OBJECTIVES: Assess effects of benzodiazepine administration on the propofol dose required to induce anaesthesia in healthy cats, investigate differences between midazolam and diazepam, and determine an optimal benzodiazepine dose for co-induction.
STUDY DESIGN: Prospective, randomised, blinded, placebo-controlled clinical trial.
ANIMALS: Ninety client-owned cats (ASA I and II) with a median (interquartile range) body mass of 4.0 (3.4-4.9) kg.
METHODS: All cats received 0.01 mg kg-1 acepromazine and 0.2 mg kg-1 methadone intravenously (IV). Fifteen minutes later, sedation was scored on a scale of 1-5, with 5 indicating greatest sedation. Propofol, 2 mg kg-1 , administered IV, was followed by either midazolam or diazepam at 0.2, 0.3, 0.4 or 0.5 mg kg-1 or saline 0.1 mL kg-1 . Further propofol was administered until endotracheal intubation was possible. Patient signalment, sedation score, propofol dosage and adverse reactions were recorded.
RESULTS: Midazolam and diazepam (all doses) significantly reduced the propofol dose required compared with saline (p < 0.001). There was no difference between midazolam and diazepam in propofol dose reduction (p = 0.488). All individual doses of midazolam reduced propofol requirement compared with saline (0.2 mg kg-1 , p = 0.028; 0.3 mg kg-1 , p = 0.006; 0.4 mg kg-1 , p < 0.001; 0.5 mg kg-1 , p = 0.009). Diazepam 0.2 mg kg-1 did not reduce the propofol dose compared with saline (p = 0.087), but the remaining doses did (0.3 mg kg-1 , p = 0.001; 0.4 mg kg-1 , p = 0.032; 0.5 mg kg-1 , p = 0.041). Cats with sedation scores of 3 required less propofol than cats with scores of 2 (p = 0.008). There was no difference between groups in adverse events. CONCLUSIONS AND CLINICAL RELEVANCE: Midazolam (0.2-0.5 mg kg-1 ) and diazepam (0.3-0.5 mg kg-1 ) administered IV after 2 mg kg-1propofol significantly reduced the propofol dose required for tracheal intubation. The study is from the Department of Veterinary Clinical Sciences, Royal Veterinary College, University of London, London, UK. Robinson R, Borer-Weir K. Vet Anaesth Analg 2015 Feb 14 [Epub ahead of print].