Perfusion index in the very preterm infant

Aim: Perfusion Index (PI) is a quantifiable measurement of peripheral perfusion and may be a useful adjunct to the assessment of circulatory status in the newborn. (i) To assess reproducibility of PI and (ii) To determine whether there is a difference between simultaneously obtained limb measurements of PI in newborns <32 weeks GA in the transitional period. Methods: Perfusion Index was measured in newborns <32 weeks during the first 48 h of life. To examine reproducibility, the pulse oximetry probe was replaced on the same limb consecutively by the same operator. Upper and lower limbs were then simultaneously evaluated over a 5-min period. Heart rate, blood pressure, birth weight, ventilation requirement, inotrope use, lactate, PCO2 and CRIB-II score were also recorded. Results: Thirty infants were assessed. Intraclass correlation coefficient for reproducibility in the same limb was high (r value = 0.982 p < 0.001). Measurements obtained in the right upper limb were consistently higher than either lower limb. The median (IQR) PI for the entire cohort was 0.70 (0.29-1.35). No correlation existed between gestational age, birth weight, CRIB scores, systolic and diastolic blood pressure, mean blood pressure and median PI values. Conclusion: Perfusion Index measurement is reproducible, and values are highest in the right upper limb. Wide differences between right upper and lower limb readings are most likely related to transitional circulatory changes.