Evaluation of the cardiorespiratory effects of the alpha-2 adrenoceptor agonists xylazine, medetomidine and dexmedetomidine in combination with ketamine in dogs

Abstract

In this study, we compared the effects of xylazine, medetomidine and dexmedetomidine in combination with ketamine on heart rate, respiratory rate, blood gas values, temperature and sedation scores. A total of 30 dogs were evaluated. The dogs were randomly allocated into three anaesthesia groups, each of which included ten dogs. The first group, denoted the xylazine/ketamine group, intravenously received xylazine (0.5 mg/kg) for premedication and ketamine (5 mg/kg) for induction. The second group, the medetomidine/ketamine group, intravenously received medetomidine (10 µg/kg) followed by ketamine (5 mg/kg). The third group received the dexmedetomidine/ketamine combination. This group intravenously received dexmedetomidine (3 µg/kg) for premedication and ketamine (5 mg/kg). Heart rate, respiratory rate, oxygen saturation, blood gas parameters and temperature were recorded for all patients immediately before sedation onset (T<sub>0</sub>), five minutes after sedation onset (T<sub>1</sub>) and five minutes after endotracheal intubation following ketamine injection (T<sub>2</sub>). The end tidal carbon dioxide level was recorded at T<sub>2</sub>. A significant decrease in heart rate occurred following premedication in all groups. However, the decrease was most marked in the medetomidine/ketamine group. An increase was observed in venous partial pressure of carbon dioxide values at T<sub>2</sub> in the xylazine/ketamine group compared to the medetomidine/ketamine and dexmedetomidine/ketamine groups. The end tidal carbon dioxide levels were higher in the medetomidine/ketamine group than in the other two groups, and oxygen saturation of haemoglobin levels in the same group were found to be lower than in the others. It was determined that none of α<sub>2</sub>-agonists, namely xylazine, medetomidine or dexmedetomidine, had superior properties over the others. If medetomidine is used, special care should be taken because of the rapid decrease in heart rate.

Efficacy and Safety of Dexmedetomidine Premedication in Balanced Anesthesia: A Systematic Review and Meta-Analysis in Dogs

“…Among the 222 trials initially identified from the search strategy, 13 studies were included in this meta-analysis [ 17 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ], involving a total of 576 dogs of various breeds. Most of the selected dogs were classified as having ASA 1 and ASA 2 physical status.…”

“…The authors investigated doses of dexmedetomidine ranging from 1 to 10 μg.kg −1 (1 μg.kg −1 ≈25 μg.m −2 ) [ 17 , 27 , 29 , 31 , 35 ], combined with methadone [ 24 , 28 ], ketamine [ 32 , 37 ] or buprenorphine [ 26 , 32 , 35 , 36 ] as premedication. Four included trials used alfaxalone to induce or maintain anesthesia [ 26 , 29 , 33 , 35 ], and eight used propofol [ 17 , 28 , 30 , 31 , 33 , 34 , 35 , 36 ].…”

“…Other interventions than dexmedetomidine were the comparisons. Four studies set acepromazine as the comparison [ 26 , 33 , 35 , 36 ], four studies used α-2 receptor agonists as the comparison [ 28 , 30 , 32 , 37 ] and five studies had opioids in the comparison [ 17 , 27 , 29 , 31 , 34 ]. Six studies set more than one comparison [ 30 , 31 , 33 , 34 , 35 , 37 ].…”

“…Four studies set acepromazine as the comparison [ 26 , 33 , 35 , 36 ], four studies used α-2 receptor agonists as the comparison [ 28 , 30 , 32 , 37 ] and five studies had opioids in the comparison [ 17 , 27 , 29 , 31 , 34 ]. Six studies set more than one comparison [ 30 , 31 , 33 , 34 , 35 , 37 ]. Three articles compared the effects of different doses of dexmedetomidine to the comparisons during balanced anesthesia [ 17 , 29 , 36 ].…”

“…The risk of bias, according to the Cochrane Collaboration Risk of Bias tool, is presented in Figure 2 . Some of the studies did not entirely blind participants/personnel/outcome assessment, which were assessed as high risk [ 17 , 26 , 29 , 32 , 33 , 37 ]. Those who mentioned blinding but did not describe the measures used were rated as unclear risk [ 28 , 35 , 36 ].…”