A Frontiers in Veterinary Science study has identified several factors associated with hypotension in dogs under general anaesthesia, based on 390 anaesthetic records from a university teaching hospital. Hypotension was defined as a mean arterial pressure of 60mmHg or lower for at least three consecutive measurements, five minutes apart.
For RVNs involved in anaesthetic monitoring, the paper is a useful reminder that blood pressure trends should be interpreted alongside the whole patient and procedure, rather than as isolated numbers on a monitor.
Why this matters for RVNs
Blood pressure monitoring is a core part of safe anaesthetic care. Hypotension can compromise tissue perfusion, and the authors note that organs with high oxygen demand and tight autoregulation, such as the brain, heart and kidneys, may be particularly vulnerable.
In practice, RVNs are often the team members recording trends, checking cuff position, recognising patterns and escalating concerns. This study does not provide a new treatment protocol, but it may help nurses identify cases where closer monitoring and earlier discussion with the vet or anaesthetist could be especially important.
What did the study do?
The researchers reviewed records from dogs undergoing general anaesthesia between October 2023 and April 2024 at the University of Liège. They collected information including signalment, ASA classification, procedure type, anaesthetic drugs, regional anaesthesia, mechanical ventilation, fluid therapy, anaesthetic duration and blood pressure monitoring method.
Records were excluded if the anaesthetic lasted less than 20 minutes, if the record was incomplete, or if mean arterial pressure was not measured. This left 390 anaesthetic records from 332 dogs. Blood pressure was measured by oscillometry in 301 anaesthetics and by invasive monitoring in 89 cases.
What did they find?
Hypotension occurred in 72 of 390 anaesthetics, or 18.5% of cases.
Several factors were associated with increased odds of hypotension. These included age under 12 months, abdominal surgery and increasing duration of anaesthesia. Dogs undergoing abdominal surgery had higher odds of hypotension than those undergoing diagnostic or orthopaedic procedures.
For every 1kg increase in body mass, the odds of hypotension decreased by 4%, while every additional minute of anaesthesia was associated with a 1% increase in the odds of hypotension.
Bodyweight also appeared relevant. For every 1kg increase in body mass, the odds of hypotension decreased by 4%, while every additional minute of anaesthesia was associated with a 1% increase in the odds of hypotension.
The study also found decreased odds of hypotension with regional anaesthesia and mechanical ventilation. Nerve blocks and epidural or spinal techniques were both associated with lower odds compared with no regional anaesthesia.
What are the limitations?
This was a retrospective study, so it can show associations but cannot prove cause and effect.
It was also carried out in a university teaching hospital, where anaesthetics were performed by residents under the supervision of board-certified anaesthesiologists. That setting may not reflect every first-opinion practice.
Blood pressure was not measured in the same way in every case. Most cases used oscillometry, while others used invasive blood pressure monitoring. The authors note that non-invasive techniques are less accurate than invasive measurement, so the reported frequency of hypotension may not be exact.
The authors also highlight the relatively small cohort and limited numbers for some variables, meaning other risk factors with smaller effects may have been missed.
What does this mean in the prep room and theatre?
For RVNs, the most practical message is not that these factors predict exactly which dog will become hypotensive. Instead, they can help shape vigilance.
A young dog, a small dog, a dog undergoing abdominal surgery, or a dog in a long anaesthetic may deserve particular attention to blood pressure trends, anaesthetic depth, fluid plan, temperature, ventilation, pain control and communication within the team.
The finding around regional anaesthesia is also relevant. The authors suggest this may reflect reduced inhalant requirements and improved analgesia, which could reduce cardiovascular depression. For RVNs, this supports the value of understanding local and regional techniques, preparing equipment, assisting safely, monitoring after blocks, and recognising that analgesic planning can affect more than pain scores alone.
However, the mechanical ventilation finding should be interpreted carefully. It does not mean every dog should be ventilated to prevent hypotension. Ventilation decisions depend on the patient, procedure, blood gases or capnography, anaesthetic depth and clinician judgement.
The bottom line for RVNs
For RVNs, the useful takeaway is that hypotension risk may be higher in young dogs, smaller patients, abdominal surgery and longer anaesthetics. These cases may benefit from especially close attention to blood pressure trends and early escalation when readings are low, persistent or inconsistent with the rest of the patient picture.
Source: Mignini B, Rives A, Degani M, Talarico C, Farnir F and Sandersen C. Risk factors for hypotension in anaesthetized dogs: a retrospective analysis of 390 cases. Frontiers in Veterinary Science, 13:1846419, 2026.
