title: Shockwave lithotripsy with renoprotective pause is associated with renovascular vasoconstriction in humans.
abstract: Animal studies have shown that shock wave lithotripsy (SWL) delivered with an initial course of low-energy shocks followed by a pause reduces renal injury. The pause correlates with increased arterial resistive index (RI) during SWL as measured by ultrasound. This suggests that renal vasoconstriction is associated with protecting the kidney from injury. This study explored whether a similar increase in RI is observed in humans. Patients were prospectively recruited from two hospitals. All received an initial dose of 250 lowest energy shocks followed by a two-minute pause. Shock power was then ramped up at the discretion of the physician; shock rate was maintained at 1 Hz. Spectral Doppler velocity measurements were taken from an interlobar artery at baseline after induction, during the pause at 250 shocks, after 750 shocks, after 1500 shocks, and at the end of the procedure. RI was calculated from the peak systolic and end diastolic velocities and a linear mixed-effects model was used to compare RIs. The statistical model accounted for age, gender, laterality, and body mass index (BMI). Measurements were taken from 15 patients. Average RI ± standard deviation pretreatment, after 250 shocks, after 750 shocks, after 1500 shocks, and post treatment was 0.68 ± 0.06, 0.71 ± 0.07, 0.73 ± 0.06, 0.75 ± 0.07 and 0.75 ± 0.06, respectively. RI was found to be significantly higher after 250 shocks compared to pretreatment (p = 0.04). RI did not correlate with age, gender, BMI, or treatment side. This is suggestive that allowing a pause for renal vascular vasoconstriction to develop may be beneficial, and can be monitored for during SWL, providing real-time feedback as to when the kidney is protected.
authors.affiliation: Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Bailey
authors.affiliation: Department of Urology, University of Washington, Seattle, USA.
authors.forename: Franklin
authors.initials: F
authors.lastname: Lee
authors.affiliation: Department of Urology, University of Washington, Seattle, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Hsi
authors.affiliation: Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, USA.
authors.forename: Marla
authors.initials: M
authors.lastname: Paun
authors.affiliation: Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, USA.
authors.forename: Barbrina
authors.initials: B
authors.lastname: Dunmire
authors.affiliation: Department of Biostatistics, Indiana University School of Medicine, Indianapolis, USA.
authors.forename: Ziyue
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Urology, University of Washington, Seattle, USA ; Division of Urology, Puget Sound Veteran Affairs Medical Center, Seattle, USA.
authors.forename: Mathew
authors.initials: M
authors.lastname: Sorensen
authors.affiliation: Department of Urology, University of Washington, Seattle, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Harper
keywords: resistive index; shock wave lithotripsy; ultrasound; vasoconstriction