Onset of the action of intravesical lidocaine after spinal cord injury

Aims To obtain objective evidence for the time to onset of action for intravesical lidocaine utilizing exaggerated sympathetic blood-pressure responsiveness in patients with spinal cord injuries (SCI). Methods This prospective observational cohort study analyzed blood pressure responses in individuals with SCI at or above T6 who did (lidocaine-instillation group) or did not (control group) receive 10 ml of 2% lidocaine gel instilled through their catheters before routine suprapubic catheter change. Care was taken to minimize any potentially confounding position change or catheter manipulation. Given the potential for C-fiber mediated systolic blood pressure (SBP) increases after SCI, the time to lidocaine's onset of action for blocking these C-fibers (as seen by the decrease in SBP more than and equal to 10 mm Hg) was assessed with serial blood pressures for 4 to 6 minutes. Results Blood pressures were evaluated in 32 individuals with SCI (lidocaine-instillation group n = 22, control group n = 10). In the lidocaine-instillation group, 45% individuals demonstrated a sustained decrease in SBP more than and equal to 10 mm Hg, which occurred at a mean of 98.1 seconds (SD 59 seconds) after lidocaine instillation. Despite up to 6 minutes of serial monitoring, the remainder of the lidocaine-instillation group and the entire control group had SBP fluctuations less than 10 mm Hg. The serial mean SBPs of those who responded to lidocaine were significantly less than the remaining groups (P < .001 for both comparisons). Conclusion Utilizing lidocaine's properties to decrease sympathetic-inducing afferents after SCI, the time to onset of action for intravesical lidocaine was found to be approximately 90 seconds. This relatively rapid initial onset on action is especially pertinent when managing autonomic dysreflexia.