Perfusion Index in Preterm Infants during the First 3 Days of Life: Reference Values and Relation with Clinical Variables

Abstract

Background: The perfusion index (PI) derived from pulse oximetry readings represents the ratio of pulsatile (arterial blood) and nonpulsatile contributors to infrared light absorption. PI has been shown to correlate with cardiac performance. In theory, PI is readily available on every pulse oximeter; therefore, no additional sensors or infant handling are required. Currently, reference values are lacking in (preterm) neonates and the association with common clinical conditions is unclear. Objectives: To establish reference values for the PI in premature infants and at the same time determine the influence of common clinical conditions. Methods: PI was prospectively monitored on the lower limb for 72 h in 311 neonates born with a gestational age <32 weeks between January 2011 and December 2013. Longitudinal mixed-effects modeling was used. Linear, quadratic, and cubic models were explored. Main effects and interactions were investigated. Results: A squared model (0-24 h) followed by a linear model (24-72 h) provided the best fit of the data. PI was lowest around 12-18 h after birth and showed a steady increase thereafter. PI was positively related with female gender, gestational age, and pulse pressure. Negative associations were found with SIMV/HFOV ventilation, dopamine administration, mean arterial blood pressure, and arterial oxygen saturation. Although more complex, the general association with a patent ductus arteriosus was positive. Conclusion: PI varied according to several clinical conditions. The association with common clinical factors suggests that PI might be used for monitoring neonatal hemodynamics and possibly as an additional guidance for interventions.

Relationship between perfusion index and patent ductus arteriosus in preterm infants

“…We believe that with PDA there is a decrease in the DC component of the postductal PI due to the overall lower perfusion and decreased mean arterial pressure at the postductal sites (30,31). Furthermore, our findings are consistent with the report by Alderliesten et al (9) who found in a study of 342 neonates that infants with hsPDA had higher postductal PI than infants without hsPDA. They attributed this finding to a hyperdynamic circulation with a widened pulse-pressure resulting in an increase in the AC component.…”

“…We expected to observe a steady preductal PI and a decreased postductal PI leading to a larger ΔPI in infants with PDA. The negative ΔPI (Figure 3) is likely a combination of a decreased preductal PI (reported by Karadag et al (25)) and a postductal PI that is either steady (reported by Vidal et al (12)) or increased (reported by Alderliesten et al (9)). These results have a combined effect towards a negative ΔPI value found in infants with PDA.…”

“…Perfusion index (PI) is a noninvasive measure for monitoring the general hemodynamic status of the preterm infant (9)(10)(11). Perfusion index provides assessment for the pulse strength and is derived from pulse oximetry.…”

“…Perfusion index provides assessment for the pulse strength and is derived from pulse oximetry. PI, measured by infrared light, is calculated as the ratio of the pulsatile (AC) to nonpulsatile components (DC) of the blood flow in tissue (9,10,12,13). In neonates, PI has clinical application.…”

Objective cardiovascular assessment in the neonatal intensive care unit

“…We also determined that this measurement was highly reproducible and that the measurements obtained in the right upper limb were consistently higher than either lower limb, which might reflect transitional circulatory changes. Reference values for continuous PI measurements during the first 3 days of life have been recently published 56. Rather than looking at absolute values, we recently evaluated the temporal evolution of different aspects of the PI signal in a cohort of ELGANs over the first 24 hours of life 57.…”