Valutation of isoflurane requirements in anesthetized cats treated with continuous rate infusions (CRI) of fentanyl or tramadol or fentanyl-tramadol

This study compared effects of fentanyl, tramadol, and fentanyl-tramadol continuous rate infusions (CRIs) on requirementes of isoflurane, analgesia and vital signs, in cats undergoing ovaristerectomy. Sixteen adult cats (weighing 3±2 kg) were enrolled and allocated in three groups: fentanyl (F),tramadol (T), fentanyl and tramadol FT. Group F was administered with fentanyl bolus 1µgkg-1 followed by a continuous intravenous infusion 5µgkg-1 h . Group T was administered with tramadol, initial bolus was 1.5mgkg-1 and was then maintained as CRI 2.6mgkg-1h .Group FT was administrated simultaneously with tramadol and fentanyl through two separate venous accesses, the tramadol dose was 0.8mgkg-1 for bolus and 1.3mgkg-1 hour-1 for CRI; fentanyl doses were 0.5µgkg-1 for bolus, and 2.5µgkg-1 hour-1 for CRI. Anesthesia was performed with dexmedetomidine 5µgkg-1 followed by alfaxolone 7mgkg-1 intramuscularly and maintenance with oxygen and isoflurane at variable flows. Heart rate (PR), respiratory rate (RR), systolic arterial pressure (SAP), End-Tidal CO2 (EtCO2), oxygen saturation (SpO2), minimum alveolar concentration (MAC) and temperature (T°), were recorded. Analgesia was assessed, by means of a cumulative pain scale, giving scores of percentage changes in vital signs evaluated. Data obtained showed that the FT protocol resulted in good stability of the monitored vital parameters, with a significant reduction in the dosage of the analgesics themselves and in the isoflurane requirement, compared with the other groups. Pain analgesic scores revealed low scores, indicating a good analgesic plan. The combination of fentanyl and tramadol provided good quality analgesia and it was shown to maintain a good anesthetic plan, without side effects. Results demonstrated that fentanyl and tramadol infusion administered in CRI had valid effects in reducing anesthetic needs in cats.