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EDITOR: While we're waiting for the rest of the finest pain experts in the world to come on line, let me ask you a question. I've always wondered if we know what's going on and how much chickens might be conscious of pain after having their heads cut off. I still see them running all over for what seemed an eternity when I was a kid. Is there any possibility of some kind of level of pain that's felt there, and what that's all about?
DAVID MORTON (DM): This has been investigated in France when they did an experiment when they chopped off this chap's head and he said I want you to watch my head carefully, and when I stop winking, or whatever it is, you'll know I don't feel any more pain.
DM: I mean surely, I don't think there's going to be much pain if that's the cortical response from the neck down within the chicken, but what could respond theoretically, is the head. Some experiments were done with people who were decapitated and they did some experiments with them and found that they responded for something like 30 seconds afterwards I think . . . Blackmore did some in New Zealand when sheeps' heads were still responding after a minute and a half or something. I saw a video of that, it was quite eerie.
EDITOR: I'm so excited to have you all together here. I mainly just want you to talk to each other about things of interest, although perhaps we can get to some of the questions I sent to you about detecting pain and alleviating pain in different species. I'll just let you go.
VERA BAUMANS: Who is starting?
DM: Manny, do you want to follow your outline?
EDITOR: Oh, we could do that. Vera, before you came on line, David was talking about what goes on with pain after a chicken's head has been cut off. It seems some research discovered that the head feels the pain, rather than the body. Perhaps David could tell you and us more.
DM: Well, I think the general point from that story is that
pain is a perception at the cortical level, and that's what we're talking about
when we talk about pain and probably distress as well. It is some
cerebrocortical integration of a response either to some physical injury or
threat of injury, or to the animal's environment in some way, depending whether
we're talking about adverse effects vs. pain, or anticipating adverse effects
when an animal may become frightened or has signs of fear or terror of some
sort. So perhaps what we've got to talk about first of all before we can talk
about treatment is how we recognize whether animals are in pain or are in
distress, or are frightened or anxious or what have you. I think as vets we
probably are fairly used to seeing animals show signs of pain. As some of you
know, I wrote a paper some time ago with Paul Griffith, where we tried to set
out general categories, although I don't know whether it's worth going through
them. But just to start the ball rolling, we had the idea that sometimes
animals could look like they were in pain: their appearance showed whether they
were in pain or not, or whether they were frightened or what have you. You have
this typical sympathetic response with dilated pupils, increased heartbeat, no
doubt that would go along with some physiologic signs as well, but appearance
is one criteria. Then, perhaps with a more chronic subacute pain, one might
look at body weight, which obviously isn't going to deal with the kind of pain
when you hit your finger with a hammer or trap a dog's tail in a door, for
example. Prolonged pain, protracted pain, may well show itself as reduced body
weight because the individual fails to eat and drink as much as he or she
normally might do. Then and perhaps most important would be the animal's
behavior, and behavior I think you can split into two parts. One is when the
subject is actually behaving on his or her own without any stimulus from
outside, and see whether the individual moves around,
whether s/he isolates
herself or himself from the herd or whether the individual is carrying out some
abnormal behaviors. Then you can have another type of behavior which is when
that individual animal responds to you, for example, touching a sensitive site,
or on another level it may be a sign that the patient is showing an intelligent
interest in life in response to a noise you make behind the cage. The response
is a significant indicator of how that individual is feeling.
The final version of the story of the five areas which is going to be clinical
signs, include the heart which rate will be markedly elevated. If an animal is
in pain the body temperature may rise, you may get all sorts of abnormal
clinical signs. The general hypothesis is that you have a patient that is
deviating in some way from the normal range of behaviors, clinical signs or
what have you that you'd associate with animals. So whilst it is difficult to
tell exactly how an animal is in pain or distressed, just like it is with a
human, one can measure objectively in some cases, semi-objectively in other
cases, how far that animal has deviated from what we think is normal. So in
that way we can start to recognize whether animals are undergoing some sort of
suffering, let me put it that way. That's my kick-off.
CHARLES SHORT (CS): To follow-up on David's comments,
postoperatively it's not unusual if animals are experiencing postoperative pain
during the first few hours there is a failure to either eat, drink, void, or
have normal functions. Sometimes this is a bit confused because the staff in
the recovery room, ICU, or in the wards may conclude, since the animal is
perhaps lying quietly and not vocalizing, there is no pain. It's recovering
from anesthesia. I think the advent of the anesthetic that allow a faster
recovery, such as propofol or isoflurane, we have now demonstrated to a lot of
people that coming out of surgery, animals do experience stress and pain more
so than they had anticipated with gradual recovery from some of the slower
contrast anesthetic agents in the past.
PAUL FLECKNELL (PF): If I can jump in - I quite agree with David saying that we need to talk about assessment before we can talk about alleviation, because we need to judge what an appropriate dose of analgesic is, how fast the drug wears off, do we need to repeat the doses and so forth. Our work with rodents suggests that Charlie's point about food and water intake being depressed certainly does hold true across a range of different surgical procedures, and that giving an analgesic can reverse that. But of course, we have included a control group in those studies so that we know both the effect of the anesthetic and we've included a group which didn't receive an analgesic, and that proves to be very problematic in many of the veterinary schools, who are now trying to launch into studies of pain assessment because the vet schools have taught that you should give analgesic, it's the appropriate thing to do. In order now to validate methods of pain assessment, they're wrestling with the problem of, should we actually withhold analgesic from these animals, when we seem to know intuitively; from all our training as vets, that these animals should have a pain-killing drug. But if we don't include an untreated control group, then a lot of the behavioral signs that we're trying to interpret as signs of pain really don't hold much water. It's interesting to note that of the five or six studies of pain assessment in clinical patients, the people who have used things like visual analog scores filled-in by either veterinary nurses or other clinicians, when you read the details of what they've based their scores on, a high percentage of those studies have used straight-forward pressure on the wound, so in other words, they were bypassing a lot of the more subtle behavioral observations that perhaps we do use intuitively. When using simply the response to pushing on the wound we observe if the animal squeaks or jerks or moves in some way. That means that we have to use pretty hefty doses of opiates to block those responses because you're asking a lot of a pain-killing drug to stop any response to a surgical wound being palpated.
VERA BAUMANS: Hi, this is Vera. Can I add something? What we are doing sometimes is to start from the other side around. We don't know for sure when the animal is in pain. We simply give them a pain-killer like buprenurphia, whatever, and then sometimes we see the animals are starting to eat better, or to behave different. From that point of view, when we are in doubt we always can give them pain-killers. When we do, we can see that the behavior is changing, although perhaps beforehand, we didn't know especially whether the animal was in pain or not.
DM: I think Paul's saying though, Vera, that if you do give those pain-killers, the pain-killer themselves may actually stimulate the appetite, so it's not necessarily because it's relieving pain, it can be the drug stimulating eating.
VB: That's possible, but you can score other behaviors as well.
DM: Yeah, sure. I think that's what we need: a broader range of behavior scoring, really a more broad assessment, and not a very narrow one, as Paul was saying, pressure on the wound for example.
CS: Part of the problem that you run into is that all of these parameters are subjective. I think there are a couple of other things that need to be considered. One, you need to have a good idea of what the normal behavior of the animal is, particularly someone, for instance, in wild animal medicine, or laboratory animal personnel caring for a group of rodents. They've been well established in the observed responses and we have a good idea of what normal behavior is in the colony or in the group prior to whatever intervention is done that may or may not be inflicting pain. The other thing is, I think it's perfectly legitimate to have a degree of anthropomorphism to evaluate these things. If we put ourselves in the place of the subject or patient, and assume if this procedure was done to me, do I think that it would cause pain or discomfort, and would it be severe enough that I would want it relieved with medication? I think that has to enter into the assessment that goes on. I know we've had surgeons who have felt that as long as the animal was not vocalizing or as long as the patient was lying quietly, there was no need for any analgesic at all. Certainly I don't believe that's the case. I think that those are issues that have to be taken into account in the assessment of the animal.
DM: Agreed, and I think the other point we do have to bear in mind is that animal technicians and pet owners are very astute as to what is a change in behavior for THEIR animals that they know well, and we should be taking a lot of notice of that, shouldn't we!
GORDON JOHN BENSON (JB): This is one of the places we're trying to become more scientific, and it becomes a disadvantage. We like to have the unbiased observer to determine subjectively whether the animal seems to be in pain or improving with our administration of analgesic, but if that unbiased observer has not seen the animal prior to surgery or prior to the injury in some instances, their evaluation may be skewed because they don't appreciate what they're attempting to go back to. This is especially true if you're dealing with a wide variety of either individual animals or different animal species because if you compare the outward responsiveness of say the sheep the calf to the dog to the cat to the horse, etc., the ones that vocalize vs. the ones that don't, the ways that the species and breeds as well as the individuals show sadness or anxiety can be quite different.
DM: I don't agree with that. I used to have a nice theory that it was all the predagees, you know, that were very stoical and didn't show pain. And then I thought of the pig, and the pig, as soon as you get anywhere near, starts to squeal. So, that theory sort of fell down. There is a world of difference in a dog in pain who will probably vocalize far quicker than a sheep or a calf. But what about a cat? What experience have your veterinary clinicians got of cats in pain? Is it true that they purr?
JB: I have not seen cats in pain purring. I have observed painful cats become euphoric and purr following the administration of morphine which appeared to relieve their pain.
VB: I did. That's true. Sometimes they do, and when they have wounds or they are in pain because they don't use a leg or whatever, they can purr. Perhaps they are not so much in pain as we think they are, but normally you would think they are in pain and sometimes they purr. That's what my experience is, also.
DM: They're probably getting a high on all the endogenous opiates.
JB: Either that or maybe they're responding to something in addition to the pain. Perhaps, they can still respond to a pleasureful stimulus in spite of the presence of pain.
CS: Some animals also will start to relax, like the cat that may return to purring. In a number of cases, we've observed that attention and caring by technical staff or by the owners will relieve the anxiety enough so that the animal will respond positively even when there is evidence of tissue damage and pain.
DM: Can I just take up something? I think it was John who said pain is subjective. I want to see if we can tackle this a little bit more because I think the experience of pain is very subjective. We cannot feel each other's pain but I think that the signs we make can be fairly objective. Say, for example, an animal that's in chronic pain may well only eat 25 or 50% of its normal intake, or may drink less, and therefore will lose body weight. Measuring body weight can be a fairly objective measure. I think measuring perhaps corticosteroid or perhaps prolactin or some of the new measures of stress in animals can start to give us an idea of some quantitative variation from normality. I would like to feel it isn't all totally subjective. Either measuring behavior, you can measure the amount of time an animals spends on their own before an operation and after an operation can be complimenting measures. It seems to me we've got to be a little bit more robust, not only in our criticism, but also of actually finding better scientific methods to measure objectively signs of pain in animals. What do you all feel about them?
JB: Well, since I used the term, I'll respond first I guess. I think that what I was getting at, is that pain is a subjective perception. Pain is a perception, number one. As opposed to nociception which is a physiologic process that if carried to completion, does result in the perception of pain. I would agree with your comments that we can become less subjective in our evaluation perhaps of our patients and subjects. We have to be very careful when we do that in the sense that if we look at some of these physiologic parameters such as catecholamine levels, cortisol levels, and so on as you mention, now that's an objective thing, you measure it, and you get the concentration in the plasma and so on. The thing that one runs into with that is those responses are somewhat nonspecific, then you run into the problem of interpretation: is, lets say, an elevation in catecholamine or cortisol the result of pain? Is it the result of the nociceptive process in the absence of the perception of pain, which it can be, or is it due to distress or suffering that is not painful in origin? Because all you see is the stress response, and that's basically what we're looking at here, but the response can be elicited via a whole host of stressors or stimuli that may or may not be painful, and now we have to become very rigorous in our interpretation and in our viewing of the state of the animal, if you will, for lack of a better way to say it right now. I think, to this point in time, the assumption has sort of been that the stress response in toto sort of goes as unit. In other words, catecholamines go up, cortisol goes up, so on and so forth, you know, when in fact there is some evidence now that perhaps in the perioperative period, if we're looking at surgical patients, what increases in one may not correlate with increases in another of these endogenous stress-related hormones. Of course, that's another thing now that comes in and muddies the water for us. It really makes it difficult, and that's not to say that it isn't a legitimate thing to be looking at. I hope it is, because that's what I'm doing.
DM: OK, but what happens if we then do the test of deletion as Bill Payton might have said, and that is we give morphine, a drug of analgesic.
JB: That would help out precisely, certainly. That would help. But it's an interesting area that we don't really know very much about at this time.
CS: I think one of the real confusing parts about this is all too often we have assumed for the surgical patient that if the patient was anesthetized we had relieved pain, and we also will protect against stress. As we begin to look at things more objectively, we find that this is not necessarily the case. We may have unconsciousness as if it were a human patient, perhaps no recall of a painful experience. But during that time, there are definitely stressors that are happening and postoperatively some of the recovery problems are due to the extent of stress that has occurred. We have found, looking at brain wave activity, that for different anesthetic regimens, particularly those that have an analgesic with them, there is at least some indication at this point that different techniques can provide a less stressful situation. In both cases, with or without them, the analgesic, there was no outward signs that the animal was moving or that anesthesia was too light. When surgical plane anesthesia had occurred without analgesia or without rather deep anesthesia in some cases, definitely I think there was stress.
PF: I think that this problem, which both Charlie and John have touched on, of the difficulty in using metabolic markers, we have to look, I think, of humans where at least we can go back and ask the patient if they were in pain or not. In other words, the only thing that exists as a gold standard is whether the patient said he hurt or not. Certainly the studies using man, going back about ten years now when this was first tried, of looking at catecholamine responses, where the catecholamine responses certainly could be changed by giving analgesics, but you could have pain-free patients who had high catecholamine levels, and their pain scores and catecholamine responses didn't correlate well. Now there have been some pretty persuasive studies in animals, I think the latest one would be the paper by Popilskis in the AVA journal, when they looked at subjective pain score, cortisol and catecholamine in dogs with two different analgesic regimes after thoracotomy, and everything went the right way. The pain scores were lower with epidural morphine compared to intravenous, and the stress response markers were lower. It certainly seems to fit, but we still don't know whether those markers are going to be a standard we could use to objectively assess pain, so I think I'd agree with John, the jury is still out on that. To go back to David's point about objectivity of behavior, I don't think we need wring our hands in despair and say we can't do it. It has been done. The work by Colpert on chronic arthritis model in the rat, for example. They were able to come up with some pretty objective criteria in terms of behavior which they could relate to onset of arthritis and so forth. And, of course, Vince Maloney and his Ph.D. student Dr. Woods work in lambs with castration and tail docking. They looked at several behaviors and looked at the effect of giving local anesthetic on those behaviors. By scoring in some detail and analyzing behavior in a much more objective fashion than just a quick 30 second view of the animal, they could come up with some testable hypotheses and behavior in parameters that could be analyzed.
DM: I would agree with that: just let me quickly touch on something else. The way people have thought to evaluate or have done, indeed for many years, husbandry systems for animals. They look at stereotypic behaviors and the percent of time that animals carry out these behaviors in various times in cages, or animal husbandry environment. The behaviors there seem to give us some idea of whether systems are animal friends or not. There is another one, I want to touch on. Do any of you read the work on electromobilization in sheep? They subjected sheep to electromobilization. They gave them a choice, either to turn right to a clear one, or left to go down the electromobilization chamber again.
JB: That was done here at the University of Illinois, I believe.
DM: Oh, right. So you know more about it than I. My understanding of it was that they seemed to have a memory that said no way do we want to go down.
JB: No way.
DM: So they do put things together.
CS: It has to confirm that pain is either an actual or a perceived problem. I recall vividly a horse that I worked with when I was actually a pre-Vet student one summer and this horse had been abused by a fellow who came home after having too much to drink. I saw the horse two or three years after this occurred, and you could open the stable door and the horse would still immediately run to the far corner of the stall, because it still had the emotional scars of having been beaten and it stood out in my mind for many years that animals do have this memory of extremely painful or stressful experiences.
DM: You don't have any equine psychotherapists over there?
CS: This was so long ago when there were no animal psychotherapists at all.
Editor: Could I focus you back on differences between species? A researcher told me that mice do not need analgesics after major surgery because they're eating within the hour. Do you think there is a place for analgesics with mice after surgery or would that be . . .
VB: I think, there are so many differences between species and that also depends on the social structure of that species. For instance, dogs will bark and attract attention from the group when they are in pain. Otherwise, they won't be helped. Ungulates like antelopes, they don't say anything because otherwise they are attracting, for instance predators, and they might even be expelled by their group. How this is in mice, we simply don't know I think. How mice act when they are in pain in the wild and when they are living in a group, I don't know. So perhaps that's another problem. When a mouse doesn't show anything, for me, that is no reason to give them nothing, no analgesic or help with possible pain.
DM: Very little major surgery is really carried out on mice. If you asked the question of a dog, and did major surgery or minor surgery, I think one would pick up the difference between it. Experimentally not much major surgery goes on with mice, so therefore that would explain perhaps how they come to eat again. If you look at toxicity testing then, of course, people can actually score various clinical signs in mice now, and that's linked up very well with the LD-50 test, fixed dose procedure, and another scoring system in Germany now replacing the LD-50 test by using clinical signs. I'm not sure of a remarkably good correlation in a multi-centered study as well, which is good.
JB: I think Paul might want to address this in more detail, but one of the points I would make on mice and other rodents is that the husbandry involved must be taken into consideration in some instances. For example, if you turn mice or rats or other rodents that are under the influence of analgesic or have had surgery back to their cage if they are awake, healthy, non-surgical animals in the same cage, they may actually attack or damage the one that comes back.
CS: Certainly true the case with the pig. The pig would do that too. It's a problem there.
JB: If attempting to be well-meaning, the veterinarian is controlling pain with analgesic, it's also necessary to remember what the environment is going to be when you return the animal.
PF: To go back to mice, and David's comment they don't undergo major surgery. We did a whole series of adult thymectomies, which I would consider major. It involved splitting the first few sternebrae at the anterior of the chest. In those mice we had a lot of problems trying to demonstrate beneficial effect of analgesic. Certainly when using our criteria of body weight change and food and water consumption reduction following surgery, we got a reduction in the mouse, but it was a much smaller than that seen in rats after surgery.
Editor: Could you react to the mouse in cancer research where they're dying of cancer. Do analgesic have any place there? It's another hard question.
DM: I'd like to ask clinical vets that one, because what about dogs with advanced mammary tumors. Do they show signs of pain? Dogs with advanced cancer, can you recognize pain in these animals, or cats?
JB: Apparently the owners don't, because they don't bring them in for that. They don't say that they're evidencing a change in behavior, they just notice that they have this nasty looking lump on their abdomen, you know.
DM: And yet in humans, it seems to be one of the major factors.
PF: If you then give these animals analgesic the owner notes an improvement in their quality of life. The original anecdote goes back, I think, to Andy Xoxall's paper in the Journal of Small Animal Practice, which is 15 years back, and one or two other people who have tried this, and you do seem to get an improvement and the owner will note it, but it's all very subjective. We have to rely on extrapolations from humans as the basis for doing it.
JB: The other thing about that is that there may be a change that comes on gradually that the owner is not aware of, or attributes it to aging, because the frequent thing that we see, not related to mammary tumors but we see these older dogs that come in that have advanced dental disease, and there is no doubt in my mind it would have to be painful, and after extensive extractions and whatnot, you send the dog home and universally the comment is that the dog acts like a puppy again. I'm sure it's because, one: you've removed a bunch of infection and cleaned that up, but also they surely are not painful anymore. What people may not recognize is that pathological conditions may induce some subtle changes in behavior of the animal that the owner may interpret as `my dog is getting older'.
CS: A number of those will end up changing diets several times before they bring them in, not realizing that the reason their dog with severe dental problems is not eating, is perhaps because it hurts to eat. Instead of recognizing that, they end up changing diets trying to get the animal to eat, then when they won't eat anything, they bring them to the veterinarian.
VB: It could also be a problem of the owner. I know when we had dogs with mammary tumors and we operated on them, the owners would say they are playing again, but that's also because the owner could have paid much more attention to the dog then he did beforehand. I don't really know whether that it was because the dog is feeling better again. When you look at rats with mammary tumors, I always am astonished by the fact that they can have large mammary tumors and may behave like they did before. You see that when you have pet rats. I have pet rats. They all died from mammary tumors, but until the end, they behaved, in my eyes, normal.
DM: You didn't take your rats to a vet, obviously Vera.
PF: One thing that intrigues me and I think may explain what we're seeing in the mouse, is the relative importance of pain to the animal. If you are a mouse, if you don't eat, then you're going to die because the metabolic rate is so fast, and you have to keep eating and drinking. Maybe the behaviors that we see in larger animals are luxuries they can afford because of their larger size, greater body reserves of energy. If you're small, you can't afford that. Maybe we won't see such major changes because after all, this will compromise the animal's ability to survive in some cases.
CS: Well, this is one of the reasons of chronic orthopedic or joint pain. Of all species, we have given the greatest attention and have the most information available on the horse. With the non-steroidal anti-inflammatory drugs and other medications that are used in an effort to keep the horse running. Yet in contrast, we don't have a similar approach to bovine disease. So here we have definitely a species difference that is based on their use in sport.
DM: And also pigs; we don't give pigs analgesium, and the farmed animals really get a pretty raw deal, don't they? We're coming back to Manny's point. It struck me that he's saying mice are not in pain because they eat. Do we really believe that simply because an animal eats they are not in pain?
JB: One of the things that's always amazed me is that when people castrated mature horses with succinyl choline, the horses would immediately eat upon regaining their feet. Placing screws in the joint to fix slab fractures of the carpal bones would seem to me to be very painful acutely postoperatively, and yet those horses not only immediately stand up, but they walk back to their stall with minimal evidence of discomfort, they don't really limp. In fact at our hospital here, the horse has to step down out of the recovery stall and they do so, and many times it's the leg that was operated on that they step out with, and they don't wince or anything like that. They come down on it and as soon as they get back to their stall, they eat. I don't think eating equates to the absence of pain.
CS: I think one of the situations that we have is that each of the different signs of pain that we've discussed, both subjectively and objectively, at the present time do not have some magic index that says this is the one that you can use across the board. It's a matter of considering disease conditions, injuries, anesthesia, or emotional factors. The most appropriate way is the evaluation of the patient and use of the multitude of signs.
DM: I would fully agree with that. But nobody, I would think, would deny that the horse with colic wasn't in pain. I'm just wondering about this lameness. I have a little girl going to be a greyhound vet, and you can start with an animal that's normal and then you can go to the other end when she's holding her leg off the ground because she can't bend to put down, and then when she's got an obvious limp. And then when you're vetting the dogs before the race, when you're saying I wonder if there is a limp or not, you know, you can actually have a semi-subjective scale going from normal all the way through to holding the leg off the ground. So I'm wondering about these horses, whether really if they don't limp at all, we know horses do limp if they are presumably in pain because it's painful to put their leg down, is it really right they're in pain because they don't step out on that foot. You're assuming they are...
JB: I would have to assume they are. If that was done to my knee I would think I would be in excruciating pain, and they're getting minimal postoperative analgesic at that point.
CS: I think I've been going through this condition personally. There is the acute pain immediately afterwards and then there's the level of pain that exists later. There is a difference between the first day post-op and over the extended recovery period.
DM: Like a twitch.
CS: Right.
JB: Well, the other thing is, to go back to something Vera said, some of these animals are not going to display pain just because of teleological development. The horse that shows pain attracts predators, and it's to their benefit from a survival standpoint to not display that, if at all possible.
Editor: So you're all recommending using analgesics a lot more than they are used, that it wouldn't hurt?
CS: I see very little downside to it, clinically anyway. One of the main problems is monitoring the patient.
DM: Does anybody know of any research that's gone on in horses with colic, for example, where all of us would have no doubt that these animals are in pain. They must get a raised body temperature, heart rate goes up. Has anybody taken any blood samples from them and looked at that?
CS: As far as blood samples for catecholamine determinations and other endocrinic values?
CS: I don't think so. Most of the work that has been done on colic with clinical cases have been rather subjective.
JB: We know that their glucose levels are very high, which presumably would be result of stress.
CS: But also, John, on the glucose levels we have another contributing factor. Many of the horses that are on treatment for colic have received an alpha 2 agonist.
JB: Yeah, that's true too.
CS: This will artificially elevate the glucose tremendously.
DM: How is this glucose elevated, assuming normal is between --
JB: It's been done. It's been published in the normal horse. I can't give you the value right now, but that work was done, published in the American Journal of Veterinary Research and was done about 1978 or 79. It was done by Therman and Stuffy.
DM: I would just be interested to know whether we got a doubling of normal or three or four times.
JB: Yes, yes it's on that order. The thing that's interesting is, in a horse hyperglycemia is not sufficient to cause glucosuria but it is in the cow. The cow develops a tremendous glucosuria, too.
Editor: Let me ask you to spend just a little more time on species differences in feeling pain, for example between a primate, a fish, and a fruit fly, for example?
CS: That's contrast!
Editor: One time at the University of Pennsylvania Veterinary School, I was told back in the '50's that primates and vertebrates feel pain all about the same, which is wrong I realize now hearing you; also that fish feel less and insects still less.
DM: We've done a study, a book called Lives in the Balance, which is worked and talked about at the Institute of Medical Ethics. I got a nice little table there. We played this game. We set a match in the animals coming onto this earth, as it were, and he didn't know anything about this, what sorts of things would you look for? We first said, "Well does it have a receptor system to begin with?" and we found that birds and mammals have it, but insects don't have it. We actually plotted it out through invertebrates such as earthworms, insects and octopus and then vertebrates, fish, amphibian, reptiles, birds and mammals, and we asked various questions. "Does it have a cerebral cortex or another good structure to that? Are the nociceptors connected to these high brain centers? Do they have opiate type receptors? Can you modify the animals response by analgesics? Does the response persist after you've given it noxious stimulus? Do they have ability to learn in order to avoid a noxious stimulus again?" You found there was quite a good correlation for the vertebrates, where the answer to all those things was "yes." With insects, the answer was zero: they didn't have any of those except for opiate receptors.
VB: There are some entomologist who believe that insects can feel pain because they show reaction to hot needles. I don't know if that explains or not. I read some, somewhere, and also about fish, I think there was some study in Holland about hooked carps, who are spitting gas after being caught by hook. They said it might be pain or fear or distress or whatever.
DM: Well, you know in England they just included the octopus vulgaris as part of the protected species, and that's the first invertebrate to be incorporated, and they did that on the basis of the animals anticipating a noxious stimulus so the animals seem to be able to learn that this person coming into the room was going to do something nasty to it, so they hid or they squirted black ink at them as they appeared in the room. So I think they have this sort of cognition, if you like, that we associate with other vertebrates.
EDITOR: I once asked Father Divine where there was the most suffering and pain in the world. He answered, "Where there is the most confusion," so the answer to the human problem might be to get rid of that confusion! Now, with non-human animals, I ask you to tell the world what you think, right now, at this point in time, where there is the most suffering and pain for them, and/or how we might alleviate the most pain and suffering. VB: Give the animals the benefit of the doubt, when you think they hurt, supply analgesia!
PF: Well, I'll restrict myself to pain arising because of human actions or inactions. In terms of sheer numbers, the farm animals should be the focus of our attention. Nevertheless, I think I can generalize and say if every animal undergoing a surgical procedure had an appropriate effective anesthetic and appropriate, effective post-operative pain relief, then we would have taken a big step forward.
JB: I believe most suffering and pain in animals is unrecognized and of a chronic nature associated with disease processes. This chronic pain is usually unrecognized because of its slow onset and subtle signs. Many pathologic conditions in people produce pain. For example, cancer pain, pain of dental disease, arthritis, etc. It is inconceivable to me that these same conditions would not be equally painful in animals. Yet, because of the slow onset of these conditions and the very nature of chronic pain, these painful conditions often go unrecognized or are assumed to be part of the normal aging process. Even when the condition is diagnosed, analgesia is not part of the treatment regimen. I believe that great progress in improving animal well-being will be made as we learn to better evaluate the presence of distress and suffering not only through behavioral signs, but through evaluation of the endocrine and metabolic changes associated with pain. Just as various hematologic and serologic variables can be used to confirm disease processes, certain parameters of endocrine and metabolic function may be related to pain and distress in animals which will allow us to better identify their presence and response to therapy.
EDITOR: Incidentally, after having our pain conversation, I talked with Sasha, a wise old Russian musician about my interest in relieving pain in the world. He told me that he has found animals are much more advanced in dealing with pain, than humans. (See the end of the conversation between Viktor Reinhardt and Helga Tacreiter in this volume re: animals in cold weather). He also reminded me that some species, and individuals within species need physical contact, such as being held, in order to relieve distress. It reminded me of the first of the effective physician's, Hippocrates. I understand that under his statue at a medical school in Paris he is quoted, "The major ingredient in the art of healing is compassion." I have seen animals respond to this genuine closeness as well as humans in finding relief for their pain and strength for their healing.
Dr. Benson has authored or coauthored 82 publications and 15 chapters in textbooks. He is currently researching the effect of medetodmidine on perioperative endocrine responses in dogs.
John has had a life-long association with animals. He has always had pet dogs and cats, including his 11 year-old dachshund, two Pembroke Welsh Corgis, and a Burmese cat. Since 1974, John has specialized in anesthesiology. He has a particular interest in pain and stress in all species of animals.
Vera enjoys spending time at home with her family, dogs, cats,
pigs, chickens, geese, and sheep. She also plays violin and is active in the
field of homeopathy and
acupuncture.
Dr. Flecknell moved to the Medical School at Newcastle upon Tyne to become director of the Comparative Biology Center in 1985 and obtained the Diploma in Laboratory Animal Science of the Royal College of Veterinary Surgeons. His current research is aimed at developing improved methods of pain assessment and alleviation in laboratory species, and the development of new anesthesia techniques. He is currently Chairman of Laboratory Animals Limited, publishers of the journal Laboratory Animals.
Paul enjoys cooking, wind-surfing, and playing computer games.
Dr. Short's long list of honors includes being named to Who's Who in the United States, Commendation for Contributions to Veterinary Medicine from the New York State Veterinary Medical Society in 1990, and receiving the Merit Award for Continuing Education from the New York State Veterinary Medical Society in 1988. He has made over 400 presentations at regional, national and international meetings, and has been published in over 180 scientific publications.
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