WVS original research - evaluating analgesia in a high-throughput sterilisation programme, Goa, India

Meunier NV, Panti A, Mazeri S, Fernandes KA, Handel IG, Bronsvoort BMC, Gamble L, Mellanby RJ. Randomised trial of perioperative tramadol for canine sterilisation pain management. Vet Record. 2019 Oct 5;185(13):406. doi: 10.1136/vr.105009.

Key Points

• Dogs receiving meloxicam alone, appeared to be no more painful post-operatively, than those who received a combination of meloxicam and tramadol.
• Individual factors, including age, sex and temperament can affect levels of pain post-operatively. Rescue analgesia should be provided when pain levels are not adequately controlled.

Research question: why did we carry out this research?

Surgical sterilisation is an important, humane method for managing free-roaming dog populations around the world. Sterilisations are frequently carried out at high-throughput clinics, which are commonly low in resources and may be operating in field conditions. It is important to optimise the welfare of dogs by ensuring that post-operative pain relief is sufficient. However, there is relatively little evidence on the use of analgesia in these environments. Further research to evaluate the use of easily accessible, and cost-effective analgesia options has the potential to improve the welfare of dogs in these settings.

This study aimed to compare the efficacy of two analgesic regimens for sterilisation: preoperative administration of meloxicam alone, vs meloxicam in combination with tramadol. The authors hypothesised that meloxicam alone would be no worse than the meloxicam-tramadol combination. Understanding whether the removal of tramadol had an impact on pain post-operatively, can help vets use resources in the most cost-effective manner, whilst still prioritising the welfare of their patients.

Methodology: what did we do?

The study took place between July-August 2017 at the WVS Hicks International Training Centre, Goa, India. This was a prospective, randomised trial, with a non-inferiority design.

A total of 125 dogs were included in the study, as part of the centre’s ongoing sterilisation programme. Any dogs with other health conditions were excluded, as well as extremely aggressive dogs who were difficult to accurately pain score.

All dogs received standard premedication (xylazine and butorphanol). Dogs were randomised at induction of anaesthesia. All dogs received meloxicam (0.2mg/kg) intravenously (IV) after induction, and dogs in the meloxicam-tramadol arm of the study also received tramadol IV (4mg/kg). 64 dogs received meloxicam and tramadol; 61 dogs received meloxicam alone.

Sterilisation was performed by experienced veterinarians. Anaesthesia was maintained by propofol which was given as an IV bolus, when needed.

Pain scoring was carried out at around 2, 4, 6 and 21 hours after surgery by one person, who was blind to treatment group. Any animal noted to be in pain was given rescue analgesia. Three pain scoring tools were used:

• Colorado State University Canine Acute Pain Scale
• Modified version of Glasgow Composite Measure Pain Scale – Short form
• 0-100 Visual Analogue Scale

Statistical parameters were set in advance to determine whether one drug regimen could be considered inferior or non-inferior to the other (predefined margins of non-inferiority).

Results: what were the findings?

The authors proved their hypothesis that meloxicam alone was no worse than meloxicam and tramadol in combination, based on the predefined margins they had set. However, the authors acknowledged it was possible there was a small benefit from the addition of tramadol, which was not detected by the parameters of the analysis. There was no significant difference in propofol rate between the treatment groups.

Other findings included that male dogs, and younger dogs, were more likely to have lower pain scores. Nervous dogs and female dogs were more likely to have higher pain scores. There was no significant difference between the number of dogs requiring rescue analgesia in the meloxicam-only group vs the meloxicam and tramadol group.

Interpretation: what insights can we gain from our findings?

The results of this study suggest that the addition of tramadol to meloxicam provides no further benefit in post-operative analgesia, in a high-throughput, low-resource setting. This lends support to other research which has evaluated the efficacy of meloxicam in other clinical environments. Given the wide availability of NSAID medication, this provides a suitable option to ensure patient welfare and good clinical outcomes. However, it should be noted that pain is considered an individual experience, and careful monitoring of patients is needed to ensure additional analgesia can be provided as necessary.

This study provides some evidence that females may feel higher levels of pain post-operatively than males. This may be due to the more invasive nature of the surgery. Careful monitoring of patients is important to assess whether additional analgesia is required.

Nervous patients were more likely to have a higher pain score. It’s likely that individual temperament may interfere with some of the evaluation of pain in these patients. The pain scoring tools were developed for owned pets, and the authors noted that the behaviours of free-roaming dogs varied from the expected in several ways (e.g. under or overreaction). Further work validating the use of pain scores in the free-roaming dog population, or those who are fearful of human contact, is required.