Background: Assessment of bladder emptying is challenging in patients who are not verbal and not toilet-trained. Without indication of voiding, delays in post-void residual (PVR) measurements can result in inaccurate values due to bladder refilling. Our pilot data previously demonstrated that an enuresis alarm detected more than 90% of voids in infants with no feasibility or safety concerns. Here, we sought to test the feasibility and efficacy of using an enuresis alarm to guide timing of PVR measurements in infants.
Methods: We prospectively enrolled 15 infants who were hospitalized between May and December 2023. Inclusion criteria were: (1) healthy infants hospitalized for routine postnatal care, feeding issues, or respiratory concerns and (2) between 36 and 50 weeks adjusted post-conceptual age. Exclusion criteria were: (1) known urological or neurological conditions, (2) active urinary tract infection, or (3) presence of indwelling urinary catheter. Every patient underwent an 8-hour study period that included a 4-hour intervention period with alarm in diaper (PVR after alarm trigger) and a 4-hour control period of routine care (PVR when nurses observe wet diapers). PVR was measured with an ultrasound bladder scanner (Verathon BladderScan® BVI 9400). The primary endpoint of PVR volume was analyzed using linear regression with volume as the dependent variable and both study period and patient weight as independent variables. Secondary endpoint of the number of detected voids was analyzed using Mann-Whitney U test.
Results: Median age was 6 weeks (range 0.7 to 20) and median weight was 3.88 kg (range 2.53 to 5.98), Table. The most common diagnoses were failure to thrive/feeding difficulties (n=8) and respiratory infection/difficulties (n=5). One of the 15 patients was excluded from analysis due to not having at least one void in both the alarm and routine care study periods. Of the remaining 14 patients, median number of voids detected was significantly greater in the alarm versus routine care periods (3 vs 2 voids, p=0.0029). There was no significant difference in the measured PVR volume between groups (mean difference: -2.23 mL, 95% CI: -7.09 to 2.63, p=0.363) after adjusting for patient weight, Figure. Every 1 kg increase in weight was associated with a mean increase of 3.88 mL (95% CI 1.23 to 6.54, p = 0.005) in PVR volumes.
Conclusions: In hospitalized infants, use of an enuresis alarm resulted in detecting significantly more voiding events but no significant difference in PVR volume. This may be related to high frequency and small volume voids in otherwise healthy, young infants. Further research may show whether it is useful in situations where frequency of voiding is relevant or where even small differences in PVR volume may be clinically important, such as during bladder function assessment in newborns with spina bifida.
