[Extracorporeal shock-wave lithotripsy: anxiety and pain perception]

Three factors in extracorporeal shock-wave lithotripsy (ESWL) result in pain: shock wave pressure, size of focal area and pressure distribution at entry in the skin. Our Lithotripsy Unit has performed 21,000 outpatient treatments (Dornier HM-4 Lithotripter) with no sedation or anaesthetics. Pain requiring treatment discontinuation resulted in 10% instances. Anxiety-associated pain increases the perceived intensity of pain and influences the emotional response to pain.

To determine whether the variability in the response to the pain stimulus caused by ESWL is related to the patient's status/trait of anxiety.

Sample 20 patients; inclusion criteria: pyelic lithiasis > 2 cm, no previous SWEL and no obesity. One SWEL session (2500 pulses, 22 Kv). Anxiety was first evaluated using the status/trait of anxiety index (STAI) questionnaire; after treatment, pain was evaluated on a Numerical Analogic Scale.

Pain scores ranged from 2 to 8, mean score 4.1 (S.D. = 1.67); mean score for trait of anxiety 21.8 (S.D. = 8.52), and status of anxiety 29 (S.D. = 5.89). A significant correlation was found between pain-anxiety trait (R = .51; p = .02), which was higher when compared to pain-anxiety status (R = .67; p = .001).

SWEL is a painful therapy (95% of sample had mild-to-moderate pain); pain perception is increased by status of anxiety (45% of pain variance) more than by the trait of anxiety (26.3%); therefore, usage of sedation-analgesia in patients with high anxiety status would improve the lithotripter efficacy ratio.