Surfactant therapy for neonatal respiratory distress syndrome: a review of Korean experiences over 17 years

Abstract

We undertook a multi-hospital collective study to evaluate outcomes of neonatal respiratory distress syndrome (RDS) patients treated with pulmonary surfactant (PS) over 17 yr in Korea (Group I; 1990/91, Group II; 1996, Group III; 2002, and Group IV; 2007). There were 60 neonates in Group I (16 hospitals), 1,179 in Group II (64), 1,595 in Group III (62), and 1,921 in Group IV (57). We adopted Bomsel's classification to evaluate initial chest radiographic findings, categorized RDS severities, and classified response types to PS therapy. Almost all cases were treated using a single dose in Groups I and II, but 19.5% received multiple-dose therapy in Group IV. In Group IV, Bomsel's stages III and IV composed 62.9% and initial severities of mild, moderate, and severe RDS were 23.0%, 42.0%, and 35.0%. More infants showed good response in Groups II, III, and IV than in Group I (71.7%, 66.8%, and 69.2% vs. 58.3%). Complications and mortality rate were lower in Group IV than in Groups I, II, and III (mortality rate: 14.3% vs. 40.0%, 30.0%, and 18.7%). We conclude that PS therapy in neonates with RDS had a remarkable impact on improving clinical course and outcomes over 17 yr in Korea.

Keywords: Analysis; Complications; Data Collection; Epidemiology; Mortality; Premature; Pulmonary Surfactants; Respiratory Distress Syndrome, Newborn; Therapeutic Use.

Fig. 1

Total number of respiratory distress syndrome (RDS) cases and of pulmonary surfactant therapy cases (S-Tx) in Group IV (2007), by gestational period (A) and birth weight (B).

Fig. 2

Preparations of PS used to treat RDS patients in the four study Groups. Surfacten® (51.3%), Newfactan® (39.3%), Curosurf® (8.3%), and mixtures of these (1.1%) were administrated in Group IV.

Fig. 3

Overall incidence of RDS by gestational period (A) and birth weight (B) among in-born neonates in Group IV. Gestational age and birth weight were found to be inversely proportional to the incidence of RDS.

Fig. 4

Proportions of RDS patients in Group IV who received PS replacement therapy by gestational period. The figure shows that use of pulmonary surfactant therapy increased as gestational age is short.

Fig. 5

Birth weight (A) and gestational period (B) distributions in RDS patients that received PS therapy. Low birth weight infants (<2,500 grams), very low birth weight infants (<1,500 grams), and extremely low birth weight infants (<1,000 grams) constituted 87.9%, 56.7%, and 27.5% of total RDS patients, respectively (A) and prematurity (gestational period <37 weeks) was 93% of total RDS patients (B). (%), Percentage in RDS patients that received PS therapy.

Fig. 6

Initial chest radiographic findings in Groups III (2002) and IV (2007). Initial chest radiographic findings before pulmonary surfactant therapy were classified using Bomsel's Classification. Patients with relatively severe RDS (stages III and IV) composed 67.7% and 62.9% of patients in Groups III and IV, respectively.

Fig. 7

Initial ventilatory indices of each study Group according to the classification of Fujiwara et al. (8). Ventilatory index is a recognized respiratory index. Mild respiratory distress patients were 23.0% of total RDS patients, moderately affected patients were 42.0%, and severe respiratory distress patients were 35.0% in Group IV.

Fig. 8

Early response rates to pulmonary surfactant therapy in the four study groups. In Group IV, 69.2% responded well, 14.4% relapsed, and 16.4% responded poorly.

Fig. 9

Changes in RDS mortality rates over the past 17 yr among those that received PS replacement therapy. Mortality rates were found to have reduced dramatically, that is, from 40%, 30%, 18.7%, to 14.3% in Groups I (1990/1), II (1996), III (2002), and IV (2007), respectively.

Fig. 10

The mortality rates of RDS patients in Group IV who received PS replacement therapy by gestational period (A) and birth weight (B). The figure shows that mortality rates were found to be inversely related to gestational age and birth weight.

Fig. 11

The mortality rates among RDS patients who received PS therapy according to the number of PS treatments administered. Mortality rates for single use in Groups III and IV were 15.6% and 13.0%, respectively, and for multiple use were 24.1% and 16% in Groups III and IV. Presumably because more severe cases were administered multiple PS.