Thomas F. Myers

Effects of dexamethasone on the hypothalamic-pituitary-adrenal axis in preterm infants

The effects of dexamethasone therapy on the hypothalamic-pituitary-adrenal axis were tested in 10 premature infants with bronchopulmonary dysplasia by means of the corticotropin-releasing hormone stimulation test before therapy and on the seventh day of therapy. Adrenocorticotropic hormone and cortisol levels were determined by radioimmunoassay. There was significant suppression of the hypothalamic-pituitary-adrenal axis after 7 days of a currently used dexamethasone treatment regimen. A site of suppression was located at the level of the pituitary gland.

Low-dose theophylline therapy in idiopathic apnea of prematurity

The effects of theophylline at a dose of 2 mg/kg/day (with resultant serum concentrations of 2.8 to 3.9 micrograms/ml) were observed in seven premature infants with severe idiopathic apnea. The frequency of apneic episodes decreased 62 +/- 9% (SEM) and the frequency of episodes of bradycardia decreased 73 +/- 9% following 24-48 hours of this therapy. No changes in ventilatory response to CO2 resting respiratory minute volume, arterial blood gas values, resting heart rate, or serum electrolyte concentrations were observed. Theophylline at this dose appears to be a safe and effective treatment for idiopathic apnea in premature infants. It works by a mechanism other than increasing CO2 sensitivity.

Early metabolic effects of sepsis in the preterm infant: Lactic acidosis and increased glucose requirement

The effects of sepsis on carbohydrate metabolism were studied in preterm newborn infants (weight > 1.2 kg, appropriate for gestational age) without maternal endocrine problems who were being examined for infection. Plasma glucose, lactate, and insulin concentrations were measured at initial evaluation and then every 8 hours for a total of 48 hours. Blood, urine, and spinal fluid were obtained for culture and counterimmunoelectrophoresis. Dextrose was administered to each patient to maintain glucose levels in the normal range. Dextrose infusion rates were calculated in milligrams per kilogram per minute. Of the 29 infants, 6 had sepsis (positive culture and counterimmunoelectrophoresis results). Infants with sepsis had significant elevations of plasma lactate concentration (p < 0.003) but normal pH. The dextrose infusion rate was also significantly elevated in the infected infants (p < 0.01). No hypoglycemia or hyperglycemia was observed in either group. No significant difference in plasma insulin concentration was observed. We conclude that significant elevations in plasma lactate concentrations and dextrose infusion rate may be early clinical markers of neonatal sepsis in the first 48 hours of life.

Effects of surfactant therapy on outcome of infants with birth weights of 600 to 750 grams

Replacement therapy with exogenous surfactant has been studied for both prevention and treatment of respiratory distress syndrome. Although reports demonstrate improved survival rates for surfactant-treated infants with RDS, the impact of this therapy on outcome of extremely low birth weight infants is unknown. TM Previous studies have not reported outcome after surfactant treatment for the subset of premature infants who are born at ELBWs and who are at the highest risk for complications of prematurity. We report the outcome of infants born with birth weights between 600 and 750 gm who underwent prospective random selection to receive either surfactant or placebo as part of a multidose prevention study.

Neonatal stroke: Description of patients and investigation into pathogenesis

We report 15 patients with neonatal stroke reviewed retrospectively. Twelve patients had left middle cerebral artery involvement--the same ratio observed in 36 previously reported patients with strokes. We studied 20 normal neonates prospectively to determine whether a difference in flow velocity could be detected between the left and right middle cerebral arteries; pulsed Doppler ultrasound, which compared both velocities, demonstrated no significant difference.

Neonatal viability in the 1990s: Held hostage by technology

The emergence of new obstetrical and neonatal technologies, as well as more aggressive clinical management, has significantly improved the survival of extremely low birth weight (ELBW) infants. This development has heightened concerns about the limits of viability. ELBW infants, weighing less than 1,000 grams and no larger than the palm of ones hand, are often described as “miracles” of late twentieth century technology. Improved survivability of ELBW infants has provided opportunities for long-term follow-up. Information on their physical and emotional development contributes to developing standards of practice regarding their care.

Dexamethasone-Induced Myocardial Hypertrophy in Neonatal Rats

Clinical trials have shown dexamethasones beneficial effects on the pulmonary status of infants with bronchopulmonary dysplasia; however, hypertrophic cardiomyopathy has been a reported complication of this therapy with no known mechanism. Our study was designed to test the hypothesis that therapeutic dexamethasone doses would induce myocardial hypertrophy. Newborn Sprague-Dawley rats were randomly assigned to receive dexamethasone 0.125 mg/kg/day, while paired littermate controls received saline placebo. The daily body weights were recorded and pups were sacrificed after 5 or 7 days of treatment. The heart weight to body weight ratio was used as a gross index of myocardial mass. Myocardial protein content, total protein to total DNA ratio, actin content and myosin heavy chain content were used as biochemical indices of hypertrophy. Our results included an increased heart weight to body weight ratio with elevation of the total protein content, actin content and total protein to total DNA ratio after both 5 and 7 days. We conclude that dexamethasone induces myocardial hypertrophy in neonatal rats.

The ethics of caring for conjoined twins. The Lakeberg twins.

In June 1993, conjoined twin Amy and Angela Lakeberg became the focus of national attention. They shared a complex six-chambered heart and one liver; only one could survive separation surgery; and even her chances were slim. The medical challenge was great and the ethical challenges were even greater.

Plasma beta-endorphin concentrations and analgesia-muscle relaxation in the newborn infant supported by mechanical ventilation

We evaluated the effects of pancuronium and opiates on plasma beta-endorphin concentrations in 25 infants supported by mechanical ventilation. Infants receiving opiate were randomly assigned to receive either fentanyl or morphine. There was no change in beta-endorphin concentrations after administration of pancuronium, whereas both fentanyl and morphine reduced beta-endorphin concentrations by approximately 60%.

Randomized clinical trial of surfactant prophylaxis in retinopathy of prematurity

Prophylactic lung surfactant is commonly used to reduce the severity of neonatal respiratory distress syndrome in premature infants. There is disagreement in the literature regarding the effect of prophylactic lung surfactant on the incidence of retinopathy of prematurity (ROP). Sixty-four infants, gestational age 23 to 32 weeks, birth weight 610 to 1250 g, were randomized to receive either intratracheal bovine surfactant prophylaxis or air control, at our institution, as part of a national double-masked multicenter trial. Forty-eight of these infants survived and underwent complete ophthalmologic examinations by a single masked examiner. ROP data were gathered retrospectively. ROP developed in 19 of the 23 (83%) who received surfactant and 15 of the 25 (60%) controls (P = .1). Analysis of the worst stage of ROP for each infant also revealed no difference between the surfactant and control groups (P = .4). Our retrospective analysis of ROP data in a prospective double-masked randomized study revealed no significant effect of surfactant on the incidence or severity of ROP.