The relationship between cardiac output, cerebral electrical activity, cerebral fractional oxygen extraction and peripheral blood flow in premature newborn infants

Relationship between cerebral oxygenation, cardiac output, and blood pressure during transitional period in extremely low gestational age neonates

Objective

To describe the relationship between cerebral oxygenation, cardiac output, arterial blood pressure (BP), and cerebral blood flow velocity in extremely low gestational age neonates (ELGANs) during transition.

Methods

This study comprises secondary analyses from a prospective observational study conducted at a tertiary Neonatal Intensive Care Unit. Recruited ELGANs underwent cerebral saturation (CrSO2) monitoring and serial echocardiography during 72 h from birth. Correlative analyses of CrSO2 and cerebral fractional tissue oxygen extraction (CFTOE) with left (LVO) and right ventricular output (RVO), superior vena cava (SVC) flow, middle cerebral artery blood flow mean velocity (MCA.MV), systolic (SBP), diastolic (DBP), and mean (MBP) BP were conducted.

Results

Fifty ELGANs with median (range) gestational age of 25.9 (23.1-27.9) weeks were recruited. Echocardiography was performed sequentially at a median (range) age 5.0 (3.8-6.6), 17.3 (15.4-19.4), 31.0 (27.0-34.1), and 53.7 (49.3-58.3) hours. RVO, LVO, CrSO2, and SBP increased over time but no changes in MBP, DBP, CFTOE, MCA.MV or SVC flow were noted. A weak correlation was identified between CrSO2 and SBP (r2 = 0.11, p = 0.047) and MBP (r2 = 0.12, p = 0.04) at 17.3 (15.4-19.4) hours. No correlation of either CrSO2 or CFTOE with any measures of blood flow was identified.

Conclusion

There is a weak correlation between measures of cardiac output, BP, and MCA.MV with both CrSO2 and CFTOE in ELGANs during transition. Whether this finding suggests intact cerebral autoregulation requires prospective evaluation in a cohort of sick ELGANs.

Insights into Neonatal Cerebral Autoregulation by Blood Pressure Monitoring and Cerebral Tissue Oxygenation: A Qualitative Systematic Review

OBJECTIVE

The aim of this qualitative systematic review was to identify publications on blood pressure monitoring in combination with cerebral tissue oxygenation monitoring during the first week after birth focusing on cerebral autoregulation.

METHODS

A systematic search was performed on PubMed. The following search terms were used: infants/newborn/neonates, blood pressure/systolic/diastolic/mean/MAP/SAP/DAP, near-infrared spectroscopy, oxygenation/saturation/oxygen, and brain/cerebral. Additional studies were identified by a manual search of references in the retrieved studies and reviews. Only human studies were included.

RESULTS

Thirty-one studies focused on preterm neonates, while five included preterm and term neonates. In stable term neonates, intact cerebral autoregulation was shown by combining cerebral tissue oxygenation and blood pressure during immediate transition, while impaired autoregulation was observed in preterm neonates with respiratory support. Within the first 24 h, stable preterm neonates had reduced cerebral tissue oxygenation with intact cerebral autoregulation, while sick neonates showed a higher prevalence of impaired autoregulation. Further cardio-circulatory treatment had a limited effect on cerebral autoregulation. Impaired autoregulation, with dependency on blood pressure and cerebral tissue oxygenation, increased the risk of intraventricular hemorrhage and abnormal neurodevelopmental outcomes.

CONCLUSIONS

Integrating blood pressure monitoring with cerebral tissue oxygenation measurements has the potential to improve treatment decisions and optimizes neurodevelopmental outcomes in high-risk neonates.

Cardiac output and regional-cerebral-oxygen-saturation in preterm neonates during immediate postnatal transition: An observational study

AIM

To examine potential correlations between cardiac output (CO) with cerebral-regional-oxygen-saturation (crSO₂ ) and cerebral-fractional-tissue-oxygen-extraction (cFTOE) during immediate foetal-to-neonatal transition in term and preterm neonates with and without respiratory support.

METHODS

Post hoc analyses of secondary outcome parameters of prospective observational studies were performed. We included neonates with cerebral near-infrared-spectroscopy (NIRS) monitoring and an oscillometric blood pressure measurement at minute 15 after birth. Heart rate (HR) and arterial oxygen saturation (SpO₂ ) were monitored. CO was calculated with Liljestrand and Zander formula and correlated with crSO₂ and cFTOE.

RESULTS

Seventy-nine preterm neonates and 207 term neonates with NIRS measurements and calculated CO were included. In 59 preterm neonates (mean gestational age (GA): 29.4 ± 3.7 weeks) with respiratory support, CO correlated significantly positively with crSO₂ and significantly negatively with cFTOE. In 20 preterm neonates (GA 34.9 ± 1.3 weeks) without respiratory support and in 207 term neonates with and without respiratory support, CO correlated neither with crSO₂ nor with cFTOE.

CONCLUSION

In compromised preterm neonates with lower gestational age and in need of respiratory support, CO was associated with crSO₂ and cFTOE, whereas in stable preterm neonates with higher gestational age as well as in term neonates with and without respiratory support, no associations were observed.

Evaluation of the Hypotensive Preterm Infant: Evidence-Based Practice at the Bedside?

Choosing the appropriate management approach for the preterm infant with low blood pressure during the transition period generally involved intervening when the blood pressure drifted below a certain threshold. It is now clear that this approach is too simplistic and does not address the underlying physiology. In this chapter, we explore the many monitoring tools available for evaluation of the hypotensive preterm and assess the evidence base supporting or refuting their use. The key challenge relates to incorporating these outputs with the clinical status of the patient and choosing the appropriate management strategy.

A Preterm Physiologically Based Pharmacokinetic Model. Part I: Physiological Parameters and Model Building

BACKGROUND

Developmental physiology can alter pharmacotherapy in preterm populations. Because of ethical and clinical constraints in studying this vulnerable age group, physiologically based pharmacokinetic models offer a viable alternative approach to predicting drug pharmacokinetics and pharmacodynamics in this population. However, such models require comprehensive information on the changes of anatomical, physiological and biochemical variables, where such data are not available in a single source.

OBJECTIVE

The objective of this study was to integrate the relevant physiological parameters required to build a physiologically based pharmacokinetic model for the preterm population.

METHODS

Published information on developmental preterm physiology and some drug-metabolising enzymes were collated and analysed. Equations were generated to describe the changes in parameter values during growth.

RESULTS

Data on organ size show different growth patterns that were quantified as functions of bodyweight to retain physiological variability and correlation. Protein binding data were quantified as functions of age as the body weight was not reported in the original articles. Ontogeny functions were derived for cytochrome P450 1A2, 3A4 and 2C9. Tissue composition values and how they change with age are limited.

CONCLUSIONS

Despite the limitations identified in the availability of some tissue composition values, the data presented in this article provide an integrated resource of system parameters needed for building a preterm physiologically based pharmacokinetic model.

Common carotid artery blood flow volume in extremely preterm infants

AIM

The aim of this study was to determine carotid blood flow volume, a surrogate for cerebral blood flow, using Doppler ultrasound in extremely preterm infants.

METHODS

In infants <29 weeks, right common carotid artery flow volume (RCCAF) was calculated from vessel diameter and intensity-weighted mean velocity measured using Doppler ultrasound on days 1 and 3. In addition, left ventricular output (LVO), ductus arteriosus characteristics and invasive mean arterial blood pressure (MABP) were obtained.

RESULTS

Sixty infants with mean gestation of 25.8 weeks were studied. The median RCCAF increased from 12 (IQR 9-15) mL/kg/min on day 1, to 14 (IQR 12-18) mL/kg/min on day 3 (p = 0.007). RCCAF was positively correlated with invasive MABP on days 1 and 3. RCCAF significantly correlated with LVO in infants with closing or closed ductus arteriosus on day 1. Using multiple regression analysis, RCCAF was significantly associated with invasive MABP on day 1 and to inotropic treatment on day 3.

CONCLUSION

Doppler ultrasound can be used to measure RCCAF in extremely preterm infants receiving intensive care. RCCAF increased during the first three days and was positively related to invasive MABP on day 1. Values were lower than previously described in more mature infants.

CLINICAL TRIAL REGISTRATION

ISRCTN 83507686.

Cerebral and peripheral tissue oxygenation in stable neonates: Absent influence of cardiac function

Aim

Cardiac function is a major factor for tissue perfusion and therefore may affect the tissue oxygen saturation. Aim was to analyse possible associations between cardiac function parameters and cerebral and peripheral tissue oxygenation in neonates on the first day after birth.

Methods

For the present study, we analysed secondary outcome parameters of a previously performed prospective single centre observational study. The prospective study was conducted at the Medical University of Graz, Austria between September 2011 and June 2013. We included preterm and term neonates who were admitted to the neonatal intensive care unit and in whom simultaneous near‐infrared spectroscopy measurements and echocardiography were obtained on the first day after birth. Cardiac function parameters were correlated to cerebral and peripheral tissue oxygen saturation and cerebral and peripheral fractional tissue oxygen extraction at the time of echocardiography.

Results

A total of 60 neonates of whom 47 were preterm and 13 were term (median gestational age: 34; IQR 33‐35 weeks, mean birth weight: 2276 ± 774 grams) were included. There were no statistically significant correlations between cardiac function parameters and regional tissue oxygenation parameters.

Conclusion

In the present study, we found no correlation between regional tissue oxygenation and parameters of cardiac function in cardio‐circulatory stable neonates on the first day after birth.

Changes in hemodynamics, cerebral oxygenation and cerebrovascular reactivity during the early transitional circulation in preterm infants

BACKGROUND

Changes in systemic and cerebral hemodynamics in preterm infants during early transitional circulation are complex and may differ between infants with or without intraventricular hemorrhage (IVH).

METHOD

In total, 43 infants born at median (range) 25 + 5 (23 + 3-31) had continuous near-infrared spectroscopy (NIRS) monitoring of tissue oxygenation index (TOI) and cerebrovascular reactivity within the first 48 h of life. Measurements of left and right cardiac outputs (LVO, RVO) and patent ductus arteriosus (PDA) were collected at 6, 12, 24, and 48 h of life.

RESULTS

LVO increased within the first 48 h in the IVH (P = 0.007) and no-IVH (P < 0.001) groups. The pattern of change in LVO and RVO was not different between these two groups. TOI was lower in the IVH (P < 0.001) group. A positive correlation between TOI and LVO (P = 0.003) and a negative correlation between the tissue oxygen reactivity index (TOx) and LVO (P = 0.04) were observed at 24 h of life in the IVH group. PDA diameter was not different between IVH groups at any time interval.

CONCLUSION

Cerebral oxygenation was lower and cerebrovascular reactivity was passive to systemic blood flow at 24 h in infants who developed an IVH.

Early inotropes use is associated with higher risk of death and/or severe brain injury in extremely premature infants

Introduction: Extremely premature infants are susceptible to fluctuations in cerebral blood flow due to immaturity of cerebral autoregulation. Inotropes may cause rapid changes to systemic blood pressure and consequently cerebral blood flow, especially within the first 72 hours of life. This period is recognized to carry the greatest risk for cerebral hemorrhage. This study evaluates the incidence of death and/or severe brain injury in extremely preterm infants treated with inotropes in the first 72 hours of life.Methods: Prospective cohort study of infants born ≤29⁺⁰ weeks gestational age (GA) between January 2013 and December 2016. Severe brain injury was defined based on head ultrasound as presence of: grade III or IV intraventricular hemorrhage (IVH), moderate to severe post-hemorrhagic ventricular dilatation (PHVD), or cystic periventricular leukomalacia (cPVL). The association between inotrope use and death and/or brain injury was explored via logistic regression controlling for predefined confounding risk factors.Results: Of 497 eligible infants, 97 (19.5%) received inotropes during the first 72 hours. GA at birth, birth weight (BW), and 5-minute Apgar scores were lower among infants who received early inotropes compared to those not treated with inotropes. A stepwise logistic regression of the predefined confounding factors showed GA, exposure for antenatal steroids, and admission hypothermia to be significant confounding factors. Adjusting for those factors, early use of inotropes was associated with increased risk of death and/or severe brain injury (AOR 4.5; 95%CI: 2.4-8.5), severe brain injury (AOR 4.2; 95% CI: 1.9-8.9), and IVH of any grade (AOR 2.9; 95%CI: 1.7-4.9).Conclusion: Early inotropes use was associated with higher risk of death and/or severe brain injury. Strict indications and strategies for minimizing inotrope use while preventing hypotension should be implemented in the early postnatal care of infants at risk for severe brain injury.

Coupling between mean blood pressure and EEG in preterm neonates is associated with reduced illness severity scores

Hypotension or low blood pressure (BP) is a common problem in preterm neonates and has been associated with adverse short and long-term neurological outcomes. Deciding when and whether to treat hypotension relies on an understanding of the relationship between BP and brain functioning. This study aims to investigate the interaction (coupling) between BP and continuous multichannel unedited EEG recordings in preterm infants less than 32 weeks of gestational age. The EEG was represented by spectral power in four frequency sub-bands: 0.3-3 Hz, 3-8 Hz, 8-15 Hz and 15-30 Hz. BP was represented as mean arterial pressure (MAP). The level of coupling between the two physiological systems was estimated using linear and nonlinear methods such as correlation, coherence and mutual information. Causality of interaction was measured using transfer entropy. The illness severity was represented by the clinical risk index for babies (CRIB II score) and contrasted to the computed level of interaction. It is shown here that correlation and coherence, which are linear measures of the coupling between EEG and MAP, do not correlate with CRIB values, whereas adjusted mutual information, a nonlinear measure, is associated with CRIB scores (r = -0.57, p = 0.003). Mutual information is independent of the absolute values of MAP and EEG powers and quantifies the level of coupling between the short-term dynamics in both signals. The analysis indicated that the dominant causality is from changes in EEG producing changes in MAP. Transfer entropy (EEG to MAP) is associated with the CRIB score (0.3-3 Hz: r = 0.428, p = 0.033, 3-8 Hz: r = 0.44, p = 0.028, 8-15 Hz: r = 0.416, p = 0.038) and indicates that a higher level of directed coupling from brain activity to blood pressure is associated with increased illness in preterm infants. This is the first study to present the nonlinear measure of interaction between brain activity and blood pressure and to demonstrate its relation to the initial illness severity in the preterm infant. The obtained results allow us to hypothesise that the normal wellbeing of a preterm neonate can be characterised by a nonlinear coupling between brain activity and MAP, whereas the presence of weak coupling with distinctive directionality of information flow is associated with an increased mortality rate in preterms.

[Impact of screening and treatment of low systemic blood flow in the prevention of severe intraventricular haemorrhage and/or death in pre-term infants]

OBJECTIVE

To assess the effect of a protocolised intervention for low systemic blood flow (SBF) in the occurrence of severe intraventricular haemorrhage (IVH) or death in pre-term infants.

METHODS

A study with a quasi-experimental design with retrospective controls was conducted on pre-term infants of less than 30weeks of gestational age, born between January 2016 and July 2017, who were consecutively included in the intervention period. The control cohort included pre-term infants (born between January 2013 and December 2015) matched by gestational age, birth weight, and gender (two controls for each case). The cases of low SBF diagnosed according to functional echocardiography during the study period received dobutamine (5-10μg/kg/min) for 48hours.

RESULTS

The study included 29 cases (intervention period) and 54 controls (pre-intervention period). Ten out of 29 (34.5%) infants received dobutamine for low SBF during the intervention period, with 3/29 (10.3%) cases of severe IVH and/or death compared to 17/54 (31.5%) in the control cohort (p=.032). There was an independent association between the intervention and a decreased occurrence of severe IVH/death after adjusting for confounding factors both in the logistic regression model [OR 0.11 (95%CI: 0.01-0.65), p=.015], as well as in the sensitivity analysis using inverse probability of treatment weighting [OR 0.23 (95%CI: 0.09-0.56); p=.001].

CONCLUSIONS

In this study with retrospective controls, a protocolised screening, and treatment for low SBF was associated with a decreased occurrence of severe IVH or death in preterm infants. Large, adequately powered trials, are needed in order to determine whether postnatal interventions directed at low SBF can improve neurological outcomes.

Investigation of EEG Activity Compared with Mean Arterial Blood Pressure in Extremely Preterm Infants

Background

Cerebral electrical activity in extremely preterm infants is affected by various factors including blood gas and circulatory parameters.

Objective

To investigate whether continuously measured invasive mean arterial blood pressure (BP) is associated with electroencephalographic (EEG) discontinuity in extremely preterm infants.

Study design

This prospective observational study examined 51 newborn infants born <29 weeks gestation in the first 3 days after birth. A single channel of raw EEG was used to quantify discontinuity. Mean BP was acquired using continuous invasive measurement and Doppler ultrasound was used to measure left ventricular output (LVO) and common carotid artery blood flow (CCAF).

Results

Median gestation and birthweight were 25.6 weeks and 760 g, respectively. Mean discontinuity reduced significantly between days 1 and 3. EEG discontinuity was significantly related to gestation, pH and BP. LVO and CCAF were not associated with EEG discontinuity.

Conclusion

Continuously measured invasive mean arterial BP was found to have a negative relationship with EEG discontinuity; increasing BP was associated with lower EEG discontinuity. This did not appear to be mediated by surrogates of systemic or cerebral blood flow. Infants receiving inotropic support had significantly increased EEG discontinuity on the first day after birth.

Advances in Diagnosis and Management of Hemodynamic Instability in Neonatal Shock

Shock in newborn infants has unique etiopathologic origins that require careful assessment to direct specific interventions. Early diagnosis is key to successful management. Unlike adults and pediatric patients, shock in newborn infants is often recognized in the uncompensated phase by the presence of hypotension, which may be too late. The routine methods of evaluation used in the adult and pediatric population are often invasive and less feasible. We aim to discuss the pathophysiology in shock in newborn infants, including the transitional changes at birth and unique features that contribute to the challenges in early identification. Special emphasis has been placed on bedside focused echocardiography/focused cardiac ultrasound, which can be used as an additional tool for early, neonatologist driven, ongoing evaluation and management. An approach to goal oriented management of shock has been described and how bed side functional echocardiography can help in making a logical choice of intervention (fluid therapy, inotropic therapy or vasopressor therapy) in infants with shock.

Neonatal Hemodynamics: From Developmental Physiology to Comprehensive Monitoring

Maintenance of neonatal circulatory homeostasis is a real challenge, due to the complex physiology during postnatal transition and the inherent immaturity of the cardiovascular system and other relevant organs. It is known that abnormal cardiovascular function during the neonatal period is associated with increased risk of severe morbidity and mortality. Understanding the functional and structural characteristics of the neonatal circulation is, therefore, essential, as therapeutic hemodynamic interventions should be based on the assumed underlying (patho)physiology. The clinical assessment of systemic blood flow (SBF) by indirect parameters, such as blood pressure, capillary refill time, heart rate, urine output, and central-peripheral temperature difference is inaccurate. As blood pressure is no surrogate for SBF, information on cardiac output and systemic vascular resistance should be obtained in combination with an evaluation of end organ perfusion. Accurate and reliable hemodynamic monitoring systems are required to detect inadequate tissue perfusion and oxygenation at an early stage before this result in irreversible damage. Also, the hemodynamic response to the initiated treatment should be re-evaluated regularly as changes in cardiovascular function can occur quickly. New insights in the understanding of neonatal cardiovascular physiology are reviewed and several methods for current and future neonatal hemodynamic monitoring are discussed.

Objective cardiovascular assessment in the neonatal intensive care unit

Traditionally, cardiovascular well-being was essentially based on whether the mean blood pressure was above or below a certain value. However, this singular crude method of assessment provides limited insight into overall cardiovascular well-being. Echocardiography has become increasingly used and incorporated into clinical care. New objective modality assessments of cardiovascular status continue to evolve and are being evaluated and incorporated into clinical care. In this review article, we will discuss some of the recent advances in objective assessment of cardiovascular well-being, including the concept of multimodal monitoring. Sophisticated haemodynamic monitoring systems are being developed, including mechanisms of data acquisition and analysis. Their incorporation into clinical care represents an exciting next stage in the management of the infant with cardiovascular compromise.

Abstention or intervention for isolated hypotension in the first 3 days of life in extremely preterm infants: association with short-term outcomes in the EPIPAGE 2 cohort study

OBJECTIVE

To compare outcomes at hospital discharge for preterm infants born before 29 weeks of gestation who had at least one episode of isolated hypotension during their first 72 hours of life for which they did or did not receive antihypotensive treatment.

DESIGN

Etude Epidémiologique sur les Petits Ages Gestationnels 2 (EPIPAGE 2) French national prospective population-based cohort study in 2011.

SETTING

60 neonatal intensive care units.

PATIENTS

All infants with a minimum mean arterial blood pressure less than gestational age (in weeks) (minMAP<GA) within 72 hours of birth. Infants whose reason for receiving antihypotensive treatments was isolated hypotension only were compared with untreated hypotensive infants by propensity score matching.

TREATMENTS

Fluid bolus and/or inotropes and/or corticosteroids.

MAIN OUTCOMES AND MEASURES

The primary outcome was survival at hospital discharge without major morbidity, defined as any of necrotising enterocolitis, severe cerebral abnormalities, severe bronchopulmonary dysplasia or severe retinopathy of prematurity.

RESULTS

Among the 1532 infants with available data, 662 had a minMAP<GA; 206 were treated for unknown or other reasons than isolated hypotension, 131 were treated for isolated hypotension only and 325 were untreated; 119 infants from each of these last two groups were matched. Treated infants had a significantly higher survival rate without major morbidity (61.3% vs 48.7%; OR, 1.67, 95% CI 1.00 to 2.78, p=0.049) and a lower rate of severe cerebral abnormalities (10.1% vs 26.5%, p=0.002).

CONCLUSIONS

In this population, antihypotensive treatment was associated with improved short-term outcomes. Therapeutic abstention should be cautiously considered for early isolated hypotension in extremely premature infants.

Blood pressure and aEEG in the 96h after birth and correlations with neurodevelopmental outcome in extremely preterm infants

BACKGROUND

The management of hypotension immediately after the birth of preterm infants is controversial.

AIM

To investigate the relationship between blood pressure (BP), amplitude-integrated electroencephalography (aEEG), and neurodevelopmental outcome in extremely preterm infants.

METHODS

BP and aEEG were monitored for 96h after birth in 36 infants born at <27weeks gestation. aEEG data were analyzed with Burdjalov scores. Correlations of aEEG findings with BP and several clinical characteristics, including the Score for Neonatal Acute Physiology, Perinatal Extension-II (SNAPPE-II) were explored. A subgroup analysis of BP, aEEG activity, and neurodevelopmental outcome at 18-22months corrected age was also performed. Poor outcome was defined as death or a developmental quotient <70.

RESULTS

Multiple regression analyses revealed no association between BP during the first 48h after birth and aEEG activity. However, BP 48-96h after birth was significantly associated with simultaneous aEEG activity (p<0.001). Within 48h after birth, SNAPPE-II was significantly associated with aEEG activity. Outcome was assessed in 32 infants; 24 and 8 of whom had good and poor outcomes, respectively. aEEG activity was significantly lower in neonates with a poor outcome than those with a good outcome (<0.001). No significant differences in outcome were observed for BP.

CONCLUSION

The activity of aEEG was associated with illness severity during the first 48h after birth. After 48h, there was no effect of illness severity but there was an association with BP. We do not know if hypotension results in a poor outcome. However, aEEG activity was associated with neurodevelopmental outcome.

Multisite Tissue Oxygenation Monitoring Indicates Organ-Specific Flow Distribution and Oxygen Delivery Related to Low Cardiac Output in Preterm Infants With Clinical Sepsis

OBJECTIVES

Cardiac output may be compromised in preterm infants with sepsis. Whether low cardiac output is associated with low tissue oxygen supply in these patients is unclear. The aim of the current study was to assess the association between cardiac output, assessed by echocardiography, and tissue oxygenation, measured with multisite near-infrared spectroscopy, in a cohort of preterm infants with clinical sepsis.

DESIGN

Prospective observational cohort study.

SETTING

Level III neonatal ICU.

PATIENTS

Twenty-four preterm infants (gestational age < 32 wk) with clinical sepsis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Clinical and echocardiographic assessment of hemodynamics was performed within 48 hours of sepsis workup and repeated at least 24 hours later. We measured cerebral, renal, and intestinal tissue oxygen saturation using near-infrared spectroscopy during an hour of stable measurements directly preceding or following echocardiography and calculated fractional tissue oxygen extraction in each tissue. We determined Spearman correlation coefficients between fractional tissue oxygen extraction and right ventricular output corrected for patent foramen ovale flow, left ventricular output corrected for ductus arteriosus flow, and superior vena cava flow. Right ventricular output corrected for patent foramen ovale and left ventricular output corrected for ductus arteriosus flow both correlated significantly with intestinal fractional tissue oxygen extraction (ρ, -0.700; p = 0.036 and ρ, -0.604; p = 0.029, respectively). In contrast, no significant correlations were found between cardiac output measurements and cerebral and renal fractional tissue oxygen extraction, respectively. Changes in cardiac output measurements were not associated with observed changes in fractional tissue oxygen extraction values.

CONCLUSIONS

Right ventricular output corrected for patent foramen ovale and left ventricular output corrected for ductus arteriosus flow, indicators of systemic blood flow in preterm infants with shunts, were negatively associated with intestinal fractional tissue oxygen extraction, but not with renal and cerebral fractional tissue oxygen extraction. These findings suggest that during low output states due to clinical sepsis intestinal perfusion is most at risk.

Peripheral Muscle Near-Infrared Spectroscopy in Neonates: Ready for Clinical Use? A Systematic Qualitative Review of the Literature

BACKGROUND

Peripheral muscle near-infrared spectroscopy (NIRS) measurements are of increasing interest especially in the care of critically ill patients.

OBJECTIVE

The aim was to perform a systematic qualitative review on peripheral muscle NIRS measurements in the clinical care of term and preterm neonates.

METHODS

A systematic search of PubMed and Ovid Embase was performed using the following terms: neonate, neonates, newborn, newborns, infant, infants, near-infrared spectroscopy, NIRS, oxygenation, perfusion, oxygen extraction, peripheral, tissue, muscle, calf, forearm and thigh. Additional articles were identified by a manual search of the cited references. Only human studies were included.

RESULTS

Twenty-one studies were identified to use peripheral muscle NIRS measurements as a single method, 17 studies combined cerebral and peripheral muscle NIRS measurements and 1 study used multi-site NIRS measurements in human neonates. Two randomized studies were identified. Two additional publications were included because they provided important general information about peripheral muscle NIRS measurements.

CONCLUSION

In the care of critically ill neonates peripheral muscle NIRS measurements alone or in combination with cerebral or multi-site NIRS measurements provide useful additional information about peripheral circulation and oxygenation. This method is a promising tool in the recognition of early states of centralization (compensated shock) in this vulnerable group of patients. However, before this method can be used in the clinical routine it has to be tested as monitoring to guide interventions in further studies.

Effect of permissive hypercapnia on background cerebral electrical activity in premature babies

BACKGROUND

Permissive hypercapnia is routinely practiced in neonatal intensive care units. The effect of permissive hypercapnia on the preterm brain and brain electrical activity is unknown. In this study, we aimed to determine the effect of chronic changes in partial pressure of blood carbon dioxide (PcO2) on brain electrical activity in preterm newborn babies born at or before 32 wk gestation.

METHODS

Eighty-three 1-h long digital electroencephalography (EEG) recordings were performed once a week for 4 wk on 25 babies with median gestational age of 29 wk (range: 23-32) after 48 h of age. Capillary blood gas measurements were performed midway through EEG recordings.

RESULTS

There are associations between EEG parameters and blood pH, PcO2, and blood glucose concentration. However, there are also strong and complex associations with gestational age and substantial individual patient effects that make it difficult to demonstrate predictive associations. PcO2 and bicarbonate are significantly correlated with relative power of θ EEG band and Δ EEG band respectively after adjustment for age and intrababy correlations, but after allowing for multiple testing these relationships are of borderline statistical significance.

CONCLUSION

Compensated respiratory acidosis may affect EEG by increased delta wave activity in preterm babies born before 32 wk gestation.

Early cerebral oxygen extraction and the risk of death or sonographic brain injury in very preterm infants

OBJECTIVE

To evaluate the relationship between cerebral fractional tissue oxygen extraction (cFTOE), a measure of oxygen delivery-consumption equilibrium, and the risk of early poor outcome in very preterm infants.

STUDY DESIGN

Cerebral blood flow, tissue oxygenation index (by near-infrared spectroscopy), and arterial oxygen content were measured, and cerebral oxygen delivery, consumption, and cFTOE were calculated at 3 intervals in the first 72 hours of life in infants ≤ 30 weeks gestational age (GA). A receiver operating characteristic curve was derived with an a priori defined dichotomized outcome of good or poor, defined as death or sonographic brain injury (grade ≥ II intraventricular hemorrhage) by day 7.

RESULTS

Seventy-one infants were enrolled, with a mean (SD) GA of 27 (2) weeks. cFTOE demonstrated better discrimination for the study outcome at <24 hours of age than at 48 or 72 hours of age (P = .01). The area under the curve for cFTOE at the initial measurement was no different from that for GA alone (0.87; 95% CI, 0.77-0.95 vs 0.81; 95% CI, 0.69-0.92), but the combined measure of cFTOE and GA had better discrimination (0.96; 95% CI, 0.91-1.0) than either cFTOE (P = .03) or GA (P = .016) alone. A cFTOE of 0.4 had a sensitivity of 82% and specificity of 75% for risk of early poor outcome.

CONCLUSION

Elevated cFTOE values are associated with increased risk of early poor outcome in very preterm infants. Its predictive value is further improved with the addition of GA.

Transitional cardiovascular physiology and comprehensive hemodynamic monitoring in the neonate: relevance to research and clinical care

A thorough understanding of developmental cardiovascular physiology is essential for early recognition of cardiovascular compromise, selective screening of at-risk groups of neonates, and individualized management using pathophysiology-targeted interventions. Although we have gained a better understanding of the physiology and pathophysiology of postnatal cardiovascular transition over the past decade with the use of sophisticated methods to study neonatal hemodynamics, most aspects of neonatal hemodynamics remain incompletely understood. In addition, targeted therapeutic interventions of neonatal hemodynamic compromise have not been shown to improve mortality and clinically relevant outcomes. However, the recent development of comprehensive hemodynamic monitoring systems capable of non-invasive, continuous and simultaneous bedside assessment of cardiac output, organ blood flow, microcirculation, and tissue oxygen delivery has made sophisticated analysis of the obtained physiologic data possible and has created new research opportunities with the potential of direct implications to patient care.

Management of hypotension in preterm infants (The HIP Trial): a randomised controlled trial of hypotension management in extremely low gestational age newborns

BACKGROUND

Extremely preterm babies (delivered at <28 completed weeks of gestation) are frequently diagnosed with hypotension and treated with inotropic and pressor drugs in the immediate postnatal period. Dopamine is the most commonly used first-line drug. Babies who are treated for hypotension more frequently sustain brain injury, have long-term disability or die compared to those who are not. Despite the widespread use of drugs to treat hypotension in such infants, evidence for efficacy is lacking, and the effect of these agents on long-term outcomes is unknown.

HYPOTHESIS

In extremely preterm babies, restricting the use of dopamine when mean blood pressure (BP) values fall below a nominal threshold and using clinical criteria to determine escalation of support ('restricted' approach) will result in improved neonatal and longer-term developmental outcomes. RESEARCH PLAN: In an international multi-centre randomised trial, 830 infants born at <28 weeks of gestation, and within 72 h of birth, will be allocated to 1 of 2 alternative treatment options (dopamine vs. restricted approach) to determine the better strategy for the management of BP, using a conventional threshold to commence treatment. The first co-primary outcome of survival without brain injury will be determined at 36 weeks' postmenstrual age and the second co-primary outcome (survival without neurodevelopmental disability) will be assessed at 2 years of age, corrected for prematurity.

DISCUSSION

It is essential that appropriately designed trials be performed to define the most appropriate management strategies for managing low BP in extremely preterm babies.

[Functional echocardiography in neonatal intensive care: 1 year experience in a unit in Spain]

INTRODUCTION

Several publications highlight the usefulness of functional echocardiography (FnECHO) in neonatal intensive care. Data is lacking on its use in units neonatal in Spain.

OBJECTIVES

To evaluate frequency of use, patient characteristics, indications, measurements, and impact on patient management of FnECHO in a neonatal intensive care unit (NICU) in Spain over a 1 year period.

METHODS

A retrospective study conducted in NICU patients during 1 year.

VARIABLES

gestational age, birthweight, admission criteria, days of life at examination, indication for FnECHO, parameters assessed, and treatment modifications.

RESULTS

168 echocardiographic studies were performed in 50 patients (mean 3,4. SD 2,83). The most frequent indication was patent ductus (PDA) assessment (58.3%), followed by hemodynamic instability (22.2%). The results of FnECHO modified treatment in 62 cases (36.9%). In 17.4% of them treatment with ibuprofen was initiated, and in 1.2% it was discontinued. In 10.8% of the cases, the results of FnECHO modified hemodynamic support. Echocardiographic evaluation included: assessment of presence/hemodynamic significance of PDA (100%); myocardiac function: ejection fraction/shortening fraction (EF/SF) 23.8%, left ventricular output 24.4%, right ventricular output 21.4%, systemic blood flow 42.3%; and signs of pulmonary hypertension 7.7%.

CONCLUSIONS

FnECHO is frequently used in the NICU, and in many cases it guides treatment. PDA assessment and hemodynamic instability are the most frequent indications. It still needs to be elucidated if the use of FnECHO modifies patient outcomes.

Relationship between systemic blood flow, blood pressure, inotropes, and aEEG in the first 48 h of life in extremely preterm infants

BACKGROUND

Significant hemodynamic changes occur immediately after birth in preterm infants. Amplitude-integrated electroencephalography (aEEG) provides a method of assessing brain activity in sick neonates; however, the relationship among systemic blood flow, blood pressure (BP), and aEEG is not clear.

METHODS

Quantitative measures of aEEG continuity and amplitude were correlated with superior vena cava (SVC) flow, right-ventricular output (RVO), and BP at 12, 24, and 48 h in 92 infants born at <29 wk gestation.

RESULTS

SVC flow, RVO, BP, aEEG amplitude, and EEG continuity all increased from 12 to 48 h. SVC flow at 12 h, but not 24 or 48 h, was significantly associated with aEEG amplitude after adjustment for gestational age (GA) and severity of illness markers (r(2) = 0.21, P = 0.004). RVO and BP showed less consistent associations with aEEG parameters. Infants receiving inotropes at 12 h, including those in whom cardiovascular parameters had normalized, had significantly lower aEEG amplitude (P < 0.01) and EEG continuity at the 10, 25, and 50 μV levels (P < 0.01) at 12, 24, and 48 h than neonates who were not receiving inotropes.

CONCLUSION

aEEG measurements in the first 48 h of life are related to SVC flow and treatment with inotropes at 12 h of life in extremely preterm infants.

aEEG and NIRS during transition and resuscitation after birth: promising additional tools; an observational study

AIM OF THE STUDY

During resuscitation no routine cerebral monitoring is available. We aimed at monitoring cerebral activity and oxygenation continuously during neonatal transition and resuscitation.

METHODS

Neonates ≥34 weeks of gestation born via cesarean section were included. Cerebral activity was continuously measured with amplitude-integrated-EEG (aEEG) and cerebral oxygenation (rSO2) with near-infrared-spectroscopy (NIRS) during the first 10 min after birth. For quantitative analysis of aEEG every minute the mean minimum amplitude (V(min)) and maximum amplitude (V(max)) was determined. Uncompromised neonates were compared to neonates in need of resuscitation.

RESULTS

Out of 224 eligible neonates 31 uncompromised and 15 in need of respiratory support were included. Uncompromised neonates showed higher values for V(min) in the third minute and higher values for V(max) in the third and fourth minute compared to the tenth minute post-partum. In uncompromised neonates rSO2 values during the first 6 min after birth were lower compared to minute ten. Neonates in need of respiratory support had lower rSO2 values over the first 8 min after birth compared to minute ten.

CONCLUSIONS

This is the first study demonstrating that monitoring of aEEG and NIRS to measure cerebral activity and oxygenation during immediate postpartum transition is feasible. During transition compromised neonates requiring resuscitation showed a different cerebral activity pattern compared to uncompromised neonates.

Effect of antihypotensive treatment on cerebral oxygenation of preterm infants without PDA

BACKGROUND

Preterm infants with hypotension (mean arterial blood pressure [MABP] < gestational age [GA]) are treated with volume expansion and/or dopamine to ensure adequate cerebral perfusion/oxygenation. We used near-infrared spectroscopy to analyze the effects of volume expansion and dopamine on cerebral oxygenation in hypotensive preterm infants without patent ductus arteriosus (PDA).

PATIENTS AND METHODS

Among 390 infants, 71 (GA < 32 weeks) were hypotensive and eligible for inclusion. Thirty-three infants received volume expansion only (NaCl 0.9%; 20 mL/kg), and 38 received additional dopamine (5 μg/kg per minute). Nine and 11 infants initially treated with dopamine subsequently needed 7.5 and 10 μg/kg per minute, respectively. Seventy-one infants without hypotension were individually matched to serve as controls. MABP, regional cerebral oxygen saturation (rSco(2)), fractional tissue oxygen extraction (cFTOE), and arterial saturation (Sao(2)) were monitored 15 minutes before and 30 and 60 minutes after volume or dopamine and at comparable postnatal ages in controls.

RESULTS

No changes in MABP, rSco(2), or cFTOE were found 30 minutes after volume expansion. MABP increased 60 minutes after 5 μg/kg per minute dopamine (median [range]: 28 [19-32] vs 33 [23-46] mm Hg; P < .001). There was a small increase and decrease, respectively, in rSco(2) (63 [43-84] vs 66 [46-87]%; P < .05) and cFTOE (0.33 [0.14-0.56] vs 0.31 [0.07-0.54]1/1; P < .05). However, no differences were found at any time point between controls and infants treated with volume or additional dopamine (5, 7.5, and 10 μg/kg per minute) for rSco(2) or cFTOE.

CONCLUSIONS

Volume expansion and additional dopamine do not cause any significant change in rSco(2) or cFTOE in hypotensive preterm infants without PDA. We speculate that very preterm infants with hypotension but without signs of a compromised cerebral oxygenation and systemic perfusion might not be in need of antihypotensive therapy.

Early postnatal hypotension and developmental delay at 24 months of age among extremely low gestational age newborns

OBJECTIVES

To evaluate in extremely low gestational age newborns, relationships between indicators of hypotension during the first 24 postnatal hours and developmental delay at 24 months of age.

METHODS

The 945 infants in this prospective study were born at <28 weeks, were assessed for three indicators of hypotension in the first 24 postnatal hours, and were evaluated with the Bayley Mental Development Index (MDI) and Psychomotor Development Index (PDI) at 24 months corrected age. Indicators of hypotension included: (1) mean arterial pressure in the lowest quartile for gestational age; (2) treatment with a vasopressor; and (3) blood pressure lability, defined as the upper quartile for the difference between the lowest and highest mean arterial pressure. Logistic regression was used to evaluate relationships between hypotension and developmental outcomes, adjusting for potential confounders.

RESULTS

78% of infants in this cohort received volume expansion or vasopressor; all who received a vasopressor were treated with volume expansion. 26% had an MDI <70 and 32% had a PDI <70. Low MDI and PDI were associated with low gestational age, which in turn, was associated with receipt of vasopressor treatment. Blood pressure in the lowest quartile for gestational age was associated with vasopressor treatment and labile blood pressure. After adjusting for potential confounders, none of the indicators of hypotension were associated with MDI <70 or PDI <70.

CONCLUSIONS

In this large cohort of extremely low gestational age newborns, we found little evidence that early postnatal hypotension indicators are associated with developmental delay at 24 months corrected gestational age.

Prenatal tobacco exposure influences cerebral oxygenation in preterm infants

AIM

Our aim was to determine the influence of prenatal tobacco exposure on regional cerebral tissue oxygen saturation (r(c)SO(2)) and fractional tissue oxygen extraction (FTOE) in preterm infants. We hypothesized that as a result of vasoconstriction caused by prenatal tobacco exposure r(c)SO(2) would be lower and FTOE would be higher during the first days after birth in infants exposed to tobacco during pregnancy.

METHODS

Sixty preterms were included in this prospective, observational cohort study (median gestational age 29.9 weeks, range 26.0-31.8, median birth weight 1248 g, range 615-2250). Fourteen infants had been exposed to tobacco during pregnancy. All mothers smoked more than five cigarettes a day till delivery. We measured r(c)SO(2) and transcutaneous arterial oxygen saturation (tcSaO(2)) in all infants on days 1-5, 8, and 15. FTOE was calculated: FTOE=(tcSaO(2)-r(c)SO(2))/tcSaO(2).

RESULTS

In preterm infants exposed to tobacco during pregnancy, r(c)SO(2) was lower during days 1, 2, and 8 after birth, median 73% versus 81%, 73% versus 80% and 71% versus 78% respectively. FTOE was higher during days 1 and 8 after birth, median 0.24 versus 0.15 and 0.26 versus 0.19 respectively. On the second day, FTOE tended to be higher, 0.18 versus 0.14.

CONCLUSIONS

During the first two days and day 8 after birth cerebral oxygen saturation is lower and oxygen extraction higher in preterm infants following prenatal tobacco exposure. Our data suggest that prenatal tobacco exposure may have an effect on cerebral oxygenation of the infant.

Systemic and cerebral hemodynamics during the transitional period after premature birth

Little is known about the effect on clinically relevant outcomes of the complex hemodynamic changes occurring during adaptation to extrauterine life in preterm neonates, particularly in very low birth weight neonates. As cardiovascular adaptation in this extremely vulnerable patient population is complicated by immaturity of all organ systems, especially that of the cardiorespiratory, central nervous, and endocrine systems, maladaptation has been suspected, but not necessarily proven, to contribute to mortality and long-term morbidities. This article describes recent advances in the understanding of hemodynamic changes in very low birth weight neonates during postnatal transition, and reviews the complex and developmentally regulated interaction between systemic and cerebral hemodynamics and the effect of this interaction on clinically relevant outcomes.

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.

Cerebral oxygen saturation and extraction in preterm infants with transient periventricular echodensities

OBJECTIVE

Our aim was to determine regional cerebral tissue oxygen saturation and fractional tissue oxygen extraction in preterm infants with transient periventricular echodensities. We hypothesized that as a result of reduced cerebral perfusion, regional cerebral tissue oxygen saturation will be lower and fractional tissue oxygen extraction will be higher during the first days after birth.

PATIENTS AND METHODS

This was a prospective, observational study of 49 preterm infants (gestational age median: 30.1 weeks [26.0-31.8 weeks]; birth weight median: 1220 g [615-2250 g]). We defined transient periventricular echodensities as echodensities that persisted for >7 days. Regional cerebral tissue oxygen saturation was measured on days 1-5, 8, and 15 after birth. Fractional tissue oxygen extraction was calculated as (transcutaneous arterial oxygen saturation--regional cerebral tissue oxygen saturation)/transcutaneous arterial oxygen saturation.

RESULTS

Transient periventricular echodensities were found in 25 of 49 infants. During the first week we found no difference between the 2 groups for cerebral tissue oxygen saturation and fractional tissue oxygen extraction values. On day 15 after birth, cerebral tissue oxygen saturation was lower in preterm infants with transient periventricular echodensities (66%) compared with infants without echodensities (76%) (P = .003). Fractional tissue oxygen extraction in infants with transient periventricular echodensities (0.30) was higher than fractional tissue oxygen extraction in infants without transient periventricular echodensities (0.20) (P < .001). The differences could not be explained by confounding variables.

CONCLUSIONS

Persistent transient periventricular echodensities may be associated with increased cerebral oxygen demand after the first week after birth, which is contrary to our hypothesis. Cerebral oxygenation may be involved in the recovery of perinatal white matter damage.