Background: Aspiration of meconium can cause chemical inflammation, resulting in significant neonatal morbidity and mortality. Meconium aspiration syndrome (MAS) has been associated with elevated inflammatory markers. Antibiotics are widely used in meconium aspiration syndrome (MAS) because the differentiation between MAS and pneumonia can be difficult, and MAS can also be complicated by secondary infection. Patterns of inflammatory marker response to MAS have not been well differentiated from response to infection, making antibiotic management difficult.
Objective: To examine the pattern of inflammatory indices in MAS during the first week of life and correlates with blood culture results.
Methods: As part of a larger antibiotic stewardship initiative, we did a retrospective cohort study of inborn neonates in an academic medical center with level III NICU diagnosed with MAS between 1/1/2015 and 12/31/2018. We included babies who had determinations of C-reactive protein (CRP), white blood cell count (WBC), immature to total neutrophil count (IT ratio) and absolute neutrophil count (ANC) during the 1st week of life. We excluded babies who were transferred or expired within 24 hours without a CRP value. We also collected data on the degree of illness and need for respiratory support.
Results: 84 infants were diagnosed with MAS during the study period, 8 were excluded, for a total study population of 76. Mean gestational age was 40 weeks and birth weight 3.4 kg. The pattern of CRP rise over time showed a peak at 48 hrs. with an average value of 44.0 mg/L (Figure 1). Infants needing respiratory support had higher CRP at 12 hours of life (HOL) (p 0.035) and 24 HOL (p 0.046) compared to infants with normal CRP. High CRP at 48 HOL (p 0.000) was associated with longer duration of antibiotic treatment. IT ratio, WBC and ANC showed similar pattern with peak at 12 HOL, but the values showed no significant correlation with positive blood culture. (Figures 2,3,4). SNAPPE II (Score for Neonatal Acute Physiology with Perinatal Extension) did not correlate with CRP. Two infants had positive blood culture for E. coli and one for Strep. Viridians. Blood culture results showed no significant correlation with the CRPs.
Conclusion: Meconium aspiration syndrome leads to a pattern of rise in CRP with a peak at 48 HOL and decline thereafter. Elevated inflammatory markers correlate poorly with blood culture results and should not be used to justify use of prolonged antibiotics in infants with MAS.
