Cardiorespiratory Physiology following Minimally Invasive Surfactant Therapy in Preterm Infants

Impact of Early Surfactant Administration on Ductus Arteriosus Assessed at 24 h in Preterm Neonates Less than 32 Weeks of Gestational Age

BACKGROUND AND OBJECTIVES

The purpose of this study was to investigate whether early surfactant administration affects the status of ductus arteriosus (DA) in preterm infants ≤ 32 weeks of gestational age (GA) within 24 h of birth.

MATERIALS AND METHODS

It is a prospective study conducted from 1 March 2022 to 31 December 2023 in a tertiary academic center. In-born infants ≤ 32 weeks of gestation (n = 88) were enrolled. The study group was further divided into surfactant (n = 44) and non-surfactant (n = 44) subgroups.

RESULTS

A total of 76% of the preterm infants who received surfactant therapy (RRR = 0.839) recorded an increase in Kindler score at 24 h of life (1 - RR = 1 - 0.24 = 76%). Surfactant administration was significantly associated with decreased pre-ductal diastolic pressure (29.9 mmHg vs. 34.8 mmHg, p = 0.0231), post-ductal diastolic pressure (28.7 mmHg vs. 32.2 mmHg, p = 0.0178), pre-ductal MAP (41.6 mmHg vs. 46.5 mmHg, p = 0.0210), and post-ductal MAP (41.0 mmHg vs. 45.3 mmHg, p = 0.0336). There were no significant changes in ductus arteriosus parameters at 24 h of life.

CONCLUSIONS

Early surfactant administration does not affect the status of ductus arteriosus in preterm infants ≤ 32 weeks of gestational age at 24 h of life.

A predictive model for patent ductus arteriosus seven days postpartum in preterm infants: an ultrasound-based assessment of ductus arteriosus intimal thickness within 24 h after birth

Objectives

To develop a predictive model for patent ductus arteriosus (PDA) in preterm infants at seven days postpartum. The model employs ultrasound measurements of the ductus arteriosus (DA) intimal thickness (IT) obtained within 24 h after birth.

Methods

One hundred and five preterm infants with gestational ages ranging from 27.0 to 36.7 weeks admitted within 24 h following birth were prospectively enrolled. Echocardiographic assessments were performed to measure DA IT within 24 h after birth, and DA status was evaluated through echocardiography on the seventh day postpartum. Potential predictors were considered, including traditional clinical risk factors, M-mode ultrasound parameters, lumen diameter of the DA (LD), and DA flow metrics. A final prediction model was formulated through bidirectional stepwise regression analysis and subsequently subjected to internal validation. The model's discriminative ability, calibration, and clinical applicability were also assessed.

Results

The final predictive model included birth weight, application of mechanical ventilation, left ventricular end-diastolic diameter (LVEDd), LD, and the logarithm of IT (logIT). The receiver operating characteristic (ROC) curve for the model, predicated on logIT, exhibited excellent discriminative power with an area under the curve (AUC) of 0.985 (95% CI: 0.966-1.000), sensitivity of 1.000, and specificity of 0.909. Moreover, the model demonstrated robust calibration and goodness-of-fit (χ2 value = 0.560, p > 0.05), as well as strong reproducibility (accuracy: 0.935, Kappa: 0.773), as evidenced by 10-fold cross-validation. A decision curve analysis confirmed the model's broad clinical utility.

Conclusions

Our study successfully establishes a predictive model for PDA in preterm infants at seven days postpartum, leveraging the measurement of DA IT. This model enables identifying, within the first 24 h of life, infants who are likely to benefit from timely DA closure, thereby informing treatment decisions.

Patent ductus arteriosus (PDA) and response to late surfactant treatment in premature infants

OBJECTIVE

To determine the clinical/echocardiography (ECHO) phenotype of patients with hypoxic respiratory failure (HRF) and response to late surfactant, according to patent ductus arteriosus (PDA) status.

STUDY DESIGN

This retrospective study included infants ≤26+6 weeks gestation who received ≥1 surfactant dose after 6 postnatal days and where PDA status was available by ECHO. Response to surfactant was appraised based on change in respiratory severity score over 48 h. The relationship between PDA status and response to surfactant was evaluated via univariate analysis.

RESULT

We studied late surfactant (n = 71 doses) administration in 35 preterm infants born at a mean weight and GA at birth were 595 g (508, 696) and 23.3 (22.7, 25) weeks, respectively of whom 16 (46%) had a diagnosis of PDA. Positive response to late surfactant treatment was independently associated with absence of PDA [OR 26 (2, 334), p = 0.01] whereas presence of PDA was independently associated with negative response [OR 12 (1.1, 126), p = 0.04].

CONCLUSIONS

In neonates ≤26+6 weeks gestation, with HRF, response to surfactant after postnatal day 6 is influenced by PDA status. Future trials should consider PDA status which may enhance diagnostic precision and refine patient selection for late surfactant treatment.

Nucleated Red Blood Cells as Markers of Perinatal Adaptation in Preterm Neonates Receiving Minimally Invasive Surfactant Therapy

OBJECTIVE

The study aimed to assess the association of nucleated red blood cells (NRBC), a surrogate of intrauterine hypoxia, and elevated pulmonic vascular resistance (E-PVR) and oxygen requirement after minimally invasive surfactant therapy (MIST).

STUDY DESIGN

Retrospective study of a cohort of preterm neonates that received MIST in a single unit.

RESULTS

NRBC were measured in 65 of 75 (87%) neonates administered MIST during the period. In total, 22 of 65 (34%) infants had pre-MIST echocardiography (ECHO).Neonates with elevated NRBC (predefined as >5 × 10⁹/L, n = 16) required higher post-MIST fraction of inspired oxygen (FiO₂) than neonates with normal NRBC (<1 × 10⁹/L, n = 17; FiO₂= 0.31 ± 0.10 and 0.24 ± 0.04, respectively, p = 0.02).NRBC correlated positively with % of time in right to left ductal shunt (r = 0.51, p = 0.052) and inversely with right ventricular stroke volume (r = -0.55, p = 0.031) and time to peak velocity to right ventricular ejection time ratio (r = -0.62, p < 0.001).

CONCLUSION

Elevated NRBC are associated with elevated FiO₂ after MIST and elevated E-PVR. Intrauterine hypoxia may impact postnatal circulatory adaptations and oxygen requirement.

KEY POINTS

· Post-MIST FiO2 requirements are significantly higher in infants with elevated NRBC.. · NRBC correlates positively with elevated PVR in neonates requiring.. · Intrauterine hypoxia may play a role in postnatal circulatory adaptations in neonates with RDS..

Cardiorespiratory adaptation to low-dose dexamethasone for lung disease in extremely preterm infants: A prospective echocardiographic study

The cardiovascular impact of dexamethasone (Dex) is not well understood. Most data are obtained from a 6 week, high-dose regimen, and are limited to findings of hypertension and cardiac hypertrophy. The present study ascertained the impact of low-dose Dex on cardiac indices when administered to extremely preterm infants for lung disease. A pre-post intervention prospective echocardiographic (Echo) study was undertaken, with cardiac assessments performed before and within 24 h after completion of first course of therapy (10 day regimen, cumulative 0.89 mg kg^-1 ). Thirty infants with a gestational age of 24.6 ± 1.1 weeks and birthweight of 612 ± 125 g, respectively, were studied. The age at Dex administration was 20 ± 9 days. Fractional inspired oxygen decreased from 0.7 ± 0.23 to 0.35 ± 0.14 (P < 0.001). Patent ductus arteriosus was noted in 20 infants at Echo1. At Echo2, the ductal diameter decreased from 2.16 ± 0.8 to 1.1 ± 0.8 mm (P = 0.0003), with complete closure in 7/20 (35%). A reduction in left pulmonary artery end-diastolic velocity was noted (17 ± 12 to 9 ± 10 cm s^-1 , P < 0.001). Pulmonary vascular resistance decreased (increased time to peak velocity/right ventricular ejection time, 0.2 ± 0.03 to 0.23  ± 0.03, P = 0.0001) and right ventricular systolic performance improved (tricuspid annular plane systolic excursion, 4.9 ± 0.8 to 5.5 ± 0.9 mm, P = 0.02). No significant changes in fractional shortening and left ventricular mass were noted. A significant increase in blood pressure was noted. As a percentage of pre-treatment baseline, the mean increase for systolic blood pressure was 20.3% (95% confidence interval = 14-26) on day 2 (P = 0.008). Low-dose Dex influenced cardiovascular parameters related to pulmonary circulation. KEY POINTS: Corticosteroid therapy is frequently used in preterm infants who are dependent on ventilator support. Echocardiographic studies in infants administered a 6 week course of steroids have noted left ventricular hypertrophy, outlet obstruction and hypertension, but no information is available on right heart indices. The cardiopulmonary effects of the current, significantly lesser cumulative dose (10 day regimen, commonly described as 'DART') have not been evaluated. The present study noted a significant influence on ductal and pulmonary circulation indices. Left heart architecture and function was maintained, whereas a significant but transient increase in blood pressure was noted.

Echocardiographic assessment of intimal thickness growth of patent ductus arteriosus in neonates and analysis of influencing factors

The spontaneous closure rate of patent ductus arteriosus (PDA) is high, and the necessity of early intervention is debated. Quantitative echocardiographic assessment of the intima in PDA has not been reported. This study evaluated intimal thickness growth in neonatal cases of PDA via echocardiography and investigated its correlation with clinical factors. Seventy-three neonates were enrolled, and echocardiography was performed three times: within 24 h post-birth (first echo), 48 h after the first echo (second echo), and before discharge (third echo). According to PDA outcome, the neonates were divided into the PDA-open group (n = 18 cases), PDA-closure at second echo group (n = 32 cases), and non-PDA at first echo group (n = 23 cases). We measured the intimal thickness (IT1 and IT2 at first and second echo, respectively), lumen diameter of ductus arteriosus (D1 and D2 at first and second echo, respectively), IT1/D1 ratio, and intimal thickness growth rate (V). Correlations between echocardiographic indicators, perinatal factors, and clinical treatment were analyzed. On first echo, the PDA-open group showed a significantly lower IT1/D1 than the combined PDA-closure group (P < 0.05). On second echo, the PDA-open group showed a significantly lower IT2 and V than the PDA-closure group as well as a significantly higher D2 (P < 0.05). Smaller gestational age correlated with a larger D2 but smaller IT2 and V (P < 0.05) and a higher level of respiratory support within 72 h post-birth correlated with a larger D2 and smaller IT 2 (P < 0.05). Increasing oxygen demand within 72 h of birth correlated with a larger D1 and D2 (P < 0.05). Echocardiographic assessment of intimal thickness growth in PDA may provide an approach for predicting spontaneous PDA closure, thereby guiding decision-making regarding early intervention.

Hemodynamic consequences of respiratory interventions in preterm infants

Advances in perinatal management have led to improvements in survival rates for premature infants. It is known that the transitional period soon after birth, and the subsequent weeks, remain periods of rapid circulatory changes. Preterm infants, especially those born at the limits of viability, are susceptible to hemodynamic effects of routine respiratory care practices. In particular, the immature myocardium and cardiovascular system is developmentally vulnerable. Standard of care (but essential) respiratory interventions, administered as part of neonatal care, may negatively impact heart function and/or pulmonary or systemic hemodynamics. The available evidence regarding the hemodynamic impact of these respiratory practices is not well elucidated. Enhanced diagnostic precision and therapeutic judiciousness are warranted. In this narrative, we outline (1) the vulnerability of preterm infants to hemodynamic disturbances (2) the hemodynamic effects of common respiratory practices; including positive pressure ventilation and surfactant therapy, and (3) identify tools to assess cardiopulmonary interactions and guide management.

Impact of surfactant when utilized during pediatric cardiac surgery admissions: analysis of a nationwide database

OBJECTIVE

Surfactant has been routinely used in the neonatal population, particularly in the setting of prematurity and neonatal respiratory distress syndrome. Current evidence, however, does not delineate the effect of surfactant use in neonates and older children during cardiac surgery admissions. This study aimed to characterize the impact of surfactant on pediatric cardiac surgery admissions.

METHODS

Admissions of those under 18 years of age with cardiac surgery were identified from the Pediatric Health Information System (PHIS) database between 2004 and 2015, using ICD-9 procedure codes. Univariate analyses were conducted to compare admission characteristics between those that did and not utilize surfactant. Variables shown to be significant were then entered as independent variables into the regression analyses. Surfactant was entered into each model as an independent variable.

RESULTS

A total of 81,313 admissions met the inclusion criteria. Of these, 109 (0.1%) had surfactant utilized. Univariate analyses identified several differences between admissions with and without surfactant use and demonstrated significantly increased mortality in the surfactant group (38.5% versus 4.6%, p < .01). Regression analyses demonstrated that surfactant was independently associated with increased mortality (odds ratio 6.0, 95% confidence interval 3.9-9.3, p < .01). Univariate analysis in only surfactant admissions demonstrated the following to be associated with inpatient mortality: younger age, prematurity, Ebstein anomaly, and hypoplastic left heart syndrome.

CONCLUSIONS

Surfactant administration during pediatric cardiac surgery admissions is independently associated with a sixfold increase in inpatient mortality. It is likely that these findings are mediated by augmentation of the decrease in pulmonary vascular resistance and a subsequent decrease in systemic blood flow in the setting of parallel circulation. Surfactant should be administered with special consideration in neonates with cardiac disease and may be best avoided in those with parallel circulation.

Outcomes after Introduction of Minimally Invasive Surfactant Therapy in Two Australian Tertiary Neonatal Units

OBJECTIVE

To assess the procedural and clinical outcomes associated with the introduction of minimally invasive surfactant therapy (MIST) into standard care at 2 tertiary Australian neonatal intensive care units.

STUDY DESIGN

A prospective audit was designed before the introduction of MIST in 2018, with data collected over a period of 18 months. Procedural data were completed by the clinical team performing MIST, including clinical observations, medication use, and adverse events. The audit team collected demographic data and subsequent clinical outcomes from medical records.

RESULTS

There were 135 MIST procedures recorded in 122 infants. For the included infants, the median gestation was 30^2/7 weeks (IQR, 27^6/7 to 32^2/7 weeks) and birth weight was 1439 g (IQR, 982-1958 g). During the MIST procedure, desaturation to a peripheral oxygen saturation of <80% was common, occurring in 75.2% of procedures. Other adverse events included need for positive pressure ventilation (10.6%) and bradycardia <100 beats per minute (13.3%). The use of atropine premedication was associated with a significantly lower incidence of bradycardia: 8.6% vs 52.9% (P < .01). Senior clinicians demonstrated higher rates of procedural success. The majority of infants (63.9%) treated with MIST did not require subsequent intubation and mechanical ventilation.

CONCLUSIONS

MIST can be successfully introduced in neonatal units with limited experience of this technique. The use of atropine premedication decreases the incidence of bradycardia during the procedure. Success rates can be optimized by limiting MIST to clinicians with greater competence in endotracheal intubation.

Assessing pulmonary circulation in severe bronchopulmonary dysplasia using functional echocardiography

Pulmonary hypertension (PH) is common in infants with severe bronchopulmonary dysplasia (BPD) and increases the risk of death. The objectives of this preliminary study were to compare responses of pulmonary circulation parameters to 100% oxygen (O₂) and inhaled nitric oxide (iNO) in infants with BPD and PH using echocardiography. Responses between fetal growth restriction (FGR) and appropriate for gestational age infants were compared. Ten infants <28 weeks GA at birth were assessed at ≥36 weeks corrected gestation. Baseline echocardiography1 was performed which was repeated (echocardiography2) after 30 minutes of O₂. After a gap of 2–3 hours, iNO was administered for 15 minutes and echocardiography3 was performed, followed by iNO weaning. The gestation and birthweight of the cohort were 25.9 ± 1.6 weeks and 612 ± 175 g. Assessments were performed at 38.7 ± 1.4 weeks corrected gestational age. Baseline time to peak velocity: right ventricular ejection time (TPV/RVETc) increased from 0.24 ± 0.02 to 0.27 ± 0.02 (O₂, p = .01) and 0.31 ± 0.03 (iNO, p < .001), indicating a decrease in pulmonary vascular resistance [PVR]. Baseline tricuspid annular plane systolic excursion (TAPSE) increased from 8.1 ± 0.6 mm to 9.3 ± 0.7 mm (O₂, p = .01) and 10.5 ± 1.1 mm (iNO, p = .0004), indicating improved ventricular systolic performance. Percentage change for all parameters was greater with iNO. Significant correlations between cardiac performance and PVR were noted. FGR infants noted higher baseline PVR (TPV/RVETc, 0.21 ± 0.02 vs. 0.25 ± 0.01, p = .002), lower ventricular performance (TAPSE, 7 ± 1.2 mm vs. 8.6 ± 6 mm, p = .003), and lower percentage change with O₂ and iNO. A reactive component of pulmonary circulation provides real‐time physiological information, which could rationalize treatment decisions.

Cardiovascular response and sequelae after minimally invasive surfactant therapy in growth-restricted preterm infants

OBJECTIVE

To study cardiovascular response to minimally invasive surfactant therapy in preterm infants with and without foetal growth restriction (FGR).

DESIGN

Poractant alfa was administered and echocardiograms were performed before and 30 min after. FGR infants were compared with those appropriate for gestational age (AGA).

RESULTS

Ten FGR infants were compared with 20 AGA infants (gestation [weeks], 28.9 ± 2 vs. 28.6 ± 1, p = 0.55 and birthweight [g], 813 ± 157 vs. 1141 ± 257, p = 0.01, respectively). The change in echocardiographic parameters was more prominent in AGA infants ([global contractility] fractional area change [FAC, %], FGR, 24.7 ± 2.2 to 27.9 ± 0.4, p = 0.08 vs. AGA, 26.6 ± 3 to 30.5 ± 1, p < 0.01, and [longitudinal contractility] tricuspid annular plane systolic excursion [mm], FGR, 3.9 ± 0.3 to 4.6 ± 0.5, p = 0.003 vs. AGA, 4.6 ± 0.3 to 5.5 ± 0.4, p = 0.0001). Significant difference was noted for change in FAC (%), FGR 2.1 ± 1.7 vs. AGA 4.1 ± 1.2, p = 0.02.

CONCLUSIONS

Differential cardiovascular response to minimally invasive surfactant therapy amongst FGR infants may reflect an in-utero maladaptive state.

Impact of Skin-to-Skin Parent-Infant Care on Preterm Circulatory Physiology

OBJECTIVES

To ascertain the impact of skin-to-skin care between parents and infants on cardiac function and cerebral blood flow in preterm infants.

STUDY DESIGN

We undertook a prospective study of 40 self-ventilating preterm infants at a quaternary center and assessed cardiac performance and cerebral blood flow. Assessments were carried out two hours before skin-to-skin care and then 60 minutes after skin-to-skin care (with the infant still on parent and turned supine).

RESULTS

Infants were 30.5 ± 0.6 weeks' gestational age and 1378 ± 133 g birthweight. Axillary temperature noted a nonsignificant increase during skin-to-skin care from 36.7 ± 0.07°C to 36.9 ± 0.07°C (P = .07). Cardiac contractility (right ventricular fractional area change [26.5% ± 0.3% vs 27.8% ± 0.4; P < .001] and tricuspid annular plane systolic excursion [0.73 ± 0.03 cm vs 0.77 ± 0.03 cm; P = .02]) increased significantly, coincident with decreased measures of pulmonary vascular resistance. An increase in systemic cardiac output was associated with increased cerebral blood flow and reduced middle cerebral artery resistive index (0.81 ± 0.02 vs 0.74 ± 0.02; P = .0001).

CONCLUSIONS

We documented a significant circulatory beneficial adaptation to a common neonatal practice. These findings align with previously documented physiologic benefits in cardiorespiratory stability and cardiac rhythm in preterm infants, and may be mediated through modulation of the autonomic nervous system.