Evaluation of analgesic, sympathetic and motor effects of 1% and 2% lidocaine administered epidurally in dogs undergoing ovariohysterectomy

Abstract Objective To compare, versus a control, the sensory, sympathetic and motor blockade of lidocaine 1% and 2% administered epidurally in bitches undergoing ovariohysterectomy. Study design Randomized, blinded, controlled clinical trial. Animals A total of 24 mixed-breed intact female dogs. Methods All dogs were administered dexmedetomidine, tramadol and meloxicam prior to general anesthesia with midazolam–propofol and isoflurane. Animals were randomly assigned for an epidural injection of lidocaine 1% (0.4 mL kg−1; group L1); 2% (0.4 mL kg−1; group L2) or no injection (group CONTROL). Heart rate (HR), respiratory rate (fR), end-tidal partial pressure of carbon dioxide (P e′ CO2), and invasive systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures were recorded every 5 minutes. Increases in physiological variables were treated with fentanyl (3 μg kg−1) intravenously (IV). Phenylephrine (1 μg kg−1) was administered IV when MAP was Results There were no differences over time or among groups for HR, fR, P e′ CO2 and SAP. MAP and DAP were lower in epidural groups than in CONTROL (p = 0.0146 and 0.0047, respectively). There was no difference in the use of phenylephrine boluses. More fentanyl was administered in CONTROL than in L1 and L2 (p = 0.011). GCPS–SF was lower for L2 than for CONTROL, and lower in L1 than in both other groups (p = 0.001). Time to ambulation was 2 (1–2) hours in L1 and 3 (2–4) hours in L2 (p = 0.004). Conclusion and clinical relevance Epidural administration of lidocaine (0.4 mL kg−1) reduced fentanyl requirements and lowered MAP and DAP. Time to ambulation decreased and postoperative pain scores were improved by use of 1% lidocaine compared with 2% lidocaine.