tailieunhanh - Critical Care Obstetrics part 13

Critical Care Obstetrics part 13 provides expert clinical guidance throughout on how you can maximize the chances of your patient and her baby surviving trauma. In this stimulating text, internationally recognized experts guide you through the most challenging situations you as an obstetrician are likely to face, enabling you to skillfully:Recognize conditions early-on which might prove life threatening, Implement immediate life-saving treatments in emergency situations, Maximize the survival prospects of both the mother and her fetus | Neonatal Resuscitation Figure Fetal circulation. Reproduced by permission from Faranoff AA Martin RJ eds. Neonatal-Perinatal Medicine Diseases of the Fetus and Newborn 7th edn. St Louis Mosby 2002 417. fetal may occur at the time of delivery or significantly before the events of parturition. It is important to note that intrauterine ischemic events even those quite remote from the delivery of the infant may extend into the newborn period resulting in a compromised infant. Response to hypoxia In the normal fetal circulation blood returning to the heart from the body and placenta is primarily shunted through the foramen ovale to the left side of the heart facilitating oxygenated blood to going to the head and the heart. Blood that reaches the right ventricle is shunted through the ductus arteriosus to the aorta bypassing the lungs as a result of a high pulmonary vascular resistance 3 . This serves the fetus well as the major organ of gas exchange is the placenta Figure . However if the fetus or newborn is subjected to hypoxic conditions the physiologic response is to exacerbate or maintain Figure Pulmonary vascular resistance PVR in the calf. From 3 . an increase in pulmonary vascular resistance. For the neonate without connection to the placenta after the cord is clamped maintenance of the fetal circulation shunts blood away from the lungs the only available organ of gas exchange. In the circumstances of progressive asphyxia the fetus or newborn responds with an increase in systemic vascular resistance or vasoconstriction. This decreases blood flow to the musculature and the intestines while attempting to increase blood flow to the head and heart. Thus blood flow to the cardiac and cerebral vessels is maximized at the expense of non-vital organs. This pattern of blood flow if prolonged results in an increasing acidosis 4 5 . The increasing acidosis along with the hypoxia further increases the pulmonary vascular resistance exacerbating the problem Figure