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ELECTRICALLY STIMULATED DETRUSOR MYOPLASTY
0022-5347/00/1643-0969/0 THE JOURNAL OF UROLOGY® Copyright © 2000 by AMERICAN UROLOGICAL ASSOCIATION, INC.®
Vol. 164, 969 –972, September 2000 Printed in U.S.A.
ELECTRICALLY STIMULATED DETRUSOR MYOPLASTY JOHN G. VAN SAVAGE, GUSTAVO P. PEREZ-ABADIA, LUCIO G. PALANCA, JANOU W. BARDOEL, THOMAS HARRALSON, BRUCE L. SLAUGHENHOUPT, MARTIN M. PALACIO, GORDON R. TOBIN, CLAUDIO MALDONADO AND JOHN H. BARKER From the Divisions of Pediatric Urology, and Plastic and Reconstructive Surgery, Department of Surgery, University of Louisville School of Medicine, Louisville, Kentucky, and Urology, Children’s Hospital, Cordoba, Argentina
ABSTRACT
Purpose: Many children with spina bifida and other causes of neurogenic bladder rely on clean intermittent catheterization to empty the hyporeflexic or areflexic bladder. Direct bladder and sacral nerve root stimulation have been met with limited success. We studied the electrical stimulation of a rectus abdominis muscle flap wrapped around the bladder to achieve bladder contractility and emptying. Materials and Methods: The feasibility of performing rectus detrusor myoplasty in humans was first studied in 8 cadavers. In male and female cadavers it was possible to wrap the distended bladder completely with the rectus abdominis muscle. The rectus abdominis muscle was surgically dissected with preservation of its insertion on the pubis bone and rotation of its mid section behind the bladder to effect a complete bladder wrap. The deep inferior epigastric artery and veins, and 2 most caudal intercostal nerves were preserved. This unilateral rectus abdominis muscle flap was then electrically stimulated with 2 pairs of bipolar electrodes inserted into the muscle near the nerve entrance. Stimulation frequencies of 40, 60 and 80 Hz. were used in each of the 8 dogs. The increase in intravesical pressure over baseline, compliance and post-void residual were measured. Paired Student’s t tests were used for statistical comparisons. Results: The increase in intravesical pressure ranged 35 ⫾ 5 to 45 ⫾ 7 cm. H2O at stimulation frequency 40 and 80 Hz., respectively. Post-void residual was 27 ⫾ 4%, 22 ⫾ 3% and 26 ⫾ 3% at stimulation frequencies 40, 60 and 80 Hz., respectively. Intravesical pressure was significantly increased over baseline bladder pressure (p ⬍0.05). Conclusions: Electrically stimulated detrusor myoplasty results in uniform increases in intravesical pressure and reasonable bladder emptying in an animal model. We are currently investigating detrusor myoplasty in a chronic study to determine whether it can be used for enhanced bladder emptying in children with poor detrusor contractility. KEY WORDS: bladder; electric stimulation; muscles; bladder, neurogenic; surgical flaps
A variety of conditions produce poor detrusor contractility and impaired bladder emptying. In children spina bifida and traumatic spinal cord injuries account for many cases of detrusor hyporeflexia and areflexia. Standard treatment options to empty the bladder include clean intermittent catheterization with or without continent urinary diversion, chronic indwelling Foley urethral catheter or suprapubic cystostomy tube, and ileal or colon conduit. There is a large body of literature on attempts to empty the bladder through electrical stimulation directly to the detrusor muscle or to the anterior sacral nerve roots using a variety of stimulation techniques and protocols.1–10 Direct bladder stimulation results have been poor, although the more recent anterior sacral nerve root stimulation protocols are improving. Because these procedures require intact sacral motor nerve roots and a detrusor muscle capable of contraction, wrapping the bladder with a skeletal muscle with its own vascular and nerve supply has been attempted.11–13 Restoration of voluntary bladder emptying by transplantation of the latissimus dorsi muscle around the bladder using the tension torsion model has shown initial promising results.14 –17 Initial enthusiasm for procedures using the rectus abdominis muscle has waned, mostly due to competition from the anterior sacral nerve root stimulation and latissimus dorsi
detrusor myoplasty.18 It was thought that electrically stimulated detrusor myoplasty using the rectus muscle might be more successful. Little work has been done on the combined use of neuromuscular electrical stimulation and detrusor myoplasty using a skeletal muscle flap wrapped around the bladder. We studied the electrical stimulation of a rectus abdominis muscle flap wrapped around the bladder to achieve bladder contractility and emptying. METHODS
Preliminary studies. Our initial goal was to produce a model of neurogenic bladder in the dog and then overcome the absence of bladder emptying with electrically stimulated detrusor myoplasty using the rectus abdominis muscle. Various degrees of cauda equina compression were used to produce detrusor hyporeflexia or areflexia. However, the undesirable effect of lower extremity paralysis and paresis could not be overcome, and these investigations were terminated.19, 20 The feasibility of performing rectus detrusor myoplasty in humans was studied in 8 cadavers. In male and female cadavers it was possible to wrap the distended bladder completely with 1 or 2 rectus abdominis muscle flaps, leaving the blood supply of the deep inferior epigastric artery and veins intact as well as the 1 or 2 most caudal intercostal nerves (fig. 1, A). The muscle segment that was rotated to the posterior aspect of the bladder had 1, 2 or 3 upper segmental intercos-
Supported by a grant from the Norton Healthcare Trust Fund, a nonprofit organization. 969
970
ELECTRICALLY STIMULATED DETRUSOR MYOPLASTY
FIG. 1. A, rectus abdominis muscle was mobilized preserving its blood supply from deep inferior epigastric artery and veins, and at least 2 most caudal intercostal nerves. B, rectus abdominis muscle was wrapped around bladder posteriorly and electrically stimulated to empty bladder. C, electrically stimulated detrusor myoplasty may be used in conjunction with electrically stimulated urinary sphincter graciloplasty to achieve bladder emptying and continence in cases of detrusor and sphincteric failure.
tal nerves transected to allow it to reach behind the bladder without tension. Based on these anatomical studies in cadavers and the work by Chancellor et al13 we believed that further study in an acute canine model was reasonable. Preoperative urodynamic studies. Experimental protocol was approved by the Institutional Review Board of the University of Louisville School of Medicine as well as the Animal Care Committee. We used 8 adult female mongrel dogs (weight 20 ⫾ 1 kg.) for these experiments. Preoperative urodynamic studies were performed with the dog supine and under anesthesia using 1 mg./kg. Zylazine intravenously or intramuscularly. A 4-channel urodynamic monitor was used to measure detrusor compliance, pressure specific bladder capacity at less than 30 cm. H2O, detrusor instability, leak point pressure, urine flow rate and post-void residual. The same parameters were measured intraoperatively for the urodynamic pressures and urine flow rates. Video fluoroscopy with intravesical contrast material was used to observe bladder emptying after electrical stimulation. Surgical procedure (fig. 1). General anesthesia was administered with 0.1 mg./kg. atropine sulfate subcutaneously, 6 to 12 mg./kg. thiopental sodium intravenously and 94% oxygen, 4% nitrous oxide and 2% halothane administered via an endotracheal tube. A midline abdominal incision was made, and measurements of the rectus muscle were recorded. The rectus abdominis muscle was divided in its mid section and at least 2 of the lowermost intercostal nerves were preserved in their entirety. The deep inferior epigastric artery and veins using the right rectus abdominis muscle were preserved. The attachment to the pubic symphysis was also preserved. The muscle was mobilized and wrapped around the posterior aspect of the bladder and sutured near the bladder neck with 4-zero polyglactin 9.0 acid suture. When the bladder was too large for the unilateral rectus abdominis muscle the lateral sides were buttressed with 2 pieces of approximately 4 ⫻ 3 cm. anterior rectus fascia to avoid lateral protrusion of the bladder during electrical stimulation. Skeletal muscle mapping was done using electromyogram needle electrodes to ensure the best position for electrode insertion with maximum rectus muscle flap stimulation. Two pairs of bipolar temporary myocardial pacing lead electrodes
(6,500 single lead) were inserted near the entry of the intercostal nerves into the rectus abdominis muscle. Electrical stimulation. We electrically stimulated the bladders directly with various stimulation frequencies and intensities, none of which created any increase in bladder pressure or emptying. The rectus abdominis muscle flap was electrically stimulated in random order using frequencies 40, 60 and 80 Hz. The pulse width was 320 microseconds and the intensity (mA.) of stimulation was normalized to motor threshold for each muscle flap. Motor threshold was defined as that stimulus intensity that induced minimal muscle contraction. Measured parameters. The bladder was filled to submaximal capacity (100 cc). It was difficult to achieve a reliable uroflow and the bladder outlet pressure varied from dog to dog. For this reason a Foley urethral catheter large enough to occlude the bladder outlet was introduced and the dogs voided against a fixed pressure of 20 cm. H2O. This voiding was performed against a hydrostatic column of 20 cm. H2O above the bladder outlet. Thus, all dogs in this experiment were standardized to void against the same fixed pressure of 20 cm. H2O regardless of depth of anesthesia, relaxation or lack thereof. The increase in intravesical pressure over baseline (cm. H2O) and half-time to muscle fatigue (seconds) were measured. Half-time to muscle fatigue was defined as the duration of time between the maximal contraction pressure and the decrease to half maximal contraction pressure. Post-void residual was measured as a percentage of the initial 100 cc instilled. Uroflow was measured in cc per second. Data are presented as mean plus or minus standard error of mean. Paired Student’s t tests were used, and p ⬍0.05 was considered significant.
RESULTS
Urodynamics. Preoperative urodynamics revealed mean pressure specific of less than 30 cm. H2O, bladder capacity 125 cc and spontaneous voiding pressure 39 cm. H2O. Mean uroflow rate was 5 cc per second. Detrusor compliance was normal preoperatively and postoperatively, and there was no evidence of detrusor instability. The baseline intravesical
ELECTRICALLY STIMULATED DETRUSOR MYOPLASTY
pressure at 100 cc filling was 15 ⫾ 1 cm. H2O, which was equivalent to the preoperative baseline intravesical pressure (see table). The maximum intravesical pressure generated by electrical stimulation of the rectus abdominis muscle flap at 40, 60 and 80 Hz. was 50 ⫾ 6, 60 ⫾ 7 and 60 ⫾ 7 cm. H2O, respectively. The intravesical pressure with electrical stimulation using any of the 3 frequencies was significantly greater than the baseline intravesical pressure (p ⬍0.05). The uroflow rate was 4 ⫾ 1 cm. H2O per second (fig. 2). Bladder emptying and muscle flap performance. Bladder emptying ranged from 60% to 98%. Post-void residuals were less than 25% in 75% at 40 Hz. and in 63% of the experimental subjects at 60 and 80 Hz. The increase in intravesical pressure and percent of bladder evacuation were similar among the 3 stimulation frequencies (p ⬎0.05). Mean muscle flap length was 20 cm. with a width of 5 cm. The optimal intensity for maximum stimulation of the detrusor myoplasty was 8 times the motor threshold of the intercostal nerves. Higher stimulation frequencies resulted in faster muscle fatigue but no further increase in bladder pressure or decrease in post-void residual measured just before muscle stimulation. The half-time to muscle fatigue was 47 ⫾ 6, 33 ⫾ 4 and 19 ⫾ 4 seconds for stimulation frequencies 40, 60 and 80 Hz., respectively (p ⬍0.05). DISCUSSION
We have shown that electrically stimulated detrusor myoplasty is a reasonable alternative for achievement of bladder emptying in an acute experimental study. This procedure may benefit the many disease states that cause permanent detrusor dysfunction through either damage to the detrusor muscle itself or to its nerve supply. Detrusor hyporeflexia or areflexia may be caused by myelomeningocele, traumatic paraplegia, diabetes, chronic bladder distention related to psychiatric disorders or medication, poliomyelitis, syphilis and surgical trauma. The treatment of choice for those patients with detrusor areflexia who wish to avoid a chronic indwelling catheter is clean intermittent catheterization. However, the patient and/or caretaker must empty the bladder with a catheter every 3 to 4 hours each day for life. This procedure may lead to symptomatic urinary tract infections or injury to the urethra.21–23 Alternatives to clean intermittent catheterization include anterior sacral nerve root or direct detrusor muscle electrical stimulation. These modalities have been hampered by the presence of detrusor-sphincter dyssynergia, and this simultaneous contraction of the bladder outlet and detrusor is deleterious to the kidneys. Perhaps the most successful of the sacral anterior root stimulator procedures has been pioneered by Brindley but this involves a dorsal rhizotomy, and many patients with neurological injuries desire to retain remaining nerve function should a cure be forthcoming.7 Our attempt to produce a model of neurogenic bladder in which
Electrically stimulated detrusor myoplasty urodynamic parameters Stimulation frequency (Hz.)
40
60
80
Mean baseline ⫾ SEM preop. intravesical bladder pressure Mean baseline ⫾ SEM postop. intravesical bladder pressure Mean max. ⫾ SEM preop. intravesical bladder pressure at 100 cc Mean max. ⫾ SEM postop. intravesical bladder pressure at 100 cc Mean increase ⫾ SEM in intravesical bladder pressure with stimulation Mean post-void ⫾ SEM residual (100 cc capacity)
5⫾1
5⫾1
5⫾1
5⫾1
4⫾1
6⫾2
15 ⫾ 1
16 ⫾ 2
13 ⫾ 2
15 ⫾ 1
15 ⫾ 2
15 ⫾ 2
35 ⫾ 5
45 ⫾ 6
45 ⫾ 7
27 ⫾ 4%
22 ⫾ 3%
26 ⫾ 3%
971
FIG. 2. Bladder pressure spike accompanied urine flow after electrical stimulation of detrusor myoplasty.
the animal was still ambulatory was unsuccessful. We believe that since the rectus abdominis muscle flap contracts with electrical stimulation independent of detrusor function or lack thereof that our model is still reasonable. To our knowledge there has not yet been an animal model of neurogenic bladder in which the animal is ambulatory and able to perform usual life activities aside from voiding. The advantage of electrically stimulated detrusor myoplasty over direct bladder or sacral nerve root stimulation is that it produces a skeletal muscle contraction around the bladder that empties it without regard to the state of the detrusor muscle or its nerve roots (see Appendix). Many children with spina bifida have sacral nerve root involvement and would not be candidates for anterior sacral nerve root stimulation. However, our procedure would require functioning intercostal nerve roots, and so it may not be successful in patients with spinal cord levels above L2. This procedure does not create a large thoracoabdominal defect as the latissimus detrusor myoplasty does, which is important because many of these patients are paraplegic and require upper body strength. A limitation of our muscle wrap procedure, which we noted in our cadaver and experimental studies, is that in some cases the bladder may be too large for a single rectus muscle and, thus, may need to be buttressed by additional rectus abdominis muscle fascia or a second rectus abdominis muscle. In cases of a large bladder and in cases of intestinocystoplasty the latissimus muscle may be more beneficial. A fifth of patients with myelomeningocele present with urodynamic alterations consistent with a combined upper and lower motor neuron lesion that can cause bladder detrusor areflexia and intrinsic sphincter dysfunction.24, 25 These patients require clean intermittent catheterization to empty the bladder and also continue to leak between catheterizations, making chronic use of diapers a requirement. If our procedure is successful in a chronic study we would combine it with electrically stimulated gracilis sphincter myoplasty to achieve bladder emptying and continence in cases of detrusor and urinary sphincter failure (fig. 1, C).26 This procedure for bladder emptying and urinary continence can be done in conjunction with antegrade continence enema procedure to rid patients of fecal incontinence.27 With a combination of skeletal muscle flaps and other surgical procedures, patients with neurogenic bladder and bowel may be able to stop using catheterization and diapers, which would have a significant effect on quality of life and is what we are striving for in the future. Dynamic myoplasty procedures have also been used to treat the failing heart (dynamic cardiomyoplasty) and fecal
972
ELECTRICALLY STIMULATED DETRUSOR MYOPLASTY
incontinence (dynamic rectal sphincteroplasty) as well, and it is possible that their role may increase in the future as the devices for electrical stimulation improve.28 CONCLUSIONS
Electrically stimulated detrusor myoplasty results in uniform increases in intravesical pressure and low post-void residuals in an animal model. We are currently investigating detrusor myoplasty in a chronic study to determine whether it can be used for enhanced bladder emptying in children with poor detrusor contractility. APPENDIX: ADVANTAGES OF THE ELECTRICALLY STIMULATED DETRUSOR MYOPLASTY
• • • • •
No catheters required Retains native bladder Works independently of bladder dysfunction etiology Does not require intact nerve supply to bladder Native or artificial bladder can be wrapped and stimulated • Augmented or neobladder may be stimulated • Dorsal rhizotomy unnecessary REFERENCES
1. Halverstadt, D. B. and Parry, W. L.: Electronic stimulation of the human bladder: 9 years later. J Urol, 113: 341, 1975 2. Heine, J. P., Schmidt, R. A. and Tanagho, E. A.: Intraspinal sacral root stimulation for controlled micturition. Invest Urol, 15: 78, 1977 3. Schmidt, R. A., Bruschini, H. and Tanagho, E. A.: Urinary bladder and sphincter responses to stimulation of dorsal and ventral sacral roots. Invest Urol, 16: 300, 1979 4. Creasey, G. H.: Electrical stimulation of sacral roots for micturition after spinal cord injury. Urol Clin North Am, 20: 505, 1993 5. Walter, J. S., Wheeler, J. S., Cogan, S. F. et al: Evaluation of direct bladder stimulation with stainless steel woven eye electrodes. J Urol, 150: 1990, 1993 6. Elabbady, A. A., Hassouna, M. M. and Elhilali, M. M.: Neural stimulation for chronic voiding dysfunctions. J Urol, 152: 2076, 1994 7. Brindley, G. S.: The first 500 patients with sacral anterior root stimulator implants: general description. Paraplegia, 32: 795, 1994 8. Rijkhoff, N. J., Wijkstra, H., van Kerrebroeck, P. E. et al: Selective detrusor activation by electrical sacral nerve root stimulation in spinal cord injury. J Urol, 157: 1504, 1997 9. Rijkhoff, N. J., Wijkstra, H., van Kerrebroeck, P. E. et al: Urinary bladder control by electrical stimulation: review of electrical stimulation techniques in spinal cord injury. Neurourol Urodyn, 16: 39, 1997 10. Tanagho, E. A.: Commentary on selective detrusor activation by electrical sacral nerve root stimulation in spinal cord injury.
J Urol, 157: 1196, 1997 11. Zang, Y. H., Shao, Q. A. and Wang, J. M.: Enveloping the bladder with displacement of flap of the rectus abdominis muscle for the treatment of neurogenic bladder. J Urol, 144: 1194, 1990 12. Chancellor, M. B., Rivas, D. A., Acosta, R. et al: Detrusormyoplasty, innervated rectus muscle transposition study, and functional effect on the spinal cord injury rat model. Neurourol Urodyn, 13: 547, 1994 13. Chancellor, M. B., Rivas, D. A. and Salzman, S. K.: Detrusormyoplasty to restore micturition. Lancet, 343: 669, 1994 14. von Heyden, B., Anthony, J. P., Kaula, N. et al: The latissimus dorsi muscle for detrusor assistance: functional recovery after nerve division and repair. J Urol, 151: 1081, 1994 15. Ninkovic´, M., Stenzl, A., Hess, M. et al: Functional urinary bladder wall substitute using a free innervated latissimus dorsi muscle flap. Plast Reconstr Surg, 100: 402, 1997 16. Stenzl, A., Ninkovic, M., Willeit, J. et al: Free neurovascular transfer of latissimus dorsi muscle to the bladder. I. Experimental studies. J Urol, 157: 1103, 1997 17. Stenzl, A., Ninkovic, M., Ko¨lle, D. et al: Restoration of voluntary emptying of the bladder by transplantation of innervated free skeletal muscle. Lancet, 351: 1483, 1998 18. Chancellor, M. B.: Personal communication 19. Bodner, D. R., Delamarter, R. B., Bohlman, H. H. et al: Urologic changes after cauda equina compression in dogs. J Urol, 143: 186, 1990 20. Hassouna, M., Li, J. S. and Elhilali, M.: Dog as an animal model for neurostimulation. Neurourol Urodyn, 13: 159, 1994 21. Koleilat, N., Sidi, A. A. and Gonzalez, R.: Urethral false passage as a complication of intermittent catheterization. J Urol, 142: 1216, 1989 22. Reisman, E. M. and Preminger, G. M.: Bladder perforation secondary to clean intermittent catheterization. J Urol, 142: 1316, 1989 23. Yamamoto, M., Yasukawa, M. and Yasai, M.: Clean intermittent catheterization in the management of spina bifida: a review of 113 cases. Hinyokika Kiyo, 37: 117, 1991 24. Dator, D. P., Hatchett, L., Dyro, F. M. et al: Urodynamic dysfunction in walking myelodysplastic children. J Urol, 148: 362, 1992 25. Bauer, S. B.: Myelodysplasia: newborn evaluation and management. In: Spina Bifida—A Multi-Disciplinary Approach. Edited by R. L. McLaurin, S. Oppenheimer, L. Dias et al. New York: Kraeger, p. 262, 1986 26. Palacio, M. M., Van Aalst, V. C., Perez Abadia, G. A. et al: Muscular urinary sphincter: electrically stimulated myoplasty for functional sphincter reconstruction. J Urol, 160: 1867, 1998 27. Malone, P. S., Ransley, P. G. and Kiely, E. M.: Preliminary report: the antegrade continence enema. Lancet, 336: 1217, 1990 28. Grandjean, P., Acker, M., Madoff, R. et al: Dynamic myoplasty: surgical transfer and stimulation of skeletal muscle for functional substitution or enhancement. J Rehabil Res Dev, 33: 133, 1996
DISCUSSION
Dr. Yves Homsy. As you know, muscle flaps have been used in humans for congestive heart failure not amenable to other forms of treatment. With respect to the increases in bladder pressure that were generated in the face of a dyssynergic sphincter, how detrimental would this be to the upper tract? Have you addressed this question in your experiment? Dr. John Van Savage. Our study was acute, and we have not evaluated the effects of it on the upper tracts or anywhere else. The initial study was to determine if the bladder could generate pressure by wrapping a rectus muscle around it, which we achieved. Dr. Stuart Bauer. Did you find that with time you had to increase the amount of the intensity of the stimulus to achieve the same response because of changes that occur with the electrode and fibrosis? Doctor Van Savage. There was a slight change.
Vol. 164, 969 –972, September 2000 Printed in U.S.A.
ELECTRICALLY STIMULATED DETRUSOR MYOPLASTY JOHN G. VAN SAVAGE, GUSTAVO P. PEREZ-ABADIA, LUCIO G. PALANCA, JANOU W. BARDOEL, THOMAS HARRALSON, BRUCE L. SLAUGHENHOUPT, MARTIN M. PALACIO, GORDON R. TOBIN, CLAUDIO MALDONADO AND JOHN H. BARKER From the Divisions of Pediatric Urology, and Plastic and Reconstructive Surgery, Department of Surgery, University of Louisville School of Medicine, Louisville, Kentucky, and Urology, Children’s Hospital, Cordoba, Argentina
ABSTRACT
Purpose: Many children with spina bifida and other causes of neurogenic bladder rely on clean intermittent catheterization to empty the hyporeflexic or areflexic bladder. Direct bladder and sacral nerve root stimulation have been met with limited success. We studied the electrical stimulation of a rectus abdominis muscle flap wrapped around the bladder to achieve bladder contractility and emptying. Materials and Methods: The feasibility of performing rectus detrusor myoplasty in humans was first studied in 8 cadavers. In male and female cadavers it was possible to wrap the distended bladder completely with the rectus abdominis muscle. The rectus abdominis muscle was surgically dissected with preservation of its insertion on the pubis bone and rotation of its mid section behind the bladder to effect a complete bladder wrap. The deep inferior epigastric artery and veins, and 2 most caudal intercostal nerves were preserved. This unilateral rectus abdominis muscle flap was then electrically stimulated with 2 pairs of bipolar electrodes inserted into the muscle near the nerve entrance. Stimulation frequencies of 40, 60 and 80 Hz. were used in each of the 8 dogs. The increase in intravesical pressure over baseline, compliance and post-void residual were measured. Paired Student’s t tests were used for statistical comparisons. Results: The increase in intravesical pressure ranged 35 ⫾ 5 to 45 ⫾ 7 cm. H2O at stimulation frequency 40 and 80 Hz., respectively. Post-void residual was 27 ⫾ 4%, 22 ⫾ 3% and 26 ⫾ 3% at stimulation frequencies 40, 60 and 80 Hz., respectively. Intravesical pressure was significantly increased over baseline bladder pressure (p ⬍0.05). Conclusions: Electrically stimulated detrusor myoplasty results in uniform increases in intravesical pressure and reasonable bladder emptying in an animal model. We are currently investigating detrusor myoplasty in a chronic study to determine whether it can be used for enhanced bladder emptying in children with poor detrusor contractility. KEY WORDS: bladder; electric stimulation; muscles; bladder, neurogenic; surgical flaps
A variety of conditions produce poor detrusor contractility and impaired bladder emptying. In children spina bifida and traumatic spinal cord injuries account for many cases of detrusor hyporeflexia and areflexia. Standard treatment options to empty the bladder include clean intermittent catheterization with or without continent urinary diversion, chronic indwelling Foley urethral catheter or suprapubic cystostomy tube, and ileal or colon conduit. There is a large body of literature on attempts to empty the bladder through electrical stimulation directly to the detrusor muscle or to the anterior sacral nerve roots using a variety of stimulation techniques and protocols.1–10 Direct bladder stimulation results have been poor, although the more recent anterior sacral nerve root stimulation protocols are improving. Because these procedures require intact sacral motor nerve roots and a detrusor muscle capable of contraction, wrapping the bladder with a skeletal muscle with its own vascular and nerve supply has been attempted.11–13 Restoration of voluntary bladder emptying by transplantation of the latissimus dorsi muscle around the bladder using the tension torsion model has shown initial promising results.14 –17 Initial enthusiasm for procedures using the rectus abdominis muscle has waned, mostly due to competition from the anterior sacral nerve root stimulation and latissimus dorsi
detrusor myoplasty.18 It was thought that electrically stimulated detrusor myoplasty using the rectus muscle might be more successful. Little work has been done on the combined use of neuromuscular electrical stimulation and detrusor myoplasty using a skeletal muscle flap wrapped around the bladder. We studied the electrical stimulation of a rectus abdominis muscle flap wrapped around the bladder to achieve bladder contractility and emptying. METHODS
Preliminary studies. Our initial goal was to produce a model of neurogenic bladder in the dog and then overcome the absence of bladder emptying with electrically stimulated detrusor myoplasty using the rectus abdominis muscle. Various degrees of cauda equina compression were used to produce detrusor hyporeflexia or areflexia. However, the undesirable effect of lower extremity paralysis and paresis could not be overcome, and these investigations were terminated.19, 20 The feasibility of performing rectus detrusor myoplasty in humans was studied in 8 cadavers. In male and female cadavers it was possible to wrap the distended bladder completely with 1 or 2 rectus abdominis muscle flaps, leaving the blood supply of the deep inferior epigastric artery and veins intact as well as the 1 or 2 most caudal intercostal nerves (fig. 1, A). The muscle segment that was rotated to the posterior aspect of the bladder had 1, 2 or 3 upper segmental intercos-
Supported by a grant from the Norton Healthcare Trust Fund, a nonprofit organization. 969
970
ELECTRICALLY STIMULATED DETRUSOR MYOPLASTY
FIG. 1. A, rectus abdominis muscle was mobilized preserving its blood supply from deep inferior epigastric artery and veins, and at least 2 most caudal intercostal nerves. B, rectus abdominis muscle was wrapped around bladder posteriorly and electrically stimulated to empty bladder. C, electrically stimulated detrusor myoplasty may be used in conjunction with electrically stimulated urinary sphincter graciloplasty to achieve bladder emptying and continence in cases of detrusor and sphincteric failure.
tal nerves transected to allow it to reach behind the bladder without tension. Based on these anatomical studies in cadavers and the work by Chancellor et al13 we believed that further study in an acute canine model was reasonable. Preoperative urodynamic studies. Experimental protocol was approved by the Institutional Review Board of the University of Louisville School of Medicine as well as the Animal Care Committee. We used 8 adult female mongrel dogs (weight 20 ⫾ 1 kg.) for these experiments. Preoperative urodynamic studies were performed with the dog supine and under anesthesia using 1 mg./kg. Zylazine intravenously or intramuscularly. A 4-channel urodynamic monitor was used to measure detrusor compliance, pressure specific bladder capacity at less than 30 cm. H2O, detrusor instability, leak point pressure, urine flow rate and post-void residual. The same parameters were measured intraoperatively for the urodynamic pressures and urine flow rates. Video fluoroscopy with intravesical contrast material was used to observe bladder emptying after electrical stimulation. Surgical procedure (fig. 1). General anesthesia was administered with 0.1 mg./kg. atropine sulfate subcutaneously, 6 to 12 mg./kg. thiopental sodium intravenously and 94% oxygen, 4% nitrous oxide and 2% halothane administered via an endotracheal tube. A midline abdominal incision was made, and measurements of the rectus muscle were recorded. The rectus abdominis muscle was divided in its mid section and at least 2 of the lowermost intercostal nerves were preserved in their entirety. The deep inferior epigastric artery and veins using the right rectus abdominis muscle were preserved. The attachment to the pubic symphysis was also preserved. The muscle was mobilized and wrapped around the posterior aspect of the bladder and sutured near the bladder neck with 4-zero polyglactin 9.0 acid suture. When the bladder was too large for the unilateral rectus abdominis muscle the lateral sides were buttressed with 2 pieces of approximately 4 ⫻ 3 cm. anterior rectus fascia to avoid lateral protrusion of the bladder during electrical stimulation. Skeletal muscle mapping was done using electromyogram needle electrodes to ensure the best position for electrode insertion with maximum rectus muscle flap stimulation. Two pairs of bipolar temporary myocardial pacing lead electrodes
(6,500 single lead) were inserted near the entry of the intercostal nerves into the rectus abdominis muscle. Electrical stimulation. We electrically stimulated the bladders directly with various stimulation frequencies and intensities, none of which created any increase in bladder pressure or emptying. The rectus abdominis muscle flap was electrically stimulated in random order using frequencies 40, 60 and 80 Hz. The pulse width was 320 microseconds and the intensity (mA.) of stimulation was normalized to motor threshold for each muscle flap. Motor threshold was defined as that stimulus intensity that induced minimal muscle contraction. Measured parameters. The bladder was filled to submaximal capacity (100 cc). It was difficult to achieve a reliable uroflow and the bladder outlet pressure varied from dog to dog. For this reason a Foley urethral catheter large enough to occlude the bladder outlet was introduced and the dogs voided against a fixed pressure of 20 cm. H2O. This voiding was performed against a hydrostatic column of 20 cm. H2O above the bladder outlet. Thus, all dogs in this experiment were standardized to void against the same fixed pressure of 20 cm. H2O regardless of depth of anesthesia, relaxation or lack thereof. The increase in intravesical pressure over baseline (cm. H2O) and half-time to muscle fatigue (seconds) were measured. Half-time to muscle fatigue was defined as the duration of time between the maximal contraction pressure and the decrease to half maximal contraction pressure. Post-void residual was measured as a percentage of the initial 100 cc instilled. Uroflow was measured in cc per second. Data are presented as mean plus or minus standard error of mean. Paired Student’s t tests were used, and p ⬍0.05 was considered significant.
RESULTS
Urodynamics. Preoperative urodynamics revealed mean pressure specific of less than 30 cm. H2O, bladder capacity 125 cc and spontaneous voiding pressure 39 cm. H2O. Mean uroflow rate was 5 cc per second. Detrusor compliance was normal preoperatively and postoperatively, and there was no evidence of detrusor instability. The baseline intravesical
ELECTRICALLY STIMULATED DETRUSOR MYOPLASTY
pressure at 100 cc filling was 15 ⫾ 1 cm. H2O, which was equivalent to the preoperative baseline intravesical pressure (see table). The maximum intravesical pressure generated by electrical stimulation of the rectus abdominis muscle flap at 40, 60 and 80 Hz. was 50 ⫾ 6, 60 ⫾ 7 and 60 ⫾ 7 cm. H2O, respectively. The intravesical pressure with electrical stimulation using any of the 3 frequencies was significantly greater than the baseline intravesical pressure (p ⬍0.05). The uroflow rate was 4 ⫾ 1 cm. H2O per second (fig. 2). Bladder emptying and muscle flap performance. Bladder emptying ranged from 60% to 98%. Post-void residuals were less than 25% in 75% at 40 Hz. and in 63% of the experimental subjects at 60 and 80 Hz. The increase in intravesical pressure and percent of bladder evacuation were similar among the 3 stimulation frequencies (p ⬎0.05). Mean muscle flap length was 20 cm. with a width of 5 cm. The optimal intensity for maximum stimulation of the detrusor myoplasty was 8 times the motor threshold of the intercostal nerves. Higher stimulation frequencies resulted in faster muscle fatigue but no further increase in bladder pressure or decrease in post-void residual measured just before muscle stimulation. The half-time to muscle fatigue was 47 ⫾ 6, 33 ⫾ 4 and 19 ⫾ 4 seconds for stimulation frequencies 40, 60 and 80 Hz., respectively (p ⬍0.05). DISCUSSION
We have shown that electrically stimulated detrusor myoplasty is a reasonable alternative for achievement of bladder emptying in an acute experimental study. This procedure may benefit the many disease states that cause permanent detrusor dysfunction through either damage to the detrusor muscle itself or to its nerve supply. Detrusor hyporeflexia or areflexia may be caused by myelomeningocele, traumatic paraplegia, diabetes, chronic bladder distention related to psychiatric disorders or medication, poliomyelitis, syphilis and surgical trauma. The treatment of choice for those patients with detrusor areflexia who wish to avoid a chronic indwelling catheter is clean intermittent catheterization. However, the patient and/or caretaker must empty the bladder with a catheter every 3 to 4 hours each day for life. This procedure may lead to symptomatic urinary tract infections or injury to the urethra.21–23 Alternatives to clean intermittent catheterization include anterior sacral nerve root or direct detrusor muscle electrical stimulation. These modalities have been hampered by the presence of detrusor-sphincter dyssynergia, and this simultaneous contraction of the bladder outlet and detrusor is deleterious to the kidneys. Perhaps the most successful of the sacral anterior root stimulator procedures has been pioneered by Brindley but this involves a dorsal rhizotomy, and many patients with neurological injuries desire to retain remaining nerve function should a cure be forthcoming.7 Our attempt to produce a model of neurogenic bladder in which
Electrically stimulated detrusor myoplasty urodynamic parameters Stimulation frequency (Hz.)
40
60
80
Mean baseline ⫾ SEM preop. intravesical bladder pressure Mean baseline ⫾ SEM postop. intravesical bladder pressure Mean max. ⫾ SEM preop. intravesical bladder pressure at 100 cc Mean max. ⫾ SEM postop. intravesical bladder pressure at 100 cc Mean increase ⫾ SEM in intravesical bladder pressure with stimulation Mean post-void ⫾ SEM residual (100 cc capacity)
5⫾1
5⫾1
5⫾1
5⫾1
4⫾1
6⫾2
15 ⫾ 1
16 ⫾ 2
13 ⫾ 2
15 ⫾ 1
15 ⫾ 2
15 ⫾ 2
35 ⫾ 5
45 ⫾ 6
45 ⫾ 7
27 ⫾ 4%
22 ⫾ 3%
26 ⫾ 3%
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FIG. 2. Bladder pressure spike accompanied urine flow after electrical stimulation of detrusor myoplasty.
the animal was still ambulatory was unsuccessful. We believe that since the rectus abdominis muscle flap contracts with electrical stimulation independent of detrusor function or lack thereof that our model is still reasonable. To our knowledge there has not yet been an animal model of neurogenic bladder in which the animal is ambulatory and able to perform usual life activities aside from voiding. The advantage of electrically stimulated detrusor myoplasty over direct bladder or sacral nerve root stimulation is that it produces a skeletal muscle contraction around the bladder that empties it without regard to the state of the detrusor muscle or its nerve roots (see Appendix). Many children with spina bifida have sacral nerve root involvement and would not be candidates for anterior sacral nerve root stimulation. However, our procedure would require functioning intercostal nerve roots, and so it may not be successful in patients with spinal cord levels above L2. This procedure does not create a large thoracoabdominal defect as the latissimus detrusor myoplasty does, which is important because many of these patients are paraplegic and require upper body strength. A limitation of our muscle wrap procedure, which we noted in our cadaver and experimental studies, is that in some cases the bladder may be too large for a single rectus muscle and, thus, may need to be buttressed by additional rectus abdominis muscle fascia or a second rectus abdominis muscle. In cases of a large bladder and in cases of intestinocystoplasty the latissimus muscle may be more beneficial. A fifth of patients with myelomeningocele present with urodynamic alterations consistent with a combined upper and lower motor neuron lesion that can cause bladder detrusor areflexia and intrinsic sphincter dysfunction.24, 25 These patients require clean intermittent catheterization to empty the bladder and also continue to leak between catheterizations, making chronic use of diapers a requirement. If our procedure is successful in a chronic study we would combine it with electrically stimulated gracilis sphincter myoplasty to achieve bladder emptying and continence in cases of detrusor and urinary sphincter failure (fig. 1, C).26 This procedure for bladder emptying and urinary continence can be done in conjunction with antegrade continence enema procedure to rid patients of fecal incontinence.27 With a combination of skeletal muscle flaps and other surgical procedures, patients with neurogenic bladder and bowel may be able to stop using catheterization and diapers, which would have a significant effect on quality of life and is what we are striving for in the future. Dynamic myoplasty procedures have also been used to treat the failing heart (dynamic cardiomyoplasty) and fecal
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ELECTRICALLY STIMULATED DETRUSOR MYOPLASTY
incontinence (dynamic rectal sphincteroplasty) as well, and it is possible that their role may increase in the future as the devices for electrical stimulation improve.28 CONCLUSIONS
Electrically stimulated detrusor myoplasty results in uniform increases in intravesical pressure and low post-void residuals in an animal model. We are currently investigating detrusor myoplasty in a chronic study to determine whether it can be used for enhanced bladder emptying in children with poor detrusor contractility. APPENDIX: ADVANTAGES OF THE ELECTRICALLY STIMULATED DETRUSOR MYOPLASTY
• • • • •
No catheters required Retains native bladder Works independently of bladder dysfunction etiology Does not require intact nerve supply to bladder Native or artificial bladder can be wrapped and stimulated • Augmented or neobladder may be stimulated • Dorsal rhizotomy unnecessary REFERENCES
1. Halverstadt, D. B. and Parry, W. L.: Electronic stimulation of the human bladder: 9 years later. J Urol, 113: 341, 1975 2. Heine, J. P., Schmidt, R. A. and Tanagho, E. A.: Intraspinal sacral root stimulation for controlled micturition. Invest Urol, 15: 78, 1977 3. Schmidt, R. A., Bruschini, H. and Tanagho, E. A.: Urinary bladder and sphincter responses to stimulation of dorsal and ventral sacral roots. Invest Urol, 16: 300, 1979 4. Creasey, G. H.: Electrical stimulation of sacral roots for micturition after spinal cord injury. Urol Clin North Am, 20: 505, 1993 5. Walter, J. S., Wheeler, J. S., Cogan, S. F. et al: Evaluation of direct bladder stimulation with stainless steel woven eye electrodes. J Urol, 150: 1990, 1993 6. Elabbady, A. A., Hassouna, M. M. and Elhilali, M. M.: Neural stimulation for chronic voiding dysfunctions. J Urol, 152: 2076, 1994 7. Brindley, G. S.: The first 500 patients with sacral anterior root stimulator implants: general description. Paraplegia, 32: 795, 1994 8. Rijkhoff, N. J., Wijkstra, H., van Kerrebroeck, P. E. et al: Selective detrusor activation by electrical sacral nerve root stimulation in spinal cord injury. J Urol, 157: 1504, 1997 9. Rijkhoff, N. J., Wijkstra, H., van Kerrebroeck, P. E. et al: Urinary bladder control by electrical stimulation: review of electrical stimulation techniques in spinal cord injury. Neurourol Urodyn, 16: 39, 1997 10. Tanagho, E. A.: Commentary on selective detrusor activation by electrical sacral nerve root stimulation in spinal cord injury.
J Urol, 157: 1196, 1997 11. Zang, Y. H., Shao, Q. A. and Wang, J. M.: Enveloping the bladder with displacement of flap of the rectus abdominis muscle for the treatment of neurogenic bladder. J Urol, 144: 1194, 1990 12. Chancellor, M. B., Rivas, D. A., Acosta, R. et al: Detrusormyoplasty, innervated rectus muscle transposition study, and functional effect on the spinal cord injury rat model. Neurourol Urodyn, 13: 547, 1994 13. Chancellor, M. B., Rivas, D. A. and Salzman, S. K.: Detrusormyoplasty to restore micturition. Lancet, 343: 669, 1994 14. von Heyden, B., Anthony, J. P., Kaula, N. et al: The latissimus dorsi muscle for detrusor assistance: functional recovery after nerve division and repair. J Urol, 151: 1081, 1994 15. Ninkovic´, M., Stenzl, A., Hess, M. et al: Functional urinary bladder wall substitute using a free innervated latissimus dorsi muscle flap. Plast Reconstr Surg, 100: 402, 1997 16. Stenzl, A., Ninkovic, M., Willeit, J. et al: Free neurovascular transfer of latissimus dorsi muscle to the bladder. I. Experimental studies. J Urol, 157: 1103, 1997 17. Stenzl, A., Ninkovic, M., Ko¨lle, D. et al: Restoration of voluntary emptying of the bladder by transplantation of innervated free skeletal muscle. Lancet, 351: 1483, 1998 18. Chancellor, M. B.: Personal communication 19. Bodner, D. R., Delamarter, R. B., Bohlman, H. H. et al: Urologic changes after cauda equina compression in dogs. J Urol, 143: 186, 1990 20. Hassouna, M., Li, J. S. and Elhilali, M.: Dog as an animal model for neurostimulation. Neurourol Urodyn, 13: 159, 1994 21. Koleilat, N., Sidi, A. A. and Gonzalez, R.: Urethral false passage as a complication of intermittent catheterization. J Urol, 142: 1216, 1989 22. Reisman, E. M. and Preminger, G. M.: Bladder perforation secondary to clean intermittent catheterization. J Urol, 142: 1316, 1989 23. Yamamoto, M., Yasukawa, M. and Yasai, M.: Clean intermittent catheterization in the management of spina bifida: a review of 113 cases. Hinyokika Kiyo, 37: 117, 1991 24. Dator, D. P., Hatchett, L., Dyro, F. M. et al: Urodynamic dysfunction in walking myelodysplastic children. J Urol, 148: 362, 1992 25. Bauer, S. B.: Myelodysplasia: newborn evaluation and management. In: Spina Bifida—A Multi-Disciplinary Approach. Edited by R. L. McLaurin, S. Oppenheimer, L. Dias et al. New York: Kraeger, p. 262, 1986 26. Palacio, M. M., Van Aalst, V. C., Perez Abadia, G. A. et al: Muscular urinary sphincter: electrically stimulated myoplasty for functional sphincter reconstruction. J Urol, 160: 1867, 1998 27. Malone, P. S., Ransley, P. G. and Kiely, E. M.: Preliminary report: the antegrade continence enema. Lancet, 336: 1217, 1990 28. Grandjean, P., Acker, M., Madoff, R. et al: Dynamic myoplasty: surgical transfer and stimulation of skeletal muscle for functional substitution or enhancement. J Rehabil Res Dev, 33: 133, 1996
DISCUSSION
Dr. Yves Homsy. As you know, muscle flaps have been used in humans for congestive heart failure not amenable to other forms of treatment. With respect to the increases in bladder pressure that were generated in the face of a dyssynergic sphincter, how detrimental would this be to the upper tract? Have you addressed this question in your experiment? Dr. John Van Savage. Our study was acute, and we have not evaluated the effects of it on the upper tracts or anywhere else. The initial study was to determine if the bladder could generate pressure by wrapping a rectus muscle around it, which we achieved. Dr. Stuart Bauer. Did you find that with time you had to increase the amount of the intensity of the stimulus to achieve the same response because of changes that occur with the electrode and fibrosis? Doctor Van Savage. There was a slight change.