How Should I Operate on a Lithotriptor for Optimum Results?





Induction bolus

Maintenance PCA device



0.8–1 mg/kg

8–10 μg/kg

0.25 mg/kg

5 μg/kg

Very good analgesia

Very flexible system

Excellent tolerance

Fast recovery

Antiemetic effect (Propofol)

Transient O2-desaturation after induction

(as compared to “blind” coupling)(obstruction >apnea): rare

Stone Targeting

In order to avoid time consuming moves later in the procedure it is advisable to pre-position the patient in as close proximity to the focus as possible.

We advocate to use ultrasound imaging whenever possible, especially in children:

  • smaller stones are easier to detect

  • it is possible to detect radiolucent stones

  • real time imaging allows far better monitoring of the entire treatment

  • there is no radiation exposure.

Following the administration of IV analgosedation once targeting is completed, the patient will relax and “sag” a little. This may move the stone slightly out of focus in the Z-axis necessitating a small adjustment in the Z-axis.

With real time ultrasonic imaging it is usually possible to fine tune positioning in such a way that the stone nicely “swings” in the focal area with respiratory movements, thus increasing the hit rate to a maximum.

This is slightly more difficult with fluoroscopy and may increase radiation exposure times. When using fluoroscopic imaging the stone needs to be targeted in both imaging projection planes (AP and CC) prior to treatment start. During treatment it is very important to re-check targeting in both image projection planes at regular intervals: small movements of the patient may pass unnoticed save for a discreet change in sound of the shockwaves. The sound of the shockwaves is muffled by the patient on top of the water cushion. A change in the quality of this muffled sound is an important indication that the patient may have slightly moved. Of course radiation dose should be reduced according to the ALARA-principle (as low as reasonably achievable). This is mainly done by reducing the image size once initial targeting is completed and by keeping the exposure times with pulsed fluoroscopy as short as possible.


The quality of coupling of the SW-source to the patient is one of the most important factors in the energy transfer and thus in the quality of stone fragmentation. Air bubbles in the coupling area considerably reduce the disintegration capability [1, 4].

Bubble free coupling is therefore essential. It is advised to use a sufficient amount of a low viscosity ultrasound gel from a large mouthed container. A thick layer of gel is applied in the center of the water cushion. While inflating the water cushion the patient is gently lowered onto the inflating cushion. This will spread the gel radially and minimize air entrapment.

Following coupling air bubbles are removed from the coupling area by gently swiping a hand between patient and water cushion; when available optical coupling control with a camera mounted in the water cushion is preferable as optically controlled swiping significantly improves the adequate removal of all air bubbles. With the use of optical coupling control (OCC) we established a significant reduction in number of SW, energy level of SW and total energy administered as compared to “blind coupling” (Table 38.2). Theoretically this reduction in total energy applied (number of SW × energy level) should also reduce the incidence and severity of SW-induced adverse effects.

Table 38.2
Optical coupling control: effects on treatments results (as compared to “blind” coupling)

RENAL stones


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Nov 21, 2017 | Posted by in UROLOGY | Comments Off on How Should I Operate on a Lithotriptor for Optimum Results?
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