Effect of dexmedetomidine infusion on the analgesic duration of peripheral nerve blocks in dogs: a randomized clinical study

Abstract The aim of this study was to evaluate whether a continuous rate infusion (CRI) of dexmedetomidine could prolong the analgesic effect of peripheral nerve blocks. Twenty client-owned dogs were enrolled and randomly divided into 2 groups. The DEX group received dexmedetomidine infusion at 1 mcg kg⁻¹ h⁻¹, and the NaCl group received an equivalent volume infusion of saline. Sciatic, saphenous and obturator nerve blocks were performed using 0.1 mL kg⁻¹ 0.5% ropivacaine/block. Intraoperative fentanyl was administered if the heart rate and/or mean arterial pressure (MAP) increased >15% from the previous measurement, and vasopressors were administered if the MAP was ≤ 70 mmHg. Postoperative pain was assessed every hour using the Glasgow Composite Pain Scale (GCPS). Postoperative rescue analgesia consisted of methadone (0.2 mg kg⁻¹ IV) and carprofen (2 mg kg⁻¹ IV). A greater number of dogs in the NaCl group required fentanyl (5/10 p= 0.03) and vasopressors (8/10, p=0.02) than did those in the DEX group (0/10 and 2/10, respectively). The duration of postoperative analgesia was significantly longer (604 ± 130 minutes) in the DEX group than in the NaCl group (400 ± 81 minutes, p=0.0005). Dexmedetomidine infusion at 1 mcg kg⁻¹ h⁻¹ reduces intraoperative analgesic and vasopressor requirements during orthopedic surgery and prolongs the postoperative analgesic effect of nerve blocks.