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Effects of Anesthesia on Urodynamic Studies in the Primate Model
0022-534719611561-0233$03.00/0 THEJOURNAL.OF UROl.OCY Copyright 0 1996 by Ahmucm UROLOGICAL ASSOCIATION,INC.
Vol. 156, 233-236, July 1996 Printed in U.S.A.
EFFECTS OF ANESTHESIA ON URODYNAMIC STUDIES IN THE PRIMATE MODEL GAMAL M. GHONIEM,* MOHAMED S. SHOUKRY From the Department
of
AND
MANOJ MONGA
Urology, Tulane Regional Primate Research Center, Couington, Louisiana and the Tulane University School Medicine, New Orleans, Louisiana
of
ABSTRACT
Purpose: To elucidate the effect of anesthesia on bladder function and urodynamic studies by performing controlled comparisons of the effects of 2 anesthetics on urodynamics in a primate model. Materials and Methods: Cystometrograms were performed in 4 awake adult female Rhesus monkeys (Macaca mulatta) via implantable transducer for continuous monitoring and compared with cystometrograms obtained under anesthetic agents. A total of 183 cystometric studies was performed (48 in the awake group, 74 under ketamine anesthesia and 61 under flurane anesthesia. Results: Maximum detrusor contraction pressure [Pdet(max)] was significantly lower under flurane than under ketamine anesthesia (33.1 ? 2.5 versus 49.1 t 8.1 cm.H,O). In the awake state Pdet(max) (47.7 ? 25.2 cm.H20) was equal to that obtained under ketamine anesthesia. Cystometric bladder capacity was significantly larger under flurane (101.5 5 81.8 ml.) than under ketamine (70.3 2 56.1 ml.) anesthesia. It was only (32.9 t 15.9 ml.) in the awake state. Cystometric bladder capacity under both anesthetics was larger than the mean voided volume (43.3 -t- 6.3 ml.), but was comparable to the largest voided volume (102.3 2 31 ml.). Cystometric reflex contractions with bladder filling occured more frequently with ketamine (96%)than with flurane anesthesia (66%). Conclusions: These findings show that anesthesia has profound effects on the bladder, and careful interpretation of urodynamic data is suggested. These findings also suggest that ketamine is a suitable anesthetic for urodynamic studies in the subhuman primate. KEY WORDS:anesthesia, general; autonomic nervous system; urodynamics
Anesthetics could alter urodynamic studies by a variety of mechanisms. They could cause central inhibition of micturition at the level of the spinal cord, brain stem, cerebellum, substantia nigra, thalamus, or cortex. They could have a direct inhibitory effect on the detrusor muscle and cause loss of the reflex-evoked relaxation of the internal sphincter. They could alter the balance of sympathetic and parasympathetic control on micturition. Any combination of the above mechanisms could also be involved. Banington first described the depressive effects of chloroform and ether on bladder activity in 1931.' His model for urodynamic studies in decerebrate animals was ideal for minimizing the effects of anesthesia; however, it eliminated the central reflexes involved in micturition. Since then, numerous nonmammalian models have been used to evaluate the effects of various anesthetic and sedative agents on bladder function, with varying results.2-8 The effects of anesthetics may be species-specific as suggested in studies on vascular smooth muscle.9 Therefore studies of bladder physiology in different animal species may not be applicable to humans. Only 1 report has examined the effect of anesthetics on urodynamic studies in humans. Although this was not a randomized, controlled study, it did suggest an inhibitory effect of general anesthetics on detrusor contracti1ity.l0 This work is the first to perform controlled comparisons of the effects of 2 anesthetics on u r o d p m i c s in a primate model phylogenetically and physiologically close to man. Our
objectives are to elucidate the effect of anesthesia on bladder function and to find the most suitable anesthetic or sedative for urodynamic studies. MATERIALS AND METHODS
Four adult female Rhesus monkeys (Macaca mulatta) with a mean age of 7.6 years and a mean weight of 5.1 kg. were used for this study. Repeated cystometries were performed on each animal under anesthesia (ketamine and flurane) and without anesthesia (table). The parameters compared were mean bladder volume a t start of contraction, cystometric bladder capacity and maximum detrusor pressure. The percentage of cystometries that ended with reflex bladder contractions were compared between the ketamine and flurane groups. Transducer implantation. A pressure transducer (Konigsberg Co., Pasadena, California) was implanted in a submucosal position, midline on the anterior bladder wall and 2 cm. from the bladder neck to allow measurement of
e p t e d for publication December 8, 1995. Requests for reprints: Department of Urology, Tulane University School of Medicine. 1430 Tulane Ave., New Orleans, Louisiana 70112. This work was supported by N.I.H.Grant RR00164. 233
Demographics and cystometries per monkey No. of cystometriedvoids Monkey
H862 7549
cog0 D584
Total
Weight (kg.)
Age (yrs.)
4.7 5.4 4.5 5.8
3 12
Ketamine
Flurane
Awake
8
15 19 18
8
22
16 20 15 10
14 12 10 12
74
61
48
234
EFFECTS OF ANESTHESIA ON BLADDER FUNCTION
intravesical pressure. Conductors were tunneled to the interscapular area, whence they could be externalized under local anesthesia and connected to the Grass polygraph (Grass Instruments, Quincy, Massachusetts). Periodic comparisons of simultaneous pressures obtained by this method and those obtained by transurethral catheter have been found by our laboratory and other investigators to correlate reliably.11 Continuous monitoring in the awake animal. The model and cage design for this experiment have been previously described.12 Animals were trained for chairing for a t least 40 days prior to study. The monkey was kept in a sitting position by the special chair. One arm was left unrestrained to allow self-feeding. The chairing time was gradually increased from a few minutes to at least 2 hours per day. A plastic cone with double screens was placed under the base of the chair, directing voided urine into a beaker on top of a uroflowmeter. An average of 7 voiding epochs was obtained for each monkey over a period of at least 12 hours of continuous monitoring. Functional bladder capacity was defined as the mean voided volume. Intravesical pressures were measured by the implanted submucosal pressure transducer described above. Ketamine study. Animals were sedated with intramuscular injection of ketamine, 1mg./kg., with supplemental doses as required to a total of 5 to 10 mg./kg. for each study. An 8 F triluminal urethral catheter was used for filling the bladder and measuring intravesical pressure. The rectal balloon catheter was placed 15 cm. into the rectum for continuous monitoring of intraabdominal pressure. Detrusor pressure was calculated as the difference between intravesical and intraabdominal pressure. All pressure channels were connected to external pressure transducers (Spectramed P23XL, Ohmeda, Madison, Wisconsin)linked to amplifiers in a Grass instrument (type 7P122, Grass Instruments). Bilateral periurethral electrode needles were inserted for continuous electromyography of the external sphincter. Contrast material (Renografin-60 Bristol Myers-Squibb, Princeton, New Jersey) was infused by Harvard pump after dilution with distilled water in a ratio of 15. The infusion rate was 9.9 ml. per minute. Animals were kept supine. Intramuscular cefanocid sodium (Monocid, Smith Kline Beacham Pharmaceuticals, Philadelphia, Pennsylvania) 250 mg. prophylaxis was given prior to the experiment. Reflex bladder contraction was documented by a sudden increase in detrusor pressure combined with a decrease in urethral pressure and urethral EMG activity, and an open bladder neck on cystogram or fluoroscopy. Urine flow was occluded by the urethral catheter, allowing isovolumetric measurements of detrusor pressure during bladder contractions. Flurane study. Endotracheal anesthesia was attained with flurane 2% and oxygen 98%. The remaining experimental design was identical to that of the ketamine study. Statistical analysis was based on the ANOVA test with p 50.05 indicating a significant difference. Software used was Graphpad Instat (1990-1993, Graphpad Software, Inc., San Diego, California).
B
A
C
FIG. 1. Effect of anesthesia on maximum detrusor pressure: significant decrease under flurane (C) (p <0.001),but unchanged by ketamine ( B )(p >0.05) when compared with awake animal (A).
I A
B
C
FIG. 2. Effect of anesthesia on bladder capacity at start of contraction: cystometric bladder capacity under both anesthetics was larger than in awake animal (A). Flurane (C) caused greater increase in bladder capacity than ketamine ( B )(p <0.01).
I1
(r
.D
A = Awake
8t
B = Kctalar
-
C = Flurane
2 . . A
B
C
FIG.3. More cystometries ended with reflex detrusor contraction with ketamine ( B )(96%)than flurane (C) (66%)(p <0.001).
(96%) than with flurane (66%) (p <0.001) (fig. 3). Bladder compliance was significantly greater under flurane anesthesia (16.5 ml./cm. H,O) than under ketamine anesthesia (8.5 ml./cm. H,O) or in the awake animal (9.7 ml./cm. H,O) (p = .01). Representative cystometrograms illustrating changes in the micturition cycle under ketamine and flurane anesthesia are provided (fig. 4).
RESULTS
DISCUSSION
Maximum detrusor contraction pressure was significantly lower under flurane (33.1 2 2.5 cm. H20)than in the awake state (47.7 2 25.2 cm. H,O) (p <0.001), but was unchanged by ketamine (49.1 5 8.1 cm. H,O) (p >0.05) (fig. 1).Cystometric bladder capacity under both anesthetics was larger than the mean voided volume (43.3 t 6.3 ml.) but was comparable to the largest voided volume (102.3 2 31 ml.) (fig. 2). Flurane caused a greater increase in bladder capacity than ketamine (p <0.01) and a greater inhibition of maximum detrusor pressure than ketamine (p <0.001). More cystometries ended with reflex detrusor contraction with ketamine
This is the first controlled study in a primate model to demonstrate a significant inhibitory effect of anesthesia on bladder function. Our studies indicate that flurane caused a 3-fold increase in bladder capacity, decreased maximum detrusor pressure by 40% and abolished reflex detrusor contractions in 31%. Ketamine caused a 2-fold increase in bladder capacity, but had minimal effects on maximum detrusor pressure and reflex detrusor contractions. Animal models have been used to study the effects of other anesthesic agents. Inhibitory effects of ether, barbiturates and bulbocapnine on urodynamic studies have been demon-
EFFECTS OF ANESTHESIA ON BLADDER FUNCTION
235
the effect of a-chloralose on micturition was localized to the parasympathetic reflex pathway, the exact location could be peripheral, spinal, or supraspinal. Urethane has been widely used in urodynamic experimental models. Both excitatory and inhibitory reflexes concerned with micturition can be elicited in urethane-anesthetized animal models. However, urethane causes a 10 to 15%direct depression of detrusor contractility.6.15Urethane anesthesia also results in significant increases in bladder capacity and decreased amplitude of micturition contraction.15.16 The above studies suggest a direct inhibitory effect of FIG.4. Cystometrograms from individual animals illustrating anesthetics on detrusor contractility6 and a n inhibitory changes in micturition cycle under ketamine ( B ) and flurane (A) anesthesia. Flurane caused increase in bladder capacity and de- effect on the neural reflex paths involved in control of In addition, anesthetics have crease in maximum detrusor pressure, while ketamine caused an bladder f~nction.~-~,7.S~10 profound effects on the autonomic nervous system, which increase in bladder capacity only. plays an intricate role in bladder function.17 Bladder distension elicits a reflex increase in parasympathetic activstrated.2 Detrusor contractions secondary to electrical stim- ity, which causes a cholinergic-mediated (acetylcholine) ulation of the pelvic nerve were abolished with pentobarbital, contraction of the detrusor smooth muscle. Sympathetic while higher doses inhibited the parasympathetic ganglion.3 activity decreases detrusor contraction by inhibiting The inhibitory effects on bladder contractility exerted the parasympathetic vesical ganglion (a-adrenergic path) by diazepam and morphine are related to both the and inhibiting the detrusor smooth muscle directly mesencephalic-pontine and sacral micturition reflex centers (p-adrenergic path). Additionally, a-adrenergic stimulathrough activation of GABA and opioid ( p and A) receptors tion of the trigonal and urethral smooth muscle increases l4 Pentobarbital, a-chloralose, ketamine, halre~pective1y.l~. urethral resistance. othane and bupivacine/2-chloroprocaine caused a complete Studies on the effects of anesthetics on the autonomic block of volume-evoked micturition reflex with overflow in- nervous system and smooth muscle activity have been focontinence a t pressures 20 to 30% higher than the bladder cused on distinct clinical scenarios: anesthesia-induced hyopening pressure in rats.7 potension, protection from bronchoconstriction, anesthesia in Reflex detrusor contractions were inhibited in 100% of pregnancy and diminishing of the ischemia associated with cystometries under ketamine, 66%with fentanyl, 53% with intracranial hemorrhage by lowering intracranial pressure. halothane, 41% with methoxyflurane, 40% with gallamine Altura et al.18 reviewed the effects of barbiturates, opiates, and 34% with pentobarbital in dogs and cats. Only xylazine intravenous and volatile anesthetics on spontaneous and provided adequate restraint without blocking micturition re- agonist-induced contraction of vascular smooth muscle. All flex detrusor contraction.4 Normal micturition reflex was have been shown to interfere with the influx of calcium a t the preserved in 86%of cystometries under intravenous xylazine vascular smooth muscle membrane and the function of the sarcoplasmic reticulum within vascular smooth muscle cells. and 83% under intramuscular xylazine.5 Doyle and Briscoelo studied the effects of sedatives (diaz- This disrupts the excitation-contraction coupling by decreasepam, pethidine, papaverturn, scopolamine, atropine) and ing the amount of calcium available to the actin-myosin elecombinations of general anesthetics and muscle relaxants ments. Barbiturates are believed to affect either intracellular (thiopentone, methohexitone, althesin, halothane, trichloro- calcium stores,19.20 membrane-bound calcium stores,2*or exethylene, suxamethonium, pancuronium, curare) on 56 hu- tracellular calcium influx by dissolving in the cell membrane man patients (8 males, 48 females) undergoing urodynamic and displacing calcium channels.22 In animal models, halothane caused a dose-dependent instudies as part of an evaluation of urinary incontinence. Urethral pressure profiles and cystometrograms were ini- hibition of sympathetic preganglionic, ganglionic and posttially performed without anesthesia, then with sedation and ganglionic neural transmission, inhibition of endogenous finally under general anesthesia. The combinations of drug norepinephrine release in response to electrical field stimuused for each patient were not randomized, nor were a vari- lation, and a direct inhibition of vascular smooth muscle ety of drugs evaluated per individual. A control group of contractility in response to phenylephrine.23 Halothane patients without complaints of incontinence was not studied. caused a dose-dependent depolarization of the intracellular Urethral pressure profile heights were significantly in- membrane potential and inhibition of the contractile recreased with use of opiates and decreased with general an- sponse to histamine and serotonin. The effect of halothane on esthetics, especially barbiturates. A trend towards increasing membrane fluidity and ion conductance was dependent on bladder capacity with general anesthesia reached statistical the resting membrane potential and previous contractile acsignificance with halothane. General anesthetics caused a tivity of the cell. Halothane causes an inhibition of contractile response to decrease in the pressure rise per unit volume (increased compliance); however, intravenous diazepam caused the re- a,-agonists, but no effect on response to al-agonists.24 It has verse effect. Nitric oxide did not affect urodynamic parame- been shown to inhibit binding of a,-agonists to their recepters, and the authors recommended a combination of trichlo- tors on myometrium and subsequently to inhibit alroethylene and nitrous oxide to minimize effects of anesthetic stimulated contraction.25 Isoflurane depressed the spontaneous contractile activity and peak tension in isolated human on results. An anesthetic agent commonly used on the premise that it myometrium.26 Contraction mediated by a,-adrenergic innervation is behas little effect on the normal spinal and sympathetic reflex function is a-chloralose. However, it has been shown to cause lieved to be dependent on release of intracellular calcium a significant reduction in voiding pressure, contraction am- stores, whereas a,-adrenergic mediated contraction is depenplitude and voiding efficiency, and dyssynergic bladder and dent on entry of extracellular calcium.27 The differences in urethral responses.8 The fact that a-chloralose did not affect reported effects of halothane may be due to differences the threshold volume for micturition suggests that the detec- in innervation of the tissues and species studied. In summary, the inhibitory effects of halothane and isoflution of afferent stimulus of bladder distension remained intact. This study was complicated by the fact that ketamine rane on adrenergic activity have been demonstrated in nusedation was used in conjunction with a-chloralose. While merous tissues and snecies. This would. however. be ewected
236
EFFECTS OF ANESTHESIA ON BLADDER FUNCTION
to promote micturition, not inhibit it as was seen in our experiment. These agents may have a more pronounced direct effect on the detrusor smooth muscle, causing depolarization followed by inhibition of contraction. Ketamine potentiates catecholamine action by inhibiting active neural uptake in densely innervated tissue and by inhibiting extraneuronal uptake in sparsely innervated tissue. The site of action of ketamine on the sympathetic nervous system is either tissue-specific or species-specific.9 The effects of ketamine on the parasympathetic nervous system are dose-dependent. High dose ketamine (higher than clinical use) inhibits bronchial and vascular smooth muscle contractile response to parasympathetic stimulation, with a more pronounced inhibition of preganglionic stimulation than postganglionic stimulation. Intermediate concentrations inhibit vascular contractile response to preganglionic stimulation but augments response to postganglionic stimulation. Low concentrations augment the vascular contractile response to either pre- or postganglionic stimulation.2s.29 In summary, the effects of ketamine appear to be tissuespecific, species-specific and concentration-dependent within the reported range of clinical plasma levels. Some inhibition of cholinergic-mediated contractions and augmentation of adrenergic effects would correlate with decreased detrusor activity and increased bladder capacities under ketamine anesthesia. Our findings suggest that ketamine may be superior to, but not ideal, for urodynamic studies. The minimal urologic changes induced by ketamine favor its use; however, other anesthetics such as xylazine and urethane need t o be evaluated in the primate model to test for superiority. In vitro effects of anesthetics on the primate bladder’s passive and active contractile response to acetylcholine and electrical stimulation need to be studied. Continuous monitoring of the awake monkey approximates physiologic conditions more closely; however, limitations on the duration and number of experiments and the need for physical restraint reemphasize the need for an ideal anesthetic. We observed a greater variability in urodynamic findings in the awake animal model than in the anesthetized animal. It is possible that sensory inputs, active in the “toilettrained” primate, may be suppressed in the unconscious state. These sensory inputs and the corresponding increase in variability in urodynamic parameters may more closely approximate physiologic conditions, lending credence t o the use of the awake animal model in the study of pathologic conditions. Anesthetics alter the integrity of the autonomic nervous system and may have direct effects on the detrusor muscle and the mesencephalic-pontine and sacral micturition centers. The mechanism of action of various anesthetics on bladder function needs to be elucidated. The potential effect of anesthetics or sedatives should be considered when conducting experimental or clinical urodynamic studies. REFERENCES
1. Barrington, F. J . F.: The relationship of the hind-brain to micturition. Brain, 44: 23, 1931. 2. Kolb, L. C. and Langworthy, D. R.: A comparative study of the effects of the barbiturates, ether and bulbocapnine on micturition. J . Pharmacol. Exp. Ther., 63: 108, 1938. 3. Martin, A. W., Kipple, H. M., Dille, J. M. and H a m s , B. G.: Spinal and peripheral synaptic susceptibility to Nembutal as shown by vesicular responses. Fed. Proc., 5: 72, 1946. 4. Oliver, J. E. and Young, W. 0.: Evaluation of pharmacologic agents for restraint in cystometry in the dog and cat. Am. J. Vet. Res., 34: 665, 1973. 5. Moreau, P. M., Lees, G. E. and Gross, D. R.: Simultaneous cystometry and uroflowmetry (micturition study) for evaluation of the caudal part of the urinary tract in dogs: reference values for healthy animals sedated with xylazine. Am. J . Vet. Res., 44: 1774, 1983.
6. Maggi, C. A. and Meli, A,: Suitability of urethane anesthesia for physiopharmacological investigations. P a r t 3. Other systems and conclusions. Experientia, 42: 531, 1986. 7. Yaksh, T. L., Durant, P. A. C. and Brent, C. R.: Micturition in rats: a chronic model for study of bladder function and effects of anesthetics. Am. J. Physiol., 251: R1177, 1986. 8. Rudy, D. C., Downie, J . W. and McAndrew, J. D.: a-chloralose alters the autonomic reflex function of t h e lower urinary tract. Am. J. Physiol., 261: R1560, 1991. 9. Lundy, P. M., Gverzdys, S. and Fren, R.: Ketamine: evidence of tissue specific inhibition of neuronal and extraneuronal catecholamine uptake processes. Can. J. Pharmacol., 63: 298,303. 10. Doyle, P. T. and Briscoe, C. E.: Effects of drugs and anesthetic agents on the urinary bladder and sphincters. Br. J . Urol., 4 8 329, 1976. 11. Takayama, K., Kitada, S. and Kumazawa, J.: New method for measuring bladder pressure. Urology, 29: 632, 1987. 12. Ghoniem, G. M., Shoukry, M. S., Walker, C. F. and Kaack, M. B.: Continuous monitoring of micturition pattern i n nonhuman primates: technique. Neurourol. Urodyn., 11: 131, 1992. 13. Kontani, H., Kawabata, Y. and Koshiura, R.: In vivo effects of y-aminobutyric acid on urinary bladder contraction accompanying micturition. Jpn. J . Pharmacol., 45: 45, 1987. 14. Kontani, H. and Kawabata, Y.: A study of morphine-induced urinary retention in anesthetized rats capable of micturition. Jpn. J. Pharmacol., 4 8 31, 1988. 15. Maggi, C. A. and Conte, B.: Effect of urethane anesthesia on the micturition reflex in capsaicin-treated rats. J. Auton. Nerv. Syst., 3 0 247, 1990. 16. Peterson, J. S., Hanson, R. C. and Noronha-Blob, L.: In vivo cystometrogram studies i n urethane-anesthetized and conscious pigs. J . Pharmacol. Methods, 21: 231, 1989. 17. DeGroat, W. C. and Booth, A. M.: Physiology of t h e urinary bladder. Ann. Int. Med., 92: 312, 1980. 18. Altura, B. M., Altura, B. T., Carella, A,, Turlapaty, P. D. M. V. and Weinberg, J.: Vascular smooth muscle and general anesthetics. Fed. Proc., 3 9 1584, 1980. 19. Marin, J., Rico, M. L. and Salaices, M.: Interference of pentobarbitone with the contraction of vascular smooth muscle in goat middle cerebral artery. J. Pharm. Pharmacol., 33: 357, 1981. 20. Marin, J., Gonzalez, M., Salaices, C., Sanchez, C. F. and Rico, M. L.: Contractile responses and noradrenaline release evoked by serotonin in cat femoral artery: influence of pentobarbital. Gen. Pharmacol., 13 117, 1982. 21. Nayler, W. G . and Szeto, J.: Effect of sodium pentobarbital on calcium in mammalian heart muscle. Am. J . Physiol., 222: 339, 1972. 22. Seeman, P.: The membrane action of anesthetics and tranquilizers. Pharmacol. Rev., 24: 583, 1972. 23. Spiss, C. K., Smith, C. M., Tsujimoto, G., Hoffman, B. B. and Maze, M.: Prolonged hyporesponsiveness of vascular smooth muscle contraction after halothane anesthesia in rabbits. Anesth. Analg., 64: 1, 1985. 24. Larach, D. R., Schuler, H. G., Derr, J . A,, Larach, M. G., Hensley, F. A. and Zelis, R.: Halothane selectively attenuates cy2adrenoreceptor mediated vasoconstriction in vivo and in vitro. Anesthesiology, 6 6 781, 1987. 25. Wikberg, J. E. S., Hede, A. R. and Lindahl, M.: Effect of general anesthesia and organic solvents on a,-adrenoreceptors in the myometrium. Acta Pharmacol. Toxicol. (Copenh.), 57: 53, 1985. 26. Calvello, D. C., Abadir, A. R., Chaudhry, M. R., Gintautas, J. and Dors, N. W.: Isoflurane effect on isolated nonpregnant human myometrium. Proc. West. Pharmacol. Soc., 3 0 179, 1987. 27. Van Meel, J . C. A,, De Jonge, A,, Kalkman, H. O., Wilffert, B., Timmermans, P. B. M. W. M. and Van Zwieten, P. A.: Vascular smooth muscle contraction initiated by post-synaptic a2adrenoreceptor activation is induced by an influx of extracelM a r calcium. Eur. J. Pharmacol.. 69: 205, 1987. 28. Juang, M. S., Yonemura, K., Morioka, T. and Tanaka, I : Ketamine acts on the peripheral nervous system of gi1inc.a pigs. Anesth. Analg.. 59: 4.5,1980. 29. Leblanc. P. H.. Rulkner, C. K., Brunson, D. B.. Lal:I\.liSCJ, 12. B. and Will, J . A.: Differential effect of ketamine on cholinergic and noncholinergic contractioiis of isolated guinea pig bronchi. Arch. Int. Pharniacodyn., 287: 120. 1987.
Vol. 156, 233-236, July 1996 Printed in U.S.A.
EFFECTS OF ANESTHESIA ON URODYNAMIC STUDIES IN THE PRIMATE MODEL GAMAL M. GHONIEM,* MOHAMED S. SHOUKRY From the Department
of
AND
MANOJ MONGA
Urology, Tulane Regional Primate Research Center, Couington, Louisiana and the Tulane University School Medicine, New Orleans, Louisiana
of
ABSTRACT
Purpose: To elucidate the effect of anesthesia on bladder function and urodynamic studies by performing controlled comparisons of the effects of 2 anesthetics on urodynamics in a primate model. Materials and Methods: Cystometrograms were performed in 4 awake adult female Rhesus monkeys (Macaca mulatta) via implantable transducer for continuous monitoring and compared with cystometrograms obtained under anesthetic agents. A total of 183 cystometric studies was performed (48 in the awake group, 74 under ketamine anesthesia and 61 under flurane anesthesia. Results: Maximum detrusor contraction pressure [Pdet(max)] was significantly lower under flurane than under ketamine anesthesia (33.1 ? 2.5 versus 49.1 t 8.1 cm.H,O). In the awake state Pdet(max) (47.7 ? 25.2 cm.H20) was equal to that obtained under ketamine anesthesia. Cystometric bladder capacity was significantly larger under flurane (101.5 5 81.8 ml.) than under ketamine (70.3 2 56.1 ml.) anesthesia. It was only (32.9 t 15.9 ml.) in the awake state. Cystometric bladder capacity under both anesthetics was larger than the mean voided volume (43.3 -t- 6.3 ml.), but was comparable to the largest voided volume (102.3 2 31 ml.). Cystometric reflex contractions with bladder filling occured more frequently with ketamine (96%)than with flurane anesthesia (66%). Conclusions: These findings show that anesthesia has profound effects on the bladder, and careful interpretation of urodynamic data is suggested. These findings also suggest that ketamine is a suitable anesthetic for urodynamic studies in the subhuman primate. KEY WORDS:anesthesia, general; autonomic nervous system; urodynamics
Anesthetics could alter urodynamic studies by a variety of mechanisms. They could cause central inhibition of micturition at the level of the spinal cord, brain stem, cerebellum, substantia nigra, thalamus, or cortex. They could have a direct inhibitory effect on the detrusor muscle and cause loss of the reflex-evoked relaxation of the internal sphincter. They could alter the balance of sympathetic and parasympathetic control on micturition. Any combination of the above mechanisms could also be involved. Banington first described the depressive effects of chloroform and ether on bladder activity in 1931.' His model for urodynamic studies in decerebrate animals was ideal for minimizing the effects of anesthesia; however, it eliminated the central reflexes involved in micturition. Since then, numerous nonmammalian models have been used to evaluate the effects of various anesthetic and sedative agents on bladder function, with varying results.2-8 The effects of anesthetics may be species-specific as suggested in studies on vascular smooth muscle.9 Therefore studies of bladder physiology in different animal species may not be applicable to humans. Only 1 report has examined the effect of anesthetics on urodynamic studies in humans. Although this was not a randomized, controlled study, it did suggest an inhibitory effect of general anesthetics on detrusor contracti1ity.l0 This work is the first to perform controlled comparisons of the effects of 2 anesthetics on u r o d p m i c s in a primate model phylogenetically and physiologically close to man. Our
objectives are to elucidate the effect of anesthesia on bladder function and to find the most suitable anesthetic or sedative for urodynamic studies. MATERIALS AND METHODS
Four adult female Rhesus monkeys (Macaca mulatta) with a mean age of 7.6 years and a mean weight of 5.1 kg. were used for this study. Repeated cystometries were performed on each animal under anesthesia (ketamine and flurane) and without anesthesia (table). The parameters compared were mean bladder volume a t start of contraction, cystometric bladder capacity and maximum detrusor pressure. The percentage of cystometries that ended with reflex bladder contractions were compared between the ketamine and flurane groups. Transducer implantation. A pressure transducer (Konigsberg Co., Pasadena, California) was implanted in a submucosal position, midline on the anterior bladder wall and 2 cm. from the bladder neck to allow measurement of
e p t e d for publication December 8, 1995. Requests for reprints: Department of Urology, Tulane University School of Medicine. 1430 Tulane Ave., New Orleans, Louisiana 70112. This work was supported by N.I.H.Grant RR00164. 233
Demographics and cystometries per monkey No. of cystometriedvoids Monkey
H862 7549
cog0 D584
Total
Weight (kg.)
Age (yrs.)
4.7 5.4 4.5 5.8
3 12
Ketamine
Flurane
Awake
8
15 19 18
8
22
16 20 15 10
14 12 10 12
74
61
48
234
EFFECTS OF ANESTHESIA ON BLADDER FUNCTION
intravesical pressure. Conductors were tunneled to the interscapular area, whence they could be externalized under local anesthesia and connected to the Grass polygraph (Grass Instruments, Quincy, Massachusetts). Periodic comparisons of simultaneous pressures obtained by this method and those obtained by transurethral catheter have been found by our laboratory and other investigators to correlate reliably.11 Continuous monitoring in the awake animal. The model and cage design for this experiment have been previously described.12 Animals were trained for chairing for a t least 40 days prior to study. The monkey was kept in a sitting position by the special chair. One arm was left unrestrained to allow self-feeding. The chairing time was gradually increased from a few minutes to at least 2 hours per day. A plastic cone with double screens was placed under the base of the chair, directing voided urine into a beaker on top of a uroflowmeter. An average of 7 voiding epochs was obtained for each monkey over a period of at least 12 hours of continuous monitoring. Functional bladder capacity was defined as the mean voided volume. Intravesical pressures were measured by the implanted submucosal pressure transducer described above. Ketamine study. Animals were sedated with intramuscular injection of ketamine, 1mg./kg., with supplemental doses as required to a total of 5 to 10 mg./kg. for each study. An 8 F triluminal urethral catheter was used for filling the bladder and measuring intravesical pressure. The rectal balloon catheter was placed 15 cm. into the rectum for continuous monitoring of intraabdominal pressure. Detrusor pressure was calculated as the difference between intravesical and intraabdominal pressure. All pressure channels were connected to external pressure transducers (Spectramed P23XL, Ohmeda, Madison, Wisconsin)linked to amplifiers in a Grass instrument (type 7P122, Grass Instruments). Bilateral periurethral electrode needles were inserted for continuous electromyography of the external sphincter. Contrast material (Renografin-60 Bristol Myers-Squibb, Princeton, New Jersey) was infused by Harvard pump after dilution with distilled water in a ratio of 15. The infusion rate was 9.9 ml. per minute. Animals were kept supine. Intramuscular cefanocid sodium (Monocid, Smith Kline Beacham Pharmaceuticals, Philadelphia, Pennsylvania) 250 mg. prophylaxis was given prior to the experiment. Reflex bladder contraction was documented by a sudden increase in detrusor pressure combined with a decrease in urethral pressure and urethral EMG activity, and an open bladder neck on cystogram or fluoroscopy. Urine flow was occluded by the urethral catheter, allowing isovolumetric measurements of detrusor pressure during bladder contractions. Flurane study. Endotracheal anesthesia was attained with flurane 2% and oxygen 98%. The remaining experimental design was identical to that of the ketamine study. Statistical analysis was based on the ANOVA test with p 50.05 indicating a significant difference. Software used was Graphpad Instat (1990-1993, Graphpad Software, Inc., San Diego, California).
B
A
C
FIG. 1. Effect of anesthesia on maximum detrusor pressure: significant decrease under flurane (C) (p <0.001),but unchanged by ketamine ( B )(p >0.05) when compared with awake animal (A).
I A
B
C
FIG. 2. Effect of anesthesia on bladder capacity at start of contraction: cystometric bladder capacity under both anesthetics was larger than in awake animal (A). Flurane (C) caused greater increase in bladder capacity than ketamine ( B )(p <0.01).
I1
(r
.D
A = Awake
8t
B = Kctalar
-
C = Flurane
2 . . A
B
C
FIG.3. More cystometries ended with reflex detrusor contraction with ketamine ( B )(96%)than flurane (C) (66%)(p <0.001).
(96%) than with flurane (66%) (p <0.001) (fig. 3). Bladder compliance was significantly greater under flurane anesthesia (16.5 ml./cm. H,O) than under ketamine anesthesia (8.5 ml./cm. H,O) or in the awake animal (9.7 ml./cm. H,O) (p = .01). Representative cystometrograms illustrating changes in the micturition cycle under ketamine and flurane anesthesia are provided (fig. 4).
RESULTS
DISCUSSION
Maximum detrusor contraction pressure was significantly lower under flurane (33.1 2 2.5 cm. H20)than in the awake state (47.7 2 25.2 cm. H,O) (p <0.001), but was unchanged by ketamine (49.1 5 8.1 cm. H,O) (p >0.05) (fig. 1).Cystometric bladder capacity under both anesthetics was larger than the mean voided volume (43.3 t 6.3 ml.) but was comparable to the largest voided volume (102.3 2 31 ml.) (fig. 2). Flurane caused a greater increase in bladder capacity than ketamine (p <0.01) and a greater inhibition of maximum detrusor pressure than ketamine (p <0.001). More cystometries ended with reflex detrusor contraction with ketamine
This is the first controlled study in a primate model to demonstrate a significant inhibitory effect of anesthesia on bladder function. Our studies indicate that flurane caused a 3-fold increase in bladder capacity, decreased maximum detrusor pressure by 40% and abolished reflex detrusor contractions in 31%. Ketamine caused a 2-fold increase in bladder capacity, but had minimal effects on maximum detrusor pressure and reflex detrusor contractions. Animal models have been used to study the effects of other anesthesic agents. Inhibitory effects of ether, barbiturates and bulbocapnine on urodynamic studies have been demon-
EFFECTS OF ANESTHESIA ON BLADDER FUNCTION
235
the effect of a-chloralose on micturition was localized to the parasympathetic reflex pathway, the exact location could be peripheral, spinal, or supraspinal. Urethane has been widely used in urodynamic experimental models. Both excitatory and inhibitory reflexes concerned with micturition can be elicited in urethane-anesthetized animal models. However, urethane causes a 10 to 15%direct depression of detrusor contractility.6.15Urethane anesthesia also results in significant increases in bladder capacity and decreased amplitude of micturition contraction.15.16 The above studies suggest a direct inhibitory effect of FIG.4. Cystometrograms from individual animals illustrating anesthetics on detrusor contractility6 and a n inhibitory changes in micturition cycle under ketamine ( B ) and flurane (A) anesthesia. Flurane caused increase in bladder capacity and de- effect on the neural reflex paths involved in control of In addition, anesthetics have crease in maximum detrusor pressure, while ketamine caused an bladder f~nction.~-~,7.S~10 profound effects on the autonomic nervous system, which increase in bladder capacity only. plays an intricate role in bladder function.17 Bladder distension elicits a reflex increase in parasympathetic activstrated.2 Detrusor contractions secondary to electrical stim- ity, which causes a cholinergic-mediated (acetylcholine) ulation of the pelvic nerve were abolished with pentobarbital, contraction of the detrusor smooth muscle. Sympathetic while higher doses inhibited the parasympathetic ganglion.3 activity decreases detrusor contraction by inhibiting The inhibitory effects on bladder contractility exerted the parasympathetic vesical ganglion (a-adrenergic path) by diazepam and morphine are related to both the and inhibiting the detrusor smooth muscle directly mesencephalic-pontine and sacral micturition reflex centers (p-adrenergic path). Additionally, a-adrenergic stimulathrough activation of GABA and opioid ( p and A) receptors tion of the trigonal and urethral smooth muscle increases l4 Pentobarbital, a-chloralose, ketamine, halre~pective1y.l~. urethral resistance. othane and bupivacine/2-chloroprocaine caused a complete Studies on the effects of anesthetics on the autonomic block of volume-evoked micturition reflex with overflow in- nervous system and smooth muscle activity have been focontinence a t pressures 20 to 30% higher than the bladder cused on distinct clinical scenarios: anesthesia-induced hyopening pressure in rats.7 potension, protection from bronchoconstriction, anesthesia in Reflex detrusor contractions were inhibited in 100% of pregnancy and diminishing of the ischemia associated with cystometries under ketamine, 66%with fentanyl, 53% with intracranial hemorrhage by lowering intracranial pressure. halothane, 41% with methoxyflurane, 40% with gallamine Altura et al.18 reviewed the effects of barbiturates, opiates, and 34% with pentobarbital in dogs and cats. Only xylazine intravenous and volatile anesthetics on spontaneous and provided adequate restraint without blocking micturition re- agonist-induced contraction of vascular smooth muscle. All flex detrusor contraction.4 Normal micturition reflex was have been shown to interfere with the influx of calcium a t the preserved in 86%of cystometries under intravenous xylazine vascular smooth muscle membrane and the function of the sarcoplasmic reticulum within vascular smooth muscle cells. and 83% under intramuscular xylazine.5 Doyle and Briscoelo studied the effects of sedatives (diaz- This disrupts the excitation-contraction coupling by decreasepam, pethidine, papaverturn, scopolamine, atropine) and ing the amount of calcium available to the actin-myosin elecombinations of general anesthetics and muscle relaxants ments. Barbiturates are believed to affect either intracellular (thiopentone, methohexitone, althesin, halothane, trichloro- calcium stores,19.20 membrane-bound calcium stores,2*or exethylene, suxamethonium, pancuronium, curare) on 56 hu- tracellular calcium influx by dissolving in the cell membrane man patients (8 males, 48 females) undergoing urodynamic and displacing calcium channels.22 In animal models, halothane caused a dose-dependent instudies as part of an evaluation of urinary incontinence. Urethral pressure profiles and cystometrograms were ini- hibition of sympathetic preganglionic, ganglionic and posttially performed without anesthesia, then with sedation and ganglionic neural transmission, inhibition of endogenous finally under general anesthesia. The combinations of drug norepinephrine release in response to electrical field stimuused for each patient were not randomized, nor were a vari- lation, and a direct inhibition of vascular smooth muscle ety of drugs evaluated per individual. A control group of contractility in response to phenylephrine.23 Halothane patients without complaints of incontinence was not studied. caused a dose-dependent depolarization of the intracellular Urethral pressure profile heights were significantly in- membrane potential and inhibition of the contractile recreased with use of opiates and decreased with general an- sponse to histamine and serotonin. The effect of halothane on esthetics, especially barbiturates. A trend towards increasing membrane fluidity and ion conductance was dependent on bladder capacity with general anesthesia reached statistical the resting membrane potential and previous contractile acsignificance with halothane. General anesthetics caused a tivity of the cell. Halothane causes an inhibition of contractile response to decrease in the pressure rise per unit volume (increased compliance); however, intravenous diazepam caused the re- a,-agonists, but no effect on response to al-agonists.24 It has verse effect. Nitric oxide did not affect urodynamic parame- been shown to inhibit binding of a,-agonists to their recepters, and the authors recommended a combination of trichlo- tors on myometrium and subsequently to inhibit alroethylene and nitrous oxide to minimize effects of anesthetic stimulated contraction.25 Isoflurane depressed the spontaneous contractile activity and peak tension in isolated human on results. An anesthetic agent commonly used on the premise that it myometrium.26 Contraction mediated by a,-adrenergic innervation is behas little effect on the normal spinal and sympathetic reflex function is a-chloralose. However, it has been shown to cause lieved to be dependent on release of intracellular calcium a significant reduction in voiding pressure, contraction am- stores, whereas a,-adrenergic mediated contraction is depenplitude and voiding efficiency, and dyssynergic bladder and dent on entry of extracellular calcium.27 The differences in urethral responses.8 The fact that a-chloralose did not affect reported effects of halothane may be due to differences the threshold volume for micturition suggests that the detec- in innervation of the tissues and species studied. In summary, the inhibitory effects of halothane and isoflution of afferent stimulus of bladder distension remained intact. This study was complicated by the fact that ketamine rane on adrenergic activity have been demonstrated in nusedation was used in conjunction with a-chloralose. While merous tissues and snecies. This would. however. be ewected
236
EFFECTS OF ANESTHESIA ON BLADDER FUNCTION
to promote micturition, not inhibit it as was seen in our experiment. These agents may have a more pronounced direct effect on the detrusor smooth muscle, causing depolarization followed by inhibition of contraction. Ketamine potentiates catecholamine action by inhibiting active neural uptake in densely innervated tissue and by inhibiting extraneuronal uptake in sparsely innervated tissue. The site of action of ketamine on the sympathetic nervous system is either tissue-specific or species-specific.9 The effects of ketamine on the parasympathetic nervous system are dose-dependent. High dose ketamine (higher than clinical use) inhibits bronchial and vascular smooth muscle contractile response to parasympathetic stimulation, with a more pronounced inhibition of preganglionic stimulation than postganglionic stimulation. Intermediate concentrations inhibit vascular contractile response to preganglionic stimulation but augments response to postganglionic stimulation. Low concentrations augment the vascular contractile response to either pre- or postganglionic stimulation.2s.29 In summary, the effects of ketamine appear to be tissuespecific, species-specific and concentration-dependent within the reported range of clinical plasma levels. Some inhibition of cholinergic-mediated contractions and augmentation of adrenergic effects would correlate with decreased detrusor activity and increased bladder capacities under ketamine anesthesia. Our findings suggest that ketamine may be superior to, but not ideal, for urodynamic studies. The minimal urologic changes induced by ketamine favor its use; however, other anesthetics such as xylazine and urethane need t o be evaluated in the primate model to test for superiority. In vitro effects of anesthetics on the primate bladder’s passive and active contractile response to acetylcholine and electrical stimulation need to be studied. Continuous monitoring of the awake monkey approximates physiologic conditions more closely; however, limitations on the duration and number of experiments and the need for physical restraint reemphasize the need for an ideal anesthetic. We observed a greater variability in urodynamic findings in the awake animal model than in the anesthetized animal. It is possible that sensory inputs, active in the “toilettrained” primate, may be suppressed in the unconscious state. These sensory inputs and the corresponding increase in variability in urodynamic parameters may more closely approximate physiologic conditions, lending credence t o the use of the awake animal model in the study of pathologic conditions. Anesthetics alter the integrity of the autonomic nervous system and may have direct effects on the detrusor muscle and the mesencephalic-pontine and sacral micturition centers. The mechanism of action of various anesthetics on bladder function needs to be elucidated. The potential effect of anesthetics or sedatives should be considered when conducting experimental or clinical urodynamic studies. REFERENCES
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