Tracheal suctioning improves gas exchange but not hemodynamics in asphyxiated lambs with meconium aspiration

Abstract

BackgroundCurrent neonatal resuscitation guidelines recommend tracheal suctioning of non-vigorous neonates born through meconium stained amniotic fluid.MethodsWe evaluated the effect of tracheal suctioning at birth in 29 lambs with asphyxia induced by cord occlusion and meconium aspiration during gasping.ResultsTracheal suctioning at birth (n=15) decreased amount of meconium in distal airways (53±29 particles/mm2 lung area) compared to no-suction (499±109 particles/mm2, n=14, p<0.001). Three lambs in the suction group had cardiac arrest during suctioning requiring chest compressions and epinephrine. Onset of ventilation was delayed in the suction group (146±11 vs. 47±3 sec in no-suction group, p=0.005). There was no difference in pulmonary blood flow, carotid blood flow, pulmonary or systemic blood pressure between the two groups. Left atrial pressure was significantly higher in the suction group. Tracheal suctioning resulted in higher PaO2/FiO2 levels (122±21 vs. 78±10 mmHg) and ventilator efficiency index (0.3±0.05 vs.0.16±0.03). Two lambs in the no-suction group required inhaled NO. Lung 3-nitrotyrosine levels were higher in the suction group (0.65±0.03 ng/μg protein) compared to the no-suction group (0.47 ± 0.06).ConclusionTracheal suctioning improves oxygenation and ventilation. Suctioning does not improve pulmonary/systemic hemodynamics or oxidative stress in an ovine model of acute meconium aspiration with asphyxia.

Neonatal resuscitation adhering to oxygen saturation guidelines in asphyxiated lambs with meconium aspiration

“…Hence resuscitation with 21% oxygen was probably adequate to achieve SpO 2 in the target range. In the current study, we have used a model with meconium aspiration resulting in elevated AaDO 2 (264 ± 37 in asphyxiated lambs and 69 ± 11 mm Hg in control lambs) secondary to ventilation–perfusion mismatch and pulmonary hypertension (9). Resuscitation with 21% oxygen alone in this model did not achieve target SpO 2 ( Figure 1 ) and limited the increase in pulmonary blood flow ( Figure 6a ).…”

“…Catheters were placed in the main pulmonary artery and left atrium for pressure monitoring as previously described (20,21). Fetal lambs were asphyxiated by umbilical cord occlusion and meconium (5 ml/kg of 20% meconium suspended in ewe amniotic fluid) was instilled into their endotracheal tube as previously described (9). The lambs were then delivered, ventilated, and blood gases were obtained at fetal (predelivery), delivery, 1 min, 2 min, 5 min, 10 min, and 15 min.…”

“…Asphyxia results in hypoxemia and acidosis (8) resulting in lower SpO 2 values at the time of birth (9). Furthermore, in the presence of lung disease (such as meconium aspiration) and increased alveolar–arterial oxygen gradient, 21% inspired oxygen may not be sufficient to achieve the target SpO 2 values recommended by the NRP.…”

“…The aim of our study was to evaluate gas exchange and pulmonary/cerebral hemodynamics during resuscitation in an ovine model of perinatal asphyxia (induced by umbilical cord occlusion) and lung disease (through instillation of meconium through the endotracheal tube) (9) adhering to the current NRP oxygen saturation target guidelines. We compared these results with lambs resuscitated with 21 and 100% inspired oxygen.…”

Continuous End-Tidal Carbon Dioxide Monitoring during Resuscitation of Asphyxiated Term Lambs

“…As previously described [15], approximately 1 g/kg of human meconium was added to warm amniotic fluid from the ewe's uterus (4 ml/kg lamb weight) to a total volume of 5 ml/kg estimated weight and homogenized to form a viscous “thick” meconium solution. The solution was aspirated using an 18G needle with syringe.…”