Research identifies analgesic could be used to predict presence of space occupying lesions and intracranial hypertension dogs
New research from CVS’ Lumbry Park Veterinary Specialists has identified that dogs with intracranial space occupying lesions (iSOLs)[i] had significantly higher median sedation scores, 15 minutes after intravenous (IV) Butorphanol administration compared to those without.
The team of researchers also found that a greater number of dogs with intracranial hypertension[ii] (ICH) achieved recumbency (90%) than those without (46.5%) when being administered IV Butorphanol.
Opioids are commonly used in veterinary medicine as pre-anaesthetic medication, to facilitate animal handling, to calm the animal, and for smooth induction of anaesthesia. The research may be of benefit to veterinary anaesthetists to also predict the presence of space occupying lesions and intracranial hypertension in dogs presenting with suspected intracranial disease. It will help clinicians adapt their anaesthetic protocols accordingly to prevent further increases in intracranial pressure.
The researchers’ primary objective was to determine whether dogs with iSOLs on MRI, or MRI-determined indicators of ICH had higher sedation scores with a more rapid onset of recumbency after the administration of IV Butorphanol than dogs without intracranial disease. They hypothesised that 0.2 mg kg-1 of butorphanol administered intravenously would result in statistically significantly higher sedation scores and quicker onset of recumbency in dogs with MRI-iSOL and MRI-ICH.
Lumbry Park researchers conducted the observational study with 53 dogs presenting for brain MRI. 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 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.
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).
Emma Sansby, Resident in Anaesthesia and Analgesia at Lumbry Park Veterinary Specialists, who led the research, said:
“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 of more than 10 within 15 minutes of Butorphanol administration, the animal should be treated with an anaesthesia protocol adapted to the presence of ICH – so as not to increase intracranial pressure.
These adaptations include but are not limited to; adequate preoxygenation - to prevent hypoxaemia and elevation of the head to no more than 30 degrees; preventing increases in central venous pressure - by avoiding jugular compression and avoiding excessive intraabdominal and intrathoracic pressure; and a smooth anaesthetic induction - ensuring an adequate depth of anaesthesia prior to tracheal intubation to prevent the cough reflex and judicious mechanical ventilation to enable a low-normal end-tidal carbon dioxide.”
The sedative effect of intravenous butorphanol in dogs with intracranial space occupying lesions or indicators of intracranial hypertension research was conducted by Emma Sansby, Colin Driver, Karla Borland, Imogen Schofield and Joanne Michou at Lumbry Park Veterinary Specialists in Alton, Hampshire. It was published in the Journal of Veterinary Anaesthesia and Analgesia 2025, 52, 61e67. The research was supported by a CVS residency research grant and was undertaken as part of residency training.
Launched in January 2022, CVS Clinical Research Awards are an industry first; offering funding for research undertaken by CVS employees and research undertaken by universities. The awards support clinical veterinary research which has a direct clinical benefit to animals and which will impact upon veterinary practice.