Comparing lidocaine, bupivacaine and a lidocaine–bupivacaine mixture as a metacarpal block in sheep

Mechanical sensory blocking effects in the metacarpi of rams were compared following perineural injection of saline, 2% lidocaine (LIDO), 0.5% bupivacaine (BUPI), and a 1:1 (volume/volume) mixture of LIDO–BUPI. Saline was also administered in the contralateral metacarpi. Compared with the saline treatment and contralateral controls, the various treatments induced larger area under the curve (AUC) values 0–60 min post-treatment (AUC0–60). Administration of BUPI and LIDO–BUPI also induced larger AUC60–120 values (P < 0.01). The AUC0–60 and AUC60–120 values with LIDO were less than those achieved with LIDO–BUPI and BUPI (P < 0.001), and AUC60–120 values with LIDO–BUPI were less than those obtained with BUPI (P < 0.05). Anaesthesia occurred within 5 min following the administration of all local anaesthetics and lasted longer in the case of BUPI (110.0 ± 47.3 min) than with LIDO (40.0 ± 13.2 min) (P < 0.01). The duration of anaesthesia was 86.9 ± 66.0 min with the LIDO–BUPI combination. Thus this combination offered no apparent advantages over the use of BUPI alone.