Cephalic circulation and oxygen consumption before and after birth

Lucas, William F.; Kirschbaum, Thomas H.; Assali, N.S.

doi:10.1152/ajplegacy.1966.210.2.287

Cited by 55 publications

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“…In two studies of newborn lambs with different invasive techniques, high cerebral blood flow values were demonstrated after clamping of the cord, and thereafter cerebral blood flow decreased as ventilation was begun (l,3). This fall in cerebral blood flow was related to a marked increase in vascular resistance (3). In a study of term newborn infants using a venous occlusion plethysmographic technique a 50% average fall in estimated cerebral blood flow was found during the first 3 h of life (5).…”

Section: Discussionmentioning

confidence: 99%

“…Hence, knowledge about normal cerebrovascular physiology is essential in order to understand the pathogenesis of these disorders and to permit prophylactic measures for infants at risk. Much data have been obtained from animal studies (1)(2)(3). However, these findings may not be applicable to newborn infants due to differences in cerebral anatomy and degree of maturation at birth.…”

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confidence: 99%

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Early Postnatal Changes in Intracranial Arterial Blood Flow Velocities in Term Infants

1987

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ABSTRACT. A range-gated Doppler technique was used to assess intracranial arterial blood flow velocity changes in 20 healthy term infants during the first 3 days after birth. Systolic, diastolic, and mean flow velocity decreased during the first 30 min after birth whereas arterial pressure and heart rate did not change. Mean flow velocity did not change from 30 min to 72 h of life, although systolic and diastolic flow velocity changed in opposite directions. Systolic flow velocity increased to 2 h of age and thereafter decreased. Diastolic flow velocity decreased to a minimum value a t 2 h and thereafter increased to 24 h of age. These flow velocity changes suggest an initial decrease in cerebral perfusion, followed by a constant cerebral blood flow during normal circulatory transition after birth. (Pediatr Res 22: [461][462][463][464]1987) Abbreviations V syst, peak systolic blood flow velocity V diast, end-diastolic blood flow velocity V mean, temporal mean blood flow velocity Disturbances in the cerebral circulation during or after birth are thought to be a major cause of cerebral hemorrhage and ischemic-hypoxic encephalopathy in the newborn infant. Hence, knowledge about normal cerebrovascular physiology is essential in order to understand the pathogenesis of these disorders and to permit prophylactic measures for infants at risk. Much data have been obtained from animal studies (1-3). However, these findings may not be applicable to newborn infants due to differences in cerebral anatomy and degree of maturation at birth. Several noninvasive techniques have been used to evaluate cerebral blood flow in the newborn infant (4). However, few attempts have been made to investigate normal cerebral circulation during the first days of life (5-8), and the effects of early neonatal cardiorespiratory transition on cerebral circulation have not been investigated. In the present study a range-gated Doppler velocimeter was used to measure changes in intracranial arterial blood flow velocities in healthy term newborn infants during the first hours of normal cardiorespiratory transition, and the following 3 days after birth. disproportion, breach presentation, or prior cesarean section. Epidural anesthesia by bupivacaine (n = 17) or general anesthesia induced by barbiturates (n = 3) were used. Parental consent was obtained prior to delivery in all cases, and the study was approved by the local Committee of Ethics.Hematocrit and pH were measured in umbilical arterial blood drawn at birth from the double clamped umbilical cord. Intracranial arterial blood flow velocities were measured with a combined continuous and range-gated Doppler instrument (Alfred, Vingmed A/S, Oslo, Norway). The high pass filter, used to remove low frequency noise, i.e. vessel wall movements, was set at the minimum level (100 Hz). A 2 MHz 8 mm diameter handheld transducer was placed on the anterior fontanel and the ultrasound beam was directed toward the internal carotid artery at the base of the skull. Guided by the velocity signal displayed on an...

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Section: Discussionmentioning

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Early Postnatal Changes in Intracranial Arterial Blood Flow Velocities in Term Infants

1987

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“…It has thus been possible to study many of the changes in circulation associated with ventilation or clamping of the umbilical vessels. Without knowledge of the effects of this technique on the physiological status of the fetus, numerous observations of the distribution of the fetal circulation have been made in fetuses exteriorized from the uterus (8,9). The introduction of techniques to study the fetus in utero (2, 3) has now allowed us to examine the effects of exteriorization on various aspects of fetal circulation.…”

Section: Discussionmentioning

confidence: 99%

Effect of Exteriorization of the Sheep Fetus on Its Cardiovascular Function

Heymann

Rudolph

1967

Circulation Research

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Exteriorized sheep or goat fetuses, with placental circulation continuing, have been extensively used for measurements of fetal cardiovascular function. However, the effects of this procedure on fetal cardiovascular function have not been assessed. We inserted vinyl catheters into an umbilical vein, an umbilical or fetal hindlimb artery, and a hindlimb vein. We measured umbilical arterial and venous blood gas tensions, umbilical blood flow using the steadystate diffusion antipyrine method, and fetal arterial and umbilical venous pressures before and after delivery by cesarean section. Following exteriorization, placental vascular resistance consistently increased and umbilical blood flow decreased. Umbilical venous Po 2 increased, but umbilical arterial and venous pH and Pco L . and arterial Po 2 did not change significantly. Thus exteriorization of the fetus produces major changes in the fetal circulation, but these changes are not indicated by any major alterations in fetal blood gases and pH.ADDITIONAL KEY WORDS fetal exteriorization fetal blood gas tensions placental vascular resistance electromagnetic flowmeter umbilical blood flow antipyrine method• Since Huggett's (1) initial description, exteriorized sheep and goat fetuses have been extensively used for the measurement of fetal cardiovascular function. Various modifications of the original method have been adopted, but they still necessitate removal of the fetus from the uterus. Although much information about fetal physiology has been derived from these experiments, no one has studied the effects of the procedure on the fetus. We have used techniques recently developed for studying the fetus in utero (2, 3) to assess how exteriorization of the fetus may affect some aspects of fetal cardiovascular function and fetal blood gas status. Method Studies were performed on 10 unregistered pregnant sheep with fetuses of gestational ages ranging from 92 to 147 days as determined from nomograms published by Barcroft (4). Following a period of fasting of 12 to 24 hours, hyperbaric low spinal analgesia was given and the ewe was blindfolded and placed on her right side on an operating table. A vinyl catheter was placed in a branch of the maternal femoral artery. We then made a small incision in the ewe's left flank and placed vinyl catheters in the umbilical and lower limb veins and umbilical or hindlimb artery as we have described previously (3). The catheters were then brought out through the incision, and the abdominal incision was closed. Umbilical blood flow was measured in utero by application of the Fick principle, using our modification (5) of the original steady-state diffusion method of Meschia and co-workers (6). Continuous infusion of about 12 mg of antipyrine/min was begun after the abdominal incision was closed; a recovery period of at least an hour was allowed before umbilical flow was first measured.Umbilical venous and arterial and maternal arterial pH, blood gas tensions and blood pressures were monitored intermittently throughout the study....

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“…Dramatic changes occur in the circulation, among which are increases in cardiac output, heart rate, and arterial blood pressure (1,2). Many previous studies designed to examine the transition period have been conducted in anesthetized, acutely exteriorized, and often open-chest preparations of fetal sheep, in which "birth" is designated as the moment the umbilical cord is cut (3)(4)(5)(6)(7). These preparations are unstable and often have cardiovascular and metabolic variables markedly different from those obtained from chronically prepared fetuses studied in utero.…”

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Effects of Birth-Related Events on Blood Flow Distribution

1987

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ABSTRACT. At birth, the cardiovascular system changes dramatically; arterial blood pressure, heart rate, and cardiac output increase, and blood flow distribution undergoes regional changes. To determine whether these changes are related to certain events occurring a t birth, we studied 18 chronically instrumented fetal sheep a t 133-138 days gestational age. We measured fetal vascular pressures and heart rate and injected radionuclide-labeled microspheres to determine combined ventricular output and its distribution. Rhythmic ventilation of the fetuses with a gas mixture that produced no change in arterial blood gases decreased heart rate slightly from 173 + 25 to 152 + 16 beatslmin, but changed neither mean arterial blood pressure nor combined ventricular output. Ventilation with oxygen decreased mean descending aortic and pulmonary arterial pressures, but had no significant effect on heart rate or combined ventricular output; subsequent umbilical cord occlusion had no significant effect on these variables. There was a redistribution of blood flow, however. Ventilation alone increased pulmonary blood flow from 159 + 68 to 641 + 513 ml . min-' ,100 g wet weight-', and oxygenation increased it further to 1040 + 426. Ventilation alone and ventilation with O2 decreased blood flow to most other fetal organs, notably the adrenal glands, brain, and heart, in a manner related to changes in arterial oxygen tension. Occlusion of the umbilical cord increased blood flow to the adrenal glands and brown fat, and also to the liver from the portal vein and hepatic artery. The changes in regional blood flow initiated by ventilathn, oxygenation, and umbilical cord occlusion are similar to those occurring a t birth and may play an important role in postnatal adaptation. (Pediatr Res 22: 634-640, 1987) The transition from intrauterine to extrauterine existence is marked by a number of events, including uterine contractions, delivery, physical expansion of the lungs, increases in blood oxygen tension and content, the removal of the placenta from the circulation, and transfer from a warm-fluid to a cool-air external environment. Dramatic changes occur in the circulation, among which are increases in cardiac output, heart rate, and arterial blood pressure (1, 2). Many previous studies designed to examine the transition period have been conducted in anesthetized, acutely exteriorized, and often open-chest preparations of fetal sheep, in which "birth" is designated as the moment the umbilical cord is cut (3-7). These preparations are unstable and often have cardiovascular and metabolic variables markedly different from those obtained from chronically prepared fetuses Received February 13, 1987; accepted July 29, 1987. Correspondence and reprint requests Harriet S. Iwamoto, Ph.D., Box 0544, HSE 1403, Unlversitv of California. San Francisco. San Francisco, CA 94143. studied in utero. A few studies have been conducted in chronically prepared fetuses undergoing spontaneous labor and delivery (8, 9), but because many events occur at once...

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Cephalic circulation and oxygen consumption before and after birth

Cited by 55 publications

References 0 publications

Early Postnatal Changes in Intracranial Arterial Blood Flow Velocities in Term Infants

Early Postnatal Changes in Intracranial Arterial Blood Flow Velocities in Term Infants

Effect of Exteriorization of the Sheep Fetus on Its Cardiovascular Function

Effects of Birth-Related Events on Blood Flow Distribution

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