Comparison of fentanil or remifentanil prolonged continuous infusion in dogs undergoing elective ovariohysterectomy

Abstract

It aimed to compare the trans anesthetic clinical and perioperative analgesic effects by prolonged continuous infusion of fentanyl (GF, bolus of 5 µg/kg and continuous infusion (CI) of 15 µg/kg/h) or remifentanil (GR, CI of 18 µg/kg/h) in dogs undergoing to elective ovariohysterectomy. Twenty female healthy dogs were premedicated with acepromazine, inducted to unconsciousness with propofol and kept under anesthesia with isoflurane. The M0 (baseline) was recorded and animals were randomly allocated in GF (n = 10) or GR (n = 10), recording clinical and blood gas parameters every 15 minutes (M15…M120) for two hours and, after, during surgery, adjusting the opioid rate according to surgical requirement. The isoflurane vaporization reduced by up to 47% and 42% in GF and GR, respectively, when compared to M0. During the first two hours of CI, six animals of each group required atropine intervention and three animals of GF required ephedrine. The number of rate adjustments during intraoperative was significant higher in GR when compared to GF (P = 0.0248). By the Log-rank test, there was a higher possibility of not receiving analgesic rescue in the first 30 minutes of postoperative in GF when compared to GR (P < 0.0001) and all animals required analgesic rescue during the firsts 3 and 6 hours in GR and GF, respectively. It is concluded that, when the proposal continuous infusions were compared, fentanyl required fewer analgesic rescues during perioperative, nonetheless, it is recommended rate adjustment during intraoperative and additional analgesia for postoperative for both treatments.