Assessment of cerebral perfusion with contrast-enhanced ultrasound during constriction of the neck mimicking malposition of the BD Odon Device™: a study in newborn piglets.

Abstract

The BD Odon Device™ is a new instrument for operative vaginal birth with potential for preventing maternal, fetal and newborn morbidity/mortality during a complicated second stage of labour. The device is a plastic sleeve with an air chamber inflated around the baby's head which is gently pulled through the birth canal. The aim was to monitor changes in cerebral circulation during constriction of the neck to evaluate a risk of potential malposition of the device. Randomised prospective study. Twelve newborn piglets. The anaesthetised piglets were exposed to hypoxia until base excess was -20 mmol/l and/or mean arterial blood pressure had decreased to 20 mmHg. At reoxygenation, an air chamber was inflated around the neck to 300 mmHg and the piglets randomised into three groups: 10 (n = 5), 5 (n = 5) or 2 (n = 2) minutes' occlusion. Cerebral perfusion was evaluated with transcranial contrast-enhanced ultrasound at four time-points, and analysed in the carotid arteries, basal ganglia, cortex and whole brain. Statistical analysis used ANOVA, linear mixed model, Kruskal-Wallis H-test. Perfusion parameters; peak intensity, time to peak intensity, upslope, mean transit time, area under the curve. The haemodynamic response was comparable between groups. Perfusion parameters showed a slight increase at end hypoxia followed by a decrease during occlusion, especially in the cortex (P = 0.00-0.2). After deflation, perfusion returned towards baseline values. Simulation of malposition of the Odon Device was performed using a newborn hypoxic piglet model. Considerable compression of the neck vessels was applied, with only a moderate decrease in perfusion and with restoration of haemodynamics/cerebral perfusion after decompression. Malposition of Odon Device™ in a piglet model revealed a reversible decrease in cerebral perfusion during neck constriction.