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291

Gallstone Extracorporeal ShockWave Lithotripsy: Time and Treatment Considerations

Rendon C. Nelson1 Gayle A. Rowland William E. Torres Bruce R. Baumgartner

We evaluated Dornier

30 gallstone

MPL-9000

hithotnpsy

Lithotripter

to determine

procedures how

time

performed was

spent

on 27 patients in the

hithotripsy

with the suite

and to evaluate the various technical reasons for interrupting the administration of shock waves during the treatment. The procedure averaged 98 ± 32 mm total time in the lithotripsy suite. This included an average of 22 ± 6 mm before the treatment, 70 ± 28 mm for administration of shock waves, and 6 ± 2 mm after the treatment. The time required to deliver the shock waves did not correlate with patient age, sex, or weight, the number of gallstones; or the number or date of the treatment. However, a trend was seen toward an association between shorter treatment times and larger stone volumes. On the average, the administration of shock waves was interrupted every 48 shock waves for various reasonS. Electronically changing the imaging plane of the in-line sonographic transducer to retarget the stone in the focal zone was by far the most frequent reason for interrupting shock-wave delivery, averaging 56 shock waves between changes. We conclude that extracorporeal shock-wave hithotripsy of gallstones is a time consuming and technically demanding procedure that requires continuous monitoring and frequent interruption in order to optimize targeting and fragmentation of the stone(s) while maintaining the patient’s comfort. AJR

154:291-294,

February

1990

Extracorporeal shock-wave lithotripsy (ESWL) is a relatively new, noninvasive means of fragmenting gallstones. Although the procedure has been performed for several years in Europe [i 2], the technique was introduced in the United States in i 988 using a protocol approved by the Food and Drug Administration (FDA). In the first year of operation, approximately 1 000 patients have undergone ESWL in the United States at a number of designated sites. As the technology expands, many centers are involved in either early clinical trials or in planning for the installation of facilities. Those involved in designing a lithotnipsy center and estabhishing treatment protocols need information about the amount of time spent by the average patient in the hithotripsy suite, as well as specific technical details related to the fragmentation procedure itself. ,

Subjects

Received August 29, 1989; accepted after revi13, 1989.

sion October

All authors: Biliary Lithotripsy Center, Crawford W. Long Hospital of Emory University, 1364 Clifton Rd., N.E., Atlanta, GA 30322. Address reprint requests to A. C. Nelson. 0361 -803x/90/1

542-0291

© American Roentgen Ray Society

and

Methods

A prospective study was conducted during a 3-month period after the lithotripsy unit had been in operation for 5 months. Data were obtained from 30 consecutive procedures performed on 27 patients. The patients included 10 men and 17 women ranging in age from 22 to 86 years (mean, 45 years). Twenty-five patients underwent the fragmentation procedure for the first time and three of those patients had a second treatment because they had residual fragments larger than 5 mm in diameter. Two patients underwent only their second treatment as part of this study. Of the 25 patients undergoing the procedure for the first time, 21 patients had one stone (mean diameter, 18 ± 7 mm) and four patients had two stones (mean diameter, 15 ± 7 mm).

NELSON

292

Of the five patients

undergoing

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one patient had three patients had numerous

the procedure

fragments fragments

for the second time,

(mean diameter, 9 mm) and four of various sizes, estimated at more

than 30 per patient. The study was performed under a protocol approved by the FDA. All of the patients met the following inclusion criteria: symptoms of biliary colic, a functioning gallbladder as determined

by oral

cholecystography,

by sonography, 3 cm

one

or less

than

a visible

to three

5 mm

stones,

gallbladder

largest

in diameter,

and

and

stone

not

no more

than

gallstone(s) greater

than

a 3-mm

rim

of central nidus of calcium as determined by plain radiography. All procedures were performed on the Dornier MPL-9000 biliary lithotnipter (Domier Medical Systems Inc., Marietta, GA) by using a total of 1500 shock waves per treatment with a kilovoltage ranging from 14 to 22 [3]. All patients were treated in the prone position. The fragmentation procedure was performed by either of two radiologists. A registered nurse with 2 years of renal ESWL experience assisted in all procedures. We used a data sheetto evaluate the lithotripsy procedure in terms of the duration of the procedure and the specific technical factors used. Time in the lithotripsy suite was divided into three categories: (1) pretreatment

treatment

time,

which

table, attaching

(electrocardiogram,

blood

included

transferring

the

patient

and

pulse

oximeter),

the

administration

of shock

waves

and

as follows:

was correlated (by using Student’s t test) with patient’s sex, number of stones, and whether it was the first or second treatment. Results

The summary of how time was spent in the hithotnipsy suite is as follows: pretreatment time averaged 22 ± 6 mm (range, 1 i -34 mm), treatment time averaged 70 ± 28 mm and was highly variable (range, 36-1 45 mm), posttreatment time averaged 6 ± 2 mm (range, 2-i 3 mm). The total time in the hithotripsy suite averaged 98 ± 32 mm, with a wide range of

60-180

mm.

There was no statistically significant correlation between treatment time and patient’s age, sex, and weight or the number of stones (Fig. i). There was a negative trend toward statistical correlation between the treatment time and total stone volume per patient

(Fig. 2), assuming

devices

that the stones are spherical

in shape (V

=

200

prelim-

mary stone localization, which on the Domier lithotripter is performed by an electronically coupled articulating sonographic transducer (outof-line transducer); (2) treatment time, the time required to administer a total of 1500 shock waves; and (3) posttreatment time, the time required to disconnect monitoring devices, estimate the adequacy of the fragmentation process by using the out-of-line transducer, and transfer the patient off the treatment table. We also used the data sheet to record the technical reason for interrupting

AJR:154, February 1990

to the

an oxygen cannula and monitoring pressure,

ET AL.

150

Rx TIme

S

A

100

.

(mln)

A

(1) out-of-

50

S.’

transducer-how often the procedure was halted to evaluate the patient with the out-of-line transducer in order to localize the stone or to monitor the degree of fragmentation; (2) additional gel-how often the procedure was halted to add gel to the space between the line

water

cushion

membrane

and

the

patient’s

skin

to

improve

image;

or decrease

the

transducer-how imaging

plane

kilovoltage

often of the

in-line

to reduce

the procedure sonographic

patient

discomfort;

was halted transducer

Fig.

the

to repo-

sition the stone or fragments into the 3 x 20 mm focal zone, a process which is performed electronically at the control console because the transducer is located within the ellipsoid of the therapy unit; (5) light pen-how often the procedure was halted to use the light pen to target the stone or fragments; (6) cushion change-how often the procedure was halted to add or remove water from the treatment chamber in order to change the distance between the stone and the focal zone; (7) table change-how often the procedure was halted to change the elevation of the treatment table with a manually operated crank in order to position the stone within the focal zone; (8) position of patient change-how often the procedure was halted to physically and manually change the patient’s position on the table in order to position the stone in the focal zone; (9) C-arm change-how often the procedure was halted to change the angle of the C-arm in order to alter the contact point between the treatment cushion

and

the

skin

medication

change-how

administer

IV medication.

to diminish often

the the

patient’s

procedure

discomfort; was

halted

and in order

2

# Stones 1.-Graph number

shows relationship between treatment time (Rx time, of gallstones per patient (# stones) There was no statistical difference between treatment time for those patients with one or two gallstones (p = .48), although number of patients with two stones was small (n = 4).

mm) and

(4) in-line

to change in order

1

the

(3) kilovoltage change-how often the procedure was halted to either increase the kilovoltage to improve fragmentation sonographic

150

100 Time

S.

(mm)

55 S

50

S

S

S

#{149}5

(10) to

The time required to deliver 1500 shock waves was correlated with patient’s age and weight, the treatment date, and the volume of the stones by using the Pearson correlation coefficient and test of significance [4]. The time required to deliver 1 500 shock waves also

n 0

2500 Volume (mm”)

5000

Fig. 2.-Graph shows relationship between treatment time (Rx time, mm) and total gallstone volume (mm”) in each patient. Note trend toward shorter treatment times with larger stone volumes (r = -.38, p = .06).

AJR:154,

GALLSTONE

February 1990

That is, there was a trend toward longer treatment times with smaller stone volumes. The relationship between treatment time and whether the patient was undergoing the initial treatment or a retreatment (Fig. 3), and the relationship between treatment time and the date of the procedure (Fig. 4) showed no statistical correlation. That is, treatment time did not improve significantly as the lithotnipsy team gained experience. The various technical reasons for interrupting the administration of shock waves are summarized in Table i . Electronically adjusting the imaging plane of the in-line transducer was by far the most frequent change, averaging 56 shock waves between changes or an average total of 30 changes per treatment. On the average the lithotnipsy procedure was halted, for whatever reason, a total of 35 ± 1 4 times (48 shock waves between changes) during the 1 500-shock-wave treatment period. During seven (20%) of the 35 times the procedure

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7rr3).

200

293

ESWL

TABLE 1: Summary of the Technical Reasons the Administration of Shock Waves (Maximum Waves/Treatment)

Reas

No. of Shock Waves Between Changes

0n

In-line transducer Out-of-line transducer Kilovoltage change C-arm change Table change Medication change Additional gel Cushion change Light

56 423 487 696 771 964 1028 1 146 1 1 48 1346

pen

Position of patient change

was halted,

± ± ± ± ± ± ± ± ± ±

for Interrupting Shock

1500

No.

21

30.1

328

3.8

246 437 471 520

3.8 1 .9 1 .7 1 .2

539

1 .5 0.7

454 523

1 .1

362

0.4

more than one kind of change

commonly

The

halted in order In fact, except change” (59%), (