Remifentanil

Pain relief

In a double-blind, crossover, randomized study 20 healthy volunteers received an infusion of either remifentanil or saline [ ]. Thermal sensory testing of the heat pain threshold was performed every 5 minutes and the dose of remifentanil was increased by 0.01 micrograms/kg/minute every 5 minutes. Remifentanil produced a dose-dependent increase in the heat pain threshold, and a dose of 0.05 micrograms/kg/minute was suggested as an effective and safe increment in healthy volunteers. The rate of adverse reactions (nausea, vomiting, and pruritus) was comparable with previous reports; there were no cardiovascular adverse reactions.

The postoperative analgesic efficacy and safety of two continuous constant-dose intravenous remifentanil infusions have been investigated in a double-blind, randomized study in 30 patients scheduled to undergo elective abdominal or thoracic surgery [ ]. The patients were randomly assigned to intravenous remifentanil 0.05 micrograms/kg/minute or 0.1 micrograms/kg/minute. There were no cases of respiratory depression, and nausea and vomiting occurred in one patient in each group. There was adequate analgesia in 75% and 78% of the patients in the low-dose and high-dose groups respectively and pethidine rescue analgesia was required in 26% and 6% respectively.

General surgery

Mixtures of remifentanil and sevoflurane have been used in two prospective, open, randomized studies [ , ], which showed that adding remifentanil results in a reduced requirement for sevoflurane for maintenance of anesthesia, leading to faster and easier recovery.

In a double-blind, randomized study a continuous infusion of remifentanil (1 microgram/kg followed by 0.5 micrograms/kg/minute) was compared with alfentanil (25 micrograms/kg followed by 1 microgram/kg/minute) during anesthesia in patients undergoing major abdominal surgery [ ]. Both systolic pressure and heart rate were significantly lower with remifentanil, with a higher incidence of hypotension (53 versus 39%) and bradycardia (10 versus 3%).

Bronchoscopy

In a randomized study, remifentanil 0.5 micrograms/kg/minute was compared with fentanyl 2 micrograms/kg in 22 patients undergoing rigid bronchoscopy [ ]. The results suggested that remifentanil attenuated the hemodynamic response to bronchoscopy without significantly increasing the incidences of hypotension or bradycardia. Four patients given remifentanil developed ST segment depression compared with eight patients given fentanyl.

Colonoscopy

Remifentanil by infusion (n = 49) has been compared with titrated boluses of pethidine (n = 51) in a randomized, double-blind study in 100 patients undergoing outpatient colonoscopy [ ]. The incidences of tachycardia, hypotension, and nausea were significantly less with remifentanil than with pethidine, but there were higher anxiety and pain scores with remifentanil. However, the study was a comparison of two opioids with different pharmacokinetic profiles, which makes it very difficult to achieve equipotent doses for the purpose of comparison.

Lithotripsy

In randomized, double-blind, controlled comparisons of anesthetic techniques for extracorporeal shock wave lithotripsy remifentanil infusion had no advantage over the combination of fentanyl bolus plus propofol infusion, but caused more adverse reactions (nausea and vomiting) [ ].

In another study remifentanil infusion provided comparable analgesia and caused less respiratory depression and fewer gastrointestinal symptoms than intravenous boluses of sufentanil [ ].

In a double-blind, randomized, placebo-controlled study, 40 patients undergoing extracorporeal shock-wave lithotripsy were given prophylactic dolasetron 12.5 mg before remifentanil (0.15 micrograms/kg/minute) [ ]. Dolasetron produced a significant reduction in the incidence of nausea and vomiting and significantly earlier discharge.

Cardiac surgery

In a prospective multicenter, double-blind, randomized study in 297 patients undergoing elective coronary artery bypass surgery, remifentanil infusion 1 microgram/kg/minute was compared with a loading dose of fentanyl 15 micrograms/kg [ ]. The most common adverse reactions were nausea and vomiting, which occurred equally often in the two groups. Hypertension and shivering were significantly more common with remifentanil.

In infants and children undergoing cardiac surgery, spinal anesthetic blockade with remifentanil significantly reduced postoperative pain and reduced the requirement for fentanyl without significant adverse reactions [ ].

Remifentanil 0.054 micrograms/kg/minute for postoperative pain after cardiac surgery produced adequate analgesia in 73% of tracheally extubated patients without causing respiratory compromise [ ]. However, the investigators suggested careful monitoring by trained personnel [ ].

In a multicenter double-blind randomized, dose-comparison study in 149 patients undergoing first-time elective coronary artery bypass grafting, the recommended remifentanil infusion rate was not more than 1 microgram/kg/minute without any adverse reactions that necessitated withdrawal [ ].

Obstetrics and gynecology

The role of remifentanil-based anesthesia in gynecological and obstetric procedures has been reviewed [ ].

In a double-blind, randomized comparison of remifentanil (0.25/0.5 micrograms/kg/minute) and alfentanil (50 micrograms and 0.5 micrograms/kg/minute) in 35 patients undergoing total abdominal hysterectomy, remifentanil provided more stable analgesia during anesthesia but caused significantly more hypotension [ ].

Orthopedic surgery

Intravenous remifentanil 0.3 micrograms/kg with propofol 2 micrograms/ml has been compared with propofol 2 micrograms/ml alone in a double-blind, randomized study in 86 day-case adults undergoing elective orthopedic surgery [ ]. The study was designed to assess whether remifentanil improves conditions for laryngeal mask airway insertion. Those given remifentanil had a better quality of airway patency, with minimal cardiorespiratory changes.

Orthopedic and urological surgery

The respiratory depressant and gastrointestinal adverse reactions to remifentanil have been observed in a randomized, single-blind study of 125 patients undergoing elective orthopedic and urological surgery under spinal or brachial plexus anesthesia [ ]. They were randomized to either remifentanil (a bolus of 0.5 micrograms/kg plus an infusion of 0.1 micrograms/kg/minute) or propofol (a bolus of 500 micrograms/kg plus an infusion of 50 micrograms/kg/minute). Owing to a significantly higher rate of respiratory depression with remifentanil (46%) than with propofol (19%), the mean remifentanil infusion rate was reduced to 0.078 ± 0.028 micrograms/kg/minute. The incidence of intraoperative nausea and vomiting with remifentanil was 27% compared with 2% with propofol. Postoperatively there was no significant difference in the incidence of gastrointestinal symptoms. Remifentanil may be considered as an alternative if propofol is contraindicated (for example because of amnesic episodes).

Remifentanil + propofol and fentanyl + desflurane have been compared in 49 patients undergoing prolonged surgery (elective abdominal prostatectomy lasting more than 150 minutes) [ ]. The fentanyl + desflurane combination was associated with faster recovery and extubation, at a significantly lower cost. Significantly more patients had postoperative nausea and vomiting with desflurane.