Analgesia for the trauma cat
Updated: Oct 14, 2020
With feline trauma we need to provide analgesia during the initial triage stage of assessment, although it is not until we have spent some time undertaking diagnostic investigations that we understand the full extent of concurrent disease.
Trauma can be the result of being hit by a car, blunt force such as a kick, fall from a height or being attacked by a dog. With provision of analgesia in the acute setting our mind turns immediately to multimodal analgesia – out main three options being opioids, NSAIDs and local anaesthetics.
The opioids are our mainstay of analgesia in this circumstance - with methadone being the main option due to its rapid onset. A dose of 0.3-0.5 mg/kg IM or IV is a sensible place to start - the main caution being head trauma where there may be damage to the blood brain barrier. In such cases opioids have a profound effect on mentation and doses should be lowered (example methadone 0.05 mg/kg). If analgesia at these doses are insufficient either a further 0.1 mg/kg methadone can be given or we can consider other options. Although buprenorphine is an effective analgesic in cats the onset of action in cases with severe pre-existing pain is too slow.
Yes, but not right now!
NSAIDs will certainly be advantageous for the pain of trauma – but not in the initial stages where we are unsure of damage to the kidneys or urinary tract. It may actually be several days before we are confident in using NSAIDs in our trauma cats. Serial measurements of creatinine are often required before it is apparent that there is damage to the urinary tract.
In the conscious patient local anaesthetic techniques are less practical but should be considered top of the list for analgesia if the patient requires surgery.
Beyond these main options we look to solutions for pain management such as ketamine infusions and use of the gabapentinoids.
Ketamine infusions are a relatively simple option and can be either run alongside the patients fluids (allowing alteration in fluid rates independently) or added to the maintenance requirements. Details of rates and practicalities are here. Ketamine works effectively alongside opioids and will dramatically improve comfort levels.
Gabapentin has been documented to be efficacious as an analgesic in cats where NSAID administration is not possible. Gabapentin has various mechanisms of action including regulation of calcium channel currents in the dorsal root ganglion as well as actions on serotonin. It is also an effective anxiolytic in cats. Prospective, randomised clinical trials are lacking and use is based on experience. Dose for such effects is approx. 10 mg/kg BID or TID.
A step-wise approach
Our aims with these cases can be divided into several stages. We have to control the severe pain during triage. At some stage these cats are likely to require surgery where opioids and local anaesthetics are essential. In addition to these options I would continue the ketamine CRI during surgery and look to wean this over the next 24-48 hrs.
The next few weeks
Beyond 48hrs our aim is to transition the cat to oral options to be sent home with. NSAIDs, gabapentin and the NMDA antagonists (memantine or amantadine) are useful here to ensure any surgical pain does not persist and become maladaptive.
There are several options for each of these stages that allow us to provide effective analgesia for these cats.