Effects ofdexmedetomidine ortramadol continuous rate infusions onthe propofol requirements and cardiorespiratory variables inpropofol-ketamine-midazolam anaesthetised cats.

Abstract

The aim ofthis study was tocompare the effects ofmidazolam-ketamine alone or incombination with dexmedetomidine ortramadol inaconstant rate infusion (CRI) onthe minimum infusion rate (MIR) ofpropofol and the cardiorespiratory function incats undergoing anovariohysterectomy (OH). This was aprospective, randomised, blinded clinical study. Twenty-four healthy female mixed-breed cats were premedicated with ketamine and midazolam. Propofol was used for the induction and maintenance ofthe anaesthesia (starting at18mg/kg/h). Cats were assigned togroups (n= 8) toreceive one ofthe following intravenous treatments: midazolam-ketamine group (MKG; ketamine 0.6mg/kg/h); midazolam-ketamine-dexmedetomidine group [MKDG; ketamine 0.6mg/kg/h and dexmedetomidine loading dose (LD) 1mg/kg, CRI 1mg/kg/h)] ormidazolam-ketamine-tramadol group [MKTG; ketamine 0.6mg/kg/h and tramadol (LD 2mg/kg, CRI 1mg/kg/h)]. During the OH, the propofol infusion was adjusted based onthe clinical signs tomaintain adequate anaesthetic depth. Selected variables were measured before (T0) and after (T1) the anaesthesia induction and during six surgical time points (T2-T7). Themean arterial pressure was higher and the heart rate was lower inMKDG atT1 (than inMKG and MKTG).Themean± SD MIR ofpropofol were 17.4± 3.2, 15.0± 2.8 and 12.6± 3.5mg/kg/h for MKG, MKTG, and MKDG, respectively. Weconclude that, compared tomidazolam-ketamine alone, midazolam-ketamine-tramadol and midazolam-ketamine-dexmedetomidine reduced the MRI ofpropofol by13.8% and 27.5%, respectively, without significant changes inthe selected indicators.