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Catabolic effect of dexamethasone in the preterm baby
K G Brownlee1, P C Ng, M J Henderson
1Department of Paediatrics and Child Health, St James's University Hospital, Leeds.
Insights
Dexamethasone treatment for bronchopulmonary dysplasia increases blood urea and indicates muscle tissue loss in infants. Caution is advised due to potential risks outweighing benefits in milder cases.
Area of Science:
- Neonatal Medicine
- Pediatric Pharmacology
- Biochemistry
Background:
- Bronchopulmonary dysplasia (BPD) is a chronic lung disease in preterm infants.
- Dexamethasone is often used to treat BPD, but its metabolic effects are not fully understood.
Purpose of the Study:
- To investigate the impact of dexamethasone on protein catabolism in infants with BPD.
- To assess changes in nitrogen balance and muscle breakdown markers.
Main Methods:
- Nitrogen balance studies were conducted before and after dexamethasone initiation.
- Urinary 3-methylhistidine (3MH) to creatinine ratio was measured to assess muscle breakdown.
Main Results:
- Dexamethasone significantly increased blood urea concentration (2.3 to 7.1 mmol/l).
- Nitrogen balance studies revealed a mean deficit of 158 mg/kg/24 hours.
- Urinary 3MH:creatinine ratio increased substantially (46 to 77), indicating skeletal muscle loss.
Conclusions:
- Dexamethasone treatment for BPD leads to increased protein catabolism and muscle tissue loss in infants.
- The findings suggest a need for caution when using dexamethasone, particularly in milder BPD cases where risk-benefit ratio may be unfavorable.
Abstract:
Most babies treated with dexamethasone for bronchopulmonary dysplasia exhibit an appreciable rise in the blood urea concentration, from a mean of 2.3 mmol/l before steroid to a mean of 7.1 mmol/l after. In order to discover whether this was primarily the result of increased protein catabolism, nitrogen balance studies before and after the start of dexamethasone were performed and a mean deficit in nitrogen retention of 158 mg/kg/24 hours was found. Similarly the urinary 3-methylhistidine (3MH):creatinine ratio before and after the commencement of dexamethasone treatment in a group of preterm babies was measured. It was found that there was a substantial increase in 3MH excretion after dexamethasone: from a mean 3MH:creatinine ratio of 46 in the week before steroids to a mean ratio of 77 in the week after. As 3MH emanates almost exclusively from the breakdown of actin in skeletal muscle cell, this finding implies the loss of muscle tissue. It was also found that the babies were in less positive nitrogen balance after dexamethasone, to a degree which is significant relative to their protein reserves. The long term consequences of a period of increased catabolism are not yet known but the authors suggest caution in the use of dexamethasone, at least in babies with milder degrees of bronchopulmonary dysplasia in whom the ratio of benefit to risk may be less favourable.