Browsing by Autor "Niermeyer, Susan"

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Does neonatal resuscitation deserve a special chapter?
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2001) Niermeyer, Susan
Neonatal resuscitation has developed into a distinct sub-discipline of pediatric resuscitation, which itself stands apart from adult cardiopulmonary resuscitation. What justifies this separate and special status? Does neonatal resuscitation, in fact, deserve a special chapter? This lecture will present the unique facets of physiology and pathophysiology in the newly born infant that necessitate an approach to resuscitation different from any other time in the lifespan. Using this physiology as a basis, the specific steps in neonatal resuscitation will be examined for their differences from the general pediatric recommendations. Changes in the International Guidelines for Neonatal Resuscitation published in 2000 will be presented in the context of the supporting evidence evaluation. Future directions for neonatal resuscitation will be examined with respect to the basic science of resuscitation, clinical applications, and the unique opportunities for prevention and prenatal intervention. The physiology of the newly born infant differs from that at any other point in the lifespan of a human being. The newly born infant must make a rapid transition from reliance on the placenta as the organ of respiration to use of the lungs for oxygenation and ventilation. Within a matter of seconds, the alveoli change from sacs distended with fluid to air-filled spaces where gas exchange occurs between the atmosphere and the blood. During fetal life, pulmonary blood flow represents only a small fraction of cardiac output, as much of the fetal venous return is shunted through the foramen ovale (from the right to the left heart) and ductus arteriosus (from the pulmonary artery to the aorta) [Figure 1]. Pulmonary blood flow rises dramatically after birth as the lungs expand physically with air. Both physical expansion of the lung and the vasodilatory effect of higher oxygen concentrations in the alveoli and the bloodstream contribute to a relaxation of pulmonary arteries and arterioles and a fall in pulmonary vascular resistance and pulmonary artery pressure. With lowering of right-sided pressures, the fetal shunts at the level of the foramen ovale and ductus arteriosus close functionally, and then anatomically.
Neonatal oxygenation, pulmonary hypertension, and evolutionary adaptation to high altitutde (2013 Grover Conference series)
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2015) Niermeyer, Susan
Abstract. Andeans and Tibetans have less altitude reduction in birth weight than do shorter-resident groups, but only Tibetans are protected from pulmonary hypertension and chronic mountain sickness (CMS). We hypothesized that differences in neonatal oxygenation were involved, with arterial O2 saturation (SaO2) being highest in Tibetans, intermediate in Andeans, and lowest in Han or Europeans, and that improved oxygenation in Andeans relative to Europeans was accompanied by a greater postnatal decline in systolic pulmonary arterial pressures (Ppasys). We studied 41 healthy (36 Andeans, 5 Europeans) and 9 sick infants at 3,600 m in Bolivia. The SaO2 in healthy babies was highest at 6–24 hours of postnatal age and then declined, whereas sick babies showed the opposite pattern. Compared to that of 30 Tibetan or Han infants studied previously at 3,600 m, SaO2 was higher in Tibetans than in Han or Andeans during wakefulness and active or quiet sleep. Tibetans, as well as Andeans, had higher values than Han while feeding. The SaO2’s of healthy Andeans and Europeans were similar and, like those of Tibetans, remained at 85% or above, whereas Han values dipped below 70%. Andean and European Ppasys values were above sea-level norms and higher in sick than in healthy babies, but right heart pressure decreased across 4–6 months in all groups. We concluded that Tibetans had better neonatal oxygenation than Andeans at 3,600 m but that, counter to our hypothesis, neither was SaO2 higher nor Ppa lower in Andean than in European infants. Further, longitudinal studies in these 4 groups are warranted to determine whether neonatal oxygenation influences susceptibility to high-altitude pulmonary hypertension and CMS later in life.
Postnatal changes in the pulmonary circulation at 3700-4000 m
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2002) Niermeyer, Susan
Objective: The hypoxia of high altitude can impair postnatal changes in the pulmonary circulation. We documented pulmonary artery pressures (PPA) and persistence of fetal circulatory patterns among infants born at 3700–4000m in La Paz, Bolivia. Methods: Echocardiography was performed at 2 weeks, 1, 3, and 6 months on 16 infants. PPA was estimated using pulmonary valve systolic intervals in the regression equation of Wan-zhen. Persistence of the foramen ovale (PFO) and ductus arteriosus (PDA) was noted. Results: Twelve of 14 term infants had a PFO diagnosed in the first 3 months. Half of these persisted at 3 months. PPA was elevated in the first 3 months and at 6 months approached values considered normal during childhood at 3700m. Two premature infants experienced clinical pulmonary hypertension, one acutely after birth and one subacutely (3 months). Conclusion: Postnatal changes in the pulmonary circulation occur slowly at high altitude, with greater vulnerability to incomplete or disrupted transition