Optimisation of cat neutering anaesthesia protocols for use in the community

Abstract

The aim of this study was to compare the two opioids methadone and buprenorphine in sedative combinations administered to cats undergoing castration in a high-volume neutering setting. Both combinations were used prior to orchidectomy in cats (Routine Cat Castrations) as part of a ‘drop-in clinic’ with no prior appointments required. The overall outcome was to determine a combination to best enable a safe, quick, effective turnover of neuters with limited financial, infrastructure and staffing resources. A total of 166 cats were recruited as part of this clinical trial. This included 15 cases as part of a pilot study. The aim was to gain two equal numbers for each group over a set period of time. Quantitative planning of the total study was not known as this was incorporated as part of a working teaching unit in conjunction with Nottingham university. The drop-in clinic took place every Friday which allowed an open appointment system from different demographics such as vet triage, owned patients, multi-cat household, stray and ferals as part of an TNR programme. Cats received one of two possible combinations, medetomidine 600mcg/m² with buprenorphine 180mcg/m² (MB) or medetomidine 500mcg/m² with methadone 5mg/m² (MM) administered intramuscularly (IM). Sedation was scored using a modified simple descriptive score (SDS) 10 minutes after administering the initial injection. Anaesthesia was induced using isoflurane administered in 100% oxygen via a tight-fitting face mask connected to an Ayres T piece with Jackson Rees modification. Parameters were recorded at 5-minute intervals intraoperatively. At the end of surgery isoflurane was discontinued and one minute later atipamezole was administered IM. The recovery stage was monitored and timing to sternal recumbency followed by portal exploration were recorded. Data collection was recorded on anaesthetic record sheets and transposed to an Excel spreadsheet at a later date. The medetomidine and methadone combination had significantly higher sedation scores using the SDS modified system. This result included an element of mask induction assessment when compared to the use of the medetomidine and buprenorphine combination, which consistently scored low on the SDS system. Methadone provided superior sedation to buprenorphine prior to anaesthesia maintenance using mask induction as part of the protocol. The recovery data showed both sternal and portal times were significantly shorter with medetomidine and methadone compared to medetomidine and buprenorphine. Both combinations proved suitable for cat castration anaesthesia. Using the methadone combination can increase the turnover of patients contributing to improved welfare and optimising resources