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Biomedical subjects

W E Benitz

Publications and source records attributed to W E Benitz.

At least 37 records · Page 2Linked to original sources
PubMed1992

Noninvasive methods for estimating in vivo oxygenation.

Clinical signs of hypoxia and hyperoxia are nonspecific and unreliable, yet both are potentially injurious. Noninvasive methods of oxygen assessment fill the gap between clinical observation and invasive tests, helping physicians deliver sufficient oxygen with minimum toxicity. Potential sites for oxygen measurement vary between the blood and the mitochondria; each method measures at a different site and detects different types of hypoxia and hyperoxia. Thus, values obtained by two different methods are not equivalent, giving each method unique strengths and weaknesses. We review two clinical methods (pulse oximetry and transcutaneous oximetry), as well as four experimental methods (near-infrared spectrophotometry, magnetic resonance spectroscopy, magnetic resonance saturation imaging, and time-of-flight absorbance spectrophotometry). The principles of each method and the clinical situations in which each succeeds or fails are discussed. A fundamental understanding of each method can help in deciding which methods, if any, are appropriate for a given patient and how best to correct observed oxygenation problems once they are discovered.

Blood Gas Monitoring, Transcutaneous↗
PubMed1990

Endothelial heparan sulfate proteoglycan. I. Inhibitory effects on smooth muscle cell proliferation.

Proliferation of smooth muscle cells is an important component of pulmonary arterial morphogenesis, both during normal development and pathologic remodeling. However, little is known of the factors that regulate smooth muscle proliferation in these vessels. To investigate the hypothesis that factors produced by endothelial cells may regulate smooth muscle cell growth, we studied the effects of culture medium conditioned by fetal bovine pulmonary arterial endothelium on proliferation of smooth muscle cells in culture. This conditioned medium contains an inhibitor of smooth muscle proliferation that is degraded by nitrous acid, heparinase, and heparitinase, but resists degradation by protease, boiling, and chondroitin ABC lyase, indicating that the inhibitor is structurally similar to heparin. Inhibitor release occurs in both growing and confluent endothelial cell cultures and in the presence and absence of serum. A growth-inhibiting proteoglycan purified to homogeneity from endothelial cell-conditioned medium has physicochemical characteristics similar to those of the prototypic basement membrane heparan sulfate proteoglycan of the Englebreth-Holm-Swarm tumor: an overall size of approximately 10(6) D, heparan sulfate chains of 60,000 D, and a buoyant density of 1.33 g/ml. Antibody raised against the tumor basement proteoglycan recognizes this endothelial heparan sulfate proteoglycan, and Western blotting after SDS-PAGE demonstrates that the core proteins of both proteoglycans migrate as a doublet at apparent molecular weights of 450,000 and 360,000 D. Heparan sulfate glycosaminoglycan prepared from purified medium proteoglycan is a potent inhibitor of smooth muscle cell growth, exhibiting activity approximately 1,000 times greater than that of heparin. These results indicate that endothelial cells cultured from fetal bovine pulmonary arteries produce a basement membrane heparan sulfate proteoglycan that is a potent inhibitor of smooth muscle proliferation. This proteoglycan may mediate endothelial regulation of smooth muscle growth during development or pathologic pulmonary arterial remodeling.

Animals↗
PubMed1988

Presence of insulinlike growth factor receptors and lack of insulin receptors on fetal bovine smooth muscle cells.

Previous investigations have demonstrated specific receptors and associated mitogenic actions for insulin and insulinlike growth factors I and II (IGF-I and II) in postnatal bovine aortic smooth muscle. Using fetal tissue we have observed different patterns of binding and action for these peptides. Smooth muscle cells isolated from near-term fetal bovine aortae were studied in early passage. Specific receptors for both IGF-I and IGF-II were identified. Specific binding averaged 5.7%/2.5 X 10(5) cells for IGF-I, and 16.2% for IGF-II, and 0.3% for insulin. High affinity Kd for both IGF receptors were nanomolar. IGF-II was fivefold less potent than IGF-I in displacing IGF-I binding. IGF-I showed no affinity for the IGF-II receptor. Insulin, at physiologic concentrations, was incapable of displacing either IGF-I or IGF-II binding. Cellular incorporation of [methyl-3H]thymidine was stimulated at the lowest dose of IGF-I tested, 0.5 ng/ml. IGF-II showed no effect up to 100 ng/ml, after which a sharp increase in incorporation was noted. Insulin had a similar effect only at concentrations greater than 0.5 micrograms/ml, with a maximal response noted at 5 to 10 micrograms/ml. Our results indicate that fetal bovine aortic smooth muscle cells have an abundance of IGF receptors but lack specific insulin receptors. In addition, IGF-II binding levels are three times higher than for IGF-I. These results are consistent with observations in other species, in which a predominance of IGF over insulin receptors has been demonstrated in fetal tissue, and provide further evidence for a role for the IGFs in embryonic cellular metabolism.

Animals↗
PubMed1988

Refractory neonatal hypoxemia: diagnostic evaluation and pharmacologic management.

Hypoxemia refractory to oxygen administration and assisted ventilation is found in many clinical conditions and results from a variety of pathophysiologic disorders. Recent clinical and laboratory experience has demonstrated that the choice of therapy for an infant with refractory hypoxemia depends upon identification of the underlying etiologic and pathophysiologic conditions. The ideal therapies for many of these conditions have not yet been defined. We have provided, based on our experience, guidelines for selection of the most appropriate of the currently available therapies for many of these patients.

Blood Pressure↗
PubMed1988

Outcome of neonates with birth weights of less than 801 grams.

The follow-up results of intensive care for 68 infants with birth weights less than 801 g treated at Stanford University Hospital were reviewed. The overall survival rate for these infants was 35%, but was 50% for those infants who had been successfully resuscitated in the delivery room and were admitted to the Intensive Care Nursery. Infants under 601 g in weight or less than 25 weeks gestation were more likely to die in the delivery room, but survival among those admitted to the Intensive Care Nursery did not depend on birth weight or gestational age. One-minute and 5-minute Apgar scores less than 5 and interstitial emphysema were associated with increased risk of neonatal death. Only two of 22 survivors (9%) were severely handicapped and another eight (36%) had remediable disabilities at 2 years of age. No infant developed hydrocephalus and only one infant had spasticity. We suggest that the low incidence of major handicaps among survivors encourages the vigorous resuscitation of infants weighing less than 801 g at birth, yet strategies must be developed that will minimize both prolonged dying and the cost of intensive care for nonviable infants.

Apgar Score↗
PubMed1988

Endotoxin and pulmonary cell injury.

The physiopathologic similarity between adult respiratory distress syndrome (ARDS) secondary to sepsis and endotoxin-induced pulmonary abnormalities has provided extensive descriptive information confirming bacterial endotoxin as a factor initiating the heterogeneous pulmonary changes in ARDS. The present studies have used an established in vitro model for pulmonary cell injury to examine bacterial endotoxin 1, as a direct cytotoxic agent on the two major alveolar cell types, pulmonary endothelium and epithelium; 2, as a stimulant of neutrophil-mediated pulmonary cell injury, and 3, to examine effector mechanisms of cell-mediated damage by studying the potential effectiveness of antioxidants and antiproteolytic agents in the inhibition of this process. Endotoxin direct toxicity and stimulation of neutrophil-mediated pulmonary cell injury was observed in both pulmonary cell populations in systems free of activated serum complement. Endothelial cells were observed to be more susceptible to both the direct effect of endotoxin and to neutrophil-mediated injury when compared with epithelial cell derived monolayers. The addition of an antiprotease (soybean trypsin inhibitor [STI]) was superior to antioxidants (catalase, superoxide dismutase) in reducing the neutrophil-mediated endothelial toxicity (stimulated 51CR per cent release) observed. A 92 per cent degree of protection was observed with the highest dose of STI (5 milligrams per milliliter) used. Proteases released by activated neutrophils on endotoxin stimulation appear to be the predominant toxic species responsible for endothelial injury in this system.

Antioxidants↗
PubMed1987

Correlation of echoencephalographic findings and neurodevelopmental outcome: intracranial hemorrhage and ventriculomegaly in infants of birth weight 1,000 grams or less.

Echoencephalograms were obtained for 118 of 121 successive infants who were admitted to the Stanford intensive care nursery, weighed 1,000 g or less at birth, and survived long enough for at least one study to be performed. Eighty-eight of these infants survived and were followed up for 1 to 3 years; psychometric testing (Bayley Scales of Infant Development, Stanford-Binet Intelligence Scale, or both) was performed on 81% of these infants. Subependymal-intraventricular hemorrhages or intraparenchymal hemorrhages were associated with impaired development, but ventriculomegaly was not. The absence of echoencephalographic abnormalities did not exclude the possibility of impaired development in many infants. Periventricular leukomalacia was not observed. These data support independent scoring of subependymal-intraventricular hemorrhages, intraparenchymal hemorrhages, and ventriculomegaly, rather than use of combined scales for prognostic purposes.

Brain Damage, Chronic↗
PubMed1987

A practical approach to diagnosis and immediate care of the cyanotic neonate. Stabilization and preparation for transfer to level III nursery.

The diagnostic and therapeutic strategies described above have been presented sequentially for the sake of clarity, but in practice should be performed as quickly as possible in any infant who remains cyanotic despite receiving 100% oxygen. The practitioner must proceed with emergent stabilization of the infant with specific therapies for identified problems and nonspecific therapies for suspected problems, recognizing that the coexistence of two or more pathophysiologic entities is not uncommon. By the time of transport, the practitioner may have laid the groundwork for further diagnostic procedures and therapies by having already classified the infant into one of four primary pathophysiologic categories, as outlined in Table 4. Although congenital heart disease may be highly suspected, confirmation may not be possible without echocardiography. The practitioner, however, should not be discouraged by failure to achieve a specific etiologic diagnosis, despite careful analysis of all the information obtained from diagnostic evaluations prior to transport. Hypoxemia refractory to oxygen administration and assisted ventilation is found in many clinical conditions and results from a variety of pathophysiological disorders. The pediatrician caring for such an infant has primary responsibility for stabilization and preparation for transport of the infant to a Level III facility, and for communicating information about diagnostic procedures and therapeutic maneuvers that might facilitate extended resuscitative efforts by the neonatologist accepting responsibility for the transport and subsequent care of the infant.

Cardiovascular Diseases↗
PubMed1987

Medication error prevention by clinical pharmacists in two children's hospitals.

The purpose of this study was to record prospectively the frequency of and potential harm caused by errant medication orders at two large pediatric hospitals. The objective of the study was to assess the impact of pharmacist intervention in preventing potential harm. The study was conducted during a 6-month period. A total of 281 and 198 errors were detected at the institutions. The overall error rates for the two hospitals were 1.35 and 1.77 per 100-patient days, and 4.9 and 4.5 per 1,000 medication orders, respectively. Pediatric patients aged 2 years and less and pediatric intensive care unit patients received the greatest proportion of errant orders. Neonatal patients received the lowest rate of errant orders. The most common type of error was incorrect dosage, and the most prevalent type of error was overdosage. Antibiotics was the class of drugs for which errant orders were most common. Orders for theophylline, analgesics, and fluid and electrolytes, including hyperalimentation, were also frequently in error. In general, the error rate was greatest among physicians with the least training, but no physician group was error free. Involving pharmacists in reviewing drug orders significantly reduced the potential harm resulting from errant medication orders.

California↗
PubMed1986

Heparin inhibits proliferation of fetal vascular smooth muscle cells in the absence of platelet-derived growth factor.

Proliferation of smooth muscle cells from the pulmonary arteries and aortas of fetal calves is inhibited by heparin in vitro. This effect is reversible and dose dependent. Comparisons with effects of other polysaccharides indicate that only extensively sulfated polysaccharides inhibit proliferation of smooth muscle cells but that specific structural features of heparin are required to achieve maximum effect. Heparin-Sepharose chromatography of medium containing fetal calf serum reduces the ability of that medium to promote growth of smooth muscle cells from fetal pulmonary arteries, suggesting that heparin may remove soluble growth factors in serum. However, inhibition of fetal pulmonary artery smooth muscle cell proliferation by heparin is identical in media supplemented either with serum prepared from fetal calf plasma, in which platelet-derived growth factor (PDGF) is not detectable, or with fetal calf serum, which contains relatively abundant PDGF (114 pg/ml). Thus, inhibition of fetal pulmonary artery smooth muscle cell proliferation by heparin is not mediated solely by decreased availability or activity of exogenous PDGF. These studies suggest that morphogenesis of the smooth muscle investment of the pulmonary arteries could be regulated by local production of heparin-like inhibitors of smooth muscle cell growth.

Animals↗
PubMed1986

Hypoxia inhibits proliferation of fetal pulmonary arterial smooth muscle cells in vitro.

Normal pulmonary arterial development in the relatively hypoxic intrauterine environment and pulmonary arterial remodeling in hypoxic infants include extension of the smooth muscle layer into normally nonmuscular arteries and thickening of the arterial media in the muscular arteries. These changes require proliferation of immature smooth muscle cells or differentiation of smooth muscle cell precursors. Because the mechanisms that regulate these processes have not been clearly defined, we asked whether decreased oxygen tensions could promote either hyperplasia or hypertrophy of smooth muscle cell precursors in vitro. We have studied cells that proliferate and migrate out of explants from the media of the pulmonary arteries of near-term bovine fetuses, because these cells are representative of those that are involved in normal arterial development and possibly also in arterial remodeling. Decreases in oxygen tension within and below the physiologic range do not cause hyperplasia or hypertrophy of these cells. Instead, cell proliferation decreased at oxygen tensions below 60 mm Hg. The effects of hypoxia on proliferation of aortic and pulmonary arterial smooth muscle cells were identical, but effects on proliferation of dermal fibroblasts and endothelial cells were smaller in magnitude and evident only at lower oxygen tensions. These findings suggest that hypoxia does not act directly on smooth muscle cells to produce increased quantities of these cells in the pulmonary arteries during normal prenatal development or during remodeling of the pulmonary arteries of the hypoxic neonate, implying that other factors mediate these phenomena.

Animals↗
PubMed1986

The pharmacology of neonatal resuscitation and cardiopulmonary intensive care. Part II--Extended intensive care.

An optimal outcome for a distressed newborn infant can be achieved only if immediate resuscitation is followed by appropriate cardiopulmonary intensive care. In the preceding article in this series, we provided recommendations for drug therapy during the initial resuscitation. When an infant is stable enough for transfer to an intensive care nursery, extended cardiopulmonary intensive care should be initiated. If the infant remains distressed, this may require drug therapy to improve cardiac output, either by enhancing cardiac performance (dopamine, dobutamine or epinephrine) or by reducing afterload (nitroprusside). Drugs that alter the distribution of the circulation may be required for infants with persistent hypoxemia due to pulmonary hypertension or congenital heart disease (tolazoline, nitroprusside, prostaglandin E(1)), or with pulmonary congestion due to persistent patency of the ductus arteriosus (indomethacin). Infants with pulmonary disease may benefit from administration of agents that alter pulmonary function (furosemide, nitroprusside or neuromuscular blockers). Finally, treatment of the underlying disorder, with antibiotics or naloxone, for example, must not be neglected.

Alprostadil↗