Target-controlled infusion of remifentanil or fentanyl during extra-corporeal shock-wave lithotripsy

Abstract

Background and objective: Target-controlled infusions (TCIs) of remifentanil and fentanyl in conscious sedation regimes for extra-corporeal shock-wave lithotripsy have not been reported. We estimated the effect site concentrations of remifentanil and fentanyl needed to obtain adequate analgesia in 50% of patients (EC50) and compared both drugs in terms of intra- and post-procedure complications.

Methods: Forty-four adult patients were randomly distributed into two groups: Group R received remifentanil and Group F received fentanyl TCI with initial effect site concentrations of 1.5 and 2 ng mL(-1), respectively. Pain was assessed using a 10-point verbal analogue scale and <3 was considered adequate analgesia. Increments or decrements of 0.5 ng mL(-1) were then introduced for subsequent patients according to Dixon's up and down method. During the rest of the procedure, TO was adjusted to maintain verbal analogue scale <3.

Results: Remifentanil and fentanyl EC50 were 2.8 ng mL(-1) (95 % confidence interval (CI): 1.8-3.7 ng mL(-1)) and 2.9 ng mL(-1) (95 % Cl: 1.7-4.1 ng mL(-1)), respectively (n.s.). At EC50, the probability of having a respiratory rate <10 was 4% MIX Cl: 0-57%) for remifentanil and 56%, (95% Cl: 13-92%) for fentanyl. Hypoxaemia, vomiting and sedation were more frequent in Group F during and after the procedure (P < 0.05).

Conclusions: A similar EC50 but more respiratory depression, sedation and PONV were found with fentanyl TO than with remifentanil TCI.