RESUMO
INTRODUCTION: Adults with obstructive sleep apnea have increased sympathetic activity. It was hypothesized that in children with symptoms of obstructive sleep-disordered breathing (SDB), morning urine levels of catecholamines correlate with severity of nocturnal hypoxemia. METHODS: Children with snoring referred for polysomnography and controls without snoring were recruited. Morning urine norepinephrine, epinephrine, normetanephrine, and metanephrine levels were measured (ng/mg urine creatinine). RESULTS: Twelve children (age 5.2 +/- 2.3 years) with severe hypoxemia (oxygen saturation of hemoglobin-SpO2 nadir < or =86%), 20 subjects (age 6.1 +/- 2.1 years) with moderate hypoxemia (SpO2 nadir < or =90% and >86%), 22 children (age 6.6 +/- 1.5 years) with mild nocturnal hypoxemia (SpO2 nadir >90%), and 10 controls (age 7.1 +/- 2.8 years) were studied. Children with severe hypoxemia had significantly higher log-transformed norepinephrine levels (1.63 +/- 0.29) compared to those with moderate hypoxemia (1.43 +/- 0.22; P < 0.05) or compared to controls (1.39 +/- 0.31; P < 0.05). In subjects with SDB, log-transformed oxygen desaturation of hemoglobin index or SpO2 nadir predicted log-transformed norepinephrine levels after adjustment by age, gender and body mass index (r2 = 0.24; and r2 = 0.24, respectively; P < 0.01). CONCLUSIONS: Severity of nocturnal hypoxemia in children with intermittent upper airway obstruction during sleep correlates with morning urine levels of norepinephrine suggesting increased sympathetic tone.
