The effects of theophylline on renal function in the premature newborn

Additive diuretic response of concurrent aminophylline and furosemide in children: a case series and a brief literature review

Aminophylline exerts a renovascular effect, acting by adenosine receptor blockade or type IV phosphodiesterase inhibition. Clinically, these drugs have been used with furosemide to induce diuresis in adults and neonates. However, reports on use of aminophylline in diuretic-dependent children are limited to a few studies. We report a case series of four critically ill children unresponsive to furosemide continuous infusion who were subsequently given aminophylline as an adjunct diuretic in the treatment of fluid overload. No side effects were evident. Administration of aminophylline at low doses (3 mg/kg) successfully promoted increased urine output over the 6-h study period in all four children.

Diurétiques et prématuré

Diuretics are frequently used in preterm infants in various situations such as patent ductus arteriosus, respiratory distress syndrome, bronchopulmonary dysplasia or neonatal renal insufficiency. However, the beneficial effects reported in the literature are usually transient, without any obvious effect on important parameters such as duration of oxygen dependency, ventilator dependency, length of hospital stay, long-term outcome, or mortality. Moreover, these drugs may induce water-electrolyte disorders especially when used for a long-term period. Thus, we recommend a systematic analysis of the beneficial/risk ratio before any use of these drugs.

Coadministration of theophylline enhances diuretic response to furosemide in infants during extracorporeal membrane oxygenation: a randomized controlled pilot study

OBJECTIVE

This pilot study evaluates the efficacy of low-dose theophylline administered before furosemide to enhance diuresis in neonates recovering from fluid retention during extracorporeal membrane oxygenation (ECMO).

STUDY DESIGN

Infants receiving ECMO (n = 24) were randomized (double blind, placebo-controlled) to receive either regimen A (placebo/furosemide day 1, theophylline/furosemide day 2, placebo/furosemide day 3) or regimen B (theophylline/furosemide day 1, placebo/furosemide day 2, theophylline/furosemide day 3). Urine flows and renal functions were compared.

RESULTS

Urine flow rate before initiation of diuretic therapy was not significantly different between groups A and B (2.6 +/- 1.4 vs 3.5 +/- 1.3 ml/kg/hr, respectively, p = 0.12). Infants who received theophylline/furosemide had significantly higher urine flow rates than those who received placebo/furosemide on day 1 (11.8 +/- 4.6 vs 7.2 +/- 2.4 ml/kg/hr, p < 0.01). The 24-hour fluid volumes and balances became significantly more negative with theophylline enhancement of furosemide's effect. There were no significant differences in renal function between the two groups.

CONCLUSION

Low doses of theophylline given before furosemide administration significantly enhance diuretic response in infants with fluid retention during ECMO.

Electrolyte balance

The kidney is structurally and biochemically immature at birth. As a consequence, renal function is low (3;10;ll;18). Glomerular filtration rate (related to body surface area or to body weight) is approximately 25% of that in adults. The capacity of several different tubular transport systems is lower in the infant than in the adult (2;5;13;21;28). A low transporting capacity of the neonatal kidney will sometimes result in undesired losses of electrolytes, amino acids, and peptides. The capacity to concentrate urine is low (7;29), and disturbances of serum tonicity, therefore, are common. The low concentrating capacity can be attributed to renal immaturity. The capacity of the newborn fullterm as well as preterm infant to release antidiuretic hormone is normal 7;31).

The efficacy of oral theophylline in ventilated premature infants

40 ventilated premature infants, with gestational ages of 24-34 weeks and a mean birthweight of 1422 g, were entered into a randomised controlled trial. 20 of the infants received orally 5 mg/ml anhydrous theophylline dissolved in 20% pure alcohol, with a loading dose of 5 mg/kg and then 1.25 mg/kg every 6 h. Plasma samples were assayed via an emit enzyme immunoassay, demonstrating satisfactory serum levels in all infants at 54 h after the loading dose. Possible side-effects were seen only in two infants, in one a tachycardia (220 beats/min) and the other became agitated during treatment.

Sodium homeostasis in term and preterm neonates. III. Effect of salt supplementation

Clinical and biochemical effects of supplementing dietary sodium intake to 4 to 5 mmol(mEq)/kg/day from days 4 to 14 of life were studied in 22 infants of gestational age 27 to 34 weeks. These infants were compared with a group of 24 unsupplemented babies. Supplemented infants lost less weight postnatally and regained birthweight more quickly: their improved weight gain continued after supplementation was stopped. Sodium balance was positive at age 5 to 11 days in supplemented babies but slightly negative in controls. Potassium balance was more strongly positive in the supplemented group. Plasma sodium concentration was higher in supplemented infants during weeks 3 and 4. Hyponatraemia was significantly more common in unsupplemented (37.5%) than supplemented (13.6%) infants. No infant became oedematous, hypernatraemic, or showed evidence of circulatory overload. The incidence of patent ductus arteriosus and necrotising enterocolitis was not increased; no intracranial haemorrhages occurred. Urinary potassium:sodium ratio was lower in supplemented babies than controls suggesting responsiveness of the distal tubule to mineralocorticoids. Providing 4 to 5 mmol(mEq)/kg/day of sodium to infants born before 34 weeks' gestation for the first two postnatal weeks improves growth and biochemical status and causes no undesirable side effects.

Tracheal relaxant and cardiostimulant actions of xanthines can be differentiated from diuretic and CNS-stimulant effects. Role of adenosine antagonism?

Theophylline (1, 3-dimethylxanthine) and enprofylline (3-propylxanthine) have been examined for effects in the rat. Enprofylline was 3.8 times as potent as theophylline as a tracheal relaxant in vitro, and 1.3 times as potent as theophylline to increase the rate of isolated perfused hearts. An oral dose (5 mg/kg) of enprofylline to rats was almost completely recovered in the urine as unchanged drug, showing that this xanthine is well absorbed and negligibly metabolised. Theophylline (10 and 30 mg/kg p.o.) significantly and dose-dependently increased locomotor activity in rats whereas the same doses of enprofylline were without effect on behaviour. Theophylline ( 5-20 mg/kg p.o.) produced significant and dose-dependent natriuretic and volume diuretic effect with little augmentation of potassium excretion. Enprofylline up to 10 mg/kg was without diuretic effects. At the large dose of 20 mg/kg enprofylline decreased sodium excretion and produced some volume diuresis. It is suggested that lack of diuretic and CNS-stimulant behavioural effects by enprofylline is due to its low ability to antagonise adenosine receptor stimulation. Pharmacodynamic differences between enprofylline and the potent adenosine antagonist theophylline may indicate a functional importance of endogenous adenosine.

Apnoea of immaturity. 1. A controlled trial of theophylline and face mask continuous positive airways pressure

A randomised controlled trial of theophylline versus face-mask continuous positive airways pressure (CPAP) treatment for recurrent apnoea of immaturity was carried out in 32 infants of 25 to 32 weeks' gestation. Continuous recording of electrocardiogram and impedence pneumogram added objective assessment to the nurses' observations for 11 courses of treatment. The CPAP group had more adverse perinatal factors but the frequency of apnoeic attacks before treatment was comparable. Infants given theophylline had a greater reduction in the incidence of prolonged apnoeic attacks, and this difference persisted after allowing for the effect of perinatal complications. Continuous recordings showed a greater reduction in episodes of bradycardia of less than or equal to 80/minute with theophylline. Five of 18 infants given theophylline needed intermittent positive pressure ventilation for apnoea compared with 12 of 14 given CPAP. The poor response in 17 of 32 infants suggests a need for a more effective method of preventing or treating apnoea in very immature babies, in whom adverse perinatal factors often coexist.

The efficacy of caffeine in the treatment of recurrent idiopathic apnea in premature infants

This prospective controlled study was aimed at evaluating the efficacy of caffeine in treating recurrent idiopathic apnea in the premature infant. Eighteen preterm infants (29 to 35 weeks' gestation) were studied. Recordings during the first 24 hours and on the fifth day of caffeine treatment showed a significant decrease of severe apnea (P less than 0.01) and of mild apnea (P less than 0.001) in the treated group (group 1) as compared with the control group (group II). No treatment of apnea other than caffeine was required in group I, whereas six neonates in group II had such severe and frequent apneic episodes for more than 48 hours that withholding additional treatment was believed to be unethical. No undesirable side effects of caffeine treatment were observed.

Pharmacologic considerations in the therapy of neonatal apnea

Theophylline and caffeine are both effective stimulants of the central nervous system for the therapy of neonatal apnea. Both drugs are slowly eliminated from the body, and doses should be adjusted to account for this slow elimination. Interconversion of theophylline and caffeine occurs in the newborn infant, with the methylation of theophylline to caffeine as the probable predominant pathway. Caffeine may offer advantages over theophylline: wider therapeutic index, case of administration, less need for therapeutic drug monitoring, less fluctuation in plasma concentrations, and fewer peripheral effects. A major disadvantage of caffeine is in the lack of a readily available commercial preparation. Both drugs exert many pharmacologic actions that require further evaluation in the newborn infant. Long-term effects of these drugs administered during a critical period in the developing human remains an area of concern.