Another rotation is done (Anesthesia, check), and another one is just starting up (Large Animal Medicine!). In between, Logan and I found some time to go for a stroll along the banks of the famous Red Cedar and enjoy the Memorial Day Weekend sunshine!
On Day 1 of Anesthesia, I could not name five opiates. Now I can name seven full agonists (hydromorphone, morphine, oxymorphone, fentanyl, tramadol, methadone, and meperidine), a partial agonist (buprenorphine), and an agonist/antagonist (butorphenol).
The full agonist opioids act on mu, kappa, and delta receptors. In small animals, the mu receptors provide the most analgesia whereas in large animals the kappa receptors provide the most analgesia. You have to keep in mind though, that the mu and delta receptors are most responsible for unwanted side effects as well. Full agonist opioids have a linear effect, so that the more of the drug you give, the more effect you will get.
Fentanyl patch absorption will increase with heat - an anesthesiologist actually overdosed and died while using Fentanyl, and when they found him he had Fentanyl patches shoved in every warm and cozy crevice of his body. He was actually using the properties of the drug to increase absorption! (Be careful with Fentanyl patches because people are CRAZY!)
I learned that Buprenorphine (the partial agonist) takes a super long time to start working. It takes almost thirty minutes to have an effect when its given IV. I had to make myself REMEMBER to give my patient a dose of Buprenorphine at least a half hour before extubation.
Butorphenol is a kappa agonist and a mu antagonist. Butorphenol doesn't provide the greatest analgesia, but it has a pretty nice sedative effects. The really cool thing about Butorphenol is that you can actually use it to reverse a full agonist opioid. For example - I made my patient a little to comfortable on Hydromorphone and she didn't want to wake up after anesthesia. Within about a minute of receiving Butrophenol IV, she was looking at me asking, "What just happened?". AND unlike reversing with Naloxone (which is super expensive anyway), you don't reverse all of the analgesia (pain control) when you give Butorphenol.
PS: When you do use Naloxone to reverse an opioid, make a 10% solution in saline and give about 1mL at a time to effect.
So what are the side effects of opioids? Respiratory depression, bradycardia, dysphoria, changes in GI motility, and vomiting! Yum!
I didn't just learn about the opioids. I learned about benzodiazepines, phenothiazines, alpha 2 agonists, dissociatives, anticholinergics, ETC (all in three weeks!). I am going to try to create a journal of what I learn from day to day - because there is A LOT of cool stuff. Starting tomorrow though, I'm off the the drugs and onto ruminant medicine!
I will leave you with some pretty sweet intubation INFO: Rabbits are intubated blind. Ferrets, calves, birds, sheep/goats/llamas, dogs, and cats are intubated via visualization. Foals/horses are also intubated blind (like the rabbits). In cows, you have to intubate blind with palpation. So if you ever find yourself stuck on Noah's Ark performing anesthesia: You'll be all set!!
