Remifentanil patient controlled analgesia for patients unable to tolerate lithotripsy with enteral analgesia

Abstract

Background: Extracorporeal shock wave lithotripsy is an effective treatment for kidney stones which does not require general anaesthesia and can be performed as a daycase procedure. The fragmentation of calculi can be painful and various analgesic regimens have been described. A small minority of our patients are unable to tolerate ESWL with enteral analgesia. We offered a repeat ESWL treatment with remifentanil Patient Controlled Analgesia (R-PCA) to this group. Methods: Patients were given oral paracetamol 1g and 100mg rectal diclofenac before ESWL. Remifentanil PCA was prepared to provide a 0.5mcg/kg bolus with 2 minute lockout with dose increase as necessary. The primary outcome measure was ESWL energy level tolerated and was compared between groups with the Wilcoxon signed-rank test. Secondary outcomes included pain score, sedation score and adverse effects. Results: Twenty-one patients were treated with adjuvant R-PCA for one (n=21), two (n=7) or three (n=1) ESWL sessions. All patient were able to tolerate a significantly higher ESWL power level with R-PCA compared to enteral analgesia (p<0.01). Sedation was minimal (all sedation scores ≥ 3) with a low incidence of side effects. Conclusion: Patients treated with R-PCA tolerated a significantly higher ESWL power level and all patients completed the treatment. These patients were maintained on their intended treatment modality and avoided the operative and anaesthetic risks of alternative procedures such as ureteroscopy. On demand bolus PCA allows accurate titration of opiate to pain and is safe to use with the limited resources available in the ESWL suite. The combination of this delivery method with the minimal sedation and rapid elimination of remifentanil proved effective and safe with few adverse effects.