Patent ductus arteriosus (PDA) is the most common cardiovascular problem that develops in preterm infants. Persistent PDA may result in higher rates of death, chronic lung disease (CLD), pulmonary hemorrhage, necrotizing enterocolitis (NEC), acute kidney injury (AKI), intraventricular hemorrhage (IVH) and cerebral palsy. Currently available options to treat a PDA include indomethacin, ibuprofen or acetaminophen followed by surgical or interventional closure of the PDA if medical therapy fails.

Wide variation exists in PDA treatment practices across Canada. A survey conducted through the Canadian Neonatal Network (CNN) in 2019 showed that the most common choice of initial pharmacotherapy is standard dose ibuprofen. In view of the high pharmacotherapy failure rate with standard dose ibuprofen, there is a growing use of higher doses of ibuprofen with increasing postnatal age (with 32% of respondents currently adopting this practice) in spite of the fact that effectiveness and safety of higher ibuprofen doses have not been established in extremely preterm infants [<29 weeks gestational age (GA)]. In view of this large practice variation across Canadian neonatal intensive care units (NICUs), we are planning a comparative effectiveness study of the different primary pharmacotherapeutic agents used to treat the PDA in preterm infants.

Aims Primary: To compare the primary pharmacotherapeutic practices for PDA closure and evaluate their impact on clinical outcomes in extremely preterm infants (<29 weeks GA) Secondary: To understand the relevance of pharmacotherapeutic PDA treatment with respect to clinical outcomes in the real world.

Methods:

Participants: Extremely preterm infants (<29 weeks gestational age) with an echocardiography confirmed PDA who will be treated according to attending team

Interventions:

1. Standard dose ibuprofen [10-5-5 regimen, i.e., 10mg/kg followed by 2 doses of 5mg/kg at 24h intervals]
2. Adjustable dose ibuprofen [10-5-5 regimen if treated within the first week. Higher doses of ibuprofen up to a 20-10-10 regimen if treated after the postnatal age cut-off for lower dose as per the local center policy]
3. Intravenous indomethacin [0.1-0.3mg/kg every 12-24h for a total of 3 doses].
4. Acetaminophen [Oral/intravenous] (15mg/kg every 6h) for 3-7 days

Outcomes:

Primary: Failure of primary pharmacotherapy (Need for further medical and/or surgical/interventional treatment following an initial course of pharmacotherapy).

Secondary: (a) Receipt of 2nd course of pharmacotherapy; (b) Surgical/interventional PDA closure; (c) CLD (d) NEC (stage 2 or greater) (e) Severe IVH (Grade III-IV) (f) Definite sepsis (g) Stage 1 or greater AKI; (h) Post-treatment serum bilirubin; (i) Phototherapy duration; (j) All-cause mortality during hospital stay.

In this study, we intend to generate real-world evidence (RWE) by analyzing real-world data (RWD) (defined as data generated during routine clinical practice) from a registry-based Comparative Effectiveness Research study.

The Canadian Neonatal Network (CNN) is a well-established patient registry that includes members from 31 hospitals and 17 universities across Canada. The Network maintains a standardized NICU database and provides a unique opportunity for researchers to participate in collaborative projects. We will use the principles of Hypotheses Evaluating Treatment Effectiveness (HETE) research, which are designed to evaluate the presence or absence of a pre-specified effect and/or its magnitude. The network has recent experience in conducting such a study where one CIHR-funded study to evaluate effectiveness of two modes of non-invasive ventilation in preterm infants is already underway in 20 NICUs across Canada.

The CNN's coordinating facility is located within the Maternal-Infant Care (MiCare) Research Center, Lunenfeld-Tanenbaum Research Institute (LTRI) at Mount Sinai Hospital (Toronto). Each participating site has highly trained abstractors who enter data from patient charts into the CNN database. The abstractors will also enter data specific to our project, which will allow us to obtain real-world data at a minimal cost with easy access to investigators for troubleshooting.

Statistical Analysis overview: Since the proposed study is a CER using RWD, we will examine and account for potential confounders at the analyses stage. As recommended for HETE studies using RWD, accuracy of results will be checked by performing complementary sensitivity analyses. The analyses will be conducted in 2 stages: unit-level protocol effectiveness analysis and a secondary drug-dosage effectiveness analysis.

Inclusion Criteria:

• Extremely preterm infants (<29 weeks gestational age) with an echocardiography confirmed PDA who will be treated according to attending team

Exclusion Criteria:

• Any infant who received pharmacotherapy for a clinically symptomatic PDA without prior echocardiographic confirmation of the presence of PDA will be excluded from all analyses.

All infants born less than 29 weeks of gestation admitted to the participating sites will be included in the study. The population of interest will be those preterm infants <29 weeks gestational age (including outborns) with echocardiography confirmed PDA who will be treated according to attending team. Infants <29 weeks GA with echocardiography-confirmed PDA but never received treatment will be included as the control population. Infants <29 weeks GA who were never diagnosed with PDA will be included as the reference population