A new study published in Veterinary Record suggests that adding intravenous paracetamol to an existing multimodal protocol for dogs undergoing elective orthopaedic surgery may not deliver a meaningful opioid-sparing effect.
The methodology
Researchers randomised dogs undergoing elective orthopaedic procedures to one of two groups. One group received intravenous paracetamol at 10 mg/kg after induction of anaesthesia and then every eight hours during hospitalisation, while the control group did not. Dogs in both groups also received either meloxicam or robenacoxib at the licensed dose, interval and route. Rescue analgesia was provided with intravenous methadone when intraoperative nociception was seen or when postoperative pain scores on the Glasgow Composite Measure Pain Scale–Short Form exceeded 4/20.
The final analysis included 27 dogs: 14 in the paracetamol group and 13 in the control group.
The results
Median rescue methadone requirements were 0.0 mg/kg (range 0.0–0.2) in the paracetamol group and 0.1 mg/kg (range 0.0–0.3) in the control group. The difference was not statistically significant (p = 0.17). The authors also reported no significant difference when intraoperative and postoperative rescue analgesia were analysed separately, with p values of 0.72 and 0.24 respectively.
In practical terms, four dogs in the paracetamol group and seven in the control group needed rescue analgesia during the perioperative period, but this difference was also not statistically significant. The authors concluded that, when used as part of a multimodal analgesic protocol, intravenous paracetamol did not provide a significant opioid-sparing effect in this setting.
Study limitations
The key limitation was the low analgesia requirement in both groups, which the authors said may have led to a type II statistical error. In other words, the study may have been too small, or the overall need for rescue analgesia too low, to detect a real difference if one exists.
The bottom line for practice teams
This was not evidence that paracetamol has no role at all in canine perioperative analgesia. It was evidence that, in this small cohort of dogs already receiving NSAIDs within a multimodal plan, the additional paracetamol protocol tested here did not significantly reduce methadone use. Larger studies will be needed to clarify whether different case selection, dosing strategies or protocol combinations change that picture.
For UK practices reviewing perioperative pain protocols, this study is a useful reminder to examine whether each added drug is delivering a measurable benefit in the specific context where it is used.
Full study available here: Stallard R, Deutsch J, Murrell J. Intravenous paracetamol does not have significant opioid-sparing effects when used as part of a multimodal analgesic protocol in dogs undergoing elective orthopaedic surgery. Veterinary Record.
