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Biomedical subjects

A O Hopper

Publications and source records attributed to A O Hopper.

18 recordsLinked to original sources
PubMed1999

Extracorporeal membrane oxygenation for perioperative support in neonatal and pediatric cardiac transplantation.

Currently there is a lack of consensus on guidelines in the clinical application of extracorporeal membrane oxygenation (ECMO) in neonatal and pediatric cardiac transplantation patients. In this context, given the limited data presently available through the Extracorporeal Life Support Organization (ELSO) Registry, we conducted a preliminary survey to specifically evaluate the practice of using ECMO as a bridge to cardiac transplantation or as posttransplantation therapy for failure to wean from cardiopulmonary bypass or graft failure. We received responses to our questionnaire from 95 of 118 (81%) centers located in the U.S.A. and abroad. Of the 95 centers that responded, 36 were performing neonatal/pediatric cardiac transplants, with 29 centers reporting the concomitant use of ECMO to support cardiac transplant patients. There was wide variability in the responses from the 29 centers to a selected list of relative ECMO contraindications. However, only 7 centers had specific ECMO entry criteria for cardiac transplant patients. Fifteen of the 29 centers provided relevant data on cardiac transplant patients including the proportions of neonatal (11 of 37) and pediatric (63 of 217) patients requiring ECMO; neonatal (2 of 5) and pediatric (16 of 27) patients surviving to transplant; and neonatal (1 of 5) and pediatric (12 of 27) patients surviving to hospital discharge. These findings confirm the important role of ECMO in providing perioperative support in neonatal and pediatric cardiac transplantation patients. However, the lack of consensus among centers contributes to uncertainty in the decision making process to offer ECMO and to utilize ECMO effectively in this high risk population. We recommend that institution-specific information be collected, either using the ELSO Registry (or by a similar multicentric database) to develop specific guidelines for ECMO applications in cardiac transplant patients, and to carefully monitor and follow up EMCO treated patients to further evaluate the efficacy of this limited resource.

Cardiopulmonary Bypass↗
PubMed1997

Serum free thyroxine concentration is not reduced in premature infants with respiratory distress syndrome.

OBJECTIVE: We used improved methods of assay to determine whether pituitary-thyroid function is altered in premature infants with respiratory distress syndrome (RDS) during the first week of postnatal life. METHODS: Serum free thyroxine (T4) was measured by direct equilibrium dialysis, total thyroxine (TT4) by radioimmunoassay, and thyrotropin by a sensitive immunometric assay in 90 premature infants (45 healthy control subjects and 45 with RDS) during their first week of life after 25 to 30 weeks of gestation. Infants in the RDS group received exogenous surfactant therapy. RESULTS: Free T4 and thyrotropin concentrations of infants were not significantly different between RDS and control groups. As expected, infants with RDS had significantly lower serum total T4 concentrations compared with control infants (p < 0.001). This difference was present even after stratification for gestational age (25- to 27-week group, p = 0.012; 28- to 30-week group, p = 0.002). Lower total T4 concentrations were attributable to lower T4 binding to serum proteins among infants with RDS compared with control subjects, especially in the 25- to 27-week gestation group (p = 0.0075). CONCLUSION: These data indicate that pituitary-thyroid function is not altered in premature infants with RDS. The low total T4 state in these premature infants is attributable solely to reduced serum T4 binding, as is often seen in acute nonthyroidal illnesses.

Case-Control Studies↗
PubMed1994

Infrared end-tidal CO2 measurement does not accurately predict arterial CO2 values or end-tidal to arterial PCO2 gradients in rabbits with lung injury.

End-tidal PCO2 (PETCO2) measurements from two commercially available neonatal infrared capnometers with different sampling systems and a mass spectrometer were compared with arterial PCO2 (PaCO2) to determine whether the former could predict the latter in mechanically ventilated rabbits with and without lung injury. The effects of tidal volume, ventilator frequency and type of lung injury on the gradient between PETCO2 and PaCO2 (delta P(a-ET)CO2) were evaluated. Twenty rabbits were studied: 10 without lung injury, 5 with saline lavage and 5 with lung injury by meconium instillation. Paired measurements of PETCO2 by two infrared capnometers and a mass spectrometer were compared to PaCO2. In the rabbits without lung injury, the values from the infrared capnometers and mass spectrometer correlated strongly with PaCO2 (r > or = 0.91) despite differences in the slopes of the linear regression between PETCO2 and PaCO2 and in delta P(a-ET)CO2 (P < 0.05). Values from the mainstream IR-capnometer more closely approximated the line of identity than the regression between the sidestream IR-capnometer values or the mass spectrometer and PaCO2, but tended to overestimate PaCO2. The delta P(a-ET)CO2 was similar at all tidal volumes and ventilator frequencies, regardless of capnometer type. In the rabbits with induced lung injury, while there was a positive correlation between the slopes of the regression between PETCO2 and PaCO2 for both capnometers (r > or = 0.70), none of the regression slopes approximated the line of identity. The delta P(a-ET)CO2 was greater in rabbits with injured than noninjured lungs (P < 0.05). The delta P(a-ET)CO2 was similar among capnometers regardless of tidal volume, ventilator frequency, or type of lung injury. The 95% confidence interval of plots PaCO2 against PETCO2 was large for rabbits with injured and noninjured lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Pulmonary excretion of carbon monoxide in the human infant as an index of bilirubin production. IIc. Evidence for the possible association of cord blood erythropoietin levels and postnatal bilirubin production in infants of mothers with abnormalities of gestational glucose metabolism.

A total of 20 infants who had levels of erythropoietin (Ep), the major hormone regulating erythropoiesis, measured in their cord blood also had determinations of the pulmonary excretion rate of CO (VECO) performed, as an index of total bilirubin production. They were either infants of normal mothers or those of mothers with diabetes, gestational diabetes, and missed abnormalities of gestational glucose metabolism. The mean VECO (13.0 +/- 3.5 mu 1/kg/hr) and the mean Ep (20.0 +/- 9.7 SD mU/ml) of the infants with normal mothers (n = 9) were not different from the means previously established by our laboratories (13.9 +/- 3.5 SD mu 1/kg/hr, n = 20; and 23.7 +/- 12.8 SD mU/ml, n = 30, respectively); they were significantly lower than those of the infants of the abnormal mothers in this study. The 5 infants who had a cord blood Ep level greater than 50 mU/ml had a higher mean VECO, 27.8 +/- 7.1 mu 1/kg/hr, compared with 17.2 +/- 4.9 SD mu 1/kg/hr, of the six infants with cord blood Ep levels that were within 2 SD of the previously established normal mean cord blood Ep level (p less than .025). These data suggest that increased cord blood Ep levels and postnatal bilirubin production in infants whose mothers had abnormalities of gestational glucose metabolism are associated phenomena. Since polycythemia did not occur in these infants, ineffective erythropoiesis or mild, compensated hemolysis remains a likely cause of the increased total bilirubin production. In some cases, perinatal hypoxic stress may have affected the Ep response.(ABSTRACT TRUNCATED AT 250 WORDS)

Bilirubin↗
PubMed1984

Neonatal bilirubin production estimated from "end-tidal" carbon monoxide concentration.

The relationship between the pulmonary excretion rate of carbon monoxide (VECO) and the concentration of CO, in a sample of breath, drawn through a nasopharyngeal catheter at end-expiration, was assessed in 25 studies of nine preterm and 14 term infants. The VECO and this approximate end-tidal sample of CO (ETCO) correlated significantly over a wide range of CO elimination rates: VECO = 10.45 ETCO + 2.25 (n = 25, r = 0.95). The ETCO correctly predicted elevations in VECO greater than 2 SD of the mean VECO for normal infants (13.9 +/- 3.5 microliter/kg/h), with 90% sensitivity and 73% specificity (p less than 0.01). Three subjects with Rh isoimmune hemolytic disease were easily identified by the ETCO as well as the VECO. The ETCO is a simple, noninvasive measurement for rapidly identifying infants with significant hemolytic disease.

Bilirubin↗
PubMed1983

Maternal beta-adrenergic tocolysis and neonatal bilirubin production.

The potential for beta-adrenergic drugs to increase total bilirubin formation via cyclic adenosine monophosphate-mediated stimulation of hepatic microsomal heme oxygenase in the human neonate was evaluated. The pulmonary excretion rate of endogenously produced carbon monoxide (VeCO), an index of total bilirubin formation (TBF), was measured in 18 preterm neonates whose mothers received beta-adrenergic drugs for tocolysis and in 18 preterm neonates whose mothers were untreated. The mean VeCO of the neonates in the former group (17.2 +/- 7.3 microL/kg/hr) was the same as that in the latter group (17.4 +/- 6.2 microL/kg/hr); both values were elevated when compared with the mean VeCO of 20 term newborns (13.9 +/- 3.5 microL/kg/hr). Our findings indicate that TBF is not significantly increased in neonates whose mothers received beta-adrenergic drugs before delivery.

Adrenergic beta-Agonists↗
PubMed1983

Detection of gastric contents in tracheal fluid of infants by lactose assay.

We designed an in vitro assay to detect the presence of lactose in the tracheal aspirates of premature, ventilator-dependent infants. This method was employed to identify recurrent, unrecognized aspiration, which could prolong the requirements for ventilator support and contribute to the development of chronic lung disease. One hundred five determinations of lactose were performed on the tracheal fluid obtained from 42 ventilator-dependent infants who were receiving enteral feedings. There was a wide range of lactose levels (0 to 3,270 nmol lactose/ml tracheal aspirate). Six infants had samples that were highly suggestive of aspiration (greater than 200 nmol lactose/ml tracheal aspirate). Twenty infants had questionably positive samples (25 to 200 nmol lactose/ml tracheal aspirate), and 16 infants had samples that were considered negative for aspiration (less than 25 nmol lactose/ml tracheal aspirate).

Enteral Nutrition↗
PubMed1983

Use of end-tidal carbon monoxide to correct end-tidal hydrogen in neonates.

We evaluated the usefulness of end-tidal CO (ETCO) as an internal standard for reducing the error in end-tidal H2 (ETH2) measurements due to contamination of repeated breath samples with nonalveolar gas. Triplicate end-tidal samples were drawn from 12 healthy premature infants in small (less than 1 cc) increments through a posterior nasopharyngeal catheter at end-expiration, determined from the infant's chest wall movement. CO and H2 determinations were made on each sample by a reduction gas detector capable of determining CO and H2 concentrations to +/- 0.001 and 0.010 ppm, respectively. Respiratory breath samples were corrected for ambient CO and H2 concentrations. Since the alveolar gas fraction has the highest CO concentration of all tidal gases, the end-tidal sample with the highest CO peak was assumed to be most representative of uncontaminated alveolar gas. The other samples were "corrected" using a factor that was the ratio of the patient's highest CO peak to the given sample's CO value. The use of ETCO to correct ETH2 from samples deliberately contaminated with ambient air can significantly reduce the variability of ETH2 values. However, such correction is probably not necessary when comparing groups of infants using a standard collection technique. For individual infants, correction may reveal more marked short-term fluctuations in true alveolar H2 concentration.

Breath Tests↗
PubMed1983

Breath hydrogen analysis: a review of the methodologies and clinical applications.

Hydrogen gas (H2) is a product of the fermentation of dietary carbohydrate (CHO) by bacteria in the lumen of the gastrointestinal tract in man. Thus, H2 is actually an exogenously produced gas, which either is passed as flatus, or diffuses into the body and is exhaled. In the adult, a fairly constant fraction is expired, providing a reliable indicator of total colonic H2 production. Breath H2 analysis currently represents a useful clinical means of testing adults and older children for the malabsorption of CHO. Noninvasive and easy procedures for the collection of expired air have encouraged their increasingly widespread use in pediatrics. Evidence to date suggests that breath H2 analysis may provide the best available method for estimating semiquantitatively the degree of CHO malabsorption. The association of the results of breath H2 analysis with other clinical measures of CHO digestion and absorption is expected, but discrepancies can also be anticipated based on the nature of this particular trace gas method. The interpretation of the results of breath H2 analysis in neonates and young infants remains especially problematic because of confounding variables which are difficult to control and are measured infrequently.

Adult↗
PubMed1982

Serum free thyroxine values in term, premature, and sick infants.

Free thyroxine concentrations were determined by radioimmunoassay in 96 infants within an intensive care nursery and in 32 healthy term infants. Sera for free T4 levels were drawn simultaneously with the filter paper specimens for T4 obtained to screen these infants for congenital hypothyroidism. The mean free T4 level in 20 adults was 1.38 +/- 0.03 ng/dl (mean +/- SEM). The mean in the ICN infants was 3.48 +/- 0.18 ng/dl and in healthy term infants, 4.24 +/- 0.23 ng/dl. Like T4, free T4 correlated positively with increasing gestational age and birth weight, and was lower in infants with RDS. Although 66% of the ICN infants had T4 levels below the statistically selected screening level (fifth percentile), all of these infants had free T4 levels greater than 0.8 ng/dl. Two additional infants with untreated congenital hypothyroidism has free T4 levels of 0.3 and 0.4 ng/dl. The measurement of free T4 appears to be an accurate indicator of thyroid function in these infants.

Adult↗
PubMed1982

Pulmonary excretion rates of carbon monoxide using a modified technique: differences between premature and full-term infants.

The pathophysiology of the exaggerated hyperbilirubinemia in premature infants remains unclear. The relative contribution of bilirubin production may be estimated by measuring the pulmonary excretion rate of carbon monoxide (VeCO). We found that the mean VeCO of premature infants, 16.7 +/- 5.0 microliters/kg/h, was significantly elevated (p less than 0.05) compared with the mean VeCO of full-term infants, 13.9 +/- 3.5 microliters/kg/h. Premature infants who required phototherapy had a significantly (p less than 0.05) higher mean VeCO than those who did not. The VeCO did not correlate with gestational age, implying that factors which associate frequently but variably with gestational age may have an important influence on heme catabolism.

Carbon Monoxide↗
PubMed1982

Favorable results of neonatal intensive care for very low-birth-weight infants.

From 1961 to 1976, 229 infants with birth weights ranging from 751 to 1,000 gm were admitted to the Stanford University Hospital Intensive Care Nursery. The overall neonatal mortality for these infants was 63% (144/229), and there were ten late deaths. Before 1967, no infant in this group who required mechanical ventilation survived; thereafter, 30% (34/114) of the ventilated patients survived. Of the 75 long-term survivors 60 participated in a high-risk infant follow-up program; these included 23 infants who had received mechanical ventilation. The mean birth weight of these infants was 928 +/- 67 (SD) gm. Seventeen children (28%) had significant morbidity: seven (12%) with severe handicaps and ten (17%) with moderate handicaps. During this same period, seven infants weighing less than 750 gm at birth were also observed. The three infants who had not required ventilatory support thrived; the other four infants had required respirators and were significantly handicapped. More recently, neonatal mortality for infants with birth weights from 751 to 1,000 gm has improved: for 1977 to 1980, it was 28% (33/118). Furthermore, neonatal mortality for ventilated infants in this weight group was 27% (26/95). These data indicate an improved prognosis for very low-birth-weight infants, even with ventilatory support.

California↗
PubMed1982

Paired determinations of blood carboxyhemoglobin concentration and carbon monoxide excretion rate in term and preterm infants.

Paired determinations of COHb and VeCO were performed on 30 term infants (38 to 42 weeks' gestation) and 26 preterm infants (28 to 37 weeks' gestation) during the first week of life. All subjects were breathing room air at the time of the study. Values of COHb were corrected for RAco by linear regression of COHb (percent saturation) vs RAco (ppm). Regression coefficients for term and preterm infants with no history of pulmonary impairment were nearly identical (COHb = 0.175 RAco + 0.45, r = 0.77, n = 25 for term infants; COHb = 0.168 RAco + 0.51, r = 0.82, n = 9 for preterm infants) and agreed well with theoretical values. For the group of term infants, linear regression of Veco (microliter/kg/hr) vs. COHbc, where COHbc = COHb - 0.17 RAco, resulted in VEco = 23.4 COHbc + 4.02, r = 0.75, n = 30. The corresponding relationship for preterm infants with no history of pulmonary impairment was VEco = 24.7 COHbc + 3.85, r = 0.61, n = 13. For a subpopulation of preterm infants with a history of pulmonary dysfunction, the correlation decreased significantly, with VEco = 4.34 COHbc + 17.6, r = 0.097, n = 11. These results demonstrate that (1) COHbc is a reasonable index of VEco and consequently of the heme catabolic rate in both term and preterm infants with no clinical history of pulmonary dysfunction and (2) inference of VEco from COHbc may be misleading in certain cases without a consideration of the factors relating these two variables.

Carbon Monoxide↗
PubMedDate not supplied

Limited value of nephelometry in monitoring the administration of intravenous fat in neonates.

To evaluate the usefulness of nephelometry in predicting hyperlipidemia in neonates receiving intravenous fat (IVF), 23 infants in our neonatal intensive care nursery had simultaneous measurements of the serum IVF level (as determined by nephelometry), triglyceride, cholesterol, and free fatty acid/albumin molar ratio. There was a positive correlation between the serum IVF level and triglycerides, but the IVF level did not reliably predict elevated triglycerides, cholesterol, or free fatty acid-albumin molar ratio. Thus, neonates receiving IVF emulsions cannot be monitored by nephelometry alone. Adequate monitoring requires measurement of specific lipid fractions.

Cholesterol↗