Urinary uric acid excretion as an indicator of severe hypoxia and mortality in patients with obstructive sleep apnea and chronic obstructive pulmonary disease.

OBJECTIVE: Uric acid (UA) is the end product of adenosine triphosphate degradation, and could increase due to hypoxia. We investigated the association of UA metabolites with nocturnal hypoxemia, apnea-hypopnea index (AHI), noninvasive mechanical ventilation (NIMV) usage and five-year mortality. MATERIALS/SUBJECTS AND METHODS: We obtained urinary specimen before and after the night polysomnography in order to measure UA excretion and overnight change in urinary UA/creatinine ratio (ΔUA/Cr) in 75 subjects (14 controls, 15 chronic obstructive pulmonary disease (COPD) without nocturnal hypoxemia (NH), 15 COPD with NH, 16 obstructive sleep apnea syndrome (OSAS) without NH, 15 OSAS with NH). Percentage of time spent below SaO2 of 90% (T90%) for >10% of sleep time was considered as nocturnal hypoxemia. Patients were contacted after 5 years with a questionnaire including information on the use of NIMV treatment (n: 58) and urinary specimen analysis (n: 35). RESULTS: T90% was found to be significantly correlated with UA excretion (coefficient: 0.005, 95%CI: 0.003-0.007) and ΔUA/Cr (coefficient: 0.8, 95%CI: 0.3-1.2) after adjustments for age, gender, body mass index and apnea-hypopnea index. Median and IQR (interquartile range) of baseline UA excretion were 0.79 (0.51-0.89) and 0.41 (0.31-0.55) in 10 deceased and 58 surviving patients, respectively (p=0.001). UA excretion median and IQR of baseline and 5 years of NIMV treatment were 0.41 (0.36-0.57) and 0.29 (0.23-0.37), respectively (p=0.01). CONCLUSION: UA excretion, as a marker of tissue hypoxia, may be useful in the management of OSA and COPD patients.

Microalbuminuria in chronic obstructive pulmonary disease.

BACKGROUND: In this study, the presence of microalbuminuria in patients with chronic obstructive pulmonary disease (COPD) in whom no proteinuria was determined by conventional methods, has been studied taking into account the possible relationship between microalbuminuria and respiratory parameters and their predictive role on mortality. METHODS: Twenty-five cases with COPD who had been hospitalized because of an acute exacerbation and 25 healthy age and sex matched volunteers were included in the study. Microalbuminuria measurement, arterial blood gas analysis, and forced expiratory volume in one second (FEV1), forced vital capacity (FVC) measurements were performed in the COPD group at the beginning of hospitalisation (admission) and after therapy for an average period of 14 +/- 6 days when they were stable at the time of discharge (discharge). Urinary albumin/creatinine (a/c) ratio > or = 2.5 mg/mmol was accepted as microalbuminuria. RESULTS: Microalbuminuria was detected in 14 (56%) subjects at admission and in 7 (28%) subjects at discharge in the COPD group and in 1 (4%) subject in the control group. There were statistically significant differences among these groups (admission-control p < 0.001, discharge-control p = 0.023, admission-discharge p = 0.016). In COPD group, mean a/c ratio was 3.9 +/- 3.8 at the time of admission, 1.7 +/- 1.9 at discharge and 0.5 +/- 0.5 mg/mmol in the control group. There were statistically significant differences among these groups (admission-control p < 0.001, discharge-control p = 0.029, admission-discharge p = 0.002). In the COPD group there were negative correlation between the microalbuminuria values at admission and arterial pO2 and oxygen saturation (p = 0.031, r = -0.433 and p = 0.002, r = -0.596 respectively). There were no relation between the microalbuminuria values and age, arterial pH, pCO2, FEV1 percent predicted, FVC percent predicted and FEV1/FVC. There were no statistically significant differences between the subjects with or without microalbuminuria according to the median survival time. CONCLUSIONS: In a quite large number of patients with COPD in whom no proteinuria were determined by conventional methods, especially at the time of exacerbation, microalbuminuria could be seen. Microalbuminuria was related with hypoxemia but has no predictive role on mortality.