Prolonged versus short course of indomethacin for the treatment of patent ductus arteriosus in preterm infants

The ductus arteriosus is a blood vessel that connects the aorta and pulmonary artery. The ductus arteriosus is normally present in the fetus. It allows the majority of the output of the right side of the heart to bypass the lungs and supply the body of the fetus and placenta in-utero. In most term infants the patent ductus arteriosus (PDA) closes within days of birth, first by contraction of a muscular layer to achieve functional closure and then by endothelial remodeling. If the ductus arteriosus persists, blood is shunted from the aorta to the pulmonary circulation, which can cause overloading of the pulmonary circulation and reduced perfusion of the brain, gut and kidneys. In preterm infants, closure may be delayed or fail to occur, due in part to circulating vasodilatory prostaglandins. Indomethacin inhibits prostaglandin synthesis and it is used to treat PDA in preterm infants. Although indomethacin is successful in closing the PDA in the majority of cases, the ductus will re-open in up to 35% of infants who initially respond to the drug and a more prolonged course of indomethacin has been studied to achieve higher rates of ductal closure. Important side effects of indomethacin include renal dysfunction, decreased platelet aggregation, and necrotizing enterocolitis (NEC). Where indomethacin fails, the ductus arteriosus may be surgically ligated if clinically indicated. Five randomized trials are included in this review. These studies were published between 1988 and 2000 and included a total of 431 preterm and low birth weight infants. Indomethacin was given intravenously in four trials and orally in one, in total amounts of 0.6 to 1.6 mg/kg for the prolonged course (six to eight doses) and 0.3 to 0.6 mg/kg for the short course (two to three doses). There was no significant benefit of prolonged indomethacin administration on failure of the PDA to close after completion of allocated treatment (four studies, 361 infants). Prolonged course of indomethacin compared to the short course did not reduce the rate of PDA re-opening after initial closure (three studies, 322 infants), rate of PDA re-treatment (five studies, 431 infants), or ligation rate (four studies, 310 infants). The prolonged course was associated with decreased incidence of renal function impairment (three studies, 318 infants). However, a prolonged indomethacin course increased the risk of NEC (four studies, 310 infants). The number of deaths was no different.

Authors' conclusions: 

Implications for practice
Prolonged indomethacin course does not appear to have a significant effect on improving important outcomes, such as PDA treatment failure, CLD, IVH, or mortality. The reduction of transient renal impairment does not outweigh the increased risk of NEC associated with the prolonged course. Based on these results, a prolonged course of indomethacin cannot be recommended for the routine treatment of PDA in preterm infants.

Implications for research
There is a paucity of data on optimal dosing and duration of indomethacin therapy for the treatment of PDA, in particular for extremely low birth weight infants (ELBW) premature infants. It is likely that a single standard indomethacin regime is not the ideal for every premature infant. Therefore, individual patient response should be considered and evaluated, in particular in ELBW infants. Future randomized clinical trials should include this high risk population and investigate the effect of tailoring dose and duration of therapy to individual response in terms of echocardiographic findings and/or prostaglandin levels, focusing on clinically significant outcomes, including long-term neurodevelopmental outcomes. In addition, factors that may influence treatment effect, such as birth weight, gestational age, age at the time of randomization, total fluid intake, feeding practice, and severity of PDA, need to be taken into account when designing such studies.

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Background: 

Indomethacin is a prostaglandin inhibitor used to treat patent ductus arteriosus (PDA) in preterm infants. Although indomethacin produces ductal closure in the majority of cases, it is ineffective in up to 40% of patients. Furthermore, the ductus will re-open in up to 35% of infants who initially respond to the drug. Prolonging the course of indomethacin has the potential to achieve higher rates of ductal closure.

Objectives: 

To determine the effect of a prolonged course of indomethacin (compared to a short course) on the rate of treatment failure without unwanted side-effects in preterm infants with PDA.

Search strategy: 

The search included review of personal files, abstracts of conferences, and the following electronic databases: MEDLINE (1966 to December 2006), EMBASE (1974 to December 2006), and Oxford Database of Perinatal Trials, Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 4, 2006). No language restrictions were applied.

Selection criteria: 

Randomized or quasi-randomized controlled trials including preterm infants with PDA, diagnosed on clinical and/or echocardiographic examination that evaluated indomethacin treatment by any route given as a long course (four or more doses) vs. a short course (three or fewer doses) were included in the review. Trials needed to report on at least one of the following outcomes: failure of PDA to close, need for re-treatment, PDA re-opening, PDA ligation, mortality, duration of assisted ventilation, chronic lung disease (CLD), duration of supplemental oxygen dependence, intraventricular hemorrhage (IVH) (all and severe), diminished urine output, increased serum creatinine, necrotizing enterocolitis (NEC), bleeding diathesis, retinopathy of prematurity (ROP), and duration of hospital stay.

Data collection and analysis: 

The three review authors independently abstracted data from each study. Relative risk (RR) and Risk Difference (RD) with 95% confidence intervals (CI) using the fixed effect model for meta-analysis are reported. When a statistically significant RD was found, the number needed to treat (NNT) or number needed to harm (NNH) was also calculated with 95% CIs. The I squared statistic was used to test for heterogeneity of results among included trials.

Main results: 

Five trials met inclusion criteria and included 431 infants. Prolonged indomethacin treatment when compared to the short course did not result in a statistically significant difference in PDA closure, re-treatment, re-opening, or ligation rates. The prolonged course was associated with an increased risk of NEC [typical RR 1.87 (95% CI 1.07, 3.27); typical RD 0.08 (95% CI 0.01, 0.15); NNH 13 (7, 100)] and a decreased incidence of renal function impairment, as evidenced by a lower proportion of infants having diminished urine output [typical RR 0.27 (95% CI 0.13, 0.6); typical RD -0.19 (95% CI -0.28, -0.09); NNT 5 (4, 11)] and increased serum creatinine level [typical RR 0.51 (95% CI 0.33, 0.77); typical RD -0.14 (95% CI -0.23, -0.06); NNT 7 (4, 16)].

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