Alpha-1 proteinase inhibitor (a1PI) for preventing chronic lung disease in preterm infants

Inflammation of the pulmonary parenchyma is one of the important mechanisms implicated in development of chronic lung disease (CLD) in preterm neonates. Release of enzymes and other anti - oxidants following cell damage is considered to be responsible for the damage to lung tissue. Various strategies have been attempted to counteract enzymatic damage to pulmonary parenchyma and to prevent CLD.

This review examines the effectiveness of alpha 1 proteinase inhibitor (a1PI) for the prevention of CLD defined as requirement of supplemental oxygen at 36 weeks post menstrual age (PMA) in preterm neonates.

A literature search was performed using the following databases: MEDLINE (1966 - February 2001), EMBASE (1980 -February 2001), CINAHL (1982 - February 2001), Cochrane Controlled Trials Register (Issue 1, 2001 of Cochrane Library) and abstracts from the annual meetings of the Society of Pediatric Research, American Pediatric Society and Pediatric Academic Societies published in Pediatric Research (1991-2000). No language restrictions were applied.

Selection criteria applied to the clinical trials were: 1. The population had to be preterm neonates 2. The intervention had to be administration of a1PI compared to placebo or no treatment within the first week of life 3. The eligible studies had to include any of the following outcomes: a. prevention of CLD b. reduction in duration of assisted ventilation c. reduction in the duration of oxygen requirement d. reduction in the need for systemic antiinflammatory therapy e. reduction in mortality or f. reduction in long term adverse neurological sequelae. 4. The trial had to be randomized or quasi-randomized.

The methodological quality of the trials was assessed using the information provided in the studies and by personal communication with the authors. Data on relevant outcomes were extracted and the effect size was estimated and reported as pooled relative risk (RR), risk difference (RD) and weighted mean difference (WMD) as appropriate. Two strategies were used for analysis : 1. Comparison of 60 mg/kg/dose of a1PI administered for 4 days in first 2 weeks after birth, versus placebo and 2. Comparison of any dose of a1PI administered in first 2 weeks after birth, versus placebo.

Two eligible studies were identified. The methodological qualities of identified studies were good. One study randomized infants to either placebo, or a1PI 60 mg/kg/dose for four doses while in the second study the same investigators explored the efficacy of different dose regimens of a1PI compared to placebo. There was no statistically significant difference in the development of CLD at 36 weeks PMA amongst all randomized infants. For 60 mg/kg/dose for four doses of a1PI compared to placebo the pooled RR was 0.64 [95% CI 0.35, 1.18] and RD was -0.10 [95% CI -0.23, 0.03] while for any doses of a1PI the pooled RR was 0.79 [95% CI 0.44, 1.41], RD was -0.05 [95% CI -0.17, 0.06]. There was a trend towards reduced risk of development of oxygen dependency at 28 days postnatal age, pooled RR 0.81 [95% CI 0.64, 1.01], RD -0.14 [95% CI -0.29, 0.00] for 60 mg/kg/dose for four doses of a1PI compared to placebo. The pooled RR was statistically significant, RR 0.80 [95% CI 0.65, 0.98], RD -0.15 (95 % CI -0.29, -0.01) when any doses of a1PI were combined. The number of patients needed to treat (NNT) with a1PI to prevent one infant developing oxygen dependency at 28 weeks was 7. The benefits of short-term outcomes did not remain for long-term outcomes such as CLD and/or death at 36 weeks post menstrual age (pooled RR 0.84 [95% CI 0.53, 1.34], RD -0.06 [95% CI -0.20, 0.09] for 60 mg/kg/dose and pooled RR 0.95 [95% CI 0.61, 1.49], RD -0.02 [95% CI -0.15, 0.12] for any dose) or risk of development of long term neurodevelopmental abnormalities (pooled RR 1.29 [95% CI 0.43, 3.90], RD 0.03 [95% CI -0.11, 0.18]). In addition, no statistically significant difference was noted in other respiratory parameters such as duration of oxygen requirement or respiratory support.

Prophylactic administration of a1PI did not reduce the risk of CLD at 36 weeks or long term adverse developmental outcomes in preterm neonates.