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The Perinatal Asphyxiated Lamb Model: A Model for Newborn Resuscitation

Birth asphyxia accounts for nearly one million deaths worldwide each year, and is one of the primary causes of early neonatal morbidity and mortality. ...

University at Buffalo

Current neonatal resuscitation guidelines recommend tracheal suctioning of nonvigorous neonates born through meconium-stained amniotic fluid.

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

The oxygenation index (OI = mean airway pressure, MAP × FiO2 × 100 : PaO2) is used to assess the severity of hypoxic respiratory failure (HRF) and persistent pulmonary hypertension of the newborn (PPHN). An indwelling arterial line or arterial punctures are necessary to obtain PaO2 for the calculation of OI. Oxygenation can be continuously and noninvasively assessed using pulse oximetry. The use of the oxygen saturation index (OSI = MAP × FiO2 × 100 : SpO2) can be an alternate method of assessing the severity of HRF.

Oxygen saturation index and severity of hypoxic respiratory failure.

The Neonatal Resuscitation Program (NRP) recommends upper and lower limits of preductal saturations (SpO2) extrapolated from studies in infants resuscitated in room air. These limits have not been validated in asphyxia and lung disease.

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

The Neonatal Resuscitation Program (NRP) recommends close monitoring of oxygenation during the resuscitation of newborns using a pulse oximeter. However, there are no guidelines for monitoring carbon dioxide (CO2) to assess ventilation. Considering that cerebral blood flow (CBF) correlates directly with PaCO2, continuous capnography monitoring of end-tidal CO2 (ETCO2) may limit fluctuations in PaCO2 and, therefore, CBF during resuscitation of asphyxiated infants.

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

 Inhaled nitric oxide (iNO) is being increasingly used in preterm infants < 34 weeks with hypoxemic respiratory failure (HRF) and/or pulmonary hypertension (PH).  To evaluate the risk factors, survival characteristics, and lung histopathology in preterm infants with PH/HRF.  Retrospective chart review was conducted to determine characteristics of 93 preterm infants treated with iNO in the first 28 days and compared with 930 matched controls. Factors associated with survival with preterm HRF and smooth muscle actin from nine autopsies were evaluated.  Preterm neonates treated with iNO had a higher incidence of preterm prolonged rupture of membrane (pPROM ≥ 18 hours), oligohydramnios and delivered by C-section. In infants treated with iNO, antenatal steroids (odds ratio [OR],3.7; confidence interval [CI], 1.2-11.3;  = 0.02), pPROM (OR, 1.001; CI, 1.0-1.004;  = 0.3), and oxygenation response to iNO (OR, 3.7; CI, 1.08-13.1;  = 0.037) were associated with survival. Thirteen infants with all three characteristics had 100% (13/13) survival without severe intraventricular hemorrhage (IVH)/periventricular leukomalacia (PVL) compared with 48% survival (12/25,  = 0.004) and 16% severe IVH/PVL without any of these factors. Severity of HRF correlated with increased smooth muscle in pulmonary vasculature.  Preterm infants with HRF exposed to antenatal steroids and pPROM had improved oxygenation with iNO and survival without severe IVH/PVL. Precisely targeting this subset may be beneficial in future trials of iNO.

Early Use of Inhaled Nitric Oxide in Preterm Infants: Is there a Rationale for Selective Approach?

In neonates requiring chest compression (CC) during resuscitation, neonatal resuscitation program (NRP) recommends against relying on a single feedback device such as end-tidal carbon dioxide (ETCO) or saturations (SpO) to determine return of spontaneous circulation (ROSC) until more evidence becomes available.

Continuous capnography monitoring during resuscitation in a transitional large mammalian model of asphyxial cardiac arrest.

To study the impact of implementing a protocol to standardize the duration of observation in preterm infants with apnea/bradycardia/desaturation spells before hospital discharge on length of stay (LOS) and readmission rates.

Apnea, bradycardia and desaturation spells in premature infants: impact of a protocol for the duration of 'spell-free' observation on interprovider variability and readmission rates.

Meconium-stained amniotic fluid (MSAF) during delivery is a marker of fetal stress. Neonates born through MSAF often need resuscitation and are at risk of meconium aspiration syndrome (MAS), air leaks, hypoxic-ischemic encephalopathy, extracorporeal membrane oxygenation (ECMO), and death. The neonatal resuscitation approach to MSAF has evolved over the last three decades. Previously, nonvigorous neonates soon after delivery were suctioned under the vocal cords with direct visualization technique using a meconium aspirator. The recent neonatal resuscitation program (NRP) recommends against suctioning but favors resuscitation with positive pressure ventilation of nonvigorous neonates with MSAF. This recommendation is aimed to prevent delay in resuscitation and minimize hypoxia-ischemia often associated with MSAF. In this review, we discuss the pathophysiology, evolution and the evidence, randomized control trials, observational studies, and translational research to support these recommendations. The frequency of ECMO use for neonatal respiratory indication of MAS has declined over the years probably secondary to improvements in neonatal intensive care and reduction of postmaturity. Changes in resuscitation practices may have contributed to reduced incidence and severity of MAS. Larger randomized controlled studies are needed among nonvigorous infants with MSAF. However, ethical dilemmas and loss of equipoise pose a challenge to conduct such studies.

Approach to Infants Born Through Meconium Stained Amniotic Fluid: Evolution Based on Evidence?

Using Paralytic as Part of Premedication for Elective Intubation of Premature Neonates May Result in Transient Impairment of Ventilation.

The Neonatal Resuscitation Program recommends initial resuscitation of preterm infants with low oxygen (O) followed by titration to target preductal saturations (SpO). We studied the effect of resuscitation with titrated O on gas exchange, pulmonary, and systemic hemodynamics.

Effect of various inspired oxygen concentrations on pulmonary and systemic hemodynamics and oxygenation during resuscitation in a transitioning preterm model.

Article	Year
Tracheal suctioning improves gas exchange but not hemodynamics in asphyxiated lambs with meconium aspiration. Pediatric research\| PubMed ID: 25406897	2015
Oxygen saturation index and severity of hypoxic respiratory failure. Neonatology\| PubMed ID: 25592054	2015
Neonatal resuscitation adhering to oxygen saturation guidelines in asphyxiated lambs with meconium aspiration. Pediatric research\| PubMed ID: 26672734	2016
Continuous End-Tidal Carbon Dioxide Monitoring during Resuscitation of Asphyxiated Term Lambs. Neonatology\| PubMed ID: 26866711	2016
Early Use of Inhaled Nitric Oxide in Preterm Infants: Is there a Rationale for Selective Approach? American journal of perinatology\| PubMed ID: 27627792	2017
Continuous capnography monitoring during resuscitation in a transitional large mammalian model of asphyxial cardiac arrest. Pediatric research\| PubMed ID: 28157836	2017
Apnea, bradycardia and desaturation spells in premature infants: impact of a protocol for the duration of 'spell-free' observation on interprovider variability and readmission rates. Journal of perinatology : official journal of the California Perinatal Association\| PubMed ID: 29120450	2018
Approach to Infants Born Through Meconium Stained Amniotic Fluid: Evolution Based on Evidence? American journal of perinatology\| PubMed ID: 29341045	2018
Using Paralytic as Part of Premedication for Elective Intubation of Premature Neonates May Result in Transient Impairment of Ventilation. American journal of perinatology\| PubMed ID: 29510421	2018
Effect of various inspired oxygen concentrations on pulmonary and systemic hemodynamics and oxygenation during resuscitation in a transitioning preterm model. Pediatric research\| PubMed ID: 29967523	2018

Munmun Rawat

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