The definitions of acute and chronic pain along with some principles of treatment were described in "Real Pain Cases 1". This session expands on that by listing some of the contents in our anesthesia and pain management toolbox and more examples of acute pain management based on real cases.

The Anesthesia and Pain Management Toolbox

Opioids - Butorphanol, buprenorphine, morphine, methadone, hydromorphone, fentanyl, transdermal fentanyl solution (Recuvyra, Elanco), transdermal fentanyl patches, nalbuphine. oxymorphone.

Non-steroidal anti-inflammatory drugs - Many choices which may vary on the geographical location.

Local anesthetics - Injectable lidocaine and bupivacaine, lidocaine-prilocaine cream, lidocaine patches

N-methyl-D-aspartate receptor antagonists - Ketamine, amantadine

"Other drugs":

 Alpha2-adrenergic agonists - dexmedetomidine

 Tramadol

 Gabapentin

 Amantadine

 Trazadone

 Maropitant

Non-pharmacologic treatment modalities:

 Acupuncture

 Cryotherapy

Nixon is a 7-year-old male Golden Retriever. He was hit by a car earlier in the day and brought into the emergency service for evaluation. He has a fractured left femur, pneumothorax and an arrhythmia (ventricular premature contractions). He has a history of osteoarthritis and has been on carprofen and a "joint diet" for the past two years.

Surgery - Repair of the femur fracture

Anesthesia and Pain Management Plan

Immediate assessment - His leg was very swollen and bruised - A hematocrit and total plasma protein were run and were normal. An indirect blood pressure measurement revealed a systolic blood pressure of 80 mm Hg and a mean pressure of 54 mm Hg. An IV catheter was placed and crystalloid fluids given and his blood pressure responded well. He was given IV maropitant and morphine. After this initial treatment he was comfortable, he was not dyspneic and a pulse oximeter reading was 98%. Carprofen was stopped. He was scheduled for surgery the next day.

On the day of surgery, he was given IV morphine (0.4 mg/kg IV), diazepam (0.25 mg/kg), ketamine (5 mg/ kg), intubated and maintained on isoflurane. A bolus of lidocaine was given (2 mg/kg) followed by an infusion at 50 µg/kg/minute. Ketamine was also given as an infusion at 10 µg/kg/minute. Morphine was given as an infusion at 0.1 mg/kg/hour.

Post-operatively lidocaine was continued at 25 µg/ kg/minute and ketamine reduced to 3 µg/kg/minute. Morphine was continued at 0.1 mg/kg/hour. Lidocaine and ketamine were discontinued after 24 hours and morphine was switched to every 5–6 hours IV for the next 24 hours, then IM for another 48 hours. Application of cold packs to the surgical site was initiated immediately after surgery and continued for 2 days. Carprofen was started on post-op day 2, after Nixon was eating and drinking normally.

Hermes is a 9-year-old male neutered cat that is scheduled for a dental cleaning and tooth extractions (estimated that 6 teeth will be extracted). He was diagnosed with hyperthyroidism two months ago and has been started on methimazole and being monitored. He is nervous but could be handled to collect a blood sample. His blood work was normal except for a mild elevation in liver enzymes.

Anesthesia and Pain Management Plan

Hermes was sedated with buprenorphine (0.02 mg/kg IM) and dexmedetomidine (5 µg/kg IM). An intravenous catheter was placed and anesthesia was induced with propofol to effect and midazolam (0.3 mg/kg). Anesthesia was maintained in isoflurane in oxygen.

Local anesthetic blocks were performed in the appropriate location for the extractions. Meloxicam was given SC (0.2 mg/kg) followed 24 hours later by 0.05 mg/ kg PO and continued for 3 days.

References

1.  2015 AAHA/AAFP pain management guidelines for dogs and cats. J Am Anim Hosp Assoc. 2015;51:67–84.

2.  2015 AAHA/AAFP pain management guidelines for dogs and cats. J Feline Med Surg. 2015;17(3):251–272.

3.  Downloads for the AAHA guidelines and implementation tool kit available at: www.aaha.org/professional/resources/pain_management.aspx#gsc.tab=0 (VIN editor: Link was not accessible as of 10/11/2017).

4.  World Small Animal Veterinary Association - Global Pain Council: www.wsava.org/educational/global-pain-council.