(11) Increasing Mean Airway Pressure Is Associated with Decreased Kidney Oxygenation in Premature Neonates Receiving Positive Pressure Ventilation

Derek M. Gross, University of Wisconsin School of Medicine and Public Health, Cottage Grove, WI, United States; Matthew Harer, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States

Background: Preterm neonates frequently require positive pressure ventilation (PPV) to support respiratory function during their NICU admission. Careful titration of mean airway pressure (MAP) is essential for these patients to avoid barotrauma and hemodynamic compromise that may lead to acute kidney injury (AKI). Near infrared spectroscopy (NIRS) monitoring has the potential to evaluate the effect of different MAPs by measuring renal regional tissue oxygenation (RrSO2).

Objectives: We sought to determine if increases in MAP result in decreases in kidney oxygenation.

Design/Methods: A retrospective analysis of MAP and RrSO2 was performed on preterm neonates < 32 weeks’ gestation who were enrolled in a prospective NIRS monitoring study. INVOS NIRS sensors were placed on neonates within 48 hours of age and monitored RrSO2 every 5 seconds until 7 days of age. We obtained hourly MAP recordings from chart review and compared them with hourly averages of RrSO2 at the corresponding time points. Statistical analysis with simple linear regression, Mann-Whitney U tests, and Fisher’s exact test were performed with GraphPad Prism 9.

Results: Of the 35 neonate cohort, 18 received invasive mechanical ventilation (IMV) and 20 received noninvasive ventilation (NIV) between 2-7 days of age. The average gestational age and birth weight was lower for the IMV group compared to the NIV group (Table 1). The median MAP was greater for the IMV group) compared to the NIV group (8.4 vs. 5, p < 0.01, Figure 1). RrSO2 was negatively correlated with MAP for both the IMV group and the NIV group (r2 = 0.22, p < 0.01; r2 = 0.13, p < 0.01; Figure 2 and 3). These negative correlations remained significant after excluding neonates diagnosed with AKI during study enrollment (IMV: r2 = 0.21, p < 0.01; NIV: r2 = 0.05, p < 0.01).

Conclusion: In this pilot analysis, RrSO2 was negatively correlated with MAP regardless of the presence of AKI in preterm neonates who received IMV and in those that received NIV. These results suggest that NIRS monitoring can detect an effect of increasing MAP on kidney perfusion and oxygenation. Further studies are needed to discern the mechanisms by which PPV affects kidney perfusion and oxygenation with techniques like functional echocardiography and kidney ultrasounds. Future protocols to treat low renal oxygenation in preterm neonates could include decreasing MAP as an intervention.