A Pilot Study to Assess Effects of Self-Administered Nitrous Oxide (SANO) on Urodynamic Study (UDS) Parameters

Lower Urinary Tract Symptoms

urodynamic study, nitrous oxide, neurogenic bladder, overactive bladder, ambulatory, patient experience of care

A urodynamic study (UDS) is a common procedure done to learn more about the cause of urinary symptoms. For some patients, UDS can be associated with anxiety or discomfort. Nitrous oxide (or laughing-gas) is a well-known sedative which is frequently used in dental offices and for pediatric procedures to reduce anxiety and pain. This study is being done to see if giving low-dose (20-50%) nitrous oxide at the time of UDS affects the measurements taken during the procedure, such as how much volume your bladder can hold, and pressures during urination. If the measurements are the same with and without self-administered nitrous oxide (SANO), it could be suggested that nitrous oxide may be a useful way of reducing patient anxiety and pain during UDS.

Randomization is performed according to a 1:1 block model immediately before the start of UDS. Patients are randomized to receive oxygen followed by SANO or SANO followed by oxygen. The procedural team and patient are blinded to the treatment. Muscarinic medications are stopped 24 hours prior to UDS, and patients provide a urine sample to confirm negative cultures. In this study, the Nitrouseal® system is utilized to administer adjustable amounts of N2O (20-50%) using a single-use disposable mask. The system scavenges exhaled N2O and limits the maximum amount of N2O to 50%. After fitting the Nitrouseal mask, the patients are instructed on how to communicate with hand signals throughout the study to titrate the level of gas being administered. Patients receive SANO during catheter placement to determine their preferred N2O level. Following a "washout" period of two minutes, patients undergo two UDS fills following the randomization scheme. Residual urine is removed between runs using the UDS catheter. UDS are performed according to the 2012 AUA/SUFU Adult Urodynamic Guidelines. All UDS are performed on a Laborie Aquarius XT machine (Laborie Medical, Portsmouth, NH) using 7 Fr dual lumen fluid urethral catheters, 9 Fr dual lumen fluid-filled rectal catheters, and EMG gel patch electrodes. Filling is performed at 50 cc/min with normal saline at room temperature. During the voiding phase, patients are positioned to be sitting or standing according to their comfort. An intention-to-treat analysis is performed on 19 participants. Maximum cystometric capacity is measured as the primary outcome. Secondary outcomes include patient-reported pain and anxiety measured at baseline and immediately before maximum capacity during each UDS run using the Visual Analog Scale for Pain (VAS-P; range 0-10) and the Visual Analog Scale for Anxiety (VAS-A; range 0-10). The blinded UDS operator assesses patient responsiveness (ability to communicate) and tolerance on a 3-point Likert scale: worse than expected, as expected, or better than expected. Standard UDS parameters per International Continence Society terminology, including first sensation, first desire, strong desire, MCC, bladder compliance (volume/Pdet Max during filling), detrusor overactivity, detrusor sphincter dyssynergia, inability to void, maximum flow rate, Pdet during maximum flow rate, voided volume, post-voided residual, and voided percentage, are compared for significant differences between the SANO and Oxygen runs. Post-procedure patient surveys are administered to assess personal experience of catheter placement, desire to have SANO for future UDS, and satisfaction with N2O levels. Finally, electronic medical records are monitored for Clavien-Dindo graded complications for up to 30 days following the UDS.

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