Sciatic and femoral nerve blockade using bupivacaine alone, or in combination with dexmedetomidine or buprenorphine in cats

The aim of this study was to determine the onset and offset of antinociception after sciatic (ScN) and femoral (FN) nerve blocks. Six healthy adult cats (4.8±1.3years; 4.3±0.4 kg) were included in a randomised, crossover, blinded and controlled study. Following sedation with dexmedetomidine (25 µg/kg, intramuscular), each ScN and FN injection was performed using 0.1 ml/kg of saline (CONTROL), bupivacaine (0.46 per cent, 0.46 mg/kg; BUPI), bupivacaine and dexmedetomidine (1 µg/kg; BUPI-DEX) or bupivacaine and buprenorphine (2.5 µg/kg; BUPI-BUPRE). Atipamezole (250 µg/kg) was administered after injections. Paw withdrawal thresholds (PWT) and motor blockade were evaluated before sedation and up to 24 hours. The PWT were significantly increased at half an hour in CONTROL, from two to four hours in BUPI and BUPI-DEX when compared with baseline. Motor blockade was observed between one and three hours in treatments using bupivacaine. Ability to walk was significantly impaired in BUPI at half an hour to two hours, BUPI-DEX at one to two hours and BUPI-BUPRE at two hours. Antinociception was observed in BUPI between one and eight hours, and in BUPI-DEX and BUPI-BUPRE between one and four hours. This study could not demonstrate a benefit of administering bupivacaine with dexmedetomidine or buprenorphine in cats. Results in BUPI-DEX may have been biased by the administration of atipamezole.