A new clinical audit has looked at the impact of drug combinations on perioperative blood pressure.

Recognised with an RCVS Knowledge “Highly Commended” status at its 2024 awards, the audit conducted by head RVN Francesca Beorby, investigated administering a new combination of medication to dog and cat neutering procedures.

Carried out at Putlands Veterinary Centre in Kent, Ms Boerby noticed a trend during routine feline neutering anaesthetics where a number of patients were hypotensive during anaesthesia and required additional treatment.

A clinical audit was undertaken, with animals chosen for auditing classed American Society of Anesthesiologists 1 and younger than five years old. They received a pre-operative health check including a blood pressure reading to ensure they were normotensive.

First audit

A first audit looked at a standard premedication protocol of acepromazine (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 oscillometric monitoring machine – for systolic, diastolic and mean arterial blood pressure – and measurements recorded on an anaesthetic chart.

Second audit

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, 11% of patients had 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.

‘Positive impact’

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.”