Fisiología Neonatal: Adaptación y Cambios Fisiológicos en el Recién Nacido

Neonatal Adaptation: Understanding Neonatal Physiology

The neonatal period is a critical time for newborns as they adapt to life outside the womb. During this period, their physiology undergoes significant changes, transforming from an intrauterine state to an extrauterine one. This process supports life during the development from intrauterine physiology to adult physiology. In this article, we will discuss the neonatal physiology and the intricate changes that occur during this transition, focusing on respiratory, cardiovascular, and other systems.

Respiratory System

At birth, newborns transition from an intrauterine environment where the placenta facilitates gas exchange to an extrauterine environment where functional lungs are required for life. This transition involves the loss of the low-pressure placenta and the onset of respiratory effort, leading to increased arterial oxygen tension and decreased pulmonary vascular resistance. Lung surfactant plays a crucial role in these changes, allowing the lungs to mature upon delivery.

Cardiovascular System

Understanding the changes occurring in the cardiovascular physiology of the newborn requires an appreciation of intrauterine fetal circulation and the shunts involved, which include the ductus venosus, foramen ovale, and ductus arteriosus. In the fetal circulation, oxygenated blood from the umbilical vein bypasses the hepatic circulation and is shunted from the right atrium to the left atrium through the foramen ovale. Post-birth, the neonate's circulatory system changes dramatically. The shunts present in the infant's body need to be shut down and remodeled, or failure to do so can cause physiological imbalances and inadequate oxygenation of the brain.

Endocrine System

The endocrine system is responsible for lung maturation of the fetus and the neonate. The release of cortisol via the hypothalamus is crucial for this process, with cortisol levels increasing from 5 to 10 mcg/ml at 30 weeks gestational age, 20 mcg/ml at 36 weeks, 46 mcg/ml at 40 weeks, and 200mcg/ml during labor. Cortisol is responsible for lung maturation, thyroid hormone secretion, hepatic gluconeogenesis, catecholamine secretion, and the production of digestive enzymes. Mature thyroid function appears to help prepare the neonatal cardiovascular system and aid in the regulation of temperature.

Other Systems

The neonatal period is the period of the most dramatic physiologic changes that occur during human life, with other organ systems evolving slowly with time until the transition from intrauterine to adult physiology is complete. While the respiratory and cardiovascular systems change immediately at birth, other systems such as the gastrointestinal and renal systems continue to evolve over time.

Conclusion

The neonatal period is a critical time for humans to adapt to life outside the womb, and the rapid and ever-changing physiology of a newborn is essential in ensuring proper development and preventing physiological imbalances. Understanding the physiology associated with the newborn period allows for a deeper understanding of the complex processes involved in this transition.