Study ObjectivesTo assess the relationship between urine osmolality, cardiovascular parameters, and nocturnal enuresis in a population of children undergoing polysomnographic assessment.MethodsThis prospective observational study included consecutive children aged 5–17 years presenting for overnight polysomnography. Children were evaluated using continuous ambulatory blood pressure monitoring to assess heart rate and blood pressure. Urine samples were collected throughout the night to determine urine sodium excretion and osmolality. Comparisons of results were made between children with and without a history of nocturnal enuresis.ResultsA total of 61 children were included for analysis; 13 had a history of nocturnal enuresis. Children with nocturnal enuresis had greater disruption in respiratory parameters including higher apnea–hypopnea index (mean difference 12.2 ± 8.8 events/h, p < 0.05), attributable to more central respiratory events (mean difference 5.4 ± 4.9, p < 0.05), and higher variability in both oxygen and carbon dioxide parameters compared to those without nocturnal enuresis. Sleep parameters, urine osmolality, and blood pressure did not differ between groups. Children with nocturnal enuresis showed an increase, rather than a decrease, in heart rate across the night (+5.4 ± 19.1 vs. −6.0 ± 14.8 beats/min, p < 0.05).ConclusionsChildren with a history of nocturnal enuresis have greater respiratory abnormalities, no differences in urine osmolality or blood pressure, and loss of normal heart rate decrease across the night. This pattern suggests that autonomic control, rather than renal or hemodynamic abnormalities, may contribute to the pathophysiology of nocturnal enuresis.

In this study we compared low (125 micrograms) and conventional (500 micrograms) doses of cyclopenthiazide on the renin angiotensin system, plasma and extracellular fluid volumes and the pressor responsiveness to angiotensin II since we have previously shown that the two doses have the same antihypertensive effect but different effects on plasma renin activity. Following a two week placebo run-in period, 8 healthy male volunteers received 125 micrograms or 500 micrograms of cyclopenthiazide for 2 treatment periods of 4 weeks as part of a double blind, 2-part crossover study with treatment periods separated by a 4-week placebo washout phase. Measurements were made on two study days at the beginning and end of the active treatment periods. On the first day serum potassium, plasma renin activity and plasma angiotensin II levels were measured after a 1 h period of supine rest. Plasma and extracellular fluid volumes were also measured after appropriate equilibration times. The blood pressure responses to angiotensin II were assessed on day 2. The 500 micrograms dose of cyclopenthiazide had a greater effect than the 125 micrograms dose on plasma renin activity, serum potassium, angiotensin II levels and extracellular fluid volumes. Neither drug had any effect on plasma volume or the responsiveness to infused angiotensin II. Low dose cyclopenthiazide failed to increase angiotensin II levels, contract body fluid volumes or attenuate vascular reactivity in normotensive volunteers.