Response of the cerebral circulation to profound hypocarbia in neonatal lambs.
نویسنده
چکیده
Hyperventilation to extremely low arterial carbon dioxide tension (PaCO2) has been used in the management of persistent pulmonary hypertension in newborn infants. With progressive hypocarbia, cerebral vasoconstriction occurs, raising the concern that extreme hypocarbia may result in cerebral oxygen deprivation. Therefore, I evaluated regulation of the cerebral circulation during acute hypocarbia in 10 newborn lambs. Whole-brain and regional blood flows measured using radioactive microspheres, arterial and venous (sagittal sinus) blood gases, and oxygen contents were measured in each lamb at four arterial carbon dioxide tensions. Whole-brain oxygen delivery, oxygen consumption, and fractional oxygen extraction were calculated. Finally, arterial and venous lactate concentrations were measured to assess cerebral lactate production. Whole-brain blood flow (CBF) decreased in a nonlinear fashion as PaCO2 ranged from 46 to 12 mm Hg [In(CBF) = 0.025(PaCO2) + 3.38; r = 0.70, p less than 0.001]. Similar responses were demonstrated for all regional blood flows examined. Cerebral fractional oxygen extraction (E) increased in a nonlinear fashion [In(1-E) = 0.023(PaCO2)-1.37; r = 0.80, p less than 0.001], and cerebral metabolic rate for oxygen was unchanged with hypocarbia. Cerebral venous lactate concentration increased significantly (3.49 +/- 0.23 vs. 2.01 +/- 0.22 mM, p less than 0.001) during severe hypocarbia (PaCO2 of less than 22 mm Hg), and the arterial-venous lactate concentration difference became negative. These results demonstrate uniform responses of whole-brain and regional blood flows and stable cerebral oxygen consumption during moderate and severe hypocarbia. Although there is evidence for cerebral lactate production during severe hypocarbia, this is not likely to indicate cerebral hypoxia as oxygen consumption does not change.
منابع مشابه
Regulation of cerebral blood flow after asphyxia in neonatal lambs.
In a postasphyxia neonatal lamb model, the responses of the cerebral circulation to hypoxic hypoxia and changes in systemic arterial blood pressure were examined. Ventilated newborn lambs (n = 14) were subjected to a gradual asphyxial insult, resuscitated, and returned to control ventilator settings. During the time 2-5 hours after asphyxia, the responses of cerebral blood flow (CBF), cerebral ...
متن کاملIncomplete global cerebral ischemia alters platelet biology in neonatal and adult sheep.
Platelets are implicated as etiologic agents in cerebral ischemia and as modulators of neural injury following an ischemic insult. We examined the effects of severe, transient global ischemia on platelet aggregation during 45-min ischemia and 30-, 60-, and 120-min reperfusion in adult and neonatal lambs. We also examined postischemic platelet deposition in brain and other tissues (120-min reper...
متن کاملI-46: Obstetrical Doppler
Accurate assessment of gestational age, fetal growth, and the detection of fetal and placental abnormalities are major benefits of sonography. Color Doppler can be used to assist in the identification of vascular architecture, detection of vascular pathology and visualization of blood flow changes associated with physiologic processes and disease states. The clinical applications of obstetrical...
متن کاملFrequency of Profound Congenital Hearing Loss in Healthy Newborn Infants in Fars Province
Introduction Deafness is one of the most important sensory disturbances at birth. Hearing loss can affect the development of speaking and learning during life. Early diagnosis and intervention improve language outcome. The current study aimed to determine the frequency of profound congenital hearing loss in healthy newborn infants in Fars province. Methods In a multicenter prospective study, f...
متن کاملEffect of nimodipine on cerebral blood flow and metabolism in rats during hyperventilation.
Nimodipine shws promise in the prevention and treatment of brain ischemia. We examined the interaction of nimodipine pretreatment in a dose sufficient to prevent postischemic hypoperfusion and hyperventilation. We studied four groups of rats: normocarbia plus vehicle (Group 1, n = 5), hypocarbia plus vehicle (Group 2, n = 4), normocarbia plus nimodipine (Group 3, n = 7), and hypocarbia plus nim...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Stroke
دوره 19 11 شماره
صفحات -
تاریخ انتشار 1988