Melissa Kaplan's
Herp Care Collection
Last updated January 1, 2014

Perception of Pain in Reptiles

©1999 Roger Klingenberg DVM, The Vivarium 10(4):45-49

For those of you who haven't had the pleasure of a general anesthetic and major surgery, try to imagine the following scenario:

It's time to wake up but your eyelids fail. Perhaps you should sit up, but firm hands that belong to nothing are restraining you. As your eyelids part, ever so slightly, bright lights and noise assault your brain with a physicality you would have thought impossible. This isn't good. Close eyes and fade away. Another glimpse? Ohmygod, who is that grotesquely large and distorted person staring at you? Time to fade again.

With lurches and lapses, reality begins to set in and you return to earth. Those malevolent beasts turn out to be your nurses, doctors, and loved ones. You're going to be alright.

Wait! You're awake, but what is that awful throbbing in your lower abdomen? It feels like someone just peeled off your flesh, sprinkled it with salt, and hired little gremlins to jump up and down on the raw tissue. Oh, yeah, we forgot to tell you that while your loved ones paid for your anesthetic and surgery, they decided to save a little money on pain control.

Ridiculous? These things don't happen? They don't often happen to us, but how about our pets? The advances made in veterinary techniques for sedation, anesthesia and surgery are truly impressive. However, even in traditional (dog and cat) pet medicine, pain prevention and treatment is still one of the most ignored and underused technologies we have. Veterinary medicine has recently recognized this shortfall and is scrambling to correct it, but part of the equation is the demand for these services from you, the client. To better understand your options, we need to further understand the problem.

Will the Procedure Hurt?
In my practice, I encounter little resistance when persuading a client of the benefit providing two analgesic (pain relieving) injections, to be followed by oral analgesic medication in the 48 hours following their cats declaw procedure. Yet I often encounter tremendous resistance from the same owners when planning for post-op pain medications for an iguana needing two toes amputated because of trauma. If a client wonders aloud if the declaw will hurt the cat, I volunteer to smack each of their fingertips with a ball peen hammer. For an iguana, maybe I should administer two smacks per toe. Rather than hammering my clients, however, I ask them to picture similar incidents in their own life - stubbing a toe, for example. Have they ever noticed how an injured toe or finger throbs because of the extremely rich nerve supply in our appendages?

Bottom line - surgical procedures hurt, some more than others. Trust your veterinarian to help you understand why some procedures are more painful than others and what you can do about it.

Reptiles Don't Feel Pain...Do They?
Perhaps veterinarians and health care scientists have created the perception that reptiles don't feel pain. Historically, we just threw the poor cold-blooded beasts into the refrigerator until they were immobile enough to work on. We deluded ourselves that since they didn't respond much, it must not hurt much. Lack of response is not the same thing as lack of pain. Refrigerating herps is a practice that we now realize to be barbaric and counter-productive - it should never be used. Indeed, we now keep reptiles very warm during surgery, playing the patient on recirculating heating pads for procedures and in warm incubators post-op. We want the reptile's physiological processes at their peak to optimize immune response, drug metabolism, and healing.

We don't know nearly enough about pain perception in reptiles. For instance, why is the incidence of thermal burns so high? Most reptile veterinarians have seen literally hundreds of third- and fourth-degree burns from malfunctioning hot rocks and poorly placed basking lights. One theory is that reptiles are so primitive that, by the time the burn is perceived, they don't know the appropriate response. While I don't like this theory, there are some components which may be accurate. To begin with, the reptile was able to perceive warmth as was attracted to the hot rock. Why then did it fail to perceive that the hot rock was becoming too hot? This is an alien thought for us, as we have a well-developed withdrawal reflex. If we touch anything perceived to be too hot, we withdraw immediately and reflexively, without further mental processing. This is such a strong reflex that you would be hard pressed to force yourself to touch such a hot object.

One theory is that the nerve endings (receptors) that are able to sense heat are different from those that sense pain. Perhaps the pain receptors are poorly developed because, during evolution, objects hot enough to burn are uncommon in the wild and such receptors therefore aren't needed. One would then lack a burn/pain withdrawal reflex.

Another theory is based more on learning than evolution. If the reptile doesn't associate touching an object with a certain response, perhaps it doesn't realize that moving will help. Perhaps this "learning association" theory is at work with ball pythons and boas that remain passive while a rodent perches on its coils and chews away at their flesh and bones. Could these snakes have learned that rodents are prey but don't associate them with pain?

There is a lot to learn but when all is said and done, we know that reptiles perceive pain. This is a given. What then can be done to control this pain?

I have to pay for pain relief?
This isn't a plot by veterinarians to empty your pockets and fill ours. Although some pharmaceuticals are developed as very inexpensive drugs, this doesn't always translate into cheap medications for the end user. An interesting example would be the morphine family of drugs. Morphine is a painkiller which is used as a reference point by drug developers, whose new drug may be touted as being twice as strong as morphine. Morphine has been around for hundreds of years and can be produced for an extremely low cost. However, because layers of government bureaucrats, the cost can become considerable. The Food and Drug Administration (FDA) ensure that a drug is produced under certified and sterile conditions. Once made, the drug is then controlled by the Drug Enforcement Agency (DEA) and is sent to suppliers who have to keep it under lock and key, record the whereabouts of every tablet and cc, and ship it separate from other orders to the veterinarians who ordered it.

The veterinarian can obtain controlled drugs only if licensed by the DEA (separate from the state license to practice veterinary medicine) and, once their possession, the drugs must be kept under lock and key, with maintenance of strict records of usage. If records are not properly maintained, a veterinarian risks loss of the controlled substance and license, as well as fines and other punishments.

Don't ask your veterinarian to send home controlled substances for use on your reptiles. In chronic cases, prescriptions for oral medications may be appropriate and can be provided. All in all, the narcotic family of drugs is dispensed at fairly reasonable costs, considering the monumental hassle of dealing with these drugs. Other groups of drugs for pain control in reptiles include the synthetic narcotics and NSAIDS (non-steroidal anti-inflammatory drugs).

Why Hospitalization?
I sincerely believe that a reptile's comfort is also greatly influenced by its environment. This is why I frequently suggest hospitalization, up to several days depending o the procedure that was performed. Am I suggesting that your reptile would be happier in my hospital instead of the cage you made for it? Not happier, but likely more comfortable. Let's examine this. As an example, lets use a female green iguana who has just been through a hysterectomy to remove follicles that wouldn't progress to form eggs yet wouldn't reabsorb either. She hasn't eaten for two weeks prior to the life-saving surgery.

Her surgery goes well and she awakens in her hospital cage. Remember back to the very beginning of this article, and the confusion experienced coming out of anesthesia? Let's dim the lighting and cover up the cage sides to minimize the stimulation she has to deal with. The cat is at 85F (29C) with an optional heat strip further back in the cage, in case she wants localized heat, which often feels good on an incision. You might argue that the iguana would want to climb up on her favorite perch if she were at home, but remember that most people coming out of anesthesia wouldn't be allowed to climb branches either. As our patient slowly becomes more alert and evaluates her surroundings, we are likely to see some of the early signs of pain: an arched back, tucked up abdomen, resting the abdomen on bowls or folded towels, tail slapping, rolling, or pressing the head into a corner. In response to these behaviors, we might administer an injectable dose of a synthetic narcotic such as butorphanol which will cause visible signs of relief within 15-20 minutes. Pain medication in the form of injections and later as an oral dose are based on each individual's experience, just as with human patients.

As our patient becomes more awake and relaxed, food and water can be offered in simple, shallow containers that require little effort to reach by the reptile. Let's say that our patient is so weak from enduring follicle stasis for two or more weeks and then having undergone surgery, that she won't eat or drink. This is easily remedied by involuntary feeding with oral slurries and building up gradually to more solid offerings, and also by giving fluids and electrolytes by injection. In more severe cases, an intraosseous (within the bone) catheter can be placed for continuous fluid administration. Once rallying, we can add perches to the cage and cater to her needs as she prefers. Again, it's not home but I sincerely believe that hospitalization is essential for maximal comfort and initial recovery. Don't worry, you'll have plenty to contribute when your patient is discharged.

Conclusion
We all enjoy and value our reptiles: many of us will go the next step and say we love our reptiles. Pets are pets and each owner can place the level of attachment to them as they see fit. In the greater scheme of things, who is to argue that an anole is any less valuable or treasured than someone else's Labrador? I sincerely hope that your reptile enjoys good health and won't need any diagnostic procedures or surgeries. Rest assured that your reptile veterinarians are working very hard to make the latest technology and techniques available to your reptile. This may involve hospitalization, but we now understand why this is required. So the next time your veterinarian discusses expenses that you're not familiar with, remember that our goals are the same - to resolve the health problems in a caring and less painful manner. Get explanations and keep working together.

Suggested Reading:

Bennett, R.A. 1998. Pain and analgesia in reptiles and amphibians. Proc. Assoc. Rept. Amphib. Vet., Kansas City, pp. 1-5.

Lawton, M.P.C. 1999. Management after surgery. Proc. North Amer. Vet. Conf. Orlando, p. 782.

Article Sidebars:

Behaviors your reptile may show when in pain:

• Reluctance to move
• Lameness, difficulty moving
• Abdominal splinting (tucking)
• Aggression, protection of painful sites
• Avoidance behavior
• Depression or anxiety
• Failure to eat

Photo Captions
Pg. 44. This female iguana was spayed 24 hours earlier. Rather than touch her sore abdomen to the bottom of the cage, the iguana stood in place as long as she could, then discovered she could lay on top of her water dish, placing less pressure on the incision. Within 30 minutes of an injection of butorphanol, a synthetic narcotic, she moved away from the dish and rested her abdomen on the cage bottom. The iguana began eating about two hours after administration of pain medication. Once feeding, pain can be controlled with oral narcotics or non-steroidal anti-inflammatories as needed.

Pg. 45, top: A cagemate bit the rear leg of this green iguana which resulted in a swollen, infected leg. The iguana dragged its leg, preferring not to move more than necessary. Pain management in this case included injections of a narcotic (butorphanol) and a local anesthetic (lidocaine), effectively numbing the leg before lancing, draining and flushing the limb tissue. The effects of the injections lingered for several hours and only one oral dose of pain medication was required before the lizard was using the leg and eating well.

Pg. 45, bottom: Rodent bites from minor nips to the devastating wounds demonstrated in these two cases. It is difficult to imagine why the snakes allowed themselves to be attacked without stopping the rodents. Were the snakes too cold to respond? Had the snakes not learned that rodents are capable of pain, so didn't associate the rodents with the tissue damage and pain? These are questions we can't answer, but pain management should be an important part of the medical management of such cases.

Pg 47, top left: This juvenile iguana's front feet had to be amputated because of tissue damage from a defective hot rock. This case is another example of a reptile not responding to painful stimuli in a manner which we would expect, i.e., pulling away before tissue damage could occur. Burns can be very debilitating and warrant the use of pain medication.

Pg. 47, top right: Reptile veterinarians routinely employ heated pads during and after surgery to promote normal physiological processes. Not only is warmth safer for the patient but it also reduces recovery times, enhancing tissue healing and stimulating the immune system.