Perineural dexmedetomidine combined with bupivacaine on sciatic/femoral nerve blocks in dogs undergoing stifle joint surgery

Abstract Objective The aim of this study is to evaluate the motor and sensitive block duration, related to quality of anaesthesia and analgesia after sciatic/femoral electrolocation nerve block with bupivacaine alone and in combination with dexmedetomidine in dogs undergoing unilateral stifle joint surgery. Materials and methods Thirty-one dogs, median age 4.4 years (1 – 11) and median weight 25.2 kg (3 - 68), randomly assigned to three groups: A, B and C. Group A received bupivacaine 0,25 mgkg-1 to each nerve; Group B received bupivacaine 0,25 mgkg-1 mixed with dexmedetomidine 0,25 µgkg-1 to each nerve; Group C received bupivacaine 0,5 mgkg-1 to each nerve. Data recorded over all the anaesthesia procedure were: heart rate (HR), respiratory rate (RR), median blood pressure (MAP), carbon dioxide end-tidal (EtCO2), end-tidal isoflurane (EtISO), esophageal temperature (T°). Surgery, anaesthesia and extubation times were also collected. Short Form of the Glasgow Composite Pain Scale (GCPS-SF score) was used to assess post-operative pain at 1, 2, 4, 6, 8, 12, 16 e 20 hours after extubation. Ability to walk, proprioception and pinch test were used to assess motor and sensory block duration every one hour after the extubation and until blockade end. Results Shapiro-Wilk normality test shows that data were not normally distributed. Significant differences were found among groups in relation of body weight, but not for BCS and age. Heart and respiratory rates remained in physiological ranges in all three groups. Arterial pressure was variable along the different points of the procedure; fluid therapy support was necessary in almost all individuals for Group C to compensate a mild perianaesthetic hypotension. Pain score was increased at 16th hour compared to the 1st hour in Group B, and at 16th and 20th hours compared to the 1st in Group C; no differences are found in Group A. No significant difference were found between groups concerning motor and sensory blocks duration. Between motor and sensory block scores and dogs weights there were some correlations in Group B. Conclusions On the basis of the preliminary results of this study, the mixture of bupivacaine and dexmedetomidine used for perineural blockage of the sciatic and femoral nerves (0,25 mgkg-1 and 0,25 µgkg-1 respectively for each nerve) can significantly increase the blockade duration and improving some benefits on arterial pressure stability. To statistically confirm the tendence found by our results a larger and homogenous sample will be indispensable.