The Royal (Dick) School of Veterinary Studies
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Dogs’ size linked to blood pressure risk in surgery

Increased awareness around the links between body weight and low blood pressure under anaesthesia could curb risks, experts suggest.

Smaller dog breeds are at higher risk of experiencing low blood pressure during general anaesthesia, an evaluation has shown.

Considering these findings, the Royal (Dick) School of Veterinary Studies research team encourages heightened awareness and preparedness among vet teams during surgical or diagnostic procedures on smaller canine patients.

This could mitigate the risk of reduced blood flow to the organs as a result of low blood pressure, the team says.

Risk factors

Researchers evaluated the anaesthetic records of over 1700 dogs that had undergone surgical procedures at the Hospital for Small Animals between 2018 and 2020.

Key findings revealed a significant association between increasing body mass and lower odds of hypotension, or low blood pressure, during general anaesthesia.

Administering pre-anaesthetic medication and elevating the dog’s body temperature during general anaesthesia were linked to a lower likelihood of a drop in blood pressure.

Factors such as brachycephaly – flat-face – poor overall health, and slower heart rates in some breeds were linked to an increased risk.

Surgery preparedness

Low blood pressure during surgical procedures is thought to be linked to increased mortality in humans, but little is known about the association of body weight and blood pressure in dogs.

These findings underscore the vulnerability of dogs with lower body mass and those belonging to brachycephalic breeds, highlighting the need for special attention during anaesthesia, the team says.

Veterinary professionals are encouraged to be highly vigilant when monitoring blood pressure in these specific groups, to ensure their safety and wellbeing.

Additionally, the team recommends provisions for readily accessible treatment of hypotension, especially when working with small or brachycephalic breeds.

This research was published in the Journal of Small Animal Practice, in collaboration with colleagues from the People's Dispensary for Sick Animals (PDSA) veterinary charity.

Low blood pressure reduces blood flow to the organs, and this is something we’re keen to avoid. Our findings show that dogs of smaller body weight might be prone to episodes of low blood pressure. As anaesthesiologists, if we’re aware of that risk in advance we can be more prepared, know what to look out for and perhaps make changes to the anaesthetics we use or take preventative measures.

Dr Lucy Miller, Lecturer in Vet Anaesthesia

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About the Royal (Dick) School of Veterinary Studies 

The Royal (Dick) School of Veterinary Studies is a one-of-a-kind centre of excellence in clinical activity, teaching and research. Our purpose-built campus, set against the backdrop of the beautiful Pentland Hills Regional Park, is home to more than 800 staff and almost 1400 students, all of whom contribute to our exceptional community ethos. 

The School comprises: 

The Roslin Institute 

The Global Academy of Agriculture and Food Systems 

The Roslin Innovation Centre 

The Hospital for Small Animals 

Equine Veterinary Services 

Farm Animal Services 

Easter Bush Pathology 

The Jeanne Marchig International Centre for Animal Welfare Education 

We represent the largest concentration of animal science-related expertise in Europe, impacting local, regional, national and international communities in terms of economic growth, the provision of clinical services and the advancement of scientific knowledge.