Sedation for the painful behaviour case is a challenge we face frequently. Assessing pain in the dog with behavioural concerns can be really difficult for us and it is often safer to assume that pain is present and treat accordingly. This review covers options for sedation prior to the veterinary visit and management options at the clinic.
At home options for sedation prior to veterinary visit
Dose 1-2mg/kg PO
Test doses of benzodiazepines (BDZ) should be used to establish an effective dose prior to use for a veterinary visit. Risk of disinhibition.
Dose 5mg/kg 2hrs prior to leaving home.
Contra-indications – monoamine oxidases (MAOIs), sotalol, cisapride, pethidine, tramadol.
Regarding the following recommendations the aim in each of these cases is to ensure the dog is sedated enough to place an IV cannula. All cases should have an IV placed to give you greatest control of the situation.
Medetomidine should only be used where there is no cardiac disease.
The rationale for BDZ is retrograde amnesia and we aim to include a BDZ in each of these protocols.
Do not forget to provide multimodal analgesia to these patients – there are no contra-indications to using any of the above anxiolytics with analgesics such as opioids, NSAIDs and local anaesthetics.
Please refer to the BSAVA formulary for further information on the above drugs if required.
Remember that our pre-op assessment of these patients is often limited and you should warn the owner that this increases anaesthetic risk.
Anaesthesia with a volatile agent is preferable to repeatedly topping sedation up and the risk of the dog arousing suddenly. I have seen this happen and we must ensure safety of ourselves and our colleagues.
Sedation following at-home anxiolytics
Give BDZ or trazodone at home one hour prior to leaving the house.
On arrival at the surgery give IM injection (can all be in same syringe) at the following doses
• 0.02 mg/kg medetomidine
• 2 mg/kg ketamine
• 0.2 mg/kg butorphanol (if surgery is planned use 0.1-0.3mg/kg methadone instead of butorphanol, depending on anticipated analgesia requirement). You can use buprenorphine 0.02mg/kg but the volume is large.
Monitor these cases closely and be prepared to intubate to protect the airway if sedation is profound.
If unable to give IM injection despite oral anxiolytic give oral medetomidine 0.05 mg/kg.
Once sedated give IM injection
• 2 mg/kg ketamine
• 0.2 mg/kg butorphanol (or methadone see above)
If after oral medetomidine the dog is really flat then give IM injection at half those doses;
• 1 mg/kg ketamine
• 0.1 mg/kg butorphanol
Incorporating a BDZ to sedation or GA
If a BDZ has not been given at home give the same trio injection as above. Once an IV cannula has been placed give 0.25 mg/kg midazolam IV (or IM) once the trio injection has taken effect. This will deepen the sedation.
For GA give one quarter of the calculated dose of IV agent (propofol or alfaxalone) and then give 0.25 mg/kg midazolam IV through same port and then give additional GA agent to point of ability to intubate (which may not be the full calculated dose). This is known as co-induction.
Reversal of sedation
In dogs that are heavily sedated use the same volume of atipamezole (5mg/ml) to medetomidine (1mg/ml) IM. If sedation is starting to wear off, consider using half of the atipamezole dose IM.
Wait at least 30 minutes after giving either medetomidine, ketamine or midazolam before giving atipamezole. This is due to receptor occupancy and also to allow the ketamine to wear off.
Cases where medetomidine is contraindicated
These cases should receive one of the at home options.
Sedation at the surgery – alfaxalone 3mg/kg & opioid (butorphanol or methadone SQ). Wait 40 minutes for full effect then place an IV cannula. If a BDZ has not been used at home, it can be added to this combination either to deepen sedation (IM or IV) or used as a co-induction agent. (Do not give midazolam if the sedation is very light as this will cause paradoxical excitement).
These cases are always a challenge and often require a plan A, B and C. If in doubt, call your local referral centre and speak to an anaesthetist to aid planning the case.