Cardiopulmonary Physiology of Hypoxemic Respiratory Failure Among Preterm Infants with Septic Shock.

Objective: To examine cardiopulmonary physiological alterations associated with hypoxemic respiratory failure (HRF; fraction of inspired oxygen ≥0.60) among preterm neonates requiring vasopressors/inotropes during sepsis (septic shock).

Study Design: We conducted a retrospective cohort study from 2015 through 2022 at a tertiary neonatal intensive care unit. Neonates <34 weeks gestational age who had septic shock and underwent a comprehensive targeted neonatal echocardiography (TNE) ≤72 hours of sepsis onset were included. TNE findings of patients with shock and HRF were compared with those with shock without HRF. Indices of pulmonary vascular resistance (PVR), right ventricular (RV) and left ventricular (LV) systolic and diastolic function, measured using conventional, tissue Doppler imaging and speckle-tracking echocardiography, were examined.

Results: Of 52 included infants with septic shock, 19 (37%) also had HRF. Baseline characteristics were similar. On TNE, although the HRF group more frequently had bidirectional/right-to-left flow across the patent ductus arteriosus (67% vs 33%; P = .08), all indices of PVR and RV function were similar. However, the HRF group demonstrated reduced LV systolic function (ejection fraction, 51.8% ± 12.3% vs 62.6% ± 13.0%; global peak systolic longitudinal strain -15.2% ± 4.5% vs -18.6% ± 4.5%), diastolic function (early [2.3 ± 1.0/s vs 3.6 ± 1.2/s]) and late (2.4/s [IQR, 1.9-2.6/s] vs 2.8/s [2.3-3.5/s] diastolic strain rate), and higher frequency of LV output <150 mL/min/kg (44% vs 12%) (all P < .05).

Conclusions: Acute HRF occurring in preterm neonates with septic shock is associated with alterations in TNE measures of LV function, and not PVR or RV function. Future studies should evaluate the impact of supporting LV function in these patients.