Predictive risk factors for pain during extracorporeal shockwave lithotripsy.

PURPOSE: Extracorporeal shockwave lithotripsy (SWL) is a noninvasive but painful procedure. The aim of this study was to identify predictive risk factors for pain during SWL. PATIENTS AND METHODS: Two hundred twenty-two SWL treatments with the Lithostar lithotripter (Siemens) were included in a monocentric study. Patient and stone characteristics were prospectively collected in a database, and a standardized pain control protocol was administered 1 hour before treatment: paracetamol, nefopam, ketoprofen, and alprazolam. Subjective pain level was assessed with visual analog scale (VAS, 0-10). If VAS was >or=3, tramadol was added. If VAS was still >or=3, shockwave intensity was decreased or treatment was interrupted. The efficacy on stone fragmentation was evaluated 1 month after treatment. The need for adjuvant analgesia was compared with patient and stone characteristics to find out predictive risk factors for pain.
RESULTS: The average subjective pain was 3.1. The need for supplementary analgesia was more frequent in women (p = 0.035), younger patients (p < 0.001), anxious and depressed patients (p = 0.018), in patients with previous SWL (p = 0.0185), in patients with a rib projected stone (p < 0.001), in patients with renal stones (p = 0.0535), and finally in patients with homogeneous stones (p = 0.02). Multivariate analysis revealed two independent risk factors for pain: young age (odds ratio = 5; p < 0.001) and rib projected stone (odds ratio = 5.23; p < 0.001). Stone fragmentation was worse in patients with an adjuvant analgesia requirement (p = 0.0311).
CONCLUSION: Predictive risk factors for pain during SWL treatments were found: young age, rib projected stones, anxious and depressed patients, previous SWL treatment, and homogeneous stones. A higher analgesic requirement is necessary for these preselected patients to perform SWL and optimize its efficacy.