Drops in mean arterial blood pressure reduced from 42% to just 11% with new medication
New Clinical Audit Significantly Improves Perioperative Blood Pressure During Neutering Anaesthesia
2 weeks ago 
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A new clinical audit has dramatically reduced the propensity for mean arterial blood pressure to go under the recommended minimum value of 60mmHg during anaesthesia.
The initiative has been recognised with a RCVS Knowledge ‘Highly Commended’ status at its 2024 awards.
Conducted by Head Veterinary Nurse Francesca Beorby at Putlands Veterinary Centre, the study investigated administering a new combination of medication to cats and dogs during routine neutering procedures.
Francesca noticed a trend during routine feline neutering anaesthetics where a number of patients were hypotensive during anaesthesia and required additional treatment. Clinical evidence suggests a minimum value of 60mmHg for perfusion of vital organs such as the brain, heart and kidneys. Hypoperfusion of these organs means inadequate oxygen is delivered to the tissues and there is poor removal of waste products. This can lead to organ dysfunction and shock.
So a clinical audit was undertaken to look at perioperative blood pressure in both cats and dogs having routine neutering procedures. The target was for patients to maintain a mean arterial blood pressure of 60mmHg during their anaesthetic.
The animals chosen for auditing were to be classed ASA 1 and under 5 years old. They received a pre-operative health check including a blood pressure reading to ensure they were normotensive.
A first audit looked at a standard premedication protocol of ACP at a dose rate of 0.02mg/kg combined with Methadone at a dose rate of 0.3mg/kg. A second audit initiated a change to the pre-medication drugs, using 0.005mg/kg Medetomidine combined with the same dose of Methadone.
Both received anaesthesia induction with Propoflo at a dose rate of 6mg/kg for cats and 4mg/kg for dogs. All patients under anaesthetic were maintained using Isoflurane and kept at a surgical plane of anaesthesia appropriate for that patient.
The patients were monitored throughout their surgical procedure using an oscilliometric monitoring machine - for systolic, diastolic and mean arterial blood pressure – and measurements recorded on an anaesthetic chart.
The collected data revealed that in the first audit, where patients received ACP and Methadone, 42% had a mean arterial blood pressure lower than 60mmHg after the first five blood pressure readings post induction. This related to 50% of cats and 38% of dogs.
In the second audit, with Medetomidine combined with Methadone, only 11% of patients with a mean arterial blood pressure lower than 60mmHg. This related to 0% of cats and 15% of dogs.
The results showed a vast improvement in the decrease of hypotensive patients during anaesthesia when a medication of Medetomidine combined with Methadone was used. The audit also suggests a link to hypotension with ACP used as a premedication in anaesthetised patients.
Francesca Beorby, Head Nurse at Putlands Veterinary Surgery, said: “My passion in veterinary nursing is anaesthesia. And there is always room for improvement and striving to achieve gold standard care.
“These results clearly show that a change from our current premedication protocol of ACP and Methodone to Medetomidine and Methadone decreased the number of patients having hypotension during anaesthesia. The change means fewer patients were at risk of developing the side effects associated with hypoperfusion of the vital organs.
“Our quality improvement initiative has made a really positive impact in practice for both patient care and clinical team.”
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