of hyperventilation on oxygenation of the brain cortex of neonates

A new phosphorescence imaging method (Rumsey et al, Science (1988) 1649) has been used to continuously monitor the oxygen pressure in the blood of the cerebral cortex of newborn pigs. The animals' blood pressure was continuously measured and PaCO2, PaO2 and arterial blood pH were measured periodically. The oxygen pressure in the blood was quantitatively determined for regions of about 100 um square within the image (from a total field of about 3 mm diameter). It was observed that during hyperventilation, which lowered PaCO2 and increased pH of the blood, oxygen pressure decreased in proportion to the decrease in PaCO2. For example, hyperventilation which decreased PaCO2 from its normal value of 40 Torr to 10 Torr caused a rapid (within 5 minutes) decrease in oxygen pressure in the blood of capillaries and veins to approximately 1/4 of normal.

Cerebral blood flow velocity in term infants treated with phototherapy

The relationship between phototherapy and changes in the cerebral circulation was studied in 50 jaundiced newborn infants. The aim of the study was to determine whether important alterations in cerebral hemodynamic occur under blue light therapy. Blood flow velocity, i.e., the pulsatility index (PI) and the area under the velocity curve (AUVC), was measured in the anterior cerebral arteries (ACA) using a Duplex scan technique. No prominent changes compromise flow in the ACA. PI and AUVC values were similar during and after phototherapy (p greater than 0.5) suggesting effective cerebral autoregulation in term infants undergoing light treatment for hyperbilirubinemia.

Differences in critical cerebral blood flow with age in swine

Normal cerebral blood flow (CBF), critical CBF at a flat reading of the electroencephalogram (EEG), and reversibility of the flat EEG after reperfusion were investigated in a total of 59 pigs, including seven newborns (1 to 3 days of age), 38 juveniles (1 month old), and 14 adults (7 months old). The CBF was determined by the hydrogen clearance method; the EEG was recorded continuously and a power spectrum analysis was performed. Cerebral ischemia was produced by occlusion of both common carotid arteries and induction of hypotension (approximately 50 mm Hg). The flat EEG reversibility was investigated for 3 hours after reperfusion. As parameters of brain development, the neuronal density and the time at which the S-100 protein appeared in the brain were examined. Normal CBF was highest in neonatal pigs and decreased with age. The critical CBF at a flat EEG was lowest in newborn pigs and was elevated with development of the brain. Tolerance against cerebral ischemia was greatest in newborn pigs.

Controversies in cardiopulmonary resuscitation: pediatric considerations

This article addresses some therapeutic controversies concerning medications that may be needed during advanced pediatric life support (APLS) and the routes of administration that may be selected. The controversies that are discussed include the appropriateness and selection of various routes for drug administration during APLS; the determination of whether epinephrine hydrochloride is the adrenergic agent of choice for APLS and its appropriate dose; treatment of acidosis associated with a cardiopulmonary arrest; recommendations for atropine sulfate doses; and the role, if any, of calcium in APLS. Background information differentiating pediatric from adult cardiopulmonary arrest is presented to enable the reader to have a better understanding of the specific needs of children during this life-threatening emergency. The article also presents an overview of various drugs used for APLS and a table of their typically recommended doses and routes of administration.

Cerebral blood flow, cross-brain oxygen extraction, and fontanelle pressure after hypoxic-ischemic injury in newborn infants

The relationship between mean arterial pressure, intracranial pressure, cerebral blood flow, cross-brain oxygen extraction, cerebral metabolic rate, and outcome was studied during therapy in nine neonates on 3 consecutive days after severe hypoxic-ischemic cerebral injury. Cross-brain oxygen extraction was significantly higher (5.06 +/- 0.5 vs 2.05 +/- 0.8 ml/dl; p = 0.012) in the five neonates who survived with normal neurologic outcome than in the four who died or sustained severe brain damage. In contrast, global cerebral blood flow in the five neonates with normal neurologic outcome was significantly lower (25.6 +/- 8.2 vs 83.2 +/- 44.9 ml/100 gm brain/min; p less than 0.05) during the study period. The differences in cross-brain oxygen extraction and global cerebral blood flow between infants who had neurologic recovery and those who died or sustained brain damage occurred in the presence of acceptable values for intracranial pressure, mean arterial pressure, and cerebral perfusion pressure. Our preliminary data suggest that cross-brain oxygen extraction and possibly global cerebral blood flow may be important variables associated with severe neuronal injury and death after hypoxic-ischemic cerebral injury.

Cerebral-blood-flow-velocity measurements in neonates: technique and interobserver reliability

The interobserver reliability for absolute cerebral-blood-flow-velocity measurements by colour and duplex Doppler sonography was tested in 32 neonates with a mean birth weight of 1489 (SD 644) g, and a gestational age of 29.9 (SD 3.5) weeks. Using standardized technique, two observers recorded on videotape, the Doppler spectrum of the anterior cerebral artery, the intracranial internal carotid artery and the middle cerebral artery. Peak systolic flow, end diastolic flow, mean flow velocity, resistive index and pulsatility index were computed from 3 consecutive waveforms by each observer. The estimates of interobserver reliability using the intraclass correlation coefficient of the examiners varied from 0.95 to 1.00. Therefore, cerebral blood flow velocity can be reliably measured in premature infants.

Infantile hydrocephalus--the impact of enhanced preterm survival

The epidemiology of infantile hydrocephalus (IH) in the birth years 1983-86 was investigated in the south-western health care region of Sweden. The study was made as a continuation of a previous one which had shown a significant increase in the prevalence of IH in 1967-82. That rise was entirely referable to the relatively larger number of preterm IH infants born in 1979-82 and was considered to be due to the enhanced survival, especially of very preterm infants. The present series comprised 57 liveborn IH infants--27 preterms and 30 born at term. The livebirth prevalence of IH was 0.64 per 1,000, 0.30 for preterm and 0.34 for fullterm infants. The high prevalence of preterm IH infants in 1979-82 had persisted, but had not increased further. This might indicate an improved outcome in preterm survivors in the period 1983-86, as the survival rate had continued to increase. The striking predominance of a perinatal aetiology of IH in very preterm infants could be confirmed: 90% had had intraventricular haemorrhages verified by ultrasound in the postpartum period. The outcome in very preterm surviving infants with IH was still alarmingly poor: 78% had cerebral palsy, 72% mental deficiency, and 56% epilepsy.

Cerebral blood-flow velocity patterns in post-hemorrhagic ventricular dilation

To evaluate the effect of ventricular dilation (VD) on cerebral hemodynamics, serial cerebral bloodflow velocity patterns from the anterior and middle cerebral, and circle of Willis arteries were examined by range-gated, pulsed Doppler sonography in premature infants developing post-hemorrhagic VD. Nine infants (25 to 30 weeks gestation) without a patent ductus arteriosus were studied until resolution of VD. Forty-nine cranial sonograms from all nine infants were reviewed independently and grouped cross-sectionally into mild, moderate and severe VD prior to shunt. The corresponding pulsatility index (PI) showed a consistent trend of increase with VD in all three studied vessels. In six infants, absent or reversed diastolic flow was observed at the height of VD. Four of these infants required V-P shunt. Immediate fall in PI occurred in all three vessels. Serial measurement of PI during VD reflects global changes in cerebrovascular resistance. Results confirmed PI could be a useful index in monitoring cerebral hemodynamic changes.

Effects of indomethacin on cerebral haemodynamics in very preterm infants

Near infrared spectroscopy was used to investigate the effects of intravenously administered indomethacin (0.1-0.2 mg/kg) on cerebral haemodynamics and oxygen delivery in 13 very preterm infants treated for patent ductus arteriosus. 7 infants received indomethacin by rapid injection (30 s) and 6 by slow infusion (20-30 min). In all the infants cerebral blood flow, oxygen delivery, blood volume, and the reactivity of blood volume to changes in arterial carbon dioxide tension fell sharply after indomethacin. There were no differences in the effects of rapid and slow infusion. These falls in cerebral oxygen delivery and the disruption of cerebrovascular control might compromise cellular oxygen availability, particularly in regions of the brain where the arterial supply is precarious. Care should be taken to ensure that oxygen delivery is optimum before the administration of indomethacin to preterm infants.

Dopplersonographic classification of brain edema in infants

25 infants, 23 newborns and 2 older infants with B-mode sonographic evidence of cerebral edema (gestational age of the newborns 39.1 +/- 2.1 weeks, weight 3270 +/- 672 g) were examined by means of pulsed Doppler sonography. Pulsed Doppler recordings were obtained in the anterior cerebral, internal carotid, basilar, and middle cerebral arteries. In all measured arteries the peak systolic peak endsystolic, peak enddiastolic and the time averaged mean velocities, as well as the resistance index and the pulsatility index were determined. In addition to the flow parameters the pH, pCO2, pO2, oxygen saturation and the blood pressure were measured. The flow velocities were compared with the normal values established by our group. Three different types of flow profiles and velocities could be found: Group 1: 12 infants had normal flow velocities. Group 2: 7 infants showed increased diastolic flow velocities. Group 3: 6 infants demonstrated decreased diastolic flow velocities. There were no significant differences according to gestational age, weight, pH, pCO2, pO2, oxygen saturation and blood pressure in the three groups. The outcome of the 12 children in group 1 was favourable: normal development 10; minor retardation 2. In group 2 only 1 child showed normal development; 2 infants had minor, 1 major handicaps; 2 infants died. Patients in group 3 had the worst outcome: no patient developed normally; 4 infants died; 2 severely handicapped infants showed polycystic leucomalacia and brain atrophy; 1 infant had minor psychomotoric problems.

Intellectual impairment with regional cerebral dysfunction after low neonatal cerebral blood flow

12 children, in whom neonatal CBF had been measured, were examined at the age of 9 to 10 years by means of clinical neurological examination, neuropsychologic tests and observations, and 133Xe single photon emission computed tomography (SPECT). Performance on most neuropsychologic tests or observations correlated with neonatal CBF but only rarely with other neonatal parameters (birthweight, gestational age, Apgar score at 5 min). Poor performance on each test or observation was in most instances correlated with a distinct pattern of regional cerebral dysfunction as assessed by SPECT. The dysfunctional region tended to be located periventricularly and in the watershed regions between major cerebral arteries. It is concluded that low neonatal cerebral perfusion may be an indicator, and possibly a determinant, of later intellectual dysfunction in stressed neonates, and that specific neuropsychologic deficits are associated with specific patterns of cerebral dysfunction in the present patient group.

Blood pressure and cerebral haemorrhage and ischaemia in very low birthweight infants

Hourly blood pressures were recorded directly in 131 very low birth weight infants in intensive care during the first 4 days of life. Cranial ultrasound evidence of intraventricular haemorrhage correlated well with periods of hypotension, but not of hypertension. Ischaemic lesions did not correlate with periods of hypotension, but were associated with previous haemorrhage. The findings suggest that hypotension predisposes to primary intraventricular haemorrhage and that later parenchymal ischaemic lesions relate to local factors rather than hypotension.

Cerebral blood flow in newborn infants with and without mechanical ventilation

The influence of mechanical ventilation with low mean airway pressure (MAP) on cerebral blood flow (CBF) veolocity in newborn infants was assessed in fifteen ventilated infants by Duplex Doppler Sonography (Duplex DS). As a control, CBF velocities were examined in 15 age and weight matched non-ventilated infants. For quantitation, maximal systolic velocity, enddiastolic velocity and the semiquantitative Pourcelot index were determined as representative flow variables. There was no significant difference of these flow variables between ventilated and non-ventilated infants. The pH, pO2 and pCO2 did not differ significantly between the two groups and there was no correlation between the flow variables, pH, pO2, pCO2 or MAP. Mechanical ventilation with low MAP is not associated with adverse effects on cerebral hemodynamics in newborn infants when significant alterations of the blood gases are avoided.

Cerebral blood flow requirement for brain viability in newborn infants is lower than in adults

Measurements of regional cerebral blood flow (CBF) with positron emission tomography in adult humans with cerebrovascular disease have demonstrated consistently that values below 10 ml/(100 gm.min) occur only in infarcted brain. Although experimental data suggest that the newborn brain may be more resistant to ischemic injury than the adult brain, the minimum CBF necessary to sustain neuronal viability in newborn infants is unknown. We have measured CBF with positron emission tomography in 16 preterm and 14 term newborn infants and have determined the relationship between CBF and subsequent brain function as assessed by neurological examination and developmental assessment. The range of mean CBF in the preterm infants was 4.9 to 23 ml/(100 gm.min) and the range of mean CBF in the term infants was 9.0 to 73 ml/(100 gm.min). Five preterm infants and one term infant with mean CBF less than 10 ml/(100 gm.min) survived. Three of these 5 preterm infants, with mean CBF of 4.9, 5.2, and 9.3 ml/(100 gm.min), respectively, have normal neurological examinations and Bayley Scales of 80 or greater at 6, 6, and 24 months of age, respectively. One (mean CBF 6.9) has normal cognitive development (Bayley 103) and a mild spastic diplegia at age 19 months, and one infant (mean CBF 6.2) has a left hemiparesis and a Binet IQ score of 70 at age 33 months. The term infant, with a mean CBF of 9.0 ml/(100 gm.min), was developing normally when he died of sepsis at age 5 months.(ABSTRACT TRUNCATED AT 250 WORDS)