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Biomedical subjects

I R Holzman

Publications and source records attributed to I R Holzman.

At least 19 recordsLinked to original sources
PubMed1992

Cerebral blood flow and metabolism in hypothermic circulatory arrest.

Although hypothermic circulatory arrest has been accepted for use in cardiovascular operations, the potential for cerebral injury exists. The mechanism of the cerebral injury remains unclear. To address these questions we studied cerebral blood flow and metabolism. Sixteen puppies were randomly assigned to undergo either 45 or 90 minutes of hypothermic circulatory arrest after perfusion/surface cooling to 13 degrees C. Cerebral blood flow, cerebral oxygen and glucose metabolism, and cerebral vascular resistance measurements were obtained at 37 degrees C, 13 degrees C, 10 minutes after reperfusion, 30 degrees C and 2 and 4 hours after hypothermic circulatory arrest. No neurologic or behavioral changes were observed in any of the long-term survivors (11/16). Metabolic and cerebral blood flow data did not differ between groups. Cerebral blood flow was significantly lower in the late postarrest measurements, whereas oxygen and glucose consumption had returned to baseline values. In the presence of low cerebral blood flow and high cerebral vascular resistance it is notable that control levels of oxygen consumption were attained by abnormally high oxygen extraction. These data strongly suggest a vulnerable interval after hypothermic circulatory arrest in which cerebral metabolism is limited by cerebral blood flow.

Animals↗
PubMed1992

Effect of prazosin on hypoxemia-induced blood flow redistribution in the newborn piglet.

We examined the effect of the alpha 1-adrenergic antagonist prazosin on blood pressure, left ventricular output and blood flow redistribution during normoxemia and mild hypoxemia in the chronically instrumented, unanesthetized newborn piglet employing the radiolabeled microsphere technique. Prior to prazosin, hypoxemia caused increases in aortic pressure and blood flows to the brain, myocardium and diaphragm, accomplished by small, statistically insignificant decreases in flows to the carcass and viscera without an increase in cardiac index. Prazosin treatment during normoxemia caused a fall in blood pressure and resulted in greater blood flows of left ventricular origin to the carcass, myocardium and lung. Hypoxemia after prazosin administration increased not only aortic pressure and blood flows to the brain, myocardium and diaphragm, but also, unlike the situation before drug treatment, cardiac index. Thus, in the newborn piglet, the maintenance of critical organ oxygen delivery during hypoxemia is not blocked by prazosin, but is accomplished by an increase in cardiac index rather than simply by redistribution of blood flow.

Animals↗
PubMed1990

Evolving issues in surrogate motherhood.

Surrogate mothering is an arrangement whereby a woman who gives birth to an infant intends--through a contractual agreement--to give that baby to another couple. The recent Baby M case in the United States has raised numerous legal concerns causing many legislative bodies to consider possible statutes to regulate or prohibit surrogacy. The competing interests among and between the individuals involved in this relationship (i.e., the surrogate mother, the couple, the baby, and society) suggest various ethical issues related to benefits, risks, and autonomy. Legal and ethical concerns surrounding the technologically possible procedure of surrogate motherhood are discussed.

Adoption↗
PubMed1989

The effect of aminophylline on gastrointestinal blood flow and oxygen metabolism in the conscious newborn lamb.

Aminophylline, widely used in the neonatal period, has been reported to be associated with necrotizing enterocolitis. We hypothesized that aminophylline might alter gastrointestinal blood flow and oxygen delivery. The effects of this drug on gastrointestinal (GI) blood flow and oxygen delivery, consumption, and extraction were examined using the radioactive microsphere method in ten chronically catheterized, unanesthetized lambs aged 5-12 days. While cardiac output and systemic oxygen consumption did not change, we found statistically significant increases (p less than 0.05) in small intestinal blood flow as a function of lamb weight and as a percentage of cardiac output. Splanchnic oxygen consumption also increased significantly. The oxygen reserve available to the GI tract can be compromised by aminophylline at levels similar to those used in the human neonate for treatment of apnea.

Aminophylline↗
PubMed1986

Blood flow and oxygen delivery to the organs of the neonatal lamb as a function of hematocrit.

We chronically catheterized 15 newborn lambs (9.5 +/- 2.8 days) and measured the distribution of cardiac output by the radionuclide-microsphere technique at hematocrits ranging from 10 volumes % to 55 volumes %. Seven animals were made progressively anemic and eight polycythemic by means of exchange transfusions. Cardiac output and heart rate increased with decreasing hematocrit while whole body oxygen consumption showed a small decrease during severe anemia. Both cerebral and cardiac blood flow markedly increased during anemia which assured a relatively stable oxygen delivery to both organs. The changes seen for blood flow to the carcass (skin, bones, and muscle) were predictable from the effects of blood viscosity: small decreases in flow at the highest hematocrits and small increases in flow at the lowest hematocrits. Consequently, oxygen delivery was as low as 1 ml of oxygen/min/100 g at a hematocrit of 10 volumes %. Renal blood flow remained unchanged while oxygen delivery fell when hematocrit was decreased. Hepatic oxygenation was measured using a modification of the Fick principle. Hepatic blood flow showed only a small decrease as hematocrit increased and changed minimally during anemia resulting in a falling delivery of oxygen with anemia. A stable hepatic oxygen consumption was assured by a marked increase in oxygen extraction during anemia. Two differing organ responses to changes in hematocrit can be seen in the newborn: the brain and heart vary blood flow to assure an adequate delivery of oxygen while a number of other organs show less blood flow regulation and, most likely, vary oxygen removal from blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia↗
PubMed1985

A method to maintain infant temperature.

A new insulating material (Thinsulate) was used to provide thermal protection for newborn infants. Infant core temperature was measured as part of a randomized study comparing the efficacy of an insulated bunting, an insulated hat, and routine management. The new bunting was superior in terms of its ability to maintain the infant's core temperature on arrival in the regular nursery. Nursing staff and parental acceptance was high, and further consideration should be given to defining the role of this new insulating material in the care of the newborn.

Bedding and Linens↗
PubMed1985

Effects of varying hematocrit on intestinal oxygen uptake in neonatal lambs.

We chronically catheterized 15 newborn lambs (9.5 +/- 2.8 days) and measured intestinal blood flow (Qi) by the radionuclide microsphere technique at hematocrit levels ranging from 10 to 55%. Seven animals were made progressively anemic and eight polycythemic by means of exchange transfusions. Using the Fick principle, we calculated intestinal oxygen delivery (Di o2), oxygen consumption (Vi o2), and oxygen extraction. Initial base-line values were Qi = 195.5 ml . min-1 . 100 g intestine-1, Di o2 = 22.1 ml . min-1 . 100 g-1, Vi o2 = 4.8 ml . min-1 . 100 g-1, and O2 extraction = 22.5%. As the hematocrit was lowered, Di o2 decreased and O2 extraction increased and vice versa when the hematocrit was raised. Vi o2 remained constant, but Qi did not correlate with changes in hematocrit. However, intestinal blood flow, as a percent distribution of total blood flow, decreased with lower hematocrit levels. At no time was there any evidence of anaerobic metabolism as measured by excess lactate production. Our data indicate that the intestines of neonatal lambs are capable of maintaining their metabolic needs over a wide range of oxygen availability induced by a changing hematocrit. The primary mechanism is through alteration of oxygen extraction. Within the range of our experiments, no critically low oxygen availability was attained at which anaerobic metabolism became significant.

Anemia↗
PubMed1985

The effects of sodium nitroprusside on blood flow and oxygen delivery to the organs of the hypoxemic newborn lamb.

Vasodilators are used in newborns under conditions where hypoxia may be prominent. To study the effects of vasodilator therapy on organ oxygen delivery we measured blood flow (using radioactive microspheres) and arterial oxygen content in six chronically catheterized newborn lambs. Cardiac output and its distribution were measured during normoxia, hypoxia (10% O2 and 5% CO2), and hypoxia with a nitroprusside infusion. Hypoxia decreased oxygen content but did not change heart rate, mean blood pressure, or cardiac output. When nitroprusside was infused during hypoxemia, oxygen content and heart rate were not affected, but mean arterial blood pressure fell (39% decrease). During hypoxemia, blood flow increased to the heart, brain, and carcass but decreased to the gastrointestinal tract. When nitroprusside was infused during hypoxemia, blood flow decreased to the heart, brain, kidneys, and carcass. Oxygen delivery (arterial O2 content X blood flow) decreased to the brain as well as to kidneys, stomach, and carcass when nitroprusside was given to the hypoxemic lamb.

Animals↗
PubMed1984

Hepatic oxygenation during arterial hypoxemia in neonatal lambs.

We identified the effects of reductions in arterial blood oxygen concentration from 15.0 to 4.0 ml O2/dl blood on hepatic blood flow, oxygen delivery, oxygen consumption and oxygen extraction in nine chronically catheterized lambs, 9 +/- 1 (SD) days of age. Hypoxemia was induced by administering a gas mixture low in oxygen to the unanesthetized lambs. Hepatic blood flow was measured with the radioactive microsphere technique; hepatic oxygen delivery, extraction, and consumption were calculated with modifications of the Fick principle. When the lambs breathed room air, hepatic blood flow was 235 +/- 30 ml/min/100 gm (mean +/- SD); hepatic oxygen delivery, 24.6 +/- 3.0 ml O2/min/100 gm; oxygen extraction, 37 +/- 11%; and hepatic oxygen consumption, 8.9 +/- 1.9 ml O2/min/100 gm. As arterial blood oxygen concentration was reduced from 15 to 6.5 ml O2/dl blood, hepatic blood flow did not change. When the concentration was less than 6.5 ml O2/dl, hepatic blood flow decreased as a result of a decrease in portal blood flow. Hepatic oxygen delivery decreased in the whole range of arterial blood oxygen concentrations studied. Despite reductions in oxygen delivery of up to 50%, hepatic oxygen consumption did not fall because hepatic oxygen extraction increased as compensation. Oxygen consumption, however, was stable only when hepatic blood flow did not change in response to hypoxemia. When hepatic blood flow fell, hepatic oxygen consumption also fell. Our data indicate that hepatic oxygen requirements can be met during hypoxemia by increases in hepatic oxygen extraction as long as hepatic blood flow does not change. When hepatic blood flow falls, hepatic oxygen consumption decreases even though oxygen reserves are still present. These data indicate that hepatic oxygenation in the neonate, as in the adult, is dependent on stable hepatic perfusion rather than adequate oxygen supply.

Animals↗
PubMed1984

Blood flow and oxygen delivery to fetal organs as functions of fetal hematocrit.

The purpose of our experiments was to relate blood flow and oxygen delivery (blood flow x arterial blood oxygen concentration) to fetal organs as functions of fetal hematocrit. In 12 chronically catheterized fetal lambs, we observed two patterns of responses of fetal organs and tissues to isovolemic alterations in fetal hematocrit from 12% to 55%. In group 1 organs (brain, heart, adrenal glands), blood flows increased as hematocrit was either raised or lowered from normal such that oxygen delivery to these organs was stable over the entire range of hematocrits studied. In group 2 organs (gastrointestinal tract organs, spleen, kidneys, placenta, and carcass), blood flows varied little over the range of hematocrits from 12% to 40% or 45% but decreased at hematocrits greater than or equal to 40% to 45%. Because of these flow responses, oxygen delivery to these organs and tissues was maximal at hematocrits ranging from 32% to 38%. Our data indicate that the various organs of the unanesthetized fetal lamb respond in different ways to alterations in hematocrit. It is of particular interest that, in the great majority of the organs of the fetus, oxygen delivery is maximal at hematocrits considered normal for the fetal lamb in utero.

Adrenal Glands↗
PubMed1980

Nonimmunologic hydrops fetalis: a review of 19 cases.

Nineteen cases of nonimmunologic hydrops fetalis occurring during a nine-year period were reviewed. The pregnancies were complicated by hydramnios (78%) and preterm delivery (84%). Hydramnios appears to be the most useful indicator of the pregnancy at risk; its occurrence should prompt ultrasonographic investigation for evidence of hydrops. Modalities available for antenatal diagnosis of underlying fetal abnormalities include amniocentesis, serologic tests, fetal cardiac monitoring, radiography, hemoglobin electrophoresis and glucose tolerance testing. A specific cause for the hydrops may not be detectable (42% of our cases were idiopathic). Management of affected pregnancies is influenced by the frequent occurrence of fetal asphyxia and premature delivery. Outcome is poor: only 32% of the babies survived beyond the neonatal period. Symptomatic treatment for the neonate includes fluid restriction, maintenance of blood sugar, support of ventilation and attention to the complications of asphyxia.

Adult↗