Cerebral Oxygenation of Premature Lambs Supported by an Artificial Placenta

Abstract

An artificial placenta (AP) using venovenous extracorporeal life support (VV-ECLS) could represent a paradigm shift in the treatment of extremely premature infants. However, AP support could potentially alter cerebral oxygen delivery. We assessed cerebral perfusion in fetal lambs on AP support using near-infrared spectroscopy (NIRS) and carotid arterial flow (CAF). Fourteen premature lambs at estimated gestational age (EGA) 130 days (term = 145) underwent cannulation of the right jugular vein and umbilical vein with initiation of VV-ECLS. An ultrasonic flow probe was placed around the right carotid artery (CA), and a NIRS sensor was placed on the scalp. Lambs were not ventilated. CAF, percentage of regional oxygen saturation (rSO2) as measured by NIRS, hemodynamic data, and blood gases were collected at baseline (native placental support) and regularly during AP support. Fetal lambs were maintained on AP support for a mean of 55 ± 27 hours. Baseline rSO2 on native placental support was 40% ± 3%, compared with a mean rSO2 during AP support of 50% ± 11% (p = 0.027). Baseline CAF was 27.4 ± 5.4 ml/kg/min compared with an average CAF of 23.7 ± 7.7 ml/kg/min during AP support. Cerebral fractional tissue oxygen extraction (FTOE) correlated negatively with CAF (r = -0.382; p < 0.001) and mean arterial pressure (r = -0.425; p < 0.001). FTOE weakly correlated with systemic O2 saturation (r = 0.091; p = 0.017). Cerebral oxygenation and blood flow in premature lambs are maintained during support with an AP. Cerebral O2 extraction is inversely related to carotid flow and is weakly correlated with systemic O2 saturation.

Artificial placenta and womb technology: Past, current, and future challenges towards clinical translation

“…[97][98][99][100][101] The model requires vasopressors to stabilize hemodynamics, administration of supraphysiological partial oxygen pressures to ensure adequate oxygenation and reports inconsistent maintenance of ductal patency despite infusion of PGE1. 98,99,102 The group has reported the effect of their AP model on development and function of different organ systems (Table SS1) Note: Based on Berman et al and Rudolph et al 139,140 F I G U R E 1 Stages of pulmonary development and viability in humans and sheep. Based on Schittny et al 108 [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…With persistent effort, average duration of fetal survival in this model was prolonged from 1 day up to almost 2 weeks 97‐101 . The model requires vasopressors to stabilize hemodynamics, administration of supraphysiological partial oxygen pressures to ensure adequate oxygenation and reports inconsistent maintenance of ductal patency despite infusion of PGE1 98,99,102 …”

Effects of an artificial placenta on brain development and injury in premature lambs

“…[24–26] Furthermore, we have previously studied cerebral perfusion and oxygen delivery in lambs supported with the artificial placenta, and similarly observed normal CBF and oxygenation. [27] This preserved perfusion and oxygenation is likely what preserves white-matter integrity in premature lambs supported by the AP. WM injury is a known consequence of cerebral hypoxia and hypoperfusion, also demonstrated in fetal lamb models.…”

The Various Oximetric Techniques Used for the Evaluation of Blood Oxygenation

“…The review was focused on oximetric measurements on humans, but cerebral oxygenation has also been measured by NIRS and fNIRS on animals, both for physiological and pathological animal research and for the assessment of the techniques. Some references [ 172 , 173 , 174 , 175 , 176 ], not representative of studies describing cerebral NIRS and fNIRS measurements on animals, were presented.…”