Relationship between circulating platelet counts and ductus arteriosus patency after indomethacin treatment

Association between endotypes of prematurity and pharmacological closure of patent ductus arteriosus: A systematic review and meta-analysis

Introduction

Endotypes leading to very and extremely preterm birth are clustered into two groups: infection/inflammation and dysfunctional placentation. We conducted a systematic review of observational studies exploring the association between these two endotypes and the pharmacological closure of patent ductus arteriosus (PDA) induced by cyclooxygenase (COX) inhibitors. Chorioamnionitis represented the infectious-inflammatory endotype, while dysfunctional placentation proxies were hypertensive disorders of pregnancy (HDP) and small for gestational age (SGA) or intrauterine growth restriction.

Methods

PubMed/Medline and Embase databases were searched. The random-effects odds ratio (OR) and 95% confidence interval (CI) were calculated for each association. We included 30 studies (12,639 infants).

Results

Meta-analysis showed a significant association between exposure to HDP and increased rate of pharmacological closure of PDA (17 studies, OR 1.41, 95% CI 1.10-1.81, p = 0.006). In contrast, neither chorioamnionitis (13 studies, OR 0.75, 95% CI 0.47-1.18, p = 0.211) nor SGA (17 studies, OR 1.20, 95% CI 0.96-1.50, p = 0.115) were significantly associated with the response to therapy. Subgroup analyses showed that the higher response to COX inhibitors in the HDP group was significant for indomethacin (OR 1.568, 95% CI 1.147-2.141, p = 0.005) but not for ibuprofen (OR 1.107, 95% CI 0.248-4.392, p = 0.894) or for the studies using both drugs (OR 1.280, 95% CI 0.935-1.751, p = 0.124). However, meta-regression showed that this difference between the drugs was not statistically significant (p = 0.404).

Discussion/Conclusion

Our data suggest that the pathologic condition that triggers prematurity may alter the response to pharmacological treatment of PDA. The DA of infants exposed to HDP appears to be more responsive to COX inhibitors.

Association of patent ductus arteriosus with fetal factors and endotypes of prematurity

During fetal life, the ductus arteriosus (DA) acquires the mechanisms for its postnatal closure following a thorough developmental program. This program can be interrupted by preterm birth and is also susceptible to alteration during fetal life by numerous physiological and pathological stimuli. In this review, we aim to summarize the evidence on how physiological and pathological factors affect DA development, eventually leading to patent DA (PDA). Specifically, we reviewed the associations of sex, race, and pathophysiological pathways leading to very preterm birth (endotypes) with PDA incidence and pharmacological closure. Summary of evidence suggests that there are no male-female differences in the incidence of PDA among very preterm infants. In contrast, risk of developing PDA appears to be higher in infants exposed to chorioamnionitis or who are small for gestational age. Finally, hypertensive disorders of pregnancy may be associated with a better response to pharmacological treatment of PDA. All of this evidence comes from observational studies and therefore associations do not imply causation. The current trend for many neonatologists is to wait for the natural evolution of preterm PDA. Continued research is needed to identify which fetal and perinatal factors modulate the eventual late closure of PDA in very and extremely preterm infants.

Platelets and ductus arteriosus closure in neonates

Platelet plug formation is critically involved in murine ductus arteriosus closure and thrombocytopenia in preterm infants seems to negatively affect spontaneous and pharmacologically induced ductal closure. Furthermore, platelet dysfunction may contribute to ductal patency, especially in extremely immature infants. Neonatal platelets likely have multifaceted roles during ductal closure, such as secretion of several signaling molecules and facilitation of specific cell-cell interactions. The only available randomized-controlled trial on platelet transfusions in preterm infants with patent ductus arteriosus demonstrated that a liberal transfusion regimen did not promote ductal closure, but was associated with an increased rate of intraventricular hemorrhage. Herein, we discuss the available mechanistic evidence on the role of platelets in ductus arteriosus closure and their potential clinical implications in preterm infants. We further briefly outline future research directions aimed at a better understanding of platelet-endothelial interactions in neonatal health and disease.

Does Early Neonatal Thrombocytopenia Affect Ductal Therapeutic Response to Acetaminophen in Preterm Neonates?

OBJECTIVE

Perinatal thrombocytopenia has been shown to affect responsiveness to therapeutic ductal closure with cyclooxygenase (COX) inhibitors. This has not been studied in responsiveness to acetaminophen, which has less effect on platelet function. The objective of this study was to evaluate whether thrombocytopenia affects ductal responsiveness to acetaminophen.

STUDY DESIGN

This study was a retrospective review of preterm neonates <1,500 g. Echocardiograms were performed within the first week of life; if ductal status was found to be hemodynamically significant, infants were treated with acetaminophen.

RESULTS

We studied 254 infants. Fifty-seven of these (22%) had a hemodynamically significant patent ductus arteriosus (hsPDA) and were treated with acetaminophen. Forty (70%) of those treated responded with ductal closure after one to two courses of acetaminophen. Seventeen infants were considered nonresponsive, requiring the addition of ibuprofen and/or surgical ligation. Sixty seven of the 254 infants (26%) developed moderate thrombocytopenia (platelets <100,000) within the first 10 days of life, more within the hsPDA group (54 vs. 18% p < 0.001); however, no differences in platelet-related parameters were observed between those who did and did not respond to acetaminophen treatment when comparing infants with hsPDA. Twenty-six of the 67 thrombocytopenic infants were already thrombocytopenic prior to acetaminophen treatment, and 19 of these 26 (73%) with pretreatment thrombocytopenia responded to acetaminophen treatment-with the overall response rate of 70%.

CONCLUSIONS

This study is the first to document that, in contrast to the COX inhibitors, there is no association between early neonatal thrombocytopenia and ductal therapeutic responsiveness to acetaminophen.

KEY POINTS

· Perinatal thrombocytopenia affects ductal closure with COX inhibitors.. · In contrast to the COX inhibitors, acetaminophen responsiveness is not affected by thrombocytopenia.. · Acetaminophen can be recommended to close hsPDA in the presence of thrombocytopenia..

Sex Differences in Patent Ductus Arteriosus Incidence and Response to Pharmacological Treatment in Preterm Infants: A Systematic Review, Meta-Analysis and Meta-Regression

A widely accepted concept in perinatal medicine is that boys are more susceptible than girls to complications of prematurity. However, whether this ‘male disadvantage of prematurity’ also involves persistent patent ductus arteriosus (PDA) has been scarcely investigated. Our aim was to conduct a systematic review and meta-analysis on studies addressing sex differences in the risk of developing PDA among preterm infants. We also investigated whether the response to pharmacological treatment of PDA differs between boys and girls. PubMed/Medline and Embase databases were searched. The random-effects male/female risk ratio (RR) and 95% confidence interval (CI) were calculated. We included 146 studies (357,781 infants). Meta-analysis could not demonstrate sex differences in risk of developing any PDA (37 studies, RR 1.03, 95% CI 0.97 to 1.08), hemodynamically significant PDA (81 studies, RR 1.00, 95% CI 0.97 to 1.02), or in the rate of response to pharmacological treatment (45 studies, RR 1.01, 95% CI 0.98 to 1.04). Subgroup analysis and meta-regression showed that the absence of sex differences was maintained over the years and in different geographic settings. In conclusion, both the incidence of PDA in preterm infants and the response rate to pharmacological treatment of PDA are not different between preterm boys and girls.

Mouse models of patent ductus arteriosus (PDA) and their relevance for human PDA

The ductus arteriosus (DA) is a unique fetal vascular shunt, which allows blood to bypass the developing lungs in utero. After birth, changes in complex signaling pathways lead to constriction and permanent closure of the DA. The persistent patency of the DA (PDA) is a common disorder in preterm infants, yet the underlying causes of PDA are not fully defined. Although limits on the availability of human DA tissues prevent comprehensive studies on the mechanisms of DA function, mouse models have been developed that reveal critical pathways in DA regulation. Over 20 different transgenic models of PDA in mice have been described, with implications for human DA biology. Similarly, we enumerate 224 human single-gene syndromes that are associated with PDA, including a small subset that consistently feature PDA as a prominent phenotype. Comparison and functional analyses of these genes provide insight into DA development and identify key regulatory pathways that may serve as potential therapeutic targets for the management of PDA.

Current Controversy on Platelets and Patent Ductus Arteriosus Closure in Preterm Infants

Platelets are critically involved in murine patent ductus arteriosus (PDA) closure. To date, the clinical significance of these findings in human preterm infants with PDA is still controversial. We discuss the available study data on the role of platelets for PDA closure in preterm infants: Several mostly retrospective studies have yielded conflicting results on whether thrombocytopenia contributes to failed spontaneous ductal closure. The same applies to investigations on the role of thrombocytopenia as a risk factor for unsuccessful ductus arteriosus closure by pharmacological treatment with cyclooxygenase inhibitors. Nonetheless, recent meta-analyses have concluded that thrombocytopenia constitutes an independent risk factor for both failed spontaneous and pharmacological PDA closure in preterm infants. However, the available investigations differ in regard to patient characteristics, diagnostic strategies, and treatment protocols. Several studies suggest that impaired platelet function rather than platelet number is critically involved in failure of ductus arteriosus closure in the preterm infant. A recent randomized-controlled trial on platelet transfusions in preterm infants with PDA failed to show any benefit for liberal vs. restrictive transfusion thresholds on PDA closure rates. Importantly, liberal transfusions were associated with an increased rate of intraventricular hemorrhage, and thus should be avoided. In conclusion, the available evidence suggests that thrombocytopenia and platelet dysfunction contribute to failure of spontaneous and pharmacological PDA closure in preterm infants. However, these platelet effects on PDA seem to be of only moderate clinical significance. Furthermore, platelet transfusions in thrombocytopenic preterm infants in order to facilitate PDA closure appear to cause more harm than good.

Platelet Counts and Patent Ductus Arteriosus in Preterm Infants: An Updated Systematic Review and Meta-Analysis

Background: A meta-analysis published in 2015 showed a significant association between low platelet counts in the first day(s) of life and risk of patent ductus arteriosus (PDA). The meta-analysis pooled data from 11 studies cohorts (3,479 preterm infants). Objective: To update the meta-analysis by adding new studies on the topic and including other platelet parameters different from platelet counts. Methods: PubMed/Medline and Embase databases were searched. Random-effects risk ratios (RR) and differences in means (DM) and 95% confidence intervals (CI) were calculated. Results: We included 31 studies (7,638 infants). Meta-analysis showed that the risk of developing any PDA was significantly associated with platelet counts<150 × 109/L (11 studies, RR 1.58, 95% CI 1.28 to 1.95), and <100 x 109/L (7 studies, RR 1.61, 95% CI 1.14 to 2.28), but not <50 x 109/L (4 studies, RR 1.34, 95% CI 0.77 to 2.32). Risk of developing hemodynamically significant PDA (hsPDA) was significantly associated with platelet counts<150 x 109/L (12 studies, RR 1.33, 95% CI 1.09 to 1.63), and <100 x 109/L (7 studies, RR 1.39, 95% CI 1.06 to 1.82), but not <50 x 109/L (6 studies, RR 1.24, 95% CI 0.86 to 1.79). Infants with hsPDA had significantly lower mean platelet counts (19 studies, DM 22.0 x 109, 95% CI 14.9 to 29.1) and platelet mass (11 studies, DM 214.4, 95% CI 131.2 to 297.5) and significantly higher platelet distribution width (PDW, 9 studies, DM -0.53, 95% CI -1.01 to -0.05) than infants without hsPDA. Meta-analysis could not demonstrate significant differences in mean platelet volume (MPV). Conclusion: Compared to the previous analysis, this updated meta-analysis included 21 additional studies that provide stronger evidence of the association between low platelet counts and PDA/hsPDA. Other platelet parameters such as platelet mass and PDW are also associated with hsPDA risk. However, the low number of platelets may be an epiphenomenon associated with the maturity and clinical stability of preterm infants rather than a contributing factor in the pathogenesis of PDA.

Platelet Count Might Be Associated With the Closure of Hemodynamically Significant Patent Ductus Arteriosus

Background: Platelet-rich thrombosis leads to the occlusion of arteries. Whether the association between platelet count and closure of hemodynamically significant patent ductus arteriosus (hsPDA) exists remains inconclusive. Given that neonatal platelet count is significantly affected by infection, this study aims to evaluate the association of platelet parameters before ibuprofen treatment with the closure of hsPDA in very low birth weight (VLBW) infants without concurrent infection. Methods: A retrospective study was conducted at the NICU of Shenzhen Maternity and Child Healthcare Hospital from January 2016 to August 2020. VLBW infants diagnosed with hsPDA, treated with oral ibuprofen and without concurrent infection were included in this study. The platelet parameters were retrieved from the whole-blood test routinely performed within 24 h before starting treatment of oral ibuprofen. A multiple regression model was built to evaluate the association between platelet parameters before ibuprofen treatment and successful closure of hsPDA. Results: A total of 129 premature infants with hsPDA were analyzed in this study. After oral ibuprofen treatment, successful closure of hsPDA was achieved in 70 (54.3%) infants. The gestational age at birth and birth weight in infants with successful or failed closure of hsPDA after ibuprofen treatment were 28.3 vs. 27.6 weeks (p = 0.016) and 1,120 vs. 960 g (p = 0.043), respectively. The rate of mechanical ventilation in infants with successful closure of hsPDA was significantly lower compared to those with failed closure of hsPDA, 31.4 vs. 54.2%, p = 0.014. The platelet count in infants with successful closure of hsPDA after ibuprofen treatment was significantly higher compared to those with failed closure of hsPDA, 212 vs. 183 (in a unit of 10⁹/L), respectively (p = 0.024). Multivariate logistic regression analysis showed that a higher platelet count (≥181 × 10⁹/L) before ibuprofen treatment was independently associated with successful closure of hsPDA [odds ratio 2.556, 95% confidence interval (1.101-5.932), p = 0.029]. Conclusion: The findings in this study suggest that a higher platelet count before oral ibuprofen treatment may predict the probability of successful closure of hsPDA in VLBW infants.

Molecular and Mechanical Mechanisms Regulating Ductus Arteriosus Closure in Preterm Infants

Failure of ductus arteriosus closure after preterm birth is associated with significant morbidities. Ductal closure requires and is regulated by a complex interplay of molecular and mechanical mechanisms with underlying genetic factors. In utero patency of the ductus is maintained by low oxygen tension, high levels of prostaglandins, nitric oxide and carbon monoxide. After birth, ductal closure occurs first by functional closure, followed by anatomical remodeling. High oxygen tension and decreased prostaglandin levels mediated by numerous factors including potassium channels, endothelin-1, isoprostanes lead to the contraction of the ductus. Bradykinin and corticosteroids also induce ductal constriction by attenuating the sensitivity of the ductus to PGE2. Smooth muscle cells of the ductus can sense oxygen through a mitochondrial network by the role of Rho-kinase pathway which ends up with increased intracellular calcium levels and contraction of myosin light chains. Anatomical closure of the ductus is also complex with various mechanisms such as migration and proliferation of smooth muscle cells, extracellular matrix production, endothelial cell proliferation which mediate cushion formation with the interaction of blood cells. Regulation of vessel walls is affected by retinoic acid, TGF-β1, notch signaling, hyaluronan, fibronectin, chondroitin sulfate, elastin, and vascular endothelial cell growth factor (VEGF). Formation of the platelet plug facilitates luminal remodeling by the obstruction of the constricted ductal lumen. Vasa vasorum are more pronounced in the term ductus but are less active in the preterm ductus. More than 100 genes are effective in the prostaglandin pathway or in vascular smooth muscle development and structure may affect the patency of ductus. Hemodynamic changes after birth including fluid load and flow characteristics as well as shear forces within the ductus also stimulate closure. Current pharmacological treatment for the closure of a patent ductus is based on the blockage of the prostaglandin pathway mainly through COX or POX inhibition, albeit with some limitations and side effects. Further research for new agents aiming ductal closure should focus on a clear understanding of vascular biology of the ductus.

The Thromboelastographic Profile at Birth in Very Preterm Newborns with Patent Ductus Arteriosus

BACKGROUND

The role of hemostasis in the closure of patent ductus arteriosus (PDA) in preterm infants is controversial.

OBJECTIVE

To assess thromboelastography (TEG) at birth in very-low-birth-weight (VLBW) infants affected by PDA.

METHODS

This was an ancillary study of a prospective observational study aimed at defining the TEG profile in healthy VLBW infants in the first month of life. In this analysis, we included neonates of <33 weeks' gestational age (GA) with PDA and compared TEG traces based on (1) spontaneous closure versus the need for pharmacological treatment and (2) treatment response. We collected blood samples in the 1st day of life to perform recalcified native-blood TEG (reaction time, maximum amplitude, and lysis at 30 min [Ly30)]), standard coagulation tests, and a full blood count.

RESULTS

We enrolled 151 infants with a PDA at the first echocardiogram; 111 experienced spontaneous PDA closure while 40 required treatment. Mean GA was 29.7 ± 1.7 and 27.6 ± 2.1 weeks, and birth weight was 1,158 ± 256 and 933 ± 263 g in the 2 groups, respectively (p < 0.001). The hemostatic profile was similar between groups. Median hematocrit (44.6 and 48.7%; p = 0.01) and platelet count (187 and 216 × 103/μL; p = 0.04) were lower in the treated group, although differences lost significance after controlling for GA and illness severity in the multivariate analysis. Responders to PDA treatment (n = 20) had a significantly lower median Ly30 than nonresponders (0 and 0.7%; p = 0.02).

CONCLUSION

TEG at birth does not predict spontaneous PDA closure in preterm newborns. Fibrinolysis is enhanced in nonresponders to PDA treatment; this observation warrants further investigation.

Base excess and hematocrit predict response to indomethacin in very low birth weight infants with patent ductus arteriosus

Background

The treatment of patent ductus arteriosus (PDA) in very low birth weight (VLBW) infants remains a challenge. The ability to predict which infants will respond to indomethacin could spare some from the risks of unnecessary medications. Our objective was to determine if indicators of acid-base homeostasis could predict response to indomethacin treatment for ductal closure, and thus help guide treatment decisions.

Methods

We performed a retrospective analysis of medical records of VLBW (< 1500 g) neonates with hemodynamically significant PDA born at our institution between January 2009 and December 2012; all infants included in the study were treated with indomethacin for ductal closure within the first 2 weeks of life. We extracted data for a number of clinical variables including gestational age, birth weight, blood chemistries, surfactant use, hematocrit, and blood gas parameters. Our primary outcome measure was successful closure of PDA following the first round of indomethacin. Using variables that were significant on initial testing, we created multivariable regression models to determine the independent association of selected variables with indomethacin response.

Results

Of the 91 infants included in the study, 62 (68%) responded to the first course of indomethacin with successful ductal closure. Multivariable regression modeling revealed that both base excess and hematocrit were independently associated with indomethacin response; odds of PDA closure increased with increasing base excess (OR [odds ratio]: 1.81; 95% confidence interval [CI]: 1.36–2.60) and increasing hematocrit (OR: 1.21; 95% CI: 1.01–1.45). The optimal cutoff value for base excess was − 4.56, with a sensitivity of 96.8% (95% CI: 89–100) and specificity of 79.3% (95% CI: 60–92); optimal cutoff value for hematocrit was 40, with 69.4% sensitivity (95% CI: 56–80) and 65.5% specificity (95% CI: 46–82).

Conclusions

Base excess and hematocrit may be independent predictors of indomethacin response in VLBW infants with PDA. Low-cost and readily accessible, acid-base indicators such as base excess could help guide treatment decisions.

Electronic supplementary material

The online version of this article (10.1186/s13052-019-0706-y) contains supplementary material, which is available to authorized users.

Platelet Transfusion for PDA Closure in Preterm Infants: A Randomized Controlled Trial

BACKGROUND AND OBJECTIVES

Thrombocytopenia is associated with late closure of patent ductus arteriosus (PDA). There are few studies evaluating platelet transfusions to treat PDA. We compared liberal platelet-transfusion criteria (to maintain a platelet count >100 000 per µL) versus standard criteria achieve earlier PDA closure among thrombocytopenic preterm neonates (<35 weeks' gestation) with hemodynamically significant PDA (hs-PDA) presenting within the first 2 weeks of life.

METHODS

Thrombocytopenic (<100 000 per µL) preterm neonates with hs-PDA were enrolled and randomly allocated to the liberal and standard transfusion groups: 22 in each arm. They underwent echocardiography daily until closure of PDA, completion of 120 hours follow-up, or death. All subjects received standard cotreatment with nonsteroidal antiinflammatory drugs. Primary outcome of time to PDA closure was compared by survival analysis. Multivariate Cox proportional hazard regression was performed with randomization group, baseline platelet count, gestational age, and age at enrollment as predictor variables.

RESULTS

Median time to PDA closure was 72 (95% confidence interval [CI] 55.9-88.1) versus 72 (95% CI 45.5-98.4) hours in the liberal versus restrictive transfusion groups, respectively (unadjusted hazard ratio 0.88 [95% CI 0.4-1.9]; P = .697). Despite adjusting for potential confounders, there was no significant difference in time to PDA closure. In the liberal transfusion group, 41% of infants had any grade of intraventricular hemorrhage compared with 4.5% in the restrictive group (P = .009).

CONCLUSIONS

Attempting to maintain a platelet count >100 000 per µL by liberally transfusing platelets in preterm thrombocytopenic neonates with hs-PDA does not hasten PDA closure.

Intrauterine Growth Restriction and Patent Ductus Arteriosus in Very and Extremely Preterm Infants: A Systematic Review and Meta-Analysis

It is generally accepted that intrauterine growth restriction (IUGR) increases morbidity and mortality among very preterm neonates. However, evidence is hampered by the widespread practice of using the terms small for gestational age (SGA) and IUGR as synonyms. We conducted a systematic review of studies reporting on the association between IUGR/SGA and patent ductus arteriosus (PDA). PubMed/MEDLINE and EMBASE databases were searched. Of 993 studies reviewed, 47 (50,790 infants) were included. Studies were combined using a random effects model and sources of heterogeneity were determined by subgroup and meta-regression analyses. Meta-analysis of all included studies showed a significantly reduced risk of PDA in the SGA/IUGR group with an odds ratio (OR) of 0.82, and a 95% confidence interval (CI) of 0.70 to 0.96 (p = 0.015). Of the 47 studies, only 7 used a definition for growth restriction that went beyond birth weight (BW) for gestational age (GA). When pooled, meta-analysis could not demonstrate a significant effect size (OR 1.31, 95% CI 0.75 to 2.27, p = 0.343). Moreover, the significantly reduced risk of PDA was found in the 25 studies defining SGA as BW <10th percentile (OR 0.81, 95% CI 0.66 to 0.98, p = 0.032), but not in the 6 studies defining SGA as BW <3rd (OR 1.09, 95% CI 0.70 to 1.71, p = 0.694), or in the 27 studies using a more refined definition of PDA (i.e., hemodynamically significant PDA or PDA requiring treatment, OR 0.87, 95% CI 0.72 to 1.04, p = 0.133). In addition, we found that GA was significantly higher in the SGA/IUGR group (18 studies, mean difference 0.63 weeks, 95% CI 0.24 to 1.03, p = 0.002). Meta-regression analysis confirmed the correlation between this difference in GA and PDA risk. In summary, we observed marked heterogeneity across studies in the definition of growth restriction and PDA, and we found differences between the control and growth-restricted groups in relevant baseline characteristics, such as GA. Therefore, our meta-analysis could not provide conclusive evidence on the association between growth restriction and PDA.

Influence of platelet count, platelet mass index, and platelet function on the spontaneous closure of ductus arteriosus in the prematurity

BACKGROUND

This study aims at evaluating the influence of platelet count, platelet mass index, and platelet function on the spontaneous closure of ductus arteriosus in prematurity.

METHODS

All preterm babies were divided into two groups, including Group 1 with "open PDA" and Group 2 with "closed PDA". The variables of platelet count, mean platelet volume, platelet mass index, and platelet function were analyzed and compared between two groups of patients to identify the factors that significantly influenced spontaneous closure of ductus arteriosus.

RESULTS

Twenty-four patients were in the "open PDA" group, whereas 36 patients were in the "closed PDA" group. Mean GA and BW were 27.6 ± 1.8 (23.1-30.4) and 28 ± 1.6 (23.4-30.6) weeks and 1009 ± 270 (585-1480) g and 1035 ± 298 (505-1500) g in "open PDA" and "closed PDA" groups, respectively (p > 0.05). The incidence of "Collagen-ADP > 130 s" was significantly higher in the "open PDA" group, and the levels of hemoglobin and hematocrit were significantly lower in the "open PDA" group (p < 0.05). Multivariate logistic regression analysis showed that respiratory distress syndrome (OR: 9, CI: 1.5-51.8) and collagen-ADP > 130 s (OR: 5.7 CI: 1.55-21.3) are two independent factors associated with ductal patency.

CONCLUSION

This is the first study in the English literature providing evidence of the influence of platelet dysfunction on the spontaneous closure of ductus arteriosus in prematurity. Longer collagen-ADP duration is identified as a risk factor of ductal closure.

Association between Platelet Counts before and during Pharmacological Therapy for Patent Ductus Arteriosus and Treatment Failure in Preterm Infants

BACKGROUND

The role of platelets for mediating closure of the ductus arteriosus in human preterm infants is controversial. Especially, the effect of low platelet counts on pharmacological treatment failure is still unclear.

METHODS

In this retrospective study of 471 preterm infants [<1,500 g birth weight (BW)], who were treated for a patent ductus arteriosus (PDA) with indomethacin or ibuprofen, we investigated whether platelet counts before or during pharmacological treatment had an impact on the successful closure of a hemodynamically significant PDA. The effects of other factors, such as sepsis, preeclampsia, gestational age, BW, and gender, were also evaluated.

RESULTS

Platelet counts before initiation of pharmacological PDA treatment did not differ between infants with later treatment success or failure. However, we found significant associations between low platelet counts during pharmacological PDA therapy and treatment failure (p < 0.05). Receiver operating characteristic (ROC) curve analysis showed that platelet counts after the first, and before and after the second cyclooxygenase inhibitor (COXI) cycle were significantly associated with treatment failure (area under the curve of >0.6). However, ROC curve analysis did not reveal a specific platelet cutoff-value that could predict PDA treatment failure. Multivariate logistic regression analysis showed that lower platelet counts, a lower BW, and preeclampsia were independently associated with COXI treatment failure.

CONCLUSION

We provide further evidence for an association between low platelet counts during pharmacological therapy for symptomatic PDA and treatment failure, while platelet counts before initiation of therapy did not affect treatment outcome.

Is there a relationship between platelet parameters and patency of ductus arteriosus in preterm infants?

Postnatal closure of the ductus arteriosus is a complicated two-phase process involving functional and structural changes. So far, the precise mechanisms regulating this process are not fully understood. A growing body of evidence from recent studies suggests that platelets play a key role in inflammatory processes including ductal closure via interaction with endothelial cells. The aim of this study is to assess whether a relationship exists between the occurrence and/or closure of hemodynamically significant ductus arteriosus (HSDA) and platelet parameters (platelet count, circulating platelet mass, mean platelet volume, platelet distribution width) in preterm newborns. This single-center, retrospective study included 824 premature infants between 24 and 34 gestational weeks, evaluated by echocardiography at postnatal 72-96 h. Infants with and without HSDA (n = 208 vs. n = 616) were compared in terms of platelet parameters recorded within the first 3 days of life. Oral or intravenous ibuprofen was commenced for medical treatment, and echocardiography was repeated 24 h thereafter to determine ductal closure. No statistically significant difference could be demonstrated between the groups in terms of baseline platelet parameters. HSDA was independently associated with early-onset neonatal sepsis. Thrombocytopenia, low circulating platelet mass, high platelet distribution width, or high mean platelet volume could not be demonstrated as a risk factor for HSDA. None of the platelet parameters had an influence on ductal closure after medical treatment. Unlike most reports in the literature, presence of HSDA was not associated with any platelet parameter in our study. We could not demonstrate an association between any platelet parameter and either persistence or closure after medical treatment.

Chorioamnionitis appears not to be a Risk Factor for Patent Ductus Arteriosus in Preterm Infants: A Systematic Review and Meta-Analysis

The contribution of chorioamnionitis (CA) to mortality and morbidity in preterm infants is difficult to assess because observational studies frequently present significant differences in baseline characteristics of the infants exposed or non-exposed to CA. In an attempt to perform a thorough assessment of the possible association between CA and patent ductus arteriosus (PDA) in preterm infants, we conducted a meta-analysis in which adjusted odds ratios (ORs) were pooled and we analyzed the effects of potential confounders, such as gestational age (GA) or birth weight (BW). We identified 45 relevant studies (27186 patients, 7742 CA cases). Random effects meta-analysis of crude ORs showed a significant positive association between CA and PDA (OR 1.352, 95% CI 1.172 to 1.560). Adjusted ORs were reported in 11 studies (19577 infants). Meta-analysis of these studies showed a significant negative association between CA and PDA (OR 0.802, 95% CI 0.751 to 0.959). Meta-regression showed that the differences in GA or BW between the CA-exposed and non-exposed groups were significantly correlated with the effect size of the association between PDA and CA. In conclusion, our study confirms that confounders need to be taken into account when assessing the association between CA and clinical outcomes in preterm infants.

Predictors of successful closure of patent ductus arteriosus with indomethacin

OBJECTIVE

To determine whether platelet counts can predict the likelihood of successful closure of patent ductus arteriosus (PDA) with indomethacin.

STUDY DESIGN

This was a retrospective cohort study of infants <32 weeks' gestational age (GA) and birth weight <1500 g with PDA. Clinical characteristics between infants who achieved ductal closure with indomethacin and those who failed were compared. Multivariable logistic regression was used to identify predictors of successful ductal closure.

RESULTS

In infants with hemodynamically significant PDA, older GA (odds ratio=1.54; 95% confidence interval: 1.12 to 2.13), male gender (odds ratio=3.02; 95% confidence interval: 1.08 to 8.49) and higher platelet count (odds ratio=1.5; 95% confidence interval: 1.04 to 2.17) prior to indomethacin treatment were associated with successful ductal closure with indomethacin.

CONCLUSION

Older GA, male gender and higher platelet count at time of treatment of hemodynamically significant PDA are predictors of successful ductal closure with indomethacin.

Is platelet mass a more significant indicator than platelet count of closure of patent ductus arteriosus?

BACKGROUND

The purpose of this study was to evaluate whether or not platelet mass contributes to closure of patent ductus arteriosus (PDA) in premature newborns.

STUDY DESIGN AND SUBJECTS

This retrospective study included 115 preterm newborns with hemodynamically significant PDA (hPDA) and 120 newborns without PDA. The newborns' platelet count, mean platelet volume (MPV) and platelet distribution width (PDW) were noted from their files and the platelet mass (platelet count plus MPV/10(3)) was calculated. Patients with congenital abnormality, persistent pulmonary hypertension or sepsis were not included in the study.

RESULTS

Platelet count and PDW were found to not be risk factors for closure of hPDA (p > 0.05), but both high platelet mass (OR 1.25; 95% CI 1.12-1.41) and MPV (OR 1.87; 95% CI 2.52-3.85) were determined to be independent risk factors for hPDA.

CONCLUSIONS

Platelet mass may be a more significant indicator than platelet count of closure of hPDA in preterm newborns.

Management of patent ductus arteriosus in premature infants

Patency of the ductus arteriosus is required for fetal survival in utero. In infants born prematurely, ductus fails to close and shunt reverses from left to right. Incidence of patent ductus arteriosus (PDA) is inversely proportional to the gestational age. A large PDA (>1.5 mm diameter) with left to right shunt in very low birth weight infants can cause pulmonary edema, congestive heart failure, pulmonary hemorrhage and increase the risk for bronchopulmonary dysplasia. Attempts to prevent or close the duct by pharmacological or surgical methods have not changed the morbidity or the long term outcome. Pharmacological treatment with indomethacin or ibuprofen is successful in 75 to 80 % of infants but its use also exposes these infants to undesirable side effects like gastrointestinal bleeding, perforation and necrotizing enterocolitis. Prophylactic therapy with indomethacin or ibuprofen to prevent PDA has not altered the morbidity or long term outcome. Currently, there is a dilemma as to how to treat, when to treat and whom to treat. Recent literature suggests a trial of conservative management during the first week followed by selective use of anti-inflammatory drugs. Surgical ligation is reserved for infants who fail medical therapy and still remain symptomatic. Spontaneous closure of the PDA has been reported in up to 40-67 % of very low birth weight (VLBW) infants by 7 d. In this review authors discuss these controversies and propose a more rational approach.

Platelet Counts and Patent Ductus Arteriosus in Preterm Infants: A Systematic Review and Meta-Analysis

BACKGROUND

Several cohort studies have shown an association between low platelet counts in the first day(s) of life and patent ductus arteriosus (PDA) in preterm infants. However, these results have not been confirmed by other studies.

OBJECTIVE

To perform a meta-analysis of all the studies addressing the relationship between platelet counts in the first day(s) of life and PDA in preterm infants.

METHODS

PubMed/MEDLINE and EMBASE were searched from their inception until December 2014. Results from 11 cohort studies involving 3,479 preterm infants (gestational age <32 weeks) were pooled using random-effects modeling.

RESULTS

Meta-analysis showed a significant positive association between PDA and platelet counts <150 × 10(9)/l [6 studies, risk ratio (RR) = 1.215, 95% CI: 1.027-1.436], between PDA and platelet counts <100 × 10(9)/l (5 studies, RR = 1.255, 95% CI: 1.034-1.525), and between significant PDA (SPDA) and platelet counts <100 × 10(9)/l (5 studies, RR = 1.254, 95% CI: 1.021-1.540). The association between SPDA and platelet counts <150 × 10(9)/l was not statistically significant (6 studies, RR = 1.289, 95% CI: 0.925-1.795). Pooled standard differences in mean platelet counts between infants with and without PDA/SPDA were not statistically different.

CONCLUSION

This meta-analysis reveals a marginal but significant association between low platelet counts in the first day(s) of life and PDA/SPDA in very preterm infants. This association needs to be confirmed in prospective studies.

Platelet counts in the first seven days of life and patent ductus arteriosus in preterm very low-birth-weight infants

BACKGROUND

Decreased platelet number and/or function are related to patent ductus arteriosus (PDA) in mice. Whether this is also the case in human infants remains controversial.

OBJECTIVES

To investigate the association between platelet count nadir within the first 7 days of life and the rate of hemodynamically significant PDA (HSPDA), as well as the rate of response to the treatment with cyclooxygenase (COX) inhibitors.

METHODS

This is a retrospective study of a cohort of 194 very low-birth-weight (VLBW) infants (<1,500 g) with gestational age <30 weeks. HSPDA was assessed by echocardiography on day 3 of life.

RESULTS

HSPDA was present in 105 infants (54.1%). Of these, 101 were treated with COX inhibitors. The treatment failure rate was 21.8%. Median platelet count nadir and rate of thrombocytopenia - defined as platelet count <150 × 10(9)/l and graded as mild (100 to <150 × 10(9)/l), moderate (50 to <100 × 10(9)/l) or severe (<50 × 10(9)/l) - within the first 2 days of life were not significantly associated with the presence of HSPDA on day 3. Moreover, low platelet counts, either on days 1-2 or 3-7, were not significantly associated with the rate of response to treatment with COX inhibitors.

CONCLUSIONS

Our data provide further evidence for the lack of association between platelet counts within the first days of life and either spontaneous or pharmacological closure of the ductus arteriosus in VLBW infants.

Comparison of oral paracetamol versus ibuprofen in premature infants with patent ductus arteriosus: a randomized controlled trial

TRIAL DESIGN

Oral ibuprofen has demonstrated good effects on symptomatic patent ductus arteriosus (PDA) but with many contraindications and potential side-effects. In the past two years, oral paracetamol administration to several preterm infants with PDA has been reported. Here, a randomized, non-blinded, parallel-controlled and non-inferiority trial was designed to evaluate the efficacy and safety profiles of oral paracetamol to those of standard ibuprofen for PDA closure in premature infants.

METHODS

One hundred and sixty infants (gestational age ≤ 34 weeks) with echocardiographically confirmed PDA were randomly assigned to receive either oral paracetamol (n = 80) or ibuprofen (n = 80). After the initial treatment course in both groups, the need for a second course was determined by echocardiographic evaluation. The main outcome was rate of ductal closure, and secondary outcomes were adverse effects and complications.

RESULT

The ductus was closed in 65 (81.2%) infants of the paracetamol group compared with 63 (78.8%) of the ibuprofen group. The 95% confidence interval of the difference between these groups was [-0.080,0.128], demonstrating that the effectiveness of paracetamol treatment was not inferior to that of ibuprofen. In fact, the incidence of hyperbilirubinemia or gastrointestinal bleeding in the paracetamol group was significantly lower than that of the ibuprofen group. No significant differences in other clinical side effects or complications were noted.

CONCLUSION

This comparison of drug efficacy and safety profiles in premature infants with PDA revealed that oral paracetamol was comparable to ibuprofen in terms of the rate of ductal closure and even showed a decreased risk of hyperbilirubinemia or gastrointestinal bleeding. Therefore, paracetamol may be accepted as a first-line drug treatment for PDA in preterm infants.

TRIAL REGISTRATION

ChiCTR.org ChiCTR-TRC-12002177.

Low platelet count is associated with ductus arteriosus patency in preterm newborns

BACKGROUND/AIM

To determine whether there is an association between platelet counts and patent ductus arteriosus (PDA) incidence and/or closure in preterm newborns.

STUDY DESIGN AND SUBJECTS

Premature infants with hemodynamically significant PDA (n=154) and a control group without PDA (n=207) who were hospitalized in the NICU were retrospectively evaluated. Platelet counts and other platelet indices including mean platelet volume (MPV) and platelet distribution width (PDW) of the infants in both groups during the first 3 days of life were recorded. Ibuprofen was started in infants with hemodynamically significant PDA and echocardiography was repeated 48 h thereafter to assess the closure of ductus.

RESULTS

Median gestational age and birth weight of the infants with PDA were 28 (range 26-29) weeks and 1060 (range 892-1250) g respectively. Platelet counts were significantly lower in the patient group than in the control group (p<0.001). Multivariate analysis including gestational age, presence of RDS, presence of thrombocytopenia and PDW showed that hemodynamically significant PDA was independently associated with platelet count <150,000 (OR=2.13, 95% CI 1.26-3.61; p=0.005), high PDW (>17) (OR=2.68, 95% CI 1.41-5.09; p=0.003) and the presence of RDS (OR=2.25, 95% CI 1.41-3.59; p=0.001). Baseline platelet counts of the infants in whom ductus closed or persisted after ibuprofen treatment were similar.

CONCLUSIONS

PDA was associated with low platelet count and high PDW but not with other platelet indices in preterm infants. We could not show an association between platelet counts and persistence or closure after medical treatment.

Thrombocytopenia in the first 24 hours after birth and incidence of patent ductus arteriosus

BACKGROUND

Experimental studies suggest that platelet-triggered ductal sealing is critically involved in definite ductus arteriosus closure. Whether thrombocytopenia contributes to persistently patent ductus arteriosus (PDA) in humans is controversial. This was a retrospective study of 1350 very low birth weight (VLBW; <1500 g) infants, including 592 extremely low birth weight (ELBW; <1000 g) infants.

METHODS

All infants who had a platelet count in the first 24 hours after birth and an echocardiogram performed on day of life 4 to 5 were included. The incidence of thrombocytopenia was analyzed in infants with and without PDA, and in those who did or did not undergo PDA intervention. The impact of thrombocytopenia, gestational age, birth weight, gender, and sepsis on PDA was determined by receiver operating characteristic curve, odds ratio, and regression analyses.

RESULTS

Platelet numbers within the first 24 hours after birth did not differ between VLBW/ELBW infants with and without spontaneous ductal closure. Platelet numbers were not associated with subsequent PDA treatment. Low platelet counts were not related to failure of pharma-cologic PDA treatment and the need for subsequent surgical ligation. Lower gestational age or birth weight, male gender, and sepsis were linked to the presence of PDA in VLBW infants on day of life 4 to 5.

CONCLUSIONS

Thrombocytopenia in the first 24 hours after birth was not associated with PDA in this largest VLBW/ELBW infant cohort studied to date. Impaired platelet function, due to immaturity and critical illness, rather than platelet number, might play a role in ductus arteriosus patency.

Mechanisms for ductus arteriosus closure

Closure of the ductus arteriosus at birth is a complex phenomenon being conditioned by antenatal events and progressing in preprogrammed steps. Functional at first, narrowing of the vessel is determined by 2 overlapping processes--removal of the prostaglandin E(2)-based relaxation sustaining prenatal patency and activation of a constrictor mechanism by the natural rise in blood oxygen tension. Two schemes have been proposed for oxygen action--one involving a cytochrome P450 hemoprotein (sensor)/endothelin-1 (effector) complex and the other a set of voltage-gated K(+) channels. These proposals, however, are not mutually exclusive. Structural closure follows the constriction through a remodeling process initiated antenatally with the development of intimal cushions and completed postnatally by a host of humoral and mechanical stimuli. Research in this area has already provided clinical applications. Nevertheless, management of premature infants with persistent ductus remains troublesome and calls for an alternative approach to the prostaglandin E(2) inhibitors now in use. Studies in progress on the oxygen-sensing system may lead to a definitive solution for this problem.

Current Perspectives on Pathobiology of the Ductus Arteriosus

The ductus arteriosus (DA) shunts blood away from the lungs during fetal life, but at birth this shunt is no longer needed and the vessel rapidly constricts. Postnatal persistence of the DA, patent ductus arteriosus (PDA), is predominantly a detrimental condition for preterm infants but is simultaneously a condition required to maintain systemic blood flow for infants born with certain severe congenital heart defects. Although PDA in preterm infants is associated with significant morbidities, there is controversy regarding whether PDA is truly causative. Despite advances in our understanding of the pathobiology of PDA, the optimal treatment strategy for PDA in preterm infants is unclear. Here we review recent studies that have continued to elucidate the fundamental mechanisms of DA development and pathogenesis.

New therapeutic strategies for the treatment of patent ductus arteriosus in preterm infants

A high percentage of preterm infants fails to respond to a single course of indomethacin or ibuprofen. Thus, it has been suggested that the actual dose regimens of these drugs could be inadequate because of large interindividual pharmacokinetics variations in premature infants. We tested the hypothesis that a high-dose regimen of ibuprofen was more effective than the current regimen in closing PDA. We demonstrated that a single course of ibuprofen at 20-10-10 mg/kg/day is more effective than a 10-5-5 mg/kg/day course in closing PDA without significant adverse effects. Many other questions regarding the pharmacological treatment of PDA are still debated.

Anatomic closure of the premature patent ductus arteriosus: The role of CD14+/CD163+ mononuclear cells and VEGF in neointimal mound formation

Permanent closure of the newborn ductus arteriosus requires the development of neointimal mounds to completely occlude its lumen. VEGF is required for neointimal mound formation. The size of the neointimal mounds (composed of proliferating endothelial and migrating smooth muscle cells) is directly related to the number of VLA4 mononuclear cells that adhere to the ductus lumen after birth. We hypothesized that VEGF plays a crucial role in attracting CD14/CD163 mononuclear cells (expressing VLA4) to the ductus lumen and that CD14/CD163 cell adhesion to the ductus lumen is important for neointimal growth. We used neutralizing antibodies against VEGF and VLA-4 to determine their respective roles in remodeling the ductus of premature newborn baboons. Anti-VEGF treatment blocked CD14/CD163 cell adhesion to the ductus lumen and prevented neointimal growth. Anti-VLA-4 treatment blocked CD14/CD163 cell adhesion to the ductus lumen, decreased the expression of PDGF-B (which promotes smooth muscle migration), and blocked smooth muscle influx into the neointimal subendothelial space (despite the presence of increased VEGF in the ductus wall). We conclude that VEGF is necessary for CD14/CD163 cell adhesion to the ductus lumen and that CD14/CD163 cell adhesion is essential for VEGF-induced expansion of the neointimal subendothelial zone.

Prenatal cardiovascular shunts in amniotic vertebrates

During amniotic vertebrate development, the embryo and fetus employ a number of cardiovascular shunts. These shunts provide a right-to-left shunt of blood and are essential components of embryonic life ensuring proper blood circulation to developing organs and fetal gas exchanger, as well as bypassing the pulmonary circuit and the unventilated, fluid filled lungs. In this review we examine and compare the embryonic shunts available for fetal mammals and embryonic reptiles, including lizards, crocodilians, and birds. These groups have either a single ductus arteriosus (mammals) or paired ductus arteriosi that provide a right-to-left shunt of right ventricular output away from the unventilated lungs. The mammalian foramen ovale and the avian atrial foramina function as a right-to-left shunt of blood between the atria. The presence of atrial shunts in non-avian reptiles is unknown. Mammals have a venous shunt, the ductus venosus that diverts umbilical venous return away from the liver and towards the inferior vena cava and foramen ovale. Reptiles do not have a ductus venosus during the latter two thirds of development. While the fetal shunts are well characterized in numerous mammalian species, much less is known about the developmental physiology of the reptilian embryonic shunts. In the last years, the reactivity and the process of closure of the ductus arteriosus have been characterized in the chicken and the emu. In contrast, much less is known about embryonic shunts in the non-avian reptiles. It is possible that the single ventricle found in lizards, snakes, and turtles and the origin of the left aorta in the crocodilians play a significant role in the right-to-left embryonic shunt in these species.