Episode 1: Sedation and analgesia in the veterinary emergency room

Thank you for listening to our very first Emergency and Critical Care Education podcast. We were graced with the presence of Dr Andrew Foster, resident in anaesthesia and analgesia at the Royal Veterinary College. We discuss the various tools in our arsenal for managing pain and to provide sedation in the veterinary emergency room.   

Acepromazine: Mainly used as an anxiolytic/sedative for brachycephalics with upper respiratory tract obstructions. Unwanted side effects include vasodilation (and associated hypotension), splenic pooling of red blood cells (temporary decrease in PCV), and immune modulation. Can be given IV/IM/SQ. Doses range from 0.001 – 0.01 mg/kg in the ER. Higher doses are used for elective surgery in healthy patients, but in the ER 0.003-0.005 mg/kg is common. Has no discernable analgesic effects and is not reversible. 

Buprenorphine: An opiate analgesic labelled for mild to moderate pain. Reaches peak effect in 30-45 minutes. Usually dosed at 0.02 mg/kg IV/IM, but higher or lower doses can be used. Can be repeated every 6-8 hours based on pain scoring. Comes as both a multi-dose bottle or single 1 mL vials. Warning: the multi-dose vial contains preservative and stings on injection. 

Butorphanol: An effective sedative with minimal analgesic effects. Used for providing sedation/anxiolysis for patients with respiratory conditions, or non-painful conditions that require imaging. Dose range is typically 0.1-0.3 mg/kg, but doses as high as 0.5 mg/kg can be used in very stressed patients or prior to euthanasia. Can be given IM/IV/SQ. Reversible with naloxone. 

Fentanyl: A very potent opiate analgesic with a short half-life. Can be given as a bolus to help facilitate a short procedure or induce anaesthesia, or as an infusion for consistent analgesia. Helpful for cases of severe pancreatitis, polytrauma, or post-operatively. Bolus doses of 1-5 MICROgrams/kg, or 1-5 mcg/kg/minute. 

Ketamine: A potent analgesic and sedative. Dose range is variable and the effects are dose-dependent. For the acute trauma patient, 0.5 mg/kg IV can boost your analgesia, whereas 5 mg/kg may induce anaesthesia. Can cause dysphoria with boluses, but less so with infusions. Can be given IM/IV. Not reversible and stings on injection. 

Midazolam: Used to provide sedation/anxiolysis, or as part of an induction protocol for anaesthesia. Can cause dysphoria, especially in cats and when given IV. Very effective as a sedative when combined with butorphanol. Doses range from 0.2-0.4 mg/kg. Can also be used as an anti-epileptic at 0.5 mg/kg. Can be given IV/IM. Reversed with flumazenil. 

Medetomidine: A potent sedative with dose-dependent analgesic effects and side effects (hypertension/bradycardia). Typically combined with another agent such as butorphanol, methadone, midazolam, etc. Can be used to facilitate imaging or provide some anxiolysis or sooth dysphoria/euphoria from other medications. Doses range from 0.001-0.02 mg/kg, although doses higher than 0.01 mg/kg are not recommended for our ER patients. Not recommended for unstable or renal-compromised patients.  

Remember you can always titrate upwards or use propofol to effect after giving a dose. You will be surprised how little it takes to influence your patient – try with 0.002-0.005 mg/kg and titrate up from there. Reversible with imidazole. 

Methadone: A potent opiate analgesic. Often used as a first line analgesic for trauma patients. Less clinical signs (panting/nausea) compared to hydromorphone/morphine. Can be given IM/IV (or SQ if the only option) at ranges of 0.1-0.5 mg/kg q4-6hr, but can be given sooner or topped up if needed. Typical starting dose for conscious trauma patients is 0.2-0.3 mg/kg. If there is altered mentation then begin with 0.1 mg/kg – remember you can always titrate upwards. Reversed with naloxone. 

NSAIDs: Several NSAIDs exist and are effective analgesics. I do not use them frequently for my sicker patients as they can potentiate bleeding, damage kidneys, and cause GI ulcerations. Useful for lameness, smaller wounds/lacerations, and relieving pyrexia. Check your formularies for the various drugs and doses available. 

Paracetamol: Not useful for the acute trauma patient, but can be a nice adjunct to methadone or other analgesics. Dosed at 10-15 mg/kg IV or PO q8-12. 

Propofol – Handy for procedural sedation (radiographs, bandaging, etc.) in combination with other medications such as methadone/butorphanol. As an induction agent, it is used at 4-6 mg/kg (or to effect), but for sedation, you can start as low as 0.25 mg/kg and titrate from there. Propofol is a profound dose-dependent cardiopulmonary depressant, so remember to be cautious and dose carefully. 

Honourable Mention:
Alfaxalone: This is just as effective as propofol with similar side effects, but I do not like the dysphoria it causes in patients when used as a sedative.  

Case Examples

Congestive heart failure: these patients are one stressful event away from death, so avoid handling them for much more than your primary survey (+/- FAST) and to quickly administer IM medications. I will administer a combination of butorphanol 0.3 mg/kg + midazolam 0.3 mg/kg IM in the same syringe, followed by a diuretic, and let the patient settle in oxygen. It really helps take the edge off while the diuretic takes effect. 

Head trauma: it can be difficult to evaluate pain in these patients as they can have profoundly altered mentation. Pain should never be used as a stimulant or a vasopressor, but administering too much analgesia can confound your exam. I begin by placing an IV and administering methadone 0.1 mg/kg. If their mentation improves with treatment you can titrate up your methadone 0.1 mg/kg at a time. 

Fracture – minimal trauma: the Italian Greyhound who jumps out of her owner’s arms and fractures her forearm. Unlike an RTA, there are no signs of injury or trauma elsewhere. Can use methadone 0.2-0.3 mg/kg + medetomidine 0.005 mg/kg IV and achieve the rest of your sedation with propofol as necessary.