Peri-operative analgesia using constant rate infusion (CRI) of remifentanil combined with a low dose fentanyl CRI was evaluated in surgical cases of dogs. One hundred and ten dogs were premedicated with midazolam,meloxicam, and atropine. Anesthesia was induced with propofol and maintained with sevoflurane inhalation anesthesia in all dogs. During surgery, the dogs had been administered remifentanil (36μg/kg/hr, CRI) alone (group R-R, n=55) or combined with fentanyl (2μg/kg/hr, CRI) (group RF-F, n=55). The dogs had received remifentanil (4μg/kg/hr, CRI) or fentanyl (2μg/kg/hr, CRI) for 24 hours after the surgery in groups R-R and RF-F, respectively. The end-tidal concentrations of sevoflurane required for maintaining surgical anesthesia ranged from 1.32 to 1.48% in group RR and from 1.43 to 1.57% in group RF-F. During the anesthesia, all dogs were controlled by artificial ventilation. A smaller number of dogs required treatment for hypotension in group RF-F (13% versus 38% in group R-R, P=0.010). Recovery from anesthesia was prompt in all dogs. Postoperative pain was significantly reduced in group RF-F compared with group R-R (P=0.041). In conclusion, it is suggested that peri-operative analgesia using a combination of remifentanil and low dose fentanyl CRIs preserves cardiovascular function during anesthesia and provides better quality of postoperative analgesia.
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