Total intravenous anesthesia using remifentanil in extracorporeal shock wave lithotripsy (ESWL). Comparison of two dosages: a randomized clinical trial.

BACKGROUND

Extracorporeal Shock Wave Lithotripsy is usually performed in day surgery setting, consequently people who undergo to this procedure need a safe and fast recovery. Conscious sedation with remifentanil can relieve from pain and keep patients in touch with anaesthesiologists. Few publications tell about infusion rates administered to perform this procedure7. The aim of this study is to assess which is the most appropriate infusion rate.

METHODS

Patients were randomly assigned to two groups. Two different infusion rates were compared: 0,05 mcg/kg/min, GROUP A (N.=114), vs. 0.1 µg/kg/min, GROUP B (N.=114). Patients' vital signs, additional analgesic requests, PONV (postoperative nausea and vomiting) and other side effects were registered. The deepness of sedation and patient's satisfaction were evaluated referring to Obsever's Assessment of Alertness and Sedation scale (O/ASS) and using a Likert's scale respectively. Pain intensity was assessed with a 11-points VAS (visual analogue scale). Differences between groups were analyzed using Student t test for independent variables. The χ2 test was used to analyze categorical variables.

RESULTS

The study enrolled 228 patients and assigned them to two groups (N.=114). No significant differences were found regarding Likert's scale values (P=0.20), additional analgesic request (P=0.30) and mean VAS values (P>0.05) between the two groups. The difference between the two groups about PONV, hypotension, oxygen desaturation and respiratory depression was statistically significant (P<0.05), as a matter of fact in group A these side effects occurred less frequently. The fifth degree of O/ASS was estimated in about 1.61±0.19 min and 2.987±0.20 min in group A and in group B respectively (P<0.05).

CONCLUSION

According with previous results remifentanil at the infusion rate of 0.05 µg/kg/min provides an effective analgesia, causing a lower incidence of side effect than 0.1 µg/kg/min, granting a fast and safe recovery.