Minimum infusion rate and hemodynamic effects of propofol, propofol-lidocaine and propofol-lidocaine-ketamine in dogs

Abstract

Objective: To evaluate the effects of a constant rateinfusion (CRI) of lidocaine alone or in combinationwith ketamine on the minimum infusion rate (MIR)of propofol in dogs and to compare the hemody-namic effects produced by propofol, propofol-lido-caine or propofol-lidocaine-ketamine anesthesia. Study design: Prospective, randomized cross-overexperimental design. Animals: Fourteen adult mixed-breed dogs weighing15.8 ± 3.5 kg. Methods: Eight dogs were anesthetized on differentoccasions to determine the MIR of propofol aloneand propofol in combination with lidocaine (loadingdose [LD] 1.5 mg kg)1, CRI 0.25 mg kg)1minute)1) or lidocaine (LD 1.5 mg kg)1, CRI 0.25 mg kg)1minute)1) and ketamine (LD 1 mg kg)1, CRI 0.1 mgkg)1minute)1). In six other dogs, the hemodynamiceffects and bispectral index (BIS) were investigated. Each animal received each treatment (propofol,propofol-lidocaine or propofol-lidocaine-ketamine) on the basis of the MIR of propofol determined inthe first set of experiments. Results: Mean ± SD MIR of propofol was 0.51 ± 0.08mg kg)1minute)1. Lidocaine-ketamine significantlydecreased the MIR of propofol to 0.31 ± 0.07 mg kg)1 minute)1(37 ± 18% reduction), although lidocainealone did not (0.42 ± 0.08 mg kg)1minute)1,18 ± 7% reduction). Hemodynamic effects weresimilar in all treatments. Compared with theconscious state, in all treatments, heart rate, cardiacindex, mean arterial blood pressure, stroke index andoxygen delivery index decreased significantly, whereas systemic vascular resistance indexincreased. Stroke index was lower in dogs treatedwith propofol-lidocaine-ketamine at 30 minutescompared with propofol alone. The BIS was lowerduring anesthesia with propofol-lidocaine-ketaminecompared to propofol alone. Conclusions and clinical relevance: Lidocaine-keta-mine, but not lidocaine alone, reduced the MIR ofpropofol in dogs. Neither lidocaine nor lidocaine incombination with ketamine attenuated cardiovas-cular depression produced by a continuous rateinfusion of propofol.