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Effect of spinal versus general anesthesia on bladder compliance and intraabdominal pressure during transurethral procedures
Original Contributions Effect of Spinal versus General Anesthesia on Bladder Compliance and Intraabdominal Pressure During Transurethral Procedures David Olsfanger, MB ChB,* Edna Zohar, MD,* Brian Fredman, MB BCh,† Santiago Richter, MD,‡ Robert Jedeikin, BSc, MB ChB, FFA(SA)§ Department of Anesthesiology and Intensive Care, and Department of Urology, Meir Hospital, Kfar Saba, Israel; and the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
*Tutor in Anesthesiology †Lecturer in Anesthesiology ‡Lecturer in Urology §Professor of Anesthesiology Address correspondence to Dr. Jedeikin at the Department of Anesthesiology and Intensive Care, Meir Hospital, Kfar Saba 44281, Israel. E-mail: [email protected] Received for publication December 3, 1998; revised manuscript accepted for publication April 27, 1999.
Study Objective: To evaluate the influence of spinal versus general anesthesia on bladder compliance and intraabdominal pressure in elderly males undergoing elective transurethral resection of the prostate. Design: Prospective, randomized, open-label study. Setting: Teaching hospital. Patients: 21 ASA physical status I, II, and III patients at least 18 years of age, undergoing transurethral surgery. Interventions: According to a computer-generated randomization schedule, patients were allocated to one of two groups. In Group Spinal (S), 10 mg of hyperbaric tetracaine was administered intrathecally. In Group General Anesthesia (GA), patients received fentanyl intravenous (IV) 1 to 2 g/kg and propofol IV 1.0 to 2.0 mg/kg for induction of anesthesia. Thereafter, a laryngeal mask airway was inserted and, with spontaneous ventilation, anesthesia was maintained by administering isoflurane (end-tidal 0.7% to 1.2%) and 70% nitrous oxide (N2O) in oxygen. Intraabdominal pressure and bladder compliance were recorded prior to the induction of anesthesia and immediately before the onset of the surgical procedure. Measurements and Main Results: The two groups were demographically comparable. In Group S, mean bladder compliance was significantly (p ⫽ 0.003) higher and mean intraabdominal pressure significantly lower (p ⫽ 0.007) when compared to baseline preanesthetic values. In Group GA, mean intraabdominal pressure significantly (p ⫽ 0.006) decreased when compared to baseline preanesthetic recordings. Following the induction of general anesthesia, a small change in bladder compliance was noted. However, statistical significance was not reached. Data were analyzed and compared using Student’s t-test (p ⬍ 0.05 was considered statistically significant). Conclusion: Both spinal and general anesthesia induced a significant decrease in intraabdominal pressure. While both techniques were associated with an increase in bladder compliance, statistical significance was demonstrated only in the spinal anesthesia treatment group. © 1999 by Elsevier Science Inc.
Journal of Clinical Anesthesia 11:328 –331, 1999 © 1999 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010
0952-8180/99/$–see front matter PII S0952-8180(99)00057-4
Bladder function, intrathecal, and general anesthesia: Olsfanger et al.
Keywords: Anesthesia techniques: general, spinal; surgery: prostatectomy, bladder tumor resection; urology: cystometry, urodynamics.
Introduction In the elderly patient, subarachnoid anesthesia is often considered the “anesthetic of choice” for both transurethral resection of the prostate (TURP) and transurethral resection of bladder tumors1 due to a physiologic reduction in organ function as well as an increased incidence of cardiovascular and pulmonary disease. Furthermore, regional anesthesia-induced bladder atony is thought to improve surgical conditions, as well as decrease bladder spasm and postoperative bleeding.1,2 In addition, regional anesthesia has the added advantage that perioperative complications (transurethral resection syndrome and bladder perforation) are more easily detected in the awake patient. However, subarachnoid anesthesia is not without associated problems. First, because the normal aging process is associated with degenerative anatomical changes of the spine (e.g., vertebral collapse, osteophytes, calcified ligamentum flavum), the subarachnoid anesthetic technique may be difficult to administer. Second, the hemodynamic changes associated with sympathetic blockade may adversely effect the compromised elderly patient.3,4 In a previous study designed to compare the induction, maintenance, and recovery characteristics of spinal versus general anesthesia in elderly patients undergoing transurethral procedures, we determined that general anesthesia with short-acting agents and a laryngeal mask airway (LMA) facilitates shorter induction and recovery times without adversely affecting patient comfort.5 However, to date, the influence of these two anesthetic techniques on both bladder compliance and intraabdominal pressure, and their possible effect on the etiology of the complications associated with transurethral surgery, has not been assessed. Therefore, we designed a study to evaluate the effect of subarachnoid and general anesthesia on bladder compliance and intraabdominal pressure in elderly patients undergoing TURP.
Materials and Methods After obtaining informed, written consent, 21 patients undergoing transurethral prostatectomy were enrolled into a Meir Hospital Institutional Ethics Committe approved, open-label, prospective, controlled study. Patients with a history of clinically significant cardiovascular, pulmonary, and hematological diseases, as well as those receiving anticoagulant therapy, were excluded from the study. In all cases, anesthesia and surgery were performed by the same professional staff.
Anesthetic Technique On arrival in the operating room, patients were fitted with monitoring equipment, and the following parameters recorded at 1-minute to 5-minute intervals throughout the perioperative period: noninvasive blood pressure, electro-
cardiogram, and arterial hemoglobin oxygen saturation via pulse oximeter. Using a computer-generated randomization table, patients were assigned to one of two treatment groups. In Group S, 10 mg of hyperbaric tetracaine was administered intrathecally via a 25-gauge Quincke spinal needle. In Group GA, patients received intravenous (IV) fentanyl 1 to 2 g/kg and propofol 1.0 to 2.0 mg/kg IV for induction and isoflurane (end-tidal 0.7% to 1.2%) for maintenance of general anesthesia. After induction of general anesthesia, an LMA was inserted and 70% nitrous oxide (N2O) in oxygen administered. Inspired oxygen and end-tidal concentrations of carbon dioxide, isoflurane, and N2O were measured continuously using an infrared gas analyzer (Datex, AS/3, Datex Instrumnetarium, Helsinki, Finland). Throughout the procedure, spontaneous breathing was maintained and ventilation was assisted, as necessary. In Group S, supplemental oxygen was delivered via a tight-fitting facemask.
Urodynamic Studies With the patient in the supine position, using the MERKUR 4000 system (F.M. Wiest, Unterhaching, Germany), urodynamic studies were performed prior to the induction of anesthesia and immediately before the onset of the surgical procedure. Prior to performing measurements, the urethra and urinary bladder were catheterized with an 8-Fr catheter, and all residual urine was drained. Thereafter, a rectal balloon catheter was placed to facilitate measurement of intraabdominal pressure. Through the transurethral catheter, 1.5% glycine in water (at room temperature) was instilled into the bladder. Then, using the MERKUR 4000 system, intraabdominal pressure was recorded and bladder compliance calculated. To calculate maximal compliance prior to induction of anesthesia, patients were instructed to suppress the urge to urinate and to state the point at which micturition reflex became so strong that urination could no longer be prevented. Because the micturition reflex is interrupted in the anesthetized patient, following induction of anesthesia the maximal compliance was defined as the compliance at which spontaneous urination occurred. In all cases, maximal compliance was submitted for statistical analysis.
Statistical Analysis Data are expressed as mean values ⫾ SD. In all cases, normality was assessed with the Kolmogorov-Smirnov test (using Lilliefors’modification). Thereafter, data were analyzed and compared using a two-tailed Student’s t-test. In all comparisons, p ⬍ 0.05 was considered statistically significant.
Results Eleven patients in Group S and 10 patients in Group GA were studied. The two treatment groups were comparable with respect to age, weight, height, ASA physical status, as well as duration of surgical procedures and weight of resected prostate (Table 1). In Group S, the mean (range) sensory blockade was T10 (T7 to T12). J. Clin. Anesth., vol. 11, June 1999
329
Original Contributions
Table 1. Demographic Characteristics in the Two Treatment Groups
Number (n) Age (yrs) Weight (kg) Height (cm) ASA physical status (I/II/III) Surgery time (min) Resected prostatic tissue weight (g)
Group S
Group GA
11 68 (60–82) 84 (60–100) 168 ⫾ 9 1/8/2
10 71 (56–87) 71 (56–84) 165 ⫾ 10 3/5/2
45 ⫾ 28 12.6 ⫾ 10.5
40 ⫾ 10 12.7 ⫾ 5.2
Note: Values are means ⫾ SD, or numbers (range). No statistical significance was found when comparing Group S to Group GA.
Within Group S, bladder compliance was significantly (p ⫽ 0.003) higher when compared to baseline preanesthetic values (Table 2). In addition, intrathecal anesthesia was associated with a significant (p ⫽ 0.007) decrease in intraabdominal pressure when compared to baseline preanesthetic recordings. Within Group GA, there was a significant (p ⫽ 0.006) decrease in intraabdominal pressure when compared to baseline preanesthetic recordings. Following the induction of general anesthesia, a small change in bladder compliance was noted, but statistical significance was not achieved (Table 2). Finally, comparison between the groups revealed that urodynamic studies performed preinduction and postinduction of anesthesia were statistically comparable and unaffected by the anesthetic technique (Table 2).
Discussion The results of this prospective study suggest that when performing transurethral procedures, spinal anesthesia has a greater effect on bladder compliance when compared to general anesthesia. This finding is supported by the fact that following the induction of spinal anesthesia a significant increase in bladder compliance was recorded. In contrast, no significant difference in bladder compliance was demonstrated in the general anesthesia treatment group. Although transurethral procedures may be performed under either general or spinal anesthesia,5 we postulate that the increase in bladder compliance demonstrated in
our study is dependent on anesthetic technique. Because the intrathecal administration of local anesthetic drugs results in an all-or-nothing interruption of the spinal reflex when compared to light general anesthesia (with the patient breathing spontaneously via a LMA), spinal anesthesia is associated with more profound motor and sensory blockade. Although both anesthetic techniques suppress motor and sensory transmission, we hypothesize that the total denervation of the bladder following intrathecal local anesthetic administration resulted in the significant increase in bladder compliance noted in our spinal anesthesia study group. It is possible that by increasing the “depth” of the general anesthesia, a significant increase in bladder compliance may be induced. However, we compared anesthetic techniques commonly administered in clinical practice. Because patients did not respond to the painful stimulus of bladder overdistention, we conclude that clinically adequate “depth of anesthesia” was achieved in both study groups. Furthermore, it should be remembered that inappropriately “deep” general anesthesia may adversely affect perioperative hemodynamic stability and delay mental and psychomotor recovery. Performing urodynamic studies on the anesthetized patient is problematic. Because anesthesia inhibits the micturition reflex, it is not possible to use the subjective urge to urinate when calculating the point of maximal compliance. Therefore, the point of maximal bladder compliance must be determined according to other criteria. Because anesthesia induces transient bladder denervation, criteria similar to those applied when performing urodynamic studies on the paralyzed patient may be used when studying the anesthetized patient.6 Applying these criteria, we defined the point of maximal compliance as the point at which spontaneous micturition occurred. Therefore, it should be remembered that, when comparing within groups, the results of our study are limited by the fact that maximal compliance preanesthesia and postanesthesia were determined using different criteria. However, because similar criteria were used before and after induction of anesthesia, comparison of results between the groups is unaffected by the measurement technique. It is interesting to note that a similar decrease in intraabdominal pressure was recorded in both study groups. This finding may be explained by the fact that the abdominal musculature is innervated from the T4 to L1 dermatomes.7 Because adequate anesthesia for transurethral surgery requires T10 motor and sensory blockade,8
Table 2. Intraabdominal Pressure and Bladder Compliance in the Two Treatment Groups Group S
Intraabdominal pressure (cmH2O) Bladder compliance (ml/cmH2O)
Group GA
Preanesthesia
Postanesthesia
Preanesthesia
Postanesthesia
19 ⫾ 15 4.0 ⫾ 2.3
4 ⫾ 3* 8.5 ⫾ 3.5*
15 ⫾ 12 3.7 ⫾ 3.7
3 ⫾ 2* 6.1 ⫾ 4.7
Note: Values are means ⫾ SD. *p ⬍ 0.05, Group S ⫽ preanesthesia versus postanesthesia; Group GA ⫽ intraabdominal pressure preanesthesia versus postanesthesia. No statistical significance was found when comparing Group S to Group GA, or within Group GA. 330
J. Clin. Anesth., vol. 11, June 1999
Bladder function, intrathecal, and general anesthesia: Olsfanger et al.
we postulate that following induction of spinal anesthesia, intraabdominal pressure was maintained by abdominal musculature innervated by intact motor nerve roots situated above the level of the blockade. Thus, a similar decrease in intraabdominal pressure was measured between the groups. Transurethral surgery has all the advantages of endoscopic surgery.9 However, this procedure is not without associated problems. The major complications include overhydration due to intravascular absorption of irrigant fluid, surgically induced bleeding from engorged venous sinuses, and bladder perforation.1 Whereas an increase in intraabdominal pressure and consequent decrease in venous return, as well as a low bladder compliance, may be implicated in the pathophysiology of these complications, the effect of different anesthetic techniques on intraabdominal pressure and bladder compliance has not been described to date. Therefore, our findings may contribute to understanding the influence of different anesthetic techniques on transurethral surgeryrelated perioperative complications. During TURP, venous sinuses are opened within the resected tissue. Because irrigation is performed under pressure, these exposed venous sinuses may absorb large volumes of bladder irrigation fluid with consequent overhydration. In addition to fluid absorption, exposed venous sinuses constitute a site of perioperative blood loss. The extent of intravascular absorption and surgical blood loss is dependent on the venous pressure at the irrigant-blood interface and the number and size of exposed venous sinuses, as well as venous drainage and intraabdominal pressure.1 Therefore, anesthesia-associated changes in intraabdominal and venous pressures may affect perioperative overhydration and blood loss. In our study, both spinal and general anesthesia were associated with a significant decrease in intraabdominal pressure. Thus, it appears that the factors influencing venous sinus pressure (intraabdominal pressure, venous return, and the size and number of exposed venous sinuses) are unaffected by the anesthetic technique per se. However, our recordings were performed immediately before and after induction of anesthesia and do not reflect dynamic changes in intraabdominal pressure or bladder compliance. It should be remembered that the operative procedure may be associated with transient changes in intraabdominal pressure and bladder compliance. The likelihood of transient increases in venous pressure (and, consequently, fluid absorption or blood loss) due to LMA-induced straining, coughing, and “bucking” is increased during general anesthesia. Furthermore, spinal anesthesia-induced vasodilatation in combination with the lithotomy position may result in peripheral venous blood pooling and a consequent increase in venous pressure.10 However, due to technical difficulties, the influence of these changes on intraabdominal pressure and bladder compliance were beyond the scope of our study. We hypothesize that, due to the proximity of the endoscope to the bladder wall, an increase in bladder compliance (and, consequently, a thinning of the detrusor muscle) may increase the incidence of accidental bladder perforation during transurethral resection of bladder tu-
mors. Therefore, spinal anesthesia may increase the incidence of accidental bladder perforation, whereas general anesthesia may “protect” against this unwanted complication. However, inadequate depth of general anesthesia may result in unexpected patient movement, coughing, or straining, and consequent accidental bladder perforation. In contrast, because spinal anesthesia is associated with a constant motor and sensory blockade and is not subject to anesthetic drug delivery system variables, bladder perforation causd by unexpected patient movement is unlikely. This study may be criticized for the size of the two study groups. However, this study is associated with a 0.8 power (␣ ⫽ 0.05) to discover a 4.0 ml/cmH2O difference in bladder compliance and a 3.3 cmH2O difference in intraabdominal pressure. A second criticism relates to the fact that the effect of the different anesthetic techniques on the incidence to bladder perforation and perioperative blood loss was not studied. However, this was not the aim of our study. Furthermore, because outcome studies require analysis of large population groups, a multicenter investigation would be necessary. In summary, we found that spinal anesthesia was associated with a significant increase in bladder compliance. However, following induction of anesthesia, a similar decrease in intraabdominal pressure was recorded in both the spinal and general anesthesia treatment groups. Finally, the influence of these finding on transurethral-related perioperative complications requires further investigation.
References 1. Hatch PD: Surgical and anaesthetic considerations in transurethral resection of the prostate. Anaesth Intensive Care 1987;15: 203–11. 2. Abrams PH, Shah PJ, Bryning K, Gaches CG, Ashken MH, Green NA: Blood loss during transurethral resection of the prostate. Anaesthesia 1982;37:71–3. 3. Carpenter RL, Caplan RA, Brown DL, Stevenson C, Wu R: Incidence and risk factors for side effects of spinal anesthesia. Anesthesiology 1992;76:906 –16. 4. Arndt JO, Bomer W, Krauth J, Marquardt B: Incidence and time course of cardiovascular side effects during spinal anesthesia after prophylactic administration of intravenous fluids or vasoconstrictors. Anesth Analg 1998;87:347–54. 5. Fredman B, Zohar E, Philipov A, Olsfanger D, Jedeikin R: The induction, maintenance and recovery characteristics of spinal versus general anesthesia in geriatric patients. J Clin Anesth 1998;10:623–30. 6. Wein AJ: Neuromuscular dysfunction of the lower urinary tract and its treatment. In: Walsh PC, Wein AJ, Retik AB, Vaughan ED (eds): Campbell’s Urology, 7th ed. Philadelphia: WB Saunders Co., 1998:953–1006. 7. Brown DL: Celiac plexus block. In: Atlas of Regional Anesthesia. Philadelphia: WB Saunders Co., 1992:247–9. 8. Beers RA, Kane PB, Nsouli I, Krauss D: Does a mid-lumbar block level provide adequate anaesthesia for transurethral prostatectomy? Can J Anaesth 1994;41:807–12. 9. Webster GD, Kreder KJ: The neurologic evaluation. In: Walsh PC, Wein AJ, Retik AB, Vaughan Ed (eds): Campbell’s Urology, 7th ed. Philadelphia: WB Saunders Co., 1998:927–52. 10. Murray DJ: Monitoring of hemostasis. In: Rogers MC, Tinker JH, Covino BG, Longnecker DE (eds): Principles and Practice of Anesthesiology, 1st ed. St. Louis: Mosby, 1997:846 – 62. J. Clin. Anesth., vol. 11, June 1999
331
*Tutor in Anesthesiology †Lecturer in Anesthesiology ‡Lecturer in Urology §Professor of Anesthesiology Address correspondence to Dr. Jedeikin at the Department of Anesthesiology and Intensive Care, Meir Hospital, Kfar Saba 44281, Israel. E-mail: [email protected] Received for publication December 3, 1998; revised manuscript accepted for publication April 27, 1999.
Study Objective: To evaluate the influence of spinal versus general anesthesia on bladder compliance and intraabdominal pressure in elderly males undergoing elective transurethral resection of the prostate. Design: Prospective, randomized, open-label study. Setting: Teaching hospital. Patients: 21 ASA physical status I, II, and III patients at least 18 years of age, undergoing transurethral surgery. Interventions: According to a computer-generated randomization schedule, patients were allocated to one of two groups. In Group Spinal (S), 10 mg of hyperbaric tetracaine was administered intrathecally. In Group General Anesthesia (GA), patients received fentanyl intravenous (IV) 1 to 2 g/kg and propofol IV 1.0 to 2.0 mg/kg for induction of anesthesia. Thereafter, a laryngeal mask airway was inserted and, with spontaneous ventilation, anesthesia was maintained by administering isoflurane (end-tidal 0.7% to 1.2%) and 70% nitrous oxide (N2O) in oxygen. Intraabdominal pressure and bladder compliance were recorded prior to the induction of anesthesia and immediately before the onset of the surgical procedure. Measurements and Main Results: The two groups were demographically comparable. In Group S, mean bladder compliance was significantly (p ⫽ 0.003) higher and mean intraabdominal pressure significantly lower (p ⫽ 0.007) when compared to baseline preanesthetic values. In Group GA, mean intraabdominal pressure significantly (p ⫽ 0.006) decreased when compared to baseline preanesthetic recordings. Following the induction of general anesthesia, a small change in bladder compliance was noted. However, statistical significance was not reached. Data were analyzed and compared using Student’s t-test (p ⬍ 0.05 was considered statistically significant). Conclusion: Both spinal and general anesthesia induced a significant decrease in intraabdominal pressure. While both techniques were associated with an increase in bladder compliance, statistical significance was demonstrated only in the spinal anesthesia treatment group. © 1999 by Elsevier Science Inc.
Journal of Clinical Anesthesia 11:328 –331, 1999 © 1999 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010
0952-8180/99/$–see front matter PII S0952-8180(99)00057-4
Bladder function, intrathecal, and general anesthesia: Olsfanger et al.
Keywords: Anesthesia techniques: general, spinal; surgery: prostatectomy, bladder tumor resection; urology: cystometry, urodynamics.
Introduction In the elderly patient, subarachnoid anesthesia is often considered the “anesthetic of choice” for both transurethral resection of the prostate (TURP) and transurethral resection of bladder tumors1 due to a physiologic reduction in organ function as well as an increased incidence of cardiovascular and pulmonary disease. Furthermore, regional anesthesia-induced bladder atony is thought to improve surgical conditions, as well as decrease bladder spasm and postoperative bleeding.1,2 In addition, regional anesthesia has the added advantage that perioperative complications (transurethral resection syndrome and bladder perforation) are more easily detected in the awake patient. However, subarachnoid anesthesia is not without associated problems. First, because the normal aging process is associated with degenerative anatomical changes of the spine (e.g., vertebral collapse, osteophytes, calcified ligamentum flavum), the subarachnoid anesthetic technique may be difficult to administer. Second, the hemodynamic changes associated with sympathetic blockade may adversely effect the compromised elderly patient.3,4 In a previous study designed to compare the induction, maintenance, and recovery characteristics of spinal versus general anesthesia in elderly patients undergoing transurethral procedures, we determined that general anesthesia with short-acting agents and a laryngeal mask airway (LMA) facilitates shorter induction and recovery times without adversely affecting patient comfort.5 However, to date, the influence of these two anesthetic techniques on both bladder compliance and intraabdominal pressure, and their possible effect on the etiology of the complications associated with transurethral surgery, has not been assessed. Therefore, we designed a study to evaluate the effect of subarachnoid and general anesthesia on bladder compliance and intraabdominal pressure in elderly patients undergoing TURP.
Materials and Methods After obtaining informed, written consent, 21 patients undergoing transurethral prostatectomy were enrolled into a Meir Hospital Institutional Ethics Committe approved, open-label, prospective, controlled study. Patients with a history of clinically significant cardiovascular, pulmonary, and hematological diseases, as well as those receiving anticoagulant therapy, were excluded from the study. In all cases, anesthesia and surgery were performed by the same professional staff.
Anesthetic Technique On arrival in the operating room, patients were fitted with monitoring equipment, and the following parameters recorded at 1-minute to 5-minute intervals throughout the perioperative period: noninvasive blood pressure, electro-
cardiogram, and arterial hemoglobin oxygen saturation via pulse oximeter. Using a computer-generated randomization table, patients were assigned to one of two treatment groups. In Group S, 10 mg of hyperbaric tetracaine was administered intrathecally via a 25-gauge Quincke spinal needle. In Group GA, patients received intravenous (IV) fentanyl 1 to 2 g/kg and propofol 1.0 to 2.0 mg/kg IV for induction and isoflurane (end-tidal 0.7% to 1.2%) for maintenance of general anesthesia. After induction of general anesthesia, an LMA was inserted and 70% nitrous oxide (N2O) in oxygen administered. Inspired oxygen and end-tidal concentrations of carbon dioxide, isoflurane, and N2O were measured continuously using an infrared gas analyzer (Datex, AS/3, Datex Instrumnetarium, Helsinki, Finland). Throughout the procedure, spontaneous breathing was maintained and ventilation was assisted, as necessary. In Group S, supplemental oxygen was delivered via a tight-fitting facemask.
Urodynamic Studies With the patient in the supine position, using the MERKUR 4000 system (F.M. Wiest, Unterhaching, Germany), urodynamic studies were performed prior to the induction of anesthesia and immediately before the onset of the surgical procedure. Prior to performing measurements, the urethra and urinary bladder were catheterized with an 8-Fr catheter, and all residual urine was drained. Thereafter, a rectal balloon catheter was placed to facilitate measurement of intraabdominal pressure. Through the transurethral catheter, 1.5% glycine in water (at room temperature) was instilled into the bladder. Then, using the MERKUR 4000 system, intraabdominal pressure was recorded and bladder compliance calculated. To calculate maximal compliance prior to induction of anesthesia, patients were instructed to suppress the urge to urinate and to state the point at which micturition reflex became so strong that urination could no longer be prevented. Because the micturition reflex is interrupted in the anesthetized patient, following induction of anesthesia the maximal compliance was defined as the compliance at which spontaneous urination occurred. In all cases, maximal compliance was submitted for statistical analysis.
Statistical Analysis Data are expressed as mean values ⫾ SD. In all cases, normality was assessed with the Kolmogorov-Smirnov test (using Lilliefors’modification). Thereafter, data were analyzed and compared using a two-tailed Student’s t-test. In all comparisons, p ⬍ 0.05 was considered statistically significant.
Results Eleven patients in Group S and 10 patients in Group GA were studied. The two treatment groups were comparable with respect to age, weight, height, ASA physical status, as well as duration of surgical procedures and weight of resected prostate (Table 1). In Group S, the mean (range) sensory blockade was T10 (T7 to T12). J. Clin. Anesth., vol. 11, June 1999
329
Original Contributions
Table 1. Demographic Characteristics in the Two Treatment Groups
Number (n) Age (yrs) Weight (kg) Height (cm) ASA physical status (I/II/III) Surgery time (min) Resected prostatic tissue weight (g)
Group S
Group GA
11 68 (60–82) 84 (60–100) 168 ⫾ 9 1/8/2
10 71 (56–87) 71 (56–84) 165 ⫾ 10 3/5/2
45 ⫾ 28 12.6 ⫾ 10.5
40 ⫾ 10 12.7 ⫾ 5.2
Note: Values are means ⫾ SD, or numbers (range). No statistical significance was found when comparing Group S to Group GA.
Within Group S, bladder compliance was significantly (p ⫽ 0.003) higher when compared to baseline preanesthetic values (Table 2). In addition, intrathecal anesthesia was associated with a significant (p ⫽ 0.007) decrease in intraabdominal pressure when compared to baseline preanesthetic recordings. Within Group GA, there was a significant (p ⫽ 0.006) decrease in intraabdominal pressure when compared to baseline preanesthetic recordings. Following the induction of general anesthesia, a small change in bladder compliance was noted, but statistical significance was not achieved (Table 2). Finally, comparison between the groups revealed that urodynamic studies performed preinduction and postinduction of anesthesia were statistically comparable and unaffected by the anesthetic technique (Table 2).
Discussion The results of this prospective study suggest that when performing transurethral procedures, spinal anesthesia has a greater effect on bladder compliance when compared to general anesthesia. This finding is supported by the fact that following the induction of spinal anesthesia a significant increase in bladder compliance was recorded. In contrast, no significant difference in bladder compliance was demonstrated in the general anesthesia treatment group. Although transurethral procedures may be performed under either general or spinal anesthesia,5 we postulate that the increase in bladder compliance demonstrated in
our study is dependent on anesthetic technique. Because the intrathecal administration of local anesthetic drugs results in an all-or-nothing interruption of the spinal reflex when compared to light general anesthesia (with the patient breathing spontaneously via a LMA), spinal anesthesia is associated with more profound motor and sensory blockade. Although both anesthetic techniques suppress motor and sensory transmission, we hypothesize that the total denervation of the bladder following intrathecal local anesthetic administration resulted in the significant increase in bladder compliance noted in our spinal anesthesia study group. It is possible that by increasing the “depth” of the general anesthesia, a significant increase in bladder compliance may be induced. However, we compared anesthetic techniques commonly administered in clinical practice. Because patients did not respond to the painful stimulus of bladder overdistention, we conclude that clinically adequate “depth of anesthesia” was achieved in both study groups. Furthermore, it should be remembered that inappropriately “deep” general anesthesia may adversely affect perioperative hemodynamic stability and delay mental and psychomotor recovery. Performing urodynamic studies on the anesthetized patient is problematic. Because anesthesia inhibits the micturition reflex, it is not possible to use the subjective urge to urinate when calculating the point of maximal compliance. Therefore, the point of maximal bladder compliance must be determined according to other criteria. Because anesthesia induces transient bladder denervation, criteria similar to those applied when performing urodynamic studies on the paralyzed patient may be used when studying the anesthetized patient.6 Applying these criteria, we defined the point of maximal compliance as the point at which spontaneous micturition occurred. Therefore, it should be remembered that, when comparing within groups, the results of our study are limited by the fact that maximal compliance preanesthesia and postanesthesia were determined using different criteria. However, because similar criteria were used before and after induction of anesthesia, comparison of results between the groups is unaffected by the measurement technique. It is interesting to note that a similar decrease in intraabdominal pressure was recorded in both study groups. This finding may be explained by the fact that the abdominal musculature is innervated from the T4 to L1 dermatomes.7 Because adequate anesthesia for transurethral surgery requires T10 motor and sensory blockade,8
Table 2. Intraabdominal Pressure and Bladder Compliance in the Two Treatment Groups Group S
Intraabdominal pressure (cmH2O) Bladder compliance (ml/cmH2O)
Group GA
Preanesthesia
Postanesthesia
Preanesthesia
Postanesthesia
19 ⫾ 15 4.0 ⫾ 2.3
4 ⫾ 3* 8.5 ⫾ 3.5*
15 ⫾ 12 3.7 ⫾ 3.7
3 ⫾ 2* 6.1 ⫾ 4.7
Note: Values are means ⫾ SD. *p ⬍ 0.05, Group S ⫽ preanesthesia versus postanesthesia; Group GA ⫽ intraabdominal pressure preanesthesia versus postanesthesia. No statistical significance was found when comparing Group S to Group GA, or within Group GA. 330
J. Clin. Anesth., vol. 11, June 1999
Bladder function, intrathecal, and general anesthesia: Olsfanger et al.
we postulate that following induction of spinal anesthesia, intraabdominal pressure was maintained by abdominal musculature innervated by intact motor nerve roots situated above the level of the blockade. Thus, a similar decrease in intraabdominal pressure was measured between the groups. Transurethral surgery has all the advantages of endoscopic surgery.9 However, this procedure is not without associated problems. The major complications include overhydration due to intravascular absorption of irrigant fluid, surgically induced bleeding from engorged venous sinuses, and bladder perforation.1 Whereas an increase in intraabdominal pressure and consequent decrease in venous return, as well as a low bladder compliance, may be implicated in the pathophysiology of these complications, the effect of different anesthetic techniques on intraabdominal pressure and bladder compliance has not been described to date. Therefore, our findings may contribute to understanding the influence of different anesthetic techniques on transurethral surgeryrelated perioperative complications. During TURP, venous sinuses are opened within the resected tissue. Because irrigation is performed under pressure, these exposed venous sinuses may absorb large volumes of bladder irrigation fluid with consequent overhydration. In addition to fluid absorption, exposed venous sinuses constitute a site of perioperative blood loss. The extent of intravascular absorption and surgical blood loss is dependent on the venous pressure at the irrigant-blood interface and the number and size of exposed venous sinuses, as well as venous drainage and intraabdominal pressure.1 Therefore, anesthesia-associated changes in intraabdominal and venous pressures may affect perioperative overhydration and blood loss. In our study, both spinal and general anesthesia were associated with a significant decrease in intraabdominal pressure. Thus, it appears that the factors influencing venous sinus pressure (intraabdominal pressure, venous return, and the size and number of exposed venous sinuses) are unaffected by the anesthetic technique per se. However, our recordings were performed immediately before and after induction of anesthesia and do not reflect dynamic changes in intraabdominal pressure or bladder compliance. It should be remembered that the operative procedure may be associated with transient changes in intraabdominal pressure and bladder compliance. The likelihood of transient increases in venous pressure (and, consequently, fluid absorption or blood loss) due to LMA-induced straining, coughing, and “bucking” is increased during general anesthesia. Furthermore, spinal anesthesia-induced vasodilatation in combination with the lithotomy position may result in peripheral venous blood pooling and a consequent increase in venous pressure.10 However, due to technical difficulties, the influence of these changes on intraabdominal pressure and bladder compliance were beyond the scope of our study. We hypothesize that, due to the proximity of the endoscope to the bladder wall, an increase in bladder compliance (and, consequently, a thinning of the detrusor muscle) may increase the incidence of accidental bladder perforation during transurethral resection of bladder tu-
mors. Therefore, spinal anesthesia may increase the incidence of accidental bladder perforation, whereas general anesthesia may “protect” against this unwanted complication. However, inadequate depth of general anesthesia may result in unexpected patient movement, coughing, or straining, and consequent accidental bladder perforation. In contrast, because spinal anesthesia is associated with a constant motor and sensory blockade and is not subject to anesthetic drug delivery system variables, bladder perforation causd by unexpected patient movement is unlikely. This study may be criticized for the size of the two study groups. However, this study is associated with a 0.8 power (␣ ⫽ 0.05) to discover a 4.0 ml/cmH2O difference in bladder compliance and a 3.3 cmH2O difference in intraabdominal pressure. A second criticism relates to the fact that the effect of the different anesthetic techniques on the incidence to bladder perforation and perioperative blood loss was not studied. However, this was not the aim of our study. Furthermore, because outcome studies require analysis of large population groups, a multicenter investigation would be necessary. In summary, we found that spinal anesthesia was associated with a significant increase in bladder compliance. However, following induction of anesthesia, a similar decrease in intraabdominal pressure was recorded in both the spinal and general anesthesia treatment groups. Finally, the influence of these finding on transurethral-related perioperative complications requires further investigation.
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