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Water, electrolyte, and endocrine homeostasis in infants with bronchiolitis
Insights
Infant bronchiolitis causes water retention due to increased antidiuretic hormone (ADH) and hyperreninemia, leading to secondary hyperaldosteronism. Monitoring weight and osmolality is crucial for managing this condition.
Area of Science:
- Pediatrics
- Endocrinology
- Nephrology
Background:
- Bronchiolitis in infants is common and can lead to fluid and electrolyte imbalances.
- The hormonal regulation of fluid balance in infants with bronchiolitis is not fully understood.
Purpose of the Study:
- To investigate the hormonal changes related to fluid balance in infants with bronchiolitis.
- To understand the role of antidiuretic hormone (ADH) and the renin-angiotensin-aldosterone system in bronchiolitis.
Main Methods:
- Studied 23 infants with bronchiolitis, measuring body weight, plasma and urinary osmolality, ADH, plasma renin activity, and electrolytes.
- Compared findings with a control group of 10 infants with non-respiratory febrile illness.
Main Results:
- Infants with bronchiolitis showed increased body weight, elevated urinary osmolality, low plasma osmolality, and markedly high ADH levels.
- Increased ADH was associated with elevated plasma renin activity and secondary hyperaldosteronism, indicated by altered fractional excretion of sodium and potassium.
- All abnormalities resolved as bronchiolitis subsided.
Conclusions:
- Bronchiolitis in infancy is characterized by increased ADH secretion and hyperreninemia with secondary hyperaldosteronism, causing water retention.
- These hormonal changes are likely a response to perceived hypovolemia.
- Clinical management should focus on monitoring body weight and osmolality, as serum sodium levels may be misleading.
Abstract:
Twenty-two of 23 consecutive infants with bronchiolitis, 5.5 +/- 3.5 mo of age, showed a 1.9 +/- 1.4% increase in body weight, increased urinary osmolality of 737 +/- 193 mmol/L with low plasma osmolality of 275 +/- 4 mmol/L, and markedly elevated plasma antidiuretic hormone (ADH) levels of 114 +/- 225 pg/mL. Increased ADH, which usually suppresses plasma renin activity, was associated with increased plasma renin activity of 11-55 ng angiotensin 1/mL/h (normal for age less than 10 ng angiotensin 1/mL/h). Hyperaldosteronism was evident from the low fractional excretion of sodium of 0.27 +/- 0.2% and high fractional excretion of potassium of 21 +/- 15%. Serum sodium concentrations were normal. All of the pathologic findings returned to normal when the bronchiolitis subsided. A control group of 10 infants with nonrespiratory febrile illness did not show any of the above abnormalities. Thus, bronchiolitis of infancy is characterized by both increased ADH secretion and hyperreninemia with secondary hyperaldosteronism, which induce water retention but counterbalance each other with respect to serum sodium. Increased ADH secretion as well as increased plasma renin activity are not "inappropriate," but rather suggest a response to the perception of hypovolemia by intrathoracic receptors. We therefore conclude that the clinical management of bronchiolitis requires close monitoring of body wt and plasma osmolality-urinary osmolality relationship; serum sodium levels may be misleading.