Effects of fentanyl-lidocaine-ketamine versus sufentanil-lidocaine-ketamine on the isoflurane requirements in dogs undergoing total ear canal ablation and lateral bulla osteotomy.

OBJECTIVE: To compare the isoflurane-sparing effects of sufentanil-lidocaine-ketamine (SLK) and fentanyl-lidocaine-ketamine (FLK) infusions in dogs undergoing total ear canal ablation and lateral bulla osteotomy (TECA-LBO). STUDY DESIGN: Randomized blinded clinical study. ANIMALS: A group of 20 client-owned dogs undergoing TECA-LBO. METHODS: Intravenous (IV) administration of lidocaine (3 mg kg-1) and ketamine (0.6 mg kg-1) with fentanyl (5.4 µg kg-1; n = 10; FLK group) or sufentanil (0.72 µg kg-1; n = 10; SLK group) was immediately followed by the corresponding constant rate infusion (CRI) (lidocaine 3 mg kg-1 hour-1; ketamine 0.6 mg kg-1 hour-1; either fentanyl 5.4 µg kg-1 hour-1 or sufentanil 0.72 µg kg-1 hour-1). Anaesthesia was induced with propofol 3-5 mg kg-1 IV and was maintained with isoflurane. End-tidal isoflurane concentration (Fe'Iso) was decreased in 0.2% steps every 15 minutes until spontaneous movements were observed (treated with propofol 1 mg kg-1 IV) or an increase of > 30% in heart rate or mean arterial pressure from baseline occurred (treated with rescue fentanyl or sufentanil). Quality of recovery and pain were assessed at extubation using the short-form Glasgow Composite Pain Scale (SF-GCPS), Colorado State University Canine Acute Pain scale (CSU-CAP), and visual analogue scale (VAS). Data were analysed with analysis of variance, t tests, Fisher test and Spearman coefficient (p < 0.05). RESULTS: Fe'Iso decreased significantly in SLK group (45%; p = 0.0006) but not in FLK (15%; p = 0.1135) (p = 0.0136). SLK group had lower scores for recovery quality (p = 0.0204), SF-GCPS (p = 0.0071) and CSU-CAP (p = 0.0273) than FLK at extubation. Intraoperative rescue analgesia and VAS were not significantly different between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with FLK infusion, CRI of SLK at these doses decreased isoflurane requirements, decreased pain scores and improved recovery quality at extubation in dogs undergoing TECA-LBO.