JOURNAL OF ENDOUROLOGYVolume 4, Number 1, 1990Mary Ann Liebert, Inc., Publishers

Monitored Anesthesia Care with the Standard DornierHM3 Lithotripter

LAURENCE S. BASKIN, M.D., ANDREAS FLOTH, M.D.,and MARSHALL L. STOLLER, M.D.

ABSTRACT

To determine whether epidural anesthesia can be avoided in patients undergoing extracorpo¬real shock wave lithotripsy (ESWL) with the standard Dornier HM3 lithotripter, 33 patientswho received monitored anesthesia care (MAC) consisting of intravenous fentanyl andmidazolam were compared with 33 who received epidural anesthesia. Only 2 of 31 patientscould not tolerate ESWL with its auxiliary procedures under MAC. Preoperative time in thecystoscopy suite was significantly reduced with MAC (17 vs. 33 minutes; < 0.001), as was

recovery room time (143 vs. 214 minutes; < 0.001). Our study indicates that ESWL with thestandard HM3 lithotripter and most pre-ESWL procedures can be performed successfullyand safely under MAC.

INTRODUCTION

Extracorporeal shock wave lithotripsy (ESWL) has become the standard treatment for most calculi inthe urinary tract. This method uses repeated monophasic acoustical waves with short rise times

(<30 µß ) and high peak pressures (1000-1300 bar) to fragment stones. A convergent shock wave fronttransfers the energy from the extracorporeal source to the calculus through a relatively small area of bodytissue and causes pain.

The Dornier lithotripter, introduced in 1980, is still the reference standard in ESWL. Treatments have mostfrequently been performed under general endotracheal or epidural anesthesia.1 Newly developedlithotripters,2 as well as the modified HM3,3 can be operated with monitored anesthesia care (MAC) asdefined below. Our purpose was to determine whether ESWL'with the standard Dornier HM3 lithotriptercould likewise be performed with MAC.

PATIENTS AND METHODS

From June 16, 1988, until July 21, 1988, 33 patients underwent ESWL with the Dornier HM3 lithotripterand MAC, which was administered by an anesthesiologist who monitored blood pressure, heart and breathingrates, and arterial oxygen saturation. All patients received supplemental oxygen (4-6 L/min) via nasal

From the Department of Urology, University of California School of Medicine, San Francisco, CA.

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BASKIN ET AL.

Table 1. Stone Composition in Patients WhoUnderwent ESWL with Epidural Anesthesia or

MAC (N = 33 in Both Groups)Stone Composition Epidural MAC

CalciumUric acidCystineStruviteNot available

183157

192049

cannula. Analgesia was achieved with an initial intravenous loading dose of fentanyl ( 1 µg/kg of body weight)and sedation with midazolam (1 mg) with repeat doses titrated according to the amount pain and emotionaldiscomfort.

A group of 33 consecutive patients treated the preceding month with ESWL under epidural anesthesiaserved as the control. The size, location, and composition of calculi were similar in the two groups (Table 1and Fig. 1), as was the mean age (epidural group, 53 years [22-81 years]; MAC group, 54 years [26-82years]). The patients' anesthesia, operative, and postanesthesia recovery records were reviewed, the twotreatment groups being compared for the length and number of pre-ESWL endoscopie manipulations, numberof shock waves applied, maximum kilovoltage, and radiation exposure. We also compared the amount offentanyl and midazolam administered, ESWL treatment and recovery room times, endoscopie manipulationtime before ESWL, and the time interval before the start of endoscopie manipulation. Both groups weretreated as outpatients and were discharged from the recovery room to a family member or friend. The overalltreatment time from preoperative registration to discharge was 4 to 6 hours in both groups.

Patient data were evaluated with the t-test for unpaired samples.

Epidural MAC

CO co

ü5

ËE3

4l·

2 J Li1

mm 3-10 11-20 >20 3-10 11-20 >20

caliceal [¿j] pelvic £3 staghorn S ureter multipleFIG. 1. Number, size, and location of stones in patients who underwent ESWL with either epidural anesthesia or MAC(N = 33 in both groups).

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MONITORED ANESTHESIA CARE

Table 2. Adjuvant Procedures before ESWL

Epidural MACProcedure (N = 27) (N = 24)

Retrograde manipulation of ureteral calculi 10 9Double-J stent placement 15 13Ureteral localization; catheter placement 16 14

RESULTS

Twenty-seven of the patients in the epidural anesthesia group (81%) required pre-ESWL manipulation, as

did 24 (72%) in the MAC group (Table 2). The types of manipulative procedures were similar in the twogroups. Likewise, there was no significant difference between the groups in the mean number of shock wavesand the duration of fluoroscopy, ESWL, or endoscopie manipulation (Table 3). However, maximumkilovoltage was significantly less in the MAC group (Table 3), although calculus fragmentation was equal inboth groups at 6-month follow-up (Table 4). The MAC group required significantly less recovery room timeand less time in the cystoscopy suite before endoscopie manipulation (Table 3).

Intravenous medication was applied for almost all treatments. In the epidural group, 24 patients received an

average of 125 µg of fentanyl and 31 patients an average of 3.5 mg of midazolam (means and ranges for bothgroups are shown in Table 5). Significant hemodynamic instability was not encountered in either group ofpatients.

In four of the patients in the MAC group, the procedure could not be completed. Two required pre-ESWLureteroscopic manipulation to relocate ureteral stones into the renal pelvis after standard pushback proceduresfailed, and general anesthesia was chosen. Another patient reported intolerable pain despite a total dose of1000 µg of fentanyl, and her treatment under MAC was a failure. After 650 shock waves, she was removedfrom the water bath, intubated, and repositioned; and the treatment was completed under general anesthesia.An additional patient experienced claustrophobia, and the posposed bilateral procedure was terminated aftercompletion of the right renal unit.

DISCUSSION

The Dornier HM3 lithotripter has been available for clinical application of ESWL since 1980, and there are

now more than 350 machines worldwide. With this model, lithotripsy is routinely performed under generalendotracheal or epidural anesthesia. In the hope of reducing treatment time, some groups have applied generalanesthesia with high-frequency jet ventilation, thereby decreasing the respiratory excursions of the kidney andkeeping the targeted stones in focus.4,5

Table 3. Patient Treatment Data

Epidural , MAC

Times (min)Cystoscopy suite time 33 ± 14 (15-75) 17 ± 5.5 (8-30) <0.001

(before start of procedure)Retrograde manipulation 33 ± 17 (10-90) 43 ± 24.8 (1-97) 0.158ESWL 49 ± 16 (20-80) 51 ± 18 (15-100) 0.626Fluoroscopy 1.7 ± 1.1 (0.5-6.0) 1.8 ± 1.3 (0.3-6.7) 0.691Recovery room 214 ± 62 (120-400) 143 ± 65 (60-360) <0.001

Number of shocks 1811 ± 847 (600-4650) 1651 ± 580 (750-2900) 0.376Kilovoltage 20 ± 2.1 (18-24) 18 ± 2.6 (15-25) <0.001

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BASKIN ET AL.

Table 4. Stone Burden at 6 Months Assessed byPlain Film or Sonography

Epidural MAC

Stone free 21 20Gravel (inferior calix) 6 8Calculi 1 0Not available 5 5

Epidural anesthesia has been the method of choice at our institution and others. Patients are more

manageable under epidural than general endotracheal anesthesia because they are awake, with their arms freeto help facilitate their transfer from gurney to lithotripter gantry. Jantzen et al.6 demonstrated that epiduralanesthesia frequently does not guarantee sufficient analgesia, and supplemental intravenous analgetics andsedatives are at times required. Superficial pain sensation at the skin can be sufficiently ablated by a 10anesthetic level. However, pain sensation directly from the kidney is transmitted via the celiac plexus, thusrequiring a level of T5 or higher for adequate pain control. In their study, 43% of the patients requiredanalgosedative supplementation. In our study, 24 patients required both fentanyl and midazolam supplemen¬tation, and seven required midazolam alone.

Local anesthetic infiltration or a regional block technique as primary modalities for pain relief with HM3lithotripsy have been described elsewhere.7'8 These procedures are time consuming, provide no analgesia forpossible auxiliary retrograde endoscopie manipulation, and frequently necessitate fentanyl supplementation.In addition, significant bruising and ecchymosis of the infiltrated area have been described. Acupuncture hasalso been used as an anesthetic. In a recent Taiwanese study, 11 of 22 patients were treated without anysupplemental medications, but the remaining half required analgosedation.9

In our stone center, auxiliary procedures (retrograde stone manipulation, ureteroscopy, and retrogradeplacement of indwelling catheters) are required in more than 70% of our patients. For ureteral calculi abovethe iliac crest, our general approach is retrograde manipulation of the stone into the renal pelvis and ESWL.If we are able to bypass the stone with a stent but are unable to move the stone into the renal pelvis, we performeither in situ ESWL or ureteroscopy, depending on the operator's preference. As there are no reportsconcerning the feasibility of ESWL with auxiliary procedures under intravenous analgesia and sedation(MAC), the present study was undertaken to compare 33 successive patients treated with MAC with 33patients treated previously under epidural anesthesia. Patient characteristics, including stone burden,location, and associated endoscopie procedures, were similar in the two groups.

A combination of intravenous opioid analgesia and sedation in the awake patient has been utilized forESWL treatments (HM3) by two European groups.10'11 This regimen provided sufficient analgesia for allpatients in one group,10 and in the other,11 only 2 of 299 required conversion to general endotrachealanesthesia. Intravenous analgosedation had no effect on circulatory measures.

Of our 33 patients, 29 were successfully treated under MAC. Of the four in whom MAC failed, two men

required unexpected ureteroscopy. Although this had been done under local anesthesia,12 we preferred toinduce general anesthesia. Therefore, MAC proved to be insufficient for ESWL therapy in only 2 of 33patients. Although this number is higher than those previously reported,1011 patients requiring auxiliaryprocedures were not included in other studies.

MAC has some distinct advantages: it can significantly reduce preoperative time in the cystoscopy suite; itdelivers adequate analgosedation; it does not limit standard retrograde manipulations, which take no longer

Table 5. Intravenous Medication Required during ESWL

Medication Epidural MAC

Fentanyl (Mg) 125 ± 84 (50-375) 283 ± 166 (75-1000) <0.001Midazolam (mg) 3.5 ± 2.6 (1-12) 6.0 ± 2.5 (2-13) <0.001

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MONITORED ANESTHESIA CARE

than with an epidural anesthetic; and it requires significantly reduced recovery room time (particularly usefulas ESWL is often performed as an outpatient procedure). All treatments in patients undergoing ESWL withoutassociated endoscopie procedures were completed uneventfully. A significantly lower kilovoltage was used(Table 3), yet the disintegration rate at 6-month follow-up (Table 4) was no different from that in the groupgiven epidural anesthesia.

Recent advances in lithotripter technology have reduced the need for analgesia in ESWL to either minimallyinvasive methods such as MAC or no analgesia at all. This effect is achieved mainly by a decreased amountof delivered energy per cm2. To meet the new requirements, many standard lithotripters are equipped withnew generators and power delivery units.2

In conclusion, our study indicates that ESWL with the standard HM3 lithotripter, as well as most auxiliarypre-ESWL procedures, can be performed successfully and safely under MAC. In addition, preoperative andrecovery room time can be significantly reduced.

ACKNOWLEDGMENT

Ronald Miller, M.D., helped with the preparation of this manuscript.

REFERENCES

1. Drach GW, Dretler S, Fair WR, Finlayson , Gillenwater JY, Griffith D, Lingeman JE, Newman DM: Report ofUnited States Cooperative Study of Extracorporeal Shock Wave Lithotripsy. J Urol 1986;135:1127

2. Coptcoat MJ, Miller RJ, Wickham JEA: Lithotripsy II: Textbook of Second Generation Extracorporeal Lithotripsy.London: BDI Publishing, 1987, pp 15-120

3. Graff J, Schmidt A, Pastor J, Herberhold D, Rassweiler J, Hankemeier U: New generator for low pressure lithotripsywith the Dornier HM3: preliminary experience of 2 centers. J Urol 1988;139:904

4. Zeitlin GL, Roth RA: Effect of three anesthetic techniques on the success ofESWL in nephrolithiasis: Anesthesiology1988;68:272

5. Schulte am Esch J, Kocks E, Meyer WH: High frequency jet ventilation during extracorporeal shock wave

lithiotripsy. Anesthetist 1985;34:2946. Jantzen J, Erdmann K, Wilbert D, Hein A, Klein A: Management of urolithiasis: an analysis of 1293 lithotriptor

procedures. Texas Med 1986;82:377. Loening S, Kramolowsky EV, Willoughby B: Use of local anesthesia for extracorporeal shock wave lithotripsy. J

Urol 1987;137:6268. Newman RC, Riehle RA: Techniques in anesthesia. In: Riehle RA (ed): Principles of Extracorporeal Shock Wave

Lithotripsy. New York: Churchill Livingstone, 1987, pp 107-1209. Chung C, Lee WC, Lee TY, Liang HK: Acupuncture anesthesia for extracorporeal shock wave lithotripsy. Am J

Acupuncture 1988;16(1): 1110. Berger M, Brandstetter A, Chowanetz E, Mossig H, Schmidt P: Extrakorporale Stoßwellenlithotripsie in Sedoanal-

gesie. Urologe [A] 1988;27:8911. Daub D: Opioid analgesia: an alternative to general anesthesia. Anaesthetist 1985;34:48912. Rittenberg MC, Ellis DJ, Bagley DH: Ureteroscopy under local anesthesia. Urology 1987;30:475

Address reprint requests to:Dr. Laurence S. Baskin

Department of Urology, U-575University of California

San Francisco, CA 94143-0738

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