A Comparison of Single-Drug Sedation Technique Using Remifentanil Manual Infusion or Effect-Site Target-Controlled Infusion for Shock Wave Lithotripsy

Alejandro Recart MD;  Rodrigo Sepulveda MD; Pablo Sepúlveda MD
Department of Anesthesiology, Padre Hurtado General Hospital and Clinica Alemana Universidad del Desarrollo, Santiago-Chile

Introduction:

Traditionally, the pharmacokinetic characteristics of remifentanil have permitted a rapid response to any variations in the infusion rate, so administration by effect-site Target Controlled Infusion (TCI)  may further facilitate titration with this agent. This study examined the intra-operative and postoperative characteristics of  remifentanil via continous infusion alone or effect-siteTCI as single drug for sedation of patients undergoing shock wave lithotripsy (ESWL).

Methods:

Following institutional approval and informed consent, 30 ASA 1-2 outpatients receiving a MAC sedation technique for shock wave lithotripsy procedures using aStorz Modulith SLX transportable lithotripter were randomly assigned to one of the two treatment groups: Group 1 (Manual) received Remifentanil, 0,2 micro g kg(-1) bolus injection followed by a continuous IV infusion of 0.1 micro g kg(-1) min(-1)) and Group 2 (TCI) received  Remifentanil, 2 ng ml (-1) effect-site concentration using the Remifusor™ (Stutzin, A. et al., Faculty of Medicine, Universidad de Chile), drug delivery  software. During the ESWL procedure, the study drug was increased/decreased in 0.05 micro g kg(-1)  for group 1 and 0.5 ng ml (-1)  for Group 2 according to the pain scores. Patients were not premedicated. Pain was assessed using a numerical pain scale (0-10) and sedation was evaluated using the Ramsay Sedation Score. Respiratory depression was defined as a ventilatory frequency less than10 breaths min(-1) on two occasions or a peripheral oxygen saturation < or =92%. In addition, patient satisfaction with their anesthetic procedure was assessed using a 100-point verbal rating scale (with 1=none to 100=maximum) at the time they left the hospital. Ketorolac, 30 mg IV, was used for analgesic rescue once in the recovery area, and ondansetron was administered in case of PONV.

Results:

ompared with the traditional manual infusion, the use of a TCI software for remifentanil reduced the opioid requirement in 28%. No differences were observed in median Pain or Sedation scores throughout the procedure. Interestingly, 2 patients in Group 1 vs 0 patients in group 2 had episodes of arterial desaturation. Not surprisingly  37% of patients in Group 1 and 35 % of patients in group 2 required analgesic rescue during recovery, and more patients in the Manual Group required antiemetic rescue. Nevertheless, discharge time and patient satisfaction were similar between groups.

Conclusion:

These preliminary results suggest that  effect-site TCI of remifentanil may be an alternative to manual controlled infusion when used as sole agent for short, not very painful ambulatory procedures. Furthermore, it is possible that the more precise titration may result in important drug savings, but further research is needed in these area. 

References

1. De Castro V et al. Anesthesia and Analgesia 2003; 96: 33-38.