Plasma fentanyl levels in infants undergoing extracorporeal membrane oxygenation.

Plasma levels of fentanyl were analyzed in 12 infants undergoing extracorporeal membrane oxygenation who received a fentanyl bolus (5 to 10 micrograms/kg) followed by infusion at 1 to 6.3 micrograms/kg/hr. Fentanyl levels, averaging 11 samples/infant, were measured by radioimmunoassay (mean 19.7 +/- 35.7 ng/ml; n = 140). Eight of the infants, all with a primary diagnosis other than congenital diaphragmatic hernia, survived with relatively short (< 7 days) courses on extracorporeal membrane oxygenation; this group of infants did not develop tolerance to fentanyl and could be maintained on infusion rates of < 5 micrograms/kg/hr throughout. The four infants with congenital diaphragmatic hernia had longer extracorporeal membrane oxygenation runs and three did not survive; their plasma fentanyl levels were consistently higher and while the infusion rates were higher early on extracorporeal membrane oxygenation, they did not exceed 7 micrograms/kg/hr and actually decreased after 5 days on extracorporeal membrane oxygenation. Five infants (42%) received lorazepam in addition to fentanyl for at least one sampling time. The fentanyl infusion dose and plasma level were higher in the congenital diaphragmatic hernia nonsurvivors who did not receive lorazepam (p < 0.001). A decrease in fentanyl clearance correlated with renal dysfunction (p < 0.01). A bolus of fentanyl followed by infusion of relatively low doses (1 to 5 micrograms/kg/hr) provides adequate analgesia for infants on extracorporeal membrane oxygenation, particularly when it is supplemented with intravenous lorazepam whenever needed to control infant movement.

Biochemical abnormalities of the third component of complement in neonates.

The third component of complement, C3, is of central importance as an opsonin in the nonimmune host. Although gestational deficiencies in C3 levels are well recognized in neonates, defects in complement-mediated functions have not in every case correlated with low levels of complement proteins. Because opsonic functions of C3 are mediated through a reactive thiolester bond, we hypothesized that a biochemical dysfunction at this active site could explain the newborn's predisposition to infection, even with relatively normal C3 levels. We therefore examined the biochemical integrity of the C3 thiolester in an assay independent of all other complement proteins. As measured by ELISA, mean C3 levels from 44 neonates (24-43 wk) were significantly lower in infants less than 30 wk gestational age (0.79 +/- 0.13 mg/mL) than in full-term newborns (1.19 +/- 0.27 mg/ml, p less than 0.05). Furthermore, biochemical reactivity of the thiolester bond, as measured by incorporation of the radiolabeled nucleophile, methylamine, correlated significantly with gestational age (r = 0.45, p less than 0.01). Functional C3 was defined as the product of thiolester reactivity and C3 level; 9/11 premature and 2/17 full-term infants had levels of functional C3 which were less than 50% of the adult norm. Structural analysis of neonatal C3 revealed the two-chain structure in all neonates; four neonates had an additional band at 205 kD which may represent an impairment in posttranslational processing of a precursor molecule. We conclude that defects in thiolester reactivity may constitute a newly identified mechanism for the newborn's susceptibility to infection.

Congenital mesoblastic nephroma, hemorrhagic shock, and disseminated intravascular coagulation in a newborn infant.

Congenital mesoblastic nephroma is a rare tumor of infancy that usually presents as an asymptomatic abdominal mass. A full-term newborn infant with an atypical variant of this neoplasm developed hemorrhagic shock and disseminated intravascular coagulation. The stormy course was complicated by persistent fetal circulation and then the inability to withdraw ventilatory support due to the mass effect of the tumor. After the removal of the tumor at 10 days of age, transient conjugated hyperbilirubinemia developed. At 15 months of age, the infant was thriving without evidence of recurrence of the tumor.

Effect of interleukin-4 on the synthesis of the third component of complement by pulmonary epithelial cells.

Complement activation in the lung is important in a variety of physiological and pathological conditions. The third component of complement, C3, is the pivotal constituent of the complement cascade. C3 is produced in the lung by several cell types including pulmonary epithelial cells. Because pulmonary epithelial cells and T lymphocytes may interact within the lung to regulate local immune responses, we examined the effect of a T lymphocyte-derived cytokine, interleukin-4 (IL-4) on C3 production by A549 human pulmonary epithelial cells. Treatment of A549 cells with IL-4 increased C3 production in a time- and dose-dependent fashion. Concentrations of IL-4 > or = 0.1 ng/ml significantly increased C3 production. Maximal increase in C3 synthesis occurred after stimulation of A549 cells with IL-4 (10 ng/ml) for 3 days. Preincubation of IL-4 with a neutralizing anti-human IL-4 antibody inhibited IL-4's effect on C3 production. The relative abundance of C3 messenger RNA levels in A549 cells increased following IL-4 treatment, indicating that IL-4's effects on C3 production were pretranslational. Intercellular communication between T lymphocytes and pulmonary epithelial cells via cytokines such as IL-4 may be important in the local regulation of C3 gene expression during the inflammatory response.

C3 synthesis by A549 alveolar epithelial cells is increased by interferon-gamma and dexamethasone.

The third component of complement, C3, is produced in the lung by several cell types including alveolar epithelial cells. Since interferon-gamma (IFN-gamma) and dexamethasone regulate C3 gene expression in non-pulmonary cells, and because IFN-gamma and dexamethasone interact to regulate the functional activity of alveolar epithelial cells, we investigated the effects of IFN-gamma and dexamethasone on C3 production by A549 human alveolar epithelial cells. Treatment of A549 cells with IFN-gamma alone increased C3 production in a time-and dose-dependent manner. Maximal increase in C3 production occurred after stimulation of A549 cells with 500 IU/ml IFN-gamma for 3 days and was 3.4-fold greater than control. Dexamethasone (0.1 microM) stimulation of A549 cells increased C3 production 6.7-fold over controls on day 3. Treatment of A549 cells with IFN-gamma plus dexamethasone resulted in an 11-to 13-fold increase in C3 synthesis. C3 mRNA levels were increased in A549 cells treated with IFN-gamma and dexamethasone individually and in combination suggesting that IFN-gamma and dexamethasone increase C3 synthesis by a pre-translational mechanism. IFN-gamma and dexamethasone did not alter the two-chain structure of the C3 molecule produced by A549 cells, as assessed by Western blotting. We speculate that IFN-gamma and glucocorticoids may be important in the local regulation of C3 synthesis in the lung.

Effect of steroids on the synthesis of complement C3 in a human alveolar epithelial cell line.

The third component of complement, C3, is produced in the lung by several cell types, including alveolar epithelial cells. Steroid hormones are important in gene regulation in alveolar epithelial cells. The effects of steroids on C3 production were examined using A549 human pulmonary alveolar epithelial cells. Treatment of A549 cells with the glucocorticoids dexamethasone, hydrocortisone, corticosterone, and 11-deoxycortisol increased C3 production, as measured by ELISA. The glucocorticoid receptor antagonist RU486 inhibited C3 synthesis by dexamethasone- and hydrocortisone-stimulated cells. Because the glucocorticoid receptor is a member of a superfamily of receptors, the effects of steroid members of the superfamily on C3 production were examined. The mineralocorticoid, aldosterone, increased C3 production. RU486 completely inhibited aldosterone's stimulatory effects on C3 production, whereas the mineralocorticoid receptor antagonist spironolactone partially inhibited aldosterone's effects. In contrast, testosterone, progesterone 17 alpha-hydroxyprogesterone, and estradiol did not alter C3 production by A549 cells. Northern analysis showed that C3 mRNA abundance in A549 cells increased following stimulation with dexamethasone, hydrocortisone, corticosterone, and aldosterone. Testosterone, progesterone, 17 alpha-hydroxyprogesterone, and estradiol did not alter C3 mRNA levels. Therefore, among the steroids tested, only glucocorticoids and aldosterone altered C3 production by A549 cells suggesting that these steroids may play a role in the regulation of C3 in the lung.

Effect of glucocorticoids on C3 gene expression by the A549 human pulmonary epithelial cell line.

The third component of C, C3, is the key opsonin of the C cascade and is produced locally within the lung by pulmonary epithelial cells, macrophages, and fibroblasts. Because glucocorticoids regulate the maturation and expression of several physiologically important genes in pulmonary epithelial cells, we examined the effects of glucocorticoids on C3 mRNA expression and C3 synthesis by the human pulmonary epithelial cell line, A549. Treatment with dexamethasone enhanced C3 production in a time- and dose-dependent fashion such that concentrations of dexamethasone greater than or equal to 0.001 microM significantly increased C3 production on day 3 of culture. Natural glucocorticoids, corticosterone, cortisol, and 11-deoxycortisol also increased C3 concentrations in A549 supernatants. Both cycloheximide and the glucocorticoid receptor antagonist, RU486, individually inhibited the effect of dexamethasone on C3 production. Northern analysis demonstrated that the steady state 5.2-kb C3 message increased in A549 cells within 10 h of treatment with dexamethasone. RU486 inhibited the effect of dexamethasone on C3 mRNA expression. The integrity of the C3 thiolester bond, as measured by [3H]iodoacetic acid titration and hemolytic assay, was not disrupted by dexamethasone. We conclude that glucocorticoids such as dexamethasone enhance the expression of C3 mRNA and increase the production of functionally active C3 by A549 cells by a mechanism that is mediated by the intracellular glucocorticoid receptor.