Effect of butorphanol, midazolam or ketamine on romifidine based sedation in horses during standing cheek tooth removal

Abstract

Background: Standing surgery, especially dental procedures, are commonly performed in horses. This leads to an increasing demand for reliable sedation protocols. Therefore, it was the purpose of this study to investigate the influence of butorphanol, midazolam or ketamine on romifidine based sedation in horses during cheek tooth removal.

Methods: Forty horses presented for tooth extraction were divided in four groups using matched pair randomization. Group R was sedated with romifidine (bolus 0.03 mg/kg, followed by a constant rate infusion (CRI) 0.05 mg/kg/h) and group RB with romifidine (same dose) and butorphanol (0.02 mg/kg; CRI 0.04 mg/kg/h). Group RM received romifidine (same dose) and midazolam (0.02 mg/kg; CRI 0.06 mg/kg/h) whereas group RK was administered romifidine (same dose) and ketamine (0.5 mg/kg; CRI 1.2 mg/kg/h). If sedation was not adequate a top up bolus of romifidine (0.01 mg/kg) was administered. The quality of sedation and the conditions for tooth extraction, the level of ataxia, chewing, head and tongue movement were evaluated by using a scoring system. The investigator was blinded to the applied sedation protocol. Furthermore, serum cortisol concentrations before, during and after the procedure were analyzed to gain more information about the stress level of the horses.

Results: Horses in group RM showed significantly less chewing and tongue activity compared to horses sedated with romifidine alone or with butorphanol additionally, but also significantly higher levels of ataxia. The quality of sedation was significantly better if romifidine was administered in combination with ketamine compared to romifidine alone. Furthermore, horses of group RK needed less additional romifidine boli compared to all other groups. Blood cortisol concentrations during surgery in groups RB and RM remained unchanged. Horses of group R showed higher cortisol concentrations during sedation compared to horses of groups RB and RM.

Conclusion: Romifidine alone at an initial bolus dose of 0.03 mg/kg followed by a constant rate infusion of 0.05 mg/kg/h was insufficient to obtain an adequate level of sedation and led to increased stress levels, whereas the addition of butorphanol inhibited the stress response. The combination of romifidine with either midazolam or ketamine improved sedation quality and surgical conditions.

Keywords: Cheek tooth removal; Horse; Ketamine; Midazolam; Romifidine; Sedation.

Fig. 1

Degree of ataxia in 40 horses being sedated with romifidine (group R), romifidine and butorphanol (group RB), romifidine and midazolam (group RM) or romifidine and ketamine (group RK). Score values for ataxia are presented as qq-plots at the different time points. A score value of 1 stands for no signs of ataxia, whereas 5 describes recumbency (Table 1). Boxes and whiskers demonstrate interquartile range and the minimal/maximal values. * = significant difference between group RM and baseline; ^ = significant difference between group RB and RM; ° = significant difference between group RK and RM

Fig. 2

Serum cortisol concentrations (ng/ml) of 40 horses before, during and after cheek tooth extraction. Cortisol values are presented as qq-plots at different time points. Boxes and whiskers demonstrate interquartile range and standard deviation. Means are presented as points; values exceeding 1.5 times the interquartile range are presented as rhombus’. Group R= Romifidine only; group RB= Romifidine and Butorphanol; group RM= Romifidine and Midazolam; group RK= Romifidine and Ketamine. * = significantly different to baseline values; + = significantly different to the previous time point