Introduction: Perfusion index (PI) is a noninvasive method of peripheral perfusion measurement. Previous publications suggest that PI might be an useful and accurate predictor of morbidity and mortality risk in preterm newborns. This study aims: 1) to assess the PI values of preterm newborns (< 37 weeks) in the first seven days of life according to gestational age; 2) to assess differences in PI values between healthy preterm newborns and those who developed adverse outcomes during the neonatal period.
Material and methods: This is a prospective observational study performed in a Neonatal Intensive Care Unit that enrolled 60 preterm newborns with less than 37 weeks admitted between 1st February 2016 and 1st February 2017. Post-ductal PI was evaluated in the newborns’ feet in the first hour and at 24 hours, 48 hours, 72 hours and 168 hours of life. The presence of an adverse outcome and/or death in the neonatal period was assessed in clinical records, along with several other clinical variables.
Results: We found a non-significant trend towards decreasing PI values in the first 2 days of life, with an increase at 48 hours and stable values at 72 hours after birth. PI values had an inverse relationship with gestational age (p for linear trend: 24 hours, p = 0.029; 48 hours, p = 0.001; 72 hours, p = 0.037; 168 hours, p = 0.001). The most prevalent adverse outcomes were shock (n = 8, 13.2%), anemia (n = 10, 16.7%) and intraventricular hemorrhage grade > 2 (n = 10, 16.7%). Median PI values were found to be significantly lower in newborns with an adverse outcome (0.90 vs. 0.70 at 24 hours; 0.87 vs. 0.72 at 48 hours; 0.91 vs. 0.79 at 72 hours; and 0.90 vs. 0.80 at 168 hours) and/or death in neonatal period (0.87 vs. 0.55 at 1 hour; 0.80 vs. 0.70 at 24 hours; 0.81 vs. 0.55 at 48 hours; 0.88 vs. 0.74 at 72 hours; and 0.89 vs. 0.49 at 168 hours).
Conclusions: PI values differed according to gestational age and to the presence of comorbidities, confirming that it might represent a valuable tool in the early identification of adverse outcomes in the neonatal period.