Search PubMed⌕ Search

Biomedical subjects

D K Stevenson

Publications and source records attributed to D K Stevenson.

At least 235 records · Page 13Linked to original sources
PubMed1988

Interference of fetal hemoglobin with the spectrophotometric measurement of carboxyhemoglobin.

We measured the concentration of carboxyhemoglobin (HbCO) in blood samples from 32 neonates by spectrophotometry (IL282 CO-Oximeter) and gas chromatography, finding a strong positive correlation (r = 0.89) between the concentration of fetal hemoglobin (Hb F) and HbCO as measured by spectrophotometry, but not by gas chromatography. Thus, Hb F interferes with the determination of HbCO by spectrophotometric techniques by falsely increasing apparent HbCO in direct proportion to Hb F. We conclude that, when Hb F is known or suspected to be present, blood HbCO cannot be reliably determined by methods based on spectrophotometry.

Carboxyhemoglobin↗
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

Oxytocin-induced labor characteristics and uterine activity after preinduction cervical priming with prostaglandin E2 intracervical gel.

Labor characteristics and quantitation of uterine activity resulting from oxytocin induction of labor after intracervical prostaglandin E2 (PGE2) gel priming have not been previously reported. Forty-seven women with modified Bishop scores of 5 or less received preinduction priming with 0.5 mg of intracervical PGE2 gel. Oxytocin was used to induce labor after priming, and uterine activity was quantitated. A matched group of control patients was managed identically but did not receive PGE2 gel. In the gel group, modified Bishop scores improved significantly and in two patients (4%), priming alone induced labor. No uterine hyperstimulation or fetal heart rate abnormalities occurred during priming. Cesarean sections for all indications and those for failed induction were less common in the gel group. The length of the active phase and the second stage of labor were significantly shorter in the gel group. Uterine activity was similar in both groups. The data suggest a primary cervical action of the gel.

Adult↗
PubMed1988

Carboxyhemoglobin as measured by gas chromatography and with the IL 282 and 482 CO-Oximeters.

We measured the concentration of carboxyhemoglobin (HbCO) in original and CO-tonometered blood samples from 53 intensive-care patients with IL 282 and IL 482 CO-Oximeters and by gas chromatography (GC), finding very strong correlations among the three methods for HbCO concentrations greater than 2.5%. For concentrations within the normal reference interval (less than or equal to 2.5%), however, the correlation between CO-Oximetry and GC is poor (r2 less than 0.26). The capillary mode of the IL 482 has a consistently lower correlation with any other method or mode. The correlations of measurements between the CO-Oximeters for total hemoglobin and oxyhemoglobin were excellent (r2 greater than or equal to 0.98). Correlations for methemoglobin were lower, owing to its low concentrations in the samples. We conclude that the IL 482 and the IL 282 are analytically equivalent for all analytes measured, but that both instruments differentiate poorly between HbCO values that fall within the reference interval.

Carboxyhemoglobin↗
PubMed1988

Suppression of carbon monoxide excretion by zinc mesoporphyrin in adult Wistar rats: evidence for potent in vivo inhibition of bilirubin production.

We studied the effect of zinc mesoporphyrin on the CO excretion rate (VeCO) and liver heme oxygenase activity of adult rats. A subcutaneous dose of 4 mumol/kg significantly lowered the VeCO between 4 and 12 hours after injection. The liver heme oxygenase activity of treated animals was significantly lower 12 hours after treatment. These findings demonstrate that zinc mesoporphyrin is a potent inhibitor of in vivo total bilirubin production, as measured by the VeCO.

Animals↗
PubMed1988

Birth order and birth weight reexamined.

We studied the longitudinal association of birth order and birth weight in two series of very large sibships, each consisting of at least seven children, and compared the findings with those based on analysis of cross-sectional data from a large population-based survey, the Jerusalem Perinatal Study. The birth weights of the cross-sectional sample were adjusted by multiple linear regression for a number of factors known to confound cross-sectional studies, including maternal age, education, marital status, religion, smoking, height and prepregnant weight, gestational age, and sex of the newborn. Birth weight increased with increasing birth order in both adjusted cross-sectional and socioeconomically homogeneous longitudinal data.

Analysis of Variance↗
PubMed1987

Carbon monoxide generation from tin- and zinc-protoporphyrin by tissue homogenates.

Both heme and tin-protoporphyrin (TP), but not zinc-protoporphyrin (ZP), supported significant NADPH-stimulated, concentration-dependent CO production in all tissues. These rates, for 400 microM substrate, ranged: for heme 0.52 (intestine) to 4.18 (spleen); for TP 0.08 (kidney) to 0.71 (liver); and for ZP 0.01 (liver) to 0.25 (kidney) nmoles CO/hr/mg protein. All three metalloporphyrins (400 microM) supported concentration-dependent CO production in the absence of NADPH. The rates ranged: for heme 0.31 (kidney) to 0.80 (spleen); for TP 0.41 (kidney) to 1.04 (intestine); and for ZP 0.12 (kidney) to 0.51 (spleen) nmoles/hr/mg protein. We conclude that both TP and ZP are subject to in vitro degradation by 13,000 x g supernatants of adult rat organs via CO-producing reactions.

Animals↗
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

Adjunctive magnesium sulfate infusion does not alter metabolic changes associated with ritodrine tocolysis.

Magnesium sulfate, an agent whose cellular actions might cause metabolic disturbances, has been used concomitantly with ritodrine hydrochloride for preterm labor tocolysis. Although the profound metabolic effects of beta-adrenergic agents have been well described, the possibility that adjunctive magnesium might cause further or unexpected alterations in maternal metabolic parameters has not been fully evaluated. To investigate this question, we prospectively randomized patients, in a blinded fashion, to receive ritodrine plus placebo or ritodrine plus adjunctive magnesium sulfate for preterm labor tocolysis. Serial measurements of potassium, glucose, blood urea nitrogen, and hematocrit were obtained and compared between tocolytic treatment groups. The metabolic changes found were similar in each group and appear to result predominantly from beta-adrenergic stimulation with no apparent perturbations caused by the direct cellular actions of magnesium sulfate. From the metabolic standpoint, it appears that the clinician may use adjunctive magnesium sulfate without fear of accentuating or obscuring the expected beta-adrenergic-induced alterations in the above-mentioned maternal metabolic parameters.

Adult↗
PubMed1987

A technique for the administration of ribavirin to mechanically ventilated infants with severe respiratory syncytial virus infection.

Fifteen infants with respiratory syncytial virus pulmonary infection admitted to our pediatric ICU from December 1, 1985 through April 30, 1986, required mechanical ventilation. These patients were placed on an open trial of ribavirin therapy. We describe a technique for the safe delivery of aerosolized ribavirin to these infants while on the ventilator. The agent was delivered for 16 h/day for 7 days. Modifications of the ventilator circuit were needed to prevent the condensation of the drug in the ventilator tubing and to allow for the safe and effective operation of the ventilator. A common ventilator strategy was used for all patients. The highest positive inspiratory pressure generated was 42 +/- 9.5 (SD) cm H2O, the highest PEEP was 5.9 +/- 3.2 cm H2O, the duration of ventilation was 10.7 +/- 8.5 days, and exposure to fraction of inspired oxygen was greater than or equal to 0.6 for 55.3 h. Ribavirin levels were measurable in two patients, thereby demonstrating that the drug was in fact delivered and absorbed. Our preliminary results demonstrate that ribavirin can be delivered to the patients with respiratory syncytial viral infections who require mechanical ventilation; however, further studies are indicated to evaluate the efficacy and dose responsiveness, alterations in pulmonary dynamics, and safety of ribavirin in delivery to infants requiring ventilation.

Administration, Inhalation↗
PubMed1987

Carbon monoxide production in ventilated premature infants weighing less than 1500 g.

Mean pulmonary excretion rate of carbon monoxide in 13 premature babies on ventilators was significantly higher (p less than 0.001) than that of 19 healthy infants born at full term. This correlated with carboxyhaemoglobin concentrations in blood, indicating that the premature infants on ventilators produced abnormally large amounts of bilirubin.

Bilirubin↗
PubMed1987

Tin protoporphyrin inhibits carbon monoxide production in suckling mice.

The carbon monoxide excretion rate (VeCO) of groups of 1-day-old mice was measured after administration of two separate doses of 50 nmol of tin protoporphyrin (TP) per gram of body weight. The mean VeCO of the saline-treated control groups over the study period was 1.50 +/- 0.26 nmol/g/h, and that of the TP-treated groups was 1.35 +/- 0.29 nmol/g/h. Tin protoporphyrin treatment reduced the CO excretion by approximately 14% in 2-day-old mice over 24-48 h.

Animals↗
PubMed1987

Elevation of bilirubin production in neonatal rats treated with nicardipine hydrochloride.

Administration of nicardipine hydrochloride, a dihydropyridine calcium entry blocker, caused a 30% rise in the rate of bilirubin formation in neonatal rats. Plasma bilirubin concentrations also increased from 0.83 +/- 0.05 to 1.06 +/- 0.10 mg/100 ml (p less than 0.05). We conclude that maternal administration of nicardipine hydrochloride for tocolysis could affect bilirubin production in the neonate.

Animals↗
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↗