REDUCTION OF BLADDER OUTLET RESISTANCE BY SELECTIVE SACRAL ROOT STIMULATION USING HIGH-FREQUENCY BLOCKADE IN DOGS - AN ACUTE STUDY

Detrusor-sphincter dyssynergia is a main problem in supra-sacral spina l cord injured patients. The problem of high pressure voiding is also encountered in most electrically induced micturition because of the mi xed somatic and autonomic fiber components of the ventral sacral root. We studied the effect of selective high-frequency blockade at the sac ral nerve root in an acute spinalized canine model to prevent the dele terious consequences associated with the elevated bladder outlet resis tance. A new functional electrical stimulation system which can genera te one signal composed of two independent adjustable current waveforms delivered via a single bipolar electrode was used in 11 dogs. The sel ectivity resulted from the inhibition of the sphincteric somatic inner vation by a high frequency pulse while the low frequency stimuli activ ated the bladder autonomic fibers. Bladder and urethral pressure as we ll as electromyograms of external urethral sphincter were recorded to determine whether selective high-frequency blockade occurred. Our expe riments showed that we were able to achieve selective blockade of the external urethral sphincter during the simultaneous detrusor stimulati on, thus obtaining a more physiologic voiding.