Introduction: Continuous bladder irrigation (CBI) is a common intervention for the prevention of urinary tract clots for postoperative management in urologic surgery. In CBI, the color of urine outflow is assessed subjectively, and adjustments are made to flow rate to reduce the color of blood in the effluent. However, repeated subjective assessments tend to be labour intensive, unstandardized, and rarely immediately responsive to changes in effluent color. Hence, we present an open-source assembly to construct an automatic CBI monitor (hematuria monitor, HM), featuring 3D-printed enclosures and consumer-market hardware.
Methods: The HM uses the Arduino open-hardware platform. All components have full hardware specifications available online. Instructions available at www.github.com/malyalar/CBI-monitor include CAD files for enclosures, circuit schematics and layouts, source code, and data from validity analysis. The spectral sensing device is a 3D printed shroud where a white LED is mounted opposite to a AS7262 spectrophotometer module (AMS). Incident light is passed through a CBI catheter outflow tube clipped inside the shroud, resulting in a reading at the photodiode proportional to the hematuria in the tube. The device also measures flow rate through rate-of-change calculations at a load cell from which the catheter outflow bag is mounted, and is capable of detecting obstructions or inadequate saline in reserve. Telemetry is offered via a small TFT screen. Testing was conducted with 5 serial dilutions of pigs’ blood in normal saline, encompassing a full range of hematuria grades, sealed within portions of catheter outflow bag tubing.
Results: The device can continuously monitor flow rate, estimate blood concentrations, and output alarms in cases of obstruction in laboratory settings. The total cost for the HM in its most basic implementation is approximately 35 dollars CAD. No special skills or tools are required to build this system. In testing, the HM achieved a correlation coefficient of 0.97, p=0.006 for its estimations of hematuria against 5 known serial dilutions (in triplicate) of pig’s blood ranging from 0.05mL to 0.3mL in 10mL saline.
Conclusions: An automatic hematuria monitor may be helpful at reducing patient harm and resource waste during CBI. The open-source nature of our device lends itself to lower costs and easy extensibility of features. Next steps include motor control of flow-rate titration to automate the CBI process fully, and further clinical validation of the device.
.jpg)
.jpg)