The sedative effect of intravenous butorphanol in dogs with intracranial space occupying lesions or indicators of intracranial hypertension

Objective

To determine whether dogs with magnetic resonance imaging (MRI)-determined intracranial space occupying lesions (MRI-iSOLs) or intracranial hypertension (MRI-ICH) had greater sedation scores and quicker onset of recumbency following premedication with intravenous (IV) butorphanol in comparison with dogs which had normal MRI findings.

Study design

Prospective, observational study.

Animals

A total of 53 dogs presenting for brain MRI were included.

Methods

Each dog was sedated with 0.2 mg kg^–1 butorphanol IV, and the quality of sedation and the onset of recumbency were scored before drug administration and every 5 minutes after IV butorphanol administration for 15 minutes using a modified sedation scale. The maximum sedation score was 18, and onset of recumbency was recorded when a dog lay down without the ability to stand. Each MRI was assessed for the presence or absence of MRI-iSOL and MRI-ICH using T2-weighted sequences. Data were analysed using the Wilcoxon rank sum test or the chi-square test.

Results

Dogs with MRI-iSOL had significantly higher median sedation scores than dogs without MRI-iSOL (12 versus 5, respectively) 15 minutes after butorphanol administration (T15, p < 0.01). A greater number of dogs with MRI-ICH achieved recumbency (n = 9/10; 90%) than those without MRI-ICH (n = 20/43; 46.5%; p = 0.01).

Conclusions and clinical relevance

When intracranial disease is suspected, the administration of butorphanol as a premedicant for anaesthesia could be used to predict the presence of MRI-iSOL and MRI-ICH. If a dog becomes recumbent or has a sedation score > 10 within 15 minutes of butorphanol administration, the animal should be treated with an anaesthesia protocol adapted to the presence of ICH.