Perfusion index in preterm newborns: predictive value for morbimortality and association with Apgar score at five minutes and CRIB-II score

Sérgio Costa Monteiro, Liane Correia-Costa, Elisa Proença


Introduction: Perfusion index (PI) is a noninvasive indirect method of microcirculation measurement that might have a potential to predict morbimortality in preterm newborns. This study aims: 1) to define a critical value for post-ductal PI related to the morbimortality in preterm newborns under 32 weeks; 2) to define a prognostic value for post-ductal PI to predict that risk of morbimortality; and 3) to associate post-ductal PI values with the Apgar score at five minutes and the Clinical Risk Index for Babies II (CRIB-II) score.

Material and methods: This is an observational study, with a prospective character, performed in a Neonatal Intensive Care Unit that enrolled 34 preterm newborns with less than 32 weeks admitted between 1st February 2016 and 1st February 2017. Post-ductal PI values were evaluated in the newborns’ feet at 24 hours of life. The Apgar score was registered at birth and CRIB-II score was calculated. The other clinical variables, including the presence of an adverse outcome and/or death, was assessed in clinical records.

Measurements and main results: We found significant correlations between post-ductal PI values, Apgar score at five minutes and CRIB-II score. The area under ROC curve was higher for CRIB-II score and lower for Apgar score at five minutes. The best cut-off points were: 1) post-ductal PI value ≤ 0.72; 2) Apgar score at five minutes < 6; and 3) CRIB-II score > 9. Preterms within these cohorts have higher rates of morbimortality. Post-ductal PI values ≤ 0.72 were an independent predictor of mortality in preterm newborns (p-value = 0.047).

Conclusions: This study suggests that post-ductal PI value ≤ 0.72 at 24 hours of life might be a potential predictor of morbimortality in preterm newborns. However, it is important to clarify that this study has a small representative population which can reduce the accuracy of the results. The very high morbimortality rate in this cohort is another strong limitation for the quality of the results.


perfusion index; pulse oximeter; post-ductal; preterm; mortality; morbidity

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