Summary of Adaptações à vida extrauterina - Guyton capítulo 84

00:00:00 - 00:35:00

In the YouTube video titled "Adaptações à vida extrauterina - Guyton capítulo 84," the speaker discusses the various adaptations a newborn undergoes after birth to adjust to life outside the womb. Topics covered include the newborn's initial respiration, temperature change, potential causes of hypoxia during childbirth, the importance of surfactant and negative pressure for proper lung expansion, circulatory adjustments, and the process of closing the umbilical vein. The speaker also touches on newborns' circulatory system parameters, their high intake and output of fluids, and the use of the Apgar scale to evaluate newborn vitality. Throughout the discussion, the speaker emphasizes the newborn's susceptibility to hypoxia and the importance of proper adaptation to ensure their survival.

• 00:00:00 In this section of the video titled "Adaptações à vida extrauterina - Guyton capítulo 84," the speaker discusses the adaptations a newborn undergoes after birth to adjust to life outside the womb. The first topic covered is the newborn's initial respiration, which begins as soon as they leave the mother's womb. This is crucial because, before birth, the baby is in a state of hypoxia, meaning they have limited oxygen supply. Upon birth, they must adapt to the new environment and start breathing to receive oxygen. Additionally, the newborn experiences a change in temperature as they leave the warm uterine environment for the cooler outside world, which stimulates their lungs to expand and initiate respiration. The speaker emphasizes that the newborn's respiratory center is more resistant to hypoxia than an adult's, increasing their chances of survival without neurological damage for a certain period. After the initial respiration, the newborn establishes normal breathing within a minute, and any delay in breathing can lead to stimulation from hypoxia and hypercapnia, encouraging the onset of respiration.
• 00:05:00 In this section of the video titled "Adaptações à vida extrauterina - Guyton capítulo 84," the speaker discusses potential causes of hypoxia in newborns during childbirth. A prolonged internal hemorrhage or a mother's excessive use of anesthetics during cesarean or vaginal delivery can cause newborns to be born anesthetized and delay their first respiration. Additionally, compression of the umbilical cord during labor can also cause hypoxia. The contractions of the uterus during labor become increasingly powerful, which can compress the placental vessels and cause further issues. Newborns can tolerate a longer period of hypoxia than adults, but if it lasts more than 8 minutes, there is a strong likelihood of neurological damage. The expansion of the newborn's lungs is crucial for their first breath, and the alveoli are collapsed with a high surface tension that is broken by the presence of surfactant produced by the mother after 30 weeks of pregnancy.
• 00:10:00 In this section of the YouTube video titled "Adaptações à vida extrauterina - Guyton capítulo 84," the speaker discusses the importance of surfactant and sufficient negative pressure for a newborn's lungs to expand properly. When a newborn lacks sufficient surfactant or negative pressure, they may experience difficulty expanding their lungs, leading to the need for medical intervention. The speaker explains that during a newborn's first breaths, they require a high negative pressure, which can be seen in the provided graph. After the initial period of compliance, the newborn's respiration begins to normalize, resembling that of an adult. However, if a newborn is premature or lacks the ability to produce sufficient surfactant, they may develop a condition called the "hyaline membrane disease" or "acute respiratory distress syndrome," where the alveoli are filled with protein-rich liquid, making it difficult for the lungs to function properly.
• 00:15:00 In this section of the YouTube video titled "Adaptações à vida extrauterina - Guyton capítulo 84," the speaker discusses the circulatory adjustments that occur during birth. The fetus experiences an increase in systemic vascular resistance due to the loss of placental blood flow. This increase in resistance leads to an increase in both right and left atrial pressures, which is crucial for the closure of certain heart sites. The heart functions in series in an adult human, and the fetus must adapt to this new way of functioning. Additionally, there is a reduction in pulmonary vascular resistance due to the expansion of the lungs during the first breath. This reduction in resistance leads to a decrease in pulmonary arterial pressure, which has significant implications for the ductus arteriosus. Within hours of birth, the ductus arteriosus begins to constrict, leading to an inversion of flow in the double arteriosus.
• 00:20:00 In this section of the YouTube video titled "Adaptações à vida extrauterina - Guyton capítulo 84," the speaker discusses the process of closing the umbilical vein after birth. The vein, which carries oxygenated blood from the mother to the fetus, will be obstructed by fibrous tissue within one to eight days after birth. This occurs because the presence of oxygenated blood in the ductus arteriosus, which was not present before, does not stimulate the smooth muscle lining the vessel to contract and increase its size for better oxygen supply. Additionally, the large prostates that help dilate the ductus arteriosus will have reduced production and presence in the arterial wall, making it easier for the ductus to constrict. The closure of the umbilical vein is crucial for preventing blood from flowing into the liver of the newborn and instead allowing it to enter the systemic circulation. The speaker also mentions that newborns have low glycogen stores and are unable to produce enough glucose on their own, leading to hypoglycemia. They rely on their ability to use fat and proteins for nutrition until they can start feeding. Newborns also lose 5-10% of their body weight in the first two days due to fluid loss, which returns to normal with feeding. The speaker also touches on the respiratory system of newborns, which has a respiration frequency of 40 breaths per minute, a respiratory volume of 3 mL, and an inspiration volume of 640 mL per minute.
• 00:25:00 In this section of the YouTube video titled "Adaptações à vida extrauterina - Guyton capítulo 84," the speaker discusses the circulatory system and related parameters of a newborn's circulation. At birth, a newborn's volume is around 300 ml, and an umbilical cord order or longer time attached to the placenta can result in an additional 75 ml increase. This excess blood is later corrected by plasma absorption. The newborn's hemoglobin count is higher than an adult's, which can help the baby but may also lead to mild pulmonary edema. The newborn's cardiac output is about two times higher than an adult's, and their arterial pressure starts at around 70/50 mmHg, increasing to 90/60 mmHg in the first few months and reaching approximately 115/70 mmHg in adolescence. The newborn's hemoglobin count is around 4 million cells per milliliter, which can be increased due to umbilical cord orders or longer time attached to the placenta. Newborns have fewer erythropoiesis, or hemoglobin production, due to a lack of stimuli, resulting in lower hemoglobin levels. The newborn's leukocyte count is around 45,000 cells per milliliter, which is five times higher than an adult's. The speaker then discusses jaundice, which is common in newborns, and is related to hyperbilirubinemia, or an excess of bilirubin in the body. The newborn's immature liver cannot conjugate bilirubin correctly with glycorrhonic acid, leading to an inability to produce bile and excrete it through feces, resulting in jaundice. In the case of fetal hemolytic disease, the jaundice is more pronounced and does not reduce easily, as it is caused by the destruction of fetal hemoglobin and the release of excess bilirubin during fetal life.
• 00:30:00 In this section of the video titled "Adaptações à vida extrauterina - Guyton capítulo 84," the speaker discusses the newborn's high intake and output of fluids, which can lead to dehydration or overhydration due to the accelerated metabolism and immature renal function. The newborn's liver function is also reduced, leading to metabolic acidosis, hypoproteinemia, hypoglycemia, and hypocoagulability. To correct the coagulation deficiency, vitamin K is administered. The newborn's digestion and absorption of food differ from older children, with a lower capacity to metabolize carbohydrates and absorb fat. The newborn's metabolism is increased due to a high metabolic rate and poor temperature regulation, leading to a significant loss of heat. To prevent heat loss, it is recommended to keep the newborn warm by avoiding baths and wearing diapers.
• 00:35:00 In this section of the YouTube video titled "Adaptações à vida extrauterina - Guyton capítulo 84," the speaker discusses evaluating the vitality of newborn babies using the Apgar scale. Factors assessed include heart rate, respiratory effort, muscle tone, reflex irritability, and color. A newborn should not be cyanotic or pale, but rather rosy. A low score on the Apgar scale may indicate the need for reanimation. The speaker emphasizes the importance of evaluating a newborn's vitality in the first and fifth minutes of life and comparing the results to ensure proper development.