Comparison of the cardiovascular and respiratory effects and sevoflurane requirement in dogs premedicated with two doses of medetomidine and butorphanol undergoing surgical sterilization.
D. Juodzente, A. Macas, B. Karveliene, S. Petkevicius1, V. Riskeviciene, Polish Journal of Veterinary Sciences Vol. 21, No. 1 (2018), 101–110.
What did the research find?
A higher dose rate of medetomidine and butorphanol, when used as premedication, reduced inhaled sevoflurane requirements during routine surgical procedures. Both median sevoflurane concentration, and median heart rate (HR) values were significantly lower in dogs that received the higher dose drug combination (median HR: 77) than those that received the lower dose combination (median HR: 96).
How was it conducted?
30 client-owned dogs scheduled for routine neutering were included in the study. All patients were assessed to be of ASA I health status and were randomly assigned into the following groups:
- Group 1: lower dose of medetomidine (0.014 mg/kg) and butorphanol (0.14 mg/kg)
- Group 2: higher dose of medetomidine (0.024 mg/kg) and butorphanol (0.24 mg/kg)
In addition to the above, all dogs received a pre-operative dose of non-steroidal anti-inflammatory (i.e. 2mg/kg ketoprofen).
Patients received their dose of premedication intramuscularly and were then kept in a non-stimulating environment for 15 minutes. Induction, using propofol, was performed 20 minutes post premedication. All dogs were pre-oxygenated prior to intubation and maintained initially on 2% sevoflurane in pure oxygen.
Inhaled sevoflurane concentrations were then adjusted (1.6%-2.2%) according to the patient’s depth of anaesthesia. Anaesthetic management, anaesthetic depth and animal status was monitored continuously by an anaesthesiologist who was blinded to the premedication group.
Why is it important?
Premedication with alpha-2 adrenoreceptor agonists and opioids can improve the quality of anaesthesia and can reduce the required dose of volatile anaesthetic agents. However, little information is available about the effect that different dose rates of these premedicants may have when using sevoflurane for anaesthetic maintenance.
Sevoflurane is reported to cause dose-dependent hypotension, hypoventilation, impaired cardiac contractility and hypothermia (Mutoh et al. 1997), therefore its administration must be carefully titrated to avoid excessive anaesthetic depth. Due to the additive effects often observed, it is common practice in veterinary medicine to use multidrug protocols to decrease the overall required dose of volatile agent needed for anaesthetic maintenance. This may improve patient safety by minimising the negative cardiorespiratory effects volatile agents potentially elicit.
This study is relevant because it compares the cardiorespiratory effects and sevoflurane requirements in dogs premedicated with different doses of routinely used premedicant agents (i.e. medetomidine and butorphanol) for routine surgical neutering. The paper provides vet practitioners with a convenient protocol for such surgical procedures in dogs.
Link to the full article: http://journals.pan.pl/dlibra/...
Originally published: Wednesday, 4th July 2018
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