Background: Lack of cerebral autoregulation predisposes extremely low birth weight (ELBW) infants to extreme swings in cerebral blood pressure which may contribute to intraventricular hemorrhage (IVH) and brain injury. Most critical interventions occurring soon after birth in the delivery room (DR) place them at high risk for hemodynamic instability. A "midline elevated" head positioning strategy after admission to the NICU may decrease likelihood of severe IVH, improve oxygenation and survival; it forms part of quality improvement bundles to reduce IVH in several institutions. However, use of midline, elevated head positioning to optimize transition during resuscitation of ELBW infants has not been evaluated. We hypothesized that midline elevated head position during resuscitation in a periviable ovine model would optimize cerebral perfusion, reduce hemodynamic fluctuations and improve oxygen delivery.
Objective: 1.To evaluate the effect of midline, 15 deg head elevation on hemodynamic parameters: blood pressure (BP), carotid (CBF) and pulmonary (PBF) blood flows b) Cerebral oxygen delivery (DO2) in the immediate post-delivery period, in a periviable lamb model.
Methods: Periviable (120d gestation) beta mature lambs partially exteriorized and instrumented in utero, were randomized into the elevated midline group (ELEV: 15 deg elevation) or standard group (FLAT). Lambs were resuscitated per NRP guidelines with delayed cord clamping for 60 sec and initial FiO2 of 0.3. 3ml/kg of intratracheal surfactant was administered. PBF, CBF, hemodynamic parameters (BP, HR) and pulse oximetry (SpO2) were monitored continuously using Biopac and Nonin systems. Blood gases were collected, and cerebral oxygen delivery (DO2) calculated as CBF * CaO2 (arterial oxygen content). Graphpad PRISM software was used for statistical analysis with quantitative values compared Mann–Whitney U tests and continuous data analyzed by ANOVA.
Results: Baseline characteristics were similar between groups (Table 1). This periviable model demonstrates the absence of autoregulation in the first 10 min after birth with a linear relationship seen between mean arterial blood pressure (MBP) and CBF (Fig 1), in both groups. CBF trended higher and PBF was significantly higher after 5 min with ELEV. Diastolic and MBP were also significantly higher with ELEV. Arterial oxygen content and DO2 at 5 and 10 min, though higher in ELEV, did not demonstrate statistical significance (Table 2).
Conclusions: In this preterm transition model, we clearly demonstrate pressure reactive circulation immediately after delivery. Elevated midline head positioning soon after birth contributes to improved blood pressures and pulmonary blood flow in this periviable model. We speculate that improved ventilation of lower segments of the lungs and better ventilation/perfusion matching could contribute to these findings. Further studies will evaluate the effects of this position on cerebral perfusion pressure.
