Blood lactate level and meconium aspiration syndrome

Approximately 5 % of infants born with a meconium-stained amniotic fluid (MSAF) develop meconium aspiration syndrome (MAS). Early recognition of infants at highest risk for the development of MAS and the prediction of disease severity are important for optimizing the clinical strategies for prevention and treatment. The aim of the present study was to identify the risk factors for MAS and to investigate the effect of blood lactate level on the development of MAS.

Between January 2011 and January 2012, data were recorded with regard to gender, mode of delivery, gestational week, birth weight, 5-min Apgar score, and need for resuscitation of the meconium-stained depressed infants who underwent tracheal aspiration. Moreover, the number of cases developing MAS, blood pH value, and lactate level in capillary blood gases obtained during the first hour after delivery, duration of oxygen supplementation, the number of cases receiving mechanical ventilation and surfactant therapy, duration of hospital stay, and outcomes of the infants were recorded.

The number of live births during the study period was 17,202, and of them, 1,341 (7.8 %) infants were born through MSAF. Of 195 infants who were meconium-stained depressed, 90 were girls and 105 were boys. Their mean gestational week was 39.37 ± 0.89 weeks and mean birth weight was 3,426 ± 634 g. Eighty-four of them were born through cesarean section (C/S), and 111 were born via normal spontaneous labor. For 40 infants, Apgar score at fifth minute was less than 6. In total, resuscitation was performed on 43 (22.9 %) infants. Of the infants, 141 did not develop MAS and 54 developed MAS. While there were no significant differences between infants with and without MAS with regard to gender, delivery route, gestational week, and birth weight, a significant difference was observed regarding the Apgar score (p = 0.0001). The blood pH value in capillary blood gas analysis was less than 7.25 in 18 (28.5 %) cases with MAS and four (3.2 %) cases without MAS. There was no significant difference between infants with and without MAS with regard to blood pH levels (p = 0.031). The mean blood lactate level was 8.5 ± 3.4 mmol/L in the patients with MAS, and there was a significant difference between infants with and without MAS regarding blood lactate level (p = 0.0001). The mean duration of oxygen supplementation was 86.62 ± 66.52 and 44.36 ± 19.03 h in patients with MAS and without MAS, respectively. In total, 30 infants required mechanical ventilation (24 infants with MAS and 6 infants without MAS). In addition to mechanical ventilation, 16 infants with MAS were administered surfactant therapy. The mean duration of hospital stay of infants with MAS was significantly higher than infants without MAS (p = 0.0001). There was a correlation between blood lactate levels, blood pH value, and hospitalization duration (p < 0.05). All of the infants, except one patient, were discharged from the NICU.

In addition to the blood pH value and 5-min Apgar score, increased blood lactate level may be a risk factor for the development of MAS in infants born with MSAF. This may aid in the early detection of MAS and, with appropriate measures taken sooner, reduce morbidity and mortality. Further studies are needed to elucidate the role of lactate level, which is an important indicator of hypoxia during the development of MAS.