Instead of blogging, I have been shovelling snow. And sleeping off being sick. Also maybe there was some studying in there too. But I am rallying! I love New England winter! Especially when school keeps getting closed down for snow days!
Last week I had my bovine anesthesia lab. When I learned to do anesthesia on a dog, it was a precise and complicated process which took place in a hospital. The dog got pre-anesthesia medication, had a tube down her throat to help her breathe, and got post-surgical pain meds. The process is very different with a cow.
With cows, mostly you do standing surgery — surgery while the cow is awake, with local anesthesia so they don’t feel the pain. Why? Obviously, part of the reasoning is financial; farmers cannot afford to take their cows in to the hospital for surgery, and the equipment for general anesthesia is not available on the farm.
However, even if you can afford to put a cow under general anesthesia, it might not be the best thing for the cow. Putting a tube down the throat of any ruminant is somewhat more dangerous than with a dog. Ruminants are more likely to aspirate their stomach contents and get aspiration pneumonia, which is definitely something you want to avoid. More importantly, cows have these huge stomachs. The compartment called the rumen is particularly enormous, containing around 25 gallons of material. This is where all that grass (or, in today’s world, corn) marinates in a soup of saliva and bacteria, and the bacteria generate energy which the cow uses. Putting a cow on her side means that the huge rumen is lying on abdominal organs. It can make breathing very difficult.
So in bovine anesthesia lab, I injected lidocaine along specific nerves in order to block areas of the cow’s side. I have not yet seen standing surgery in a cow, but when I do, I will let you know what it is like. Reaching inside a standing animal to move things around and sew things up will definitely be an interesting thing to see.
Showing posts with label anesthesia. Show all posts
Showing posts with label anesthesia. Show all posts
Wednesday, February 2, 2011
Sunday, December 19, 2010
Learning how to tell if a dog is in pain
I completed my second spay lab, in which third year veterinary students spay a dog from a shelter or low income family. Unlike my first spay lab dog, this dog had a uterus! (In fact, she was in heat, so I was pretty confident ahead of time that she would. My boyfriend: “How can you tell she’s in heat?” Me: “She has a vulva the size of Texas.”)
Linnea was an extremely nice dog who was extremely unhappy about being in the spay clinic for two days. She pawed at the cage door so much the first night that we gave her a sedative to take the edge off. Her spay went well, but when it is only your second spay, you still don’t trust that you haven’t done something stupid and that the dog isn’t in real trouble. (One of my classmates reports that she actually went to visit her spay patient at the shelter several days later, to make sure she was okay. My classmate pretended to be interested in adopting the dog in order to get time alone with her, so she could look at her spay scar.) So when Linnea started making a lot of noise the evening after her surgery, I was very anxious.
First I asked the anesthesia technician if he thought she needed more pain medication. He pointed out that she had been a very vocal dog before the surgery, and was almost certainly just stressed now, especially due to the after- effects of all the other medications we had given her making her feel less than mentally competent. My spay partner Lily and I looked at Linnea anxiously after letting her out to pee. Lily said: “Well, she seems to be standing sort of hunched over.” I said: “Yes, I really would like to give her more meds!”
The veterinary intern came by around that time, for evening rounds, and I explained how Linnea looked painful to us. (It is veterinary jargon to say an animal is “painful” rather than “in pain,” and I have seen this usage really annoy non-veterinarians. I am not sure why we say it that way, but that is how it is.) Now, Lily and I had recently completed our anesthesia course, which had several lectures about how to tell if dogs are painful, but of course in the heat of the moment we had completely blanked on this. The veterinary intern simply put her hand gently but firmly on Linnea’s spay incision. Linnea didn’t even blink; she didn’t turn her head or growl or flinch. The intern said confidently, “She doesn’t appear to be painful,” and this time, I believed it.
Dogs do sometimes vocalize when they are in pain, but it is not the best way to tell. Many dogs in pain do not vocalize, and there are tricks of body language that you can use to tell what is going on in their heads. We had some fascinating lectures on that, unfortunately far too image-filled for me to reproduce here.
I learned from this experience. When you’re not sure how to proceed, take a deep breath and think back to what you were taught in class. We actually have received a very good foundation for clinical work, but it can be really hard in the moment to pull the appropriate fact out of the mass of information packed into our brains after three years of veterinary school!
Linnea was an extremely nice dog who was extremely unhappy about being in the spay clinic for two days. She pawed at the cage door so much the first night that we gave her a sedative to take the edge off. Her spay went well, but when it is only your second spay, you still don’t trust that you haven’t done something stupid and that the dog isn’t in real trouble. (One of my classmates reports that she actually went to visit her spay patient at the shelter several days later, to make sure she was okay. My classmate pretended to be interested in adopting the dog in order to get time alone with her, so she could look at her spay scar.) So when Linnea started making a lot of noise the evening after her surgery, I was very anxious.
First I asked the anesthesia technician if he thought she needed more pain medication. He pointed out that she had been a very vocal dog before the surgery, and was almost certainly just stressed now, especially due to the after- effects of all the other medications we had given her making her feel less than mentally competent. My spay partner Lily and I looked at Linnea anxiously after letting her out to pee. Lily said: “Well, she seems to be standing sort of hunched over.” I said: “Yes, I really would like to give her more meds!”
The veterinary intern came by around that time, for evening rounds, and I explained how Linnea looked painful to us. (It is veterinary jargon to say an animal is “painful” rather than “in pain,” and I have seen this usage really annoy non-veterinarians. I am not sure why we say it that way, but that is how it is.) Now, Lily and I had recently completed our anesthesia course, which had several lectures about how to tell if dogs are painful, but of course in the heat of the moment we had completely blanked on this. The veterinary intern simply put her hand gently but firmly on Linnea’s spay incision. Linnea didn’t even blink; she didn’t turn her head or growl or flinch. The intern said confidently, “She doesn’t appear to be painful,” and this time, I believed it.
Dogs do sometimes vocalize when they are in pain, but it is not the best way to tell. Many dogs in pain do not vocalize, and there are tricks of body language that you can use to tell what is going on in their heads. We had some fascinating lectures on that, unfortunately far too image-filled for me to reproduce here.
I learned from this experience. When you’re not sure how to proceed, take a deep breath and think back to what you were taught in class. We actually have received a very good foundation for clinical work, but it can be really hard in the moment to pull the appropriate fact out of the mass of information packed into our brains after three years of veterinary school!
Sunday, October 17, 2010
Why veterinary anesthesia is a thrill a minute
Last week I had my anesthesia and analgesia final exam. Some people seem to think that anesthesia is boring. (The Amateur Transplants refute that fallacy pretty well.) Anesthesia is in fact pretty complicated. I sort of wished that the choices you have to make for each anesthesia case could be written out in a huge decision tree, but I didn’t have the energy to do it myself. Roughly, here’s how it goes.
Premedication
First, you might want to make the animal sleepy so it doesn’t try to bite you, kick you, or run away from you. The choice of sedative or tranquilizer here is dependent on a lot of factors. How old or young is the animal? (Foals may not need any premedication at all.) How sick is it? (Healthy animals benefit from different premedications than critically ill ones.) Does it have heart disease? (Many sedative/anesthetic drugs depress the function of heart muscle and could kill an animal with heart disease.) And, of course, what species is it? For this exam, we learned details about the kinds of drugs that were best for dogs, cats, horses, goats, sheep, cows, llamas, and alpcas. We did a whirlwind tour of issues in rabbits, ferrets, rats and mice, birds, lizards, and snakes.
Induction
Once the animal is premedicated and drowsy (or if it is naturally unlikely to protest), the next step is to induce anesthesia. Many of the same questions of drugs come up, and many of the same drugs are used for this stage of the process, just in different amounts or given by different methods. It is nice to have the animal mellow for this stage, because commonly the next set of drugs is given intravenously. It is best to put in an IV catheter to do this. A catheter allows easy access later. This is useful to give more induction agent, as they are sometimes given in bursts; to give a reversal agent if necessary, which you may have to do in a hurry if there are problems; or to give other drugs while the animal is anesthetized, such as antibiotics or pain medication, without having to find a vein again.
Maintenance
Once anesthesia has been induced, it has to be maintained. You don’t just knock an animal out and hope it stays out for as long as you need — well, actually, sometimes you do. The question is how long you need to keep the animal under, how painful the procedure is going to be, and sometimes whether you have the equipment for your preferred maintenance method. If you are in the field with a horse that can’t be brought in to a hospital, you will probably not choose to intubate the horse and maintain it with an inhalant anesthetic. For a short procedure, one dose of injected anesthetic might be sufficient, or anesthesia could be maintained by an IV drip. On the other hand, for most surgeries on dogs in a veterinary hospital you will choose to employ an inhalant anesthetic.
How are you going to get the inhalant gas into the animal? Most commonly you will intubate (put a tube down the animal’s throat). In some cases, you will not be able to do that, and will put a mask on the animal’s face instead. We don’t like masks because they are liable to leak and you don’t want anyone but the animal to be getting that gas — the veterinarian would be breathing small amounts of anesthetic gas during every surgery, which is not a good thing. But sometimes intubation isn’t possible, particularly for very small animals. Interestingly, we were taught that you do intubate snakes, and that in fact you do so before inducing anesthesia — you sedate them and then put the tube in while they are still awake.
Recovery and post-operative analgesia
When the animal wakes up, there are another host of questions. Some animals are more liable to regurgitate than others. Regurgitation is a Bad Thing (it can lead to inhaled stomach contents and aspiration pneumonia, which may be fatal), and so extubation may be done using different techniques to avoid it, depending on the species.
Post-operative pain control is also extremely varied among species. As a general rule of thumb, you go for NSAIDs in horses and cows, but opioids in dogs and cats. Opioids can reduce gut motility, which is bad in animals with big complicated stomachs like horses and cows. (However, we do still use them in those animals.) On the other hand, NSAIDs can cause kidney issues in dogs and cats, while horses and cows handle those drugs really well.
NSAIDs are particularly interesting in veterinary medicine. In human medicine, there was an attempt to find COX2-selective NSAIDs, which would inhibit only the COX2 form of the enzyme (which is involved in pain) and not the COX1 form (which is essential to normal stomach wall function, among other things), in the hopes of finding NSAIDs which handled pain without causing stomach ulcers. Unfortunately, COX2-selective NSAIDs have turned out to be problematic in human medicine, causing an increased risk for heart attack, among other things. These side effects have not manifested in veterinary patients on COX2-selective NSAIDs, however, and most of the NSAIDs that we give dogs are COX2-selective. Interestingly, the COX2 selectivity of any particular NSAID is different in different species. In other words, a drug that selectively inhibits COX2 in a dog may inhibit COX1 and COX2 equally in a human.
Which leads me to my public service announcement of the day: acetaminophen (Tylenol) can kill a cat, and ibuprofen (Advil) can destroy a dog’s kidneys. Always ask your veterinarian before giving your pet any form of pain relief. There’s lots out there for them, but the exact drugs that are appropriate differ hugely between species.
Premedication
First, you might want to make the animal sleepy so it doesn’t try to bite you, kick you, or run away from you. The choice of sedative or tranquilizer here is dependent on a lot of factors. How old or young is the animal? (Foals may not need any premedication at all.) How sick is it? (Healthy animals benefit from different premedications than critically ill ones.) Does it have heart disease? (Many sedative/anesthetic drugs depress the function of heart muscle and could kill an animal with heart disease.) And, of course, what species is it? For this exam, we learned details about the kinds of drugs that were best for dogs, cats, horses, goats, sheep, cows, llamas, and alpcas. We did a whirlwind tour of issues in rabbits, ferrets, rats and mice, birds, lizards, and snakes.
Induction
Once the animal is premedicated and drowsy (or if it is naturally unlikely to protest), the next step is to induce anesthesia. Many of the same questions of drugs come up, and many of the same drugs are used for this stage of the process, just in different amounts or given by different methods. It is nice to have the animal mellow for this stage, because commonly the next set of drugs is given intravenously. It is best to put in an IV catheter to do this. A catheter allows easy access later. This is useful to give more induction agent, as they are sometimes given in bursts; to give a reversal agent if necessary, which you may have to do in a hurry if there are problems; or to give other drugs while the animal is anesthetized, such as antibiotics or pain medication, without having to find a vein again.
Maintenance
Once anesthesia has been induced, it has to be maintained. You don’t just knock an animal out and hope it stays out for as long as you need — well, actually, sometimes you do. The question is how long you need to keep the animal under, how painful the procedure is going to be, and sometimes whether you have the equipment for your preferred maintenance method. If you are in the field with a horse that can’t be brought in to a hospital, you will probably not choose to intubate the horse and maintain it with an inhalant anesthetic. For a short procedure, one dose of injected anesthetic might be sufficient, or anesthesia could be maintained by an IV drip. On the other hand, for most surgeries on dogs in a veterinary hospital you will choose to employ an inhalant anesthetic.
How are you going to get the inhalant gas into the animal? Most commonly you will intubate (put a tube down the animal’s throat). In some cases, you will not be able to do that, and will put a mask on the animal’s face instead. We don’t like masks because they are liable to leak and you don’t want anyone but the animal to be getting that gas — the veterinarian would be breathing small amounts of anesthetic gas during every surgery, which is not a good thing. But sometimes intubation isn’t possible, particularly for very small animals. Interestingly, we were taught that you do intubate snakes, and that in fact you do so before inducing anesthesia — you sedate them and then put the tube in while they are still awake.
Recovery and post-operative analgesia
When the animal wakes up, there are another host of questions. Some animals are more liable to regurgitate than others. Regurgitation is a Bad Thing (it can lead to inhaled stomach contents and aspiration pneumonia, which may be fatal), and so extubation may be done using different techniques to avoid it, depending on the species.
Post-operative pain control is also extremely varied among species. As a general rule of thumb, you go for NSAIDs in horses and cows, but opioids in dogs and cats. Opioids can reduce gut motility, which is bad in animals with big complicated stomachs like horses and cows. (However, we do still use them in those animals.) On the other hand, NSAIDs can cause kidney issues in dogs and cats, while horses and cows handle those drugs really well.
NSAIDs are particularly interesting in veterinary medicine. In human medicine, there was an attempt to find COX2-selective NSAIDs, which would inhibit only the COX2 form of the enzyme (which is involved in pain) and not the COX1 form (which is essential to normal stomach wall function, among other things), in the hopes of finding NSAIDs which handled pain without causing stomach ulcers. Unfortunately, COX2-selective NSAIDs have turned out to be problematic in human medicine, causing an increased risk for heart attack, among other things. These side effects have not manifested in veterinary patients on COX2-selective NSAIDs, however, and most of the NSAIDs that we give dogs are COX2-selective. Interestingly, the COX2 selectivity of any particular NSAID is different in different species. In other words, a drug that selectively inhibits COX2 in a dog may inhibit COX1 and COX2 equally in a human.
Which leads me to my public service announcement of the day: acetaminophen (Tylenol) can kill a cat, and ibuprofen (Advil) can destroy a dog’s kidneys. Always ask your veterinarian before giving your pet any form of pain relief. There’s lots out there for them, but the exact drugs that are appropriate differ hugely between species.
Monday, August 16, 2010
Veterinary fact of the day: premedication
Welcome to a new feature: the veterinary fact of the day. See the bottom of this post for more information.
Today’s veterinary fact is a brief overview of pre-medication, or premed. (This is different from a premed student.)
What’s pre-medication?
It sounds like a very general term! But in a veterinary hospital, you “premed” an animal before general anesthesia.
What’s in a premed?
Premeds are tailored to the particular animal, based on age, species/breed, temperament, pre-existing conditions, etc. Generally, a premed will include an analgesic, a sedative or tranquilizer, and sometimes an anticholinergic.
Why would you give an animal an anticholinergic in their premed? Also, what the hell is an anticholinergic?
An anticholinergic is a medication which competes with a specific kind of neurotransmitter, part of the parasympathetic nervous system. When your brain sends out messages to your body saying “time to relax, to rest and digest,” the anticholinergic blocks those messages. This makes the body do the opposite of rest and digest (increase heart rate, for example). Why would you give one of those when you are about to make the animal lose consciousness? It helps keep the heart going at the rate you want, even when the rest of the animal’s body is being artificially put into what you can think of as close to the “off” state. Also, it makes the patient make less saliva. Apparently that can be important in ruminants (cattle!). I can only imagine.
Why would you give an animal a tranquilizer or sedative in their premed?
Well, first, what is the difference between a tranquilizer and a sedative? They are really two parts to the same equation; a tranquilizer makes you feel calmer, and a sedative makes you act calmer. Why give them? To make things easier on the animal, who is in a scary situation. To make things easier on the anesthetist, who is handling an animal that might be scared.
Why would you give an animal an analgesic in their premed?
Why a pain reliever? They aren’t going to be feeling anything while they are under general anesthesia, but they will certainly be feeling something when they wake up, unless they have an analgesic on board. Also, putting in an intravenous catheter (for the general anesthesia) can be painful.
Why are you telling me all this?
I just went back to veterinary classes after a year of research. I don’t expect to have much time to blog in detail, but I figured a quick report daily (if possible; I expect to slip to every several days at least) from the trenches of the third year of vet school might be interesting. I will call it the “veterinary fact of the day.” This is the year in which we learn how to fix what’s broken. I would love feedback — let me know if I am covering things that are interesting, and if you have any requests.
What did you do today?
Two hours of Anesthesia and Analgesia lecture. Two hours of Large Animal Medicine and Surgery lecture. Lunch! (Food and statistics; I am still editing my thesis.) Two hours of Small Animal Medicine and Surgery lecture. Home!
Today’s veterinary fact is a brief overview of pre-medication, or premed. (This is different from a premed student.)
What’s pre-medication?
It sounds like a very general term! But in a veterinary hospital, you “premed” an animal before general anesthesia.
What’s in a premed?
Premeds are tailored to the particular animal, based on age, species/breed, temperament, pre-existing conditions, etc. Generally, a premed will include an analgesic, a sedative or tranquilizer, and sometimes an anticholinergic.
Why would you give an animal an anticholinergic in their premed? Also, what the hell is an anticholinergic?
An anticholinergic is a medication which competes with a specific kind of neurotransmitter, part of the parasympathetic nervous system. When your brain sends out messages to your body saying “time to relax, to rest and digest,” the anticholinergic blocks those messages. This makes the body do the opposite of rest and digest (increase heart rate, for example). Why would you give one of those when you are about to make the animal lose consciousness? It helps keep the heart going at the rate you want, even when the rest of the animal’s body is being artificially put into what you can think of as close to the “off” state. Also, it makes the patient make less saliva. Apparently that can be important in ruminants (cattle!). I can only imagine.
Why would you give an animal a tranquilizer or sedative in their premed?
Well, first, what is the difference between a tranquilizer and a sedative? They are really two parts to the same equation; a tranquilizer makes you feel calmer, and a sedative makes you act calmer. Why give them? To make things easier on the animal, who is in a scary situation. To make things easier on the anesthetist, who is handling an animal that might be scared.
Why would you give an animal an analgesic in their premed?
Why a pain reliever? They aren’t going to be feeling anything while they are under general anesthesia, but they will certainly be feeling something when they wake up, unless they have an analgesic on board. Also, putting in an intravenous catheter (for the general anesthesia) can be painful.
Why are you telling me all this?
I just went back to veterinary classes after a year of research. I don’t expect to have much time to blog in detail, but I figured a quick report daily (if possible; I expect to slip to every several days at least) from the trenches of the third year of vet school might be interesting. I will call it the “veterinary fact of the day.” This is the year in which we learn how to fix what’s broken. I would love feedback — let me know if I am covering things that are interesting, and if you have any requests.
What did you do today?
Two hours of Anesthesia and Analgesia lecture. Two hours of Large Animal Medicine and Surgery lecture. Lunch! (Food and statistics; I am still editing my thesis.) Two hours of Small Animal Medicine and Surgery lecture. Home!
Subscribe to:
Posts (Atom)
