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The Pressure Exerted by the External Sphincter of the Urethra when its Motor Nerve Fibres are Stimulated Electrically
Author(s) -
BRINDLEY G. S.,
RUSHTON D. N.,
CRAGGS M. D.
Publication year - 1974
Publication title -
british journal of urology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.773
H-Index - 148
eISSN - 1464-410X
pISSN - 0007-1331
DOI - 10.1111/j.1464-410x.1974.tb10184.x
Subject(s) - stimulation , contraction (grammar) , sphincter , anatomy , external anal sphincter , urethra , pudendal nerve , motor nerve , muscle contraction , urethral sphincter , tetanic stimulation , medicine , urology , surgery , anal canal , rectum , receptor , neurotransmission
Summary It is possible, through anal electrodes that we have designed specially for the purpose, to stimulate all the motor fibres of the pudendal nerves and thus cause maximal contractions of the muscles that they innervate. Anal and vaginal devices now in use for treating incontinence do not do this. The force exerted by the anal sphincter under tetanic stimulation of its motor nerve fibres is, during the first few seconds, greater for high than for low frequencies of stimulation. But the sphincter fatigues more at high frequencies, so that if the force is measured between the 3rd and the 10th minute of stimulation it is greater for 12 pulses/sec than for 54 pulses/sec; 24 pulses/sec gives intermediate force. The fatigue is almost complete in 2 minutes. The opening pressure for retrograde flow through the external sphincter of the urethra is roughly 120 mm Hg during prolonged maximal tetanic stimulation at 12 pulses/sec, and roughly 90 mm Hg during prolonged maximal stimulation at 54 pulses/sec. Stimulation through our anal electrodes with shocks large enough to cause maximal contraction of the pelvic floor muscles causes in both sexes, at 12 or 24 pulses/sec, complete inability to expel urine during at least 10 minutes. We give evidence that the inability is due to the contraction of the striated muscles that close the urethra, not to inhibition of detrusor contraction. The stimuli do tend to inhibit detrusor contraction, but this tendency can be overcome with practice. We confirm published observations that total bilateral pudendal block is compatible with continence and with voluntary micturition. Continence is sustained against 110 mm Hg lung pressure. Micturition, though possible, is slowed.