Urinary catecholamines during stress and ambulatory blood pressure in children born full term but small for gestational age: a pilot study

Abstract

OBJECTIVES: Increased sympathetic activity is proposed to be a mechanism of high blood pressure in children born small for gestational age. Ambulatory blood pressure monitoring is a form of blood pressure measurement that can detect high blood pressure outside the hospital in patients with normal office blood pressure. This condition is called masked hypertension. There are limited data on association between ambulatory blood pressure and urinary catecholamines during exposure to stress in children born small for gestational age. METHODS: Nineteen children born small for gestational age and 17 healthy controls ages 6-14 years old were included. Demographic data and office blood pressure were collected. Urinary catecholamines were collected before and after exposure to stress including mathematical test and venipuncture. Afterwards, ambulatory blood pressure monitoring was performed to obtain 24-hour blood pressure profiles. RESULTS: All children had normal office blood pressure but ambulatory blood pressure monitoring revealed masked hypertension in six children born small for gestational age (32%) and two controls (11.7%). After stress, median percentage of increase in urine norepinephrine levels was greater in children born small for gestational age with masked hypertension than that of children born small for gestational age without masked hypertension (9.2 vs. -13.2 μg/g creatinine, P = 0.05). There was no increase in urine norepinephrine levels in controls with masked hypertension. Among children born small for gestational age, awake SBP z-scores had significant positive correlations with pre- and post-stress urinary dopamine levels (r = 0.530, P = 0.02 and r = 0.597, P = 0.007, respectively). CONCLUSION: Masked hypertension is not uncommon in children born small for gestational age. After stress, urinary norepinephrine levels were increased in children born small for gestational age with masked hypertension.