153 ABDOMINAL PRESSURE TRANSMISSION DEVICES FOR URETHRAL SPHINCTERS: IN VITRO EFFECTS AND CLINICAL OUTCOMES

Abstract

INTRODUCTION AND OBJECTIVES: The Artificial Urinary Sphincter is generally considered to be the ‘Gold Standard’ treatment for post prostatectomy stress urinary incontinence by providing a circumferential increase in urethral pressure. Recently, a number of new hydraulic sphincter systems have been developed. We evaluated urethral pressures and clinical outcomes for two of this new generation of devices. METHODS: In vitro study: Two hydraulic sphincter systems were evaluated. The commercially available Flow Secure sphincter was compared to an AMS 800 system extended by a 4cm open “trigger”cuff for direct pressure transmission to the urethral cuff. Pressure transmission from the “trigger” to the urethral cuff (pressure rise and delay) as well as the efficacy of the pump (pressure change/pumpstroke) were evaluated. Clinical study: Five patients with AMS 800 sphincters who had additionally received the pressure transmission device (open 4 cm cuff extension) secondary to persistent urinary leakage were analyzed. Five patients after implantation of Flow Secure sphincters were also evaluated to assess continence during stress, voiding comfort and pump function. RESULTS: In vitro testing demonstrated “abdominal” pressure was transferred to the AMS cuff by 44% (+/-4%). The delay came to approximately 180 milliseconds. By compressing the pump, cuff pressure was decreased by 38 (+/4) cm H2O, thus emptying the cuff after a maximum of 3 strokes. In the Flow Secure system the pressure transmission as well as delay was equal, however, up to 30 strokes were necessary to completely empty the cuff, reducing the pressure by only 3-4 cm H2O per stroke. In clinical practice, 5/5 AMS 800 KB patients needed only 3 (+/0.8) strokes to initiate voiding and enable normal flow rates. All patients were dry on stress test. All 15 of the Flow Secure patients needed 8 or more pump strokes to initiate voiding, whilst maintaining obstructed voiding patterns. However, 68 % of patients were dry at stress test. CONCLUSIONS: Direct pressure transmission to the cuff is an interesting concept to improve clinical outcomes of hydraulic sphincters. However, possible pitfalls include obstructive voiding, especially when the transmission reservoir contains a high volume. Initiating voiding is by far more easily achieved with the AMS pump compared to the Flow Secure pump.