Persistent pulmonary hypertension in the newborn

Antenatal corticosteroids increase fetal, but not postnatal, pulmonary blood flow in sheep

The lungs of very preterm infants have immature airways and gas exchange structures and are usually surfactant deficient. Antenatal corticosteroids are commonly used to enhance fetal lung maturation in preterm infants, but little is known of their effects on pulmonary blood flow (PBF) before and immediately after birth. Our aim was to determine the effects of antenatal betamethasone on PBF before birth and during the postnatal transition in very preterm lambs. Antenatal betamethasone treatment significantly increased mean fetal PBF from 20.2 +/- 5.1 to 84.3 +/- 18.3 mL/min at 30 h after administration; the PBF waveform was also significantly altered. Mean diastolic PBF increased from -38.5 +/- 4.9 pretreatment to -10.2 +/- 11.0 mL/min at approximately 36 h after the initial betamethasone dose (negative values indicate retrograde flow away from the lungs). Within 10 min after delivery, PBF was similar in control and betamethasone-treated lambs. These data demonstrate that antenatal betamethasone significantly increases fetal PBF and alters the PBF waveform but has little effect on postnatal PBF.

Delivery room management of the newborn

Neonatal resuscitation is an attempt to facilitate the dynamic transition from fetal to neonatal physiology. This article outlines the current practices in delivery room management of the neonate. Developments in cardiopulmonary resuscitation techniques for term and preterm infants and advances in the areas of cerebral resuscitation and thermoregulation are reviewed. Resuscitation in special circumstances (such as the presence of congenital anomalies) are also covered. The importance of communication with other members of the health care team and the family is discussed. Finally, future trends in neonatal resuscitation are explored.

Positive end-expiratory pressure differentially alters pulmonary hemodynamics and oxygenation in ventilated, very premature lambs

In mature lungs, elevated positive end-expiratory pressure (PEEP) reduces pulmonary blood flow (PBF) and increases pulmonary vascular resistance (PVR). However, the effect of PEEP on PBF in preterm infants with immature lungs and a patent ductus arteriosus is unknown. Fetal sheep were catheterized at 124 days of gestation (term ∼147 days), and a flow probe was placed around the left pulmonary artery to measure PBF. At 127 days, lambs were delivered and ventilated from birth with a tidal volume of 5 ml/kg and 4-cmH2O PEEP; PEEP was changed to 0, 8, and 12 cmH2O in random order, returning to 4 cmH2O between each change. Increasing PEEP from 4 to 8 cmH2O and from 4 to 12 cmH2O decreased PBF by 20.5 and 41.0%, respectively, and caused corresponding changes in PVR; reducing PEEP from 4 to 0 cmH2O did not affect PBF. Despite decreasing PBF, increasing PEEP from 4 to 8 cmH2O and 12 cmH2O improved oxygenation of lambs. Increasing and decreasing PEEP from 4 cmH2O significantly changed the contour of the PBF waveform; at a PEEP of 12 cmH2O, end-diastolic flow was reduced by 82.8% and retrograde flow was reestablished. Although increasing PEEP improves oxygenation, it adversely affects PBF and PVR shortly after birth, alters the PBF waveform, and reestablishes retrograde flow during diastole.

Magnesium sulphate as an alternative and safe treatment for severe persistent pulmonary hypertension of the newborn

Eleven newborns admitted consecutively to the neonatal unit with respiratory failure and severe persistent pulmonary hypertension (PPHN) were included in a clinical trial to assess the efficacy of magnesium sulphate (MgSO4) in the treatment of PPHN. A loading dose of 200 mg/kg MgSO4 was given over 20 minutes, followed by a continuous infusion of 20-150 mg/kg/hour to obtain a magnesium blood concentration between 3.5 and 5.5 mmol/l. Mean (SD) duration of treatment was 75.5 (19.8) hours. No other vasodilatory drug was administered before or during the treatment and patients were not hyperventilated. Mean (SEM) PaO2 values significantly increased from 42.6 (8.8) before treatment to 70.3 (24.1) mm Hg after 24 hours, with no change in pH or PCO2. Oxygen index and alveolar-arterial oxygen gradient (A-aDO2) were significantly lower after 24 hours; respectively, 46.8 (15.2) to 28.0 (9.0) and 624.3 (11.3) to 590 (58) mm Hg. Mean airway pressure could be significantly reduced from 19.5 (3.1) to 13.9 (3.9) cm H2O after 72 hours. Mean ventilatory time support was 131 hours and mean total oxygen dependency 10 days. No systemic hypotension nor any other adverse effect were noted. All infants survived and the neurodevelopmental assessment was normal at 6 and 12 months of age. It is concluded that magnesium sulphate is a non-aggressive and low-cost treatment of short duration which is easy to apply. It may have a role in the various treatment of PPHN.