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Bailey M et al, 2015: Shockwave lithotripsy with renoprotective pause is associated with renovascular vasoconstriction in humans.

Bailey M, Lee F, Hsi R, Paun M, Dunmire B, Liu Z, Sorensen M, Harper J.
Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, USA.
Department of Urology, University of Washington, Seattle, USA.
Department of Biostatistics, Indiana University School of Medicine, Indianapolis, USA.
Department of Urology, University of Washington, Seattle, USA ; Division of Urology, Puget Sound Veteran Affairs Medical Center, Seattle, USA.

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.

IEEE Int Ultrason Symp. 2014 Sep 3;2014:1013-1016

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Comments 1

Hans-Göran Tiselius on Monday, 18 January 2016 11:31

Avoiding kidney damage is the goal of every stone removing procedure, irrespective of which modality that is used. Experimental findings have indicated that vasoconstriction during the early part of the SWL-session might decrease vascular damage. To avoid intra-renal bleeding and to prevent development of hematomas, such a routine commonly has been transferred to clinical SWL.
The principle thereby has been to start with a number of low-power shock waves followed by a pause that was arbitrarily chosen to a couple of minutes.
In the study presented in this article the authors measured resistance index (RI) in order to get information on the degree of vasoconstriction. They were able to confirm that with adherence to the principles referred to above, vasoconstriction occurred. Unfortunately, no control group was used and it was accordingly not demonstrated that the pause was necessary or at all of importance for the subsequent vasoconstriction (increased RI). In a recent animal experiment it was demonstrated that a 4-5-minute administration of low-power shock waves without a pause had a similar protective tissue effect [1].
Whether the obvious increase in RI really reflected a decreased risk of kidney damage is of course difficult to prove. There is no information on how fast RI returned to pre-treatment levels.
The authors claim that a control group treated without the renal protective protocol would be of ethical concern, because of previous experimental findings. This seems to be a weak argument for not including controls. I have doubts that this routine is so well established that it would be unethical to apply other routines for shock wave administration. Moreover, it is emphasized by the authors that also patients treated differently increase their RI.
Reference
1. Handa RK, McAteer JA, Connors BA, Liu Z, Lingeman JE, Evan AP Optimising an escalating shockwave amplitude treatment strategy to protect the kidney from injury during shockwave lithotripsy. BJU Int. 2012 Dec;110(11 Pt C):E1041-7.

Avoiding kidney damage is the goal of every stone removing procedure, irrespective of which modality that is used. Experimental findings have indicated that vasoconstriction during the early part of the SWL-session might decrease vascular damage. To avoid intra-renal bleeding and to prevent development of hematomas, such a routine commonly has been transferred to clinical SWL. The principle thereby has been to start with a number of low-power shock waves followed by a pause that was arbitrarily chosen to a couple of minutes. In the study presented in this article the authors measured resistance index (RI) in order to get information on the degree of vasoconstriction. They were able to confirm that with adherence to the principles referred to above, vasoconstriction occurred. Unfortunately, no control group was used and it was accordingly not demonstrated that the pause was necessary or at all of importance for the subsequent vasoconstriction (increased RI). In a recent animal experiment it was demonstrated that a 4-5-minute administration of low-power shock waves without a pause had a similar protective tissue effect [1]. Whether the obvious increase in RI really reflected a decreased risk of kidney damage is of course difficult to prove. There is no information on how fast RI returned to pre-treatment levels. The authors claim that a control group treated without the renal protective protocol would be of ethical concern, because of previous experimental findings. This seems to be a weak argument for not including controls. I have doubts that this routine is so well established that it would be unethical to apply other routines for shock wave administration. Moreover, it is emphasized by the authors that also patients treated differently increase their RI. Reference 1. Handa RK, McAteer JA, Connors BA, Liu Z, Lingeman JE, Evan AP Optimising an escalating shockwave amplitude treatment strategy to protect the kidney from injury during shockwave lithotripsy. BJU Int. 2012 Dec;110(11 Pt C):E1041-7.
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