Pain assessment (Proceedings)

We already know that the way we each perceive pain will be different depending on our past experiences. The way we respond to that pain also varies from person to person. These two points make recognizing and treating pain difficult, especially in regards to our veterinary patients. The International Association for the Study of Pain (IASP) has released a new definition for pain recently. "An unpleasant sensory and emotional experience associated with actual or potential tissue damage." (e.g. a vaccine or a broken leg). They go on to say "The inability to communicate verbally does not negate the possibility that an individual is experiencing pain." This was written with regards to human patients in comas, but we can transfer this to our veterinary patients.

Physiology

A noxious stimulus (like intense heat) activates receptors called nociceptors. These nociceptors send impulses through nerve fibers to the brain where the impulse is processed and a reaction is formulated. Nerve fibers can be found in skin, SQ tissues, periosteum, joints, muscles, and viscera. Nociceptive stimulation causes hyperventilation (panting), an increased secretion of catecholamines (tachycardia and hypertension), and an increased stress response (hyperglycemia, increased blood lactate, and increased ketones).

Patient Assessment

Pain is grouped into one of two basic categories, acute or chronic. Acute pain typically results from surgery or trauma, while chronic pain could be from osteoarthritis, cancer, or glaucoma. Untreated pain can cause delayed or poor wound healing, increased incidence of infection or sepsis, cardiovascular stress, increased incidence of tumor metastasis, and prolonged convalescence (longer hospitalization).

When assessing a patient for pain, there are many different things to consider. For example, what is the species of the patient? Cats react differently to pain than dogs do, they tend to hide their pain more and can sometimes be more difficult to treat.

Initial assessment should be done away from the patient, ideally outside the run or cage. Questions that can be best asked at this time are is the patient positioned oddly in the cage and is the posture and movement normal. Is the patient vocalizing, is it only at certain times?, is the patient's facial expression normal?

Looking at the vitals (TPR and BP) can help if the patient has an increase in catecholamine secretion, their heart rate and blood pressure will probably be up. Once touching the patient, does he react to palpation? To palpate a patient, make sure that either you can or that there is someone around to restrain the patient if necessary. Restraint should be mild because you do want to be able to see if the patient will react. Always start with a non-painful area to gauge patient's reaction, begin by applying mild to moderate pressure. Slowly move toward the potentially painful area continuing to apply mild to moderate pressure. If the patient has the same reaction to a non-painful area as he does a potentially painful one, he is probably not painful.

When reading through the record, one question to ask is whether or not this patient has received any analgesia. If he has, what, how much, and when was the last dose? If additional treatment is given, documentation about what affect it had is important.

In human medicine, patients are asked their level of pain on a scale of 1 – 10. In veterinary medicine pain scoring is dependent upon the observer and the species. There are different scales available, some are veterinary and some are human, these are very subjective. Since different species respond to pain in different ways, some scales are species specific.

Intra-Op Pain Assessment

During anesthesia it is sometimes more difficult to tell if a patient is painful. On some occasions it appears that the patient is light. This is because under anesthesia we rely on physiological signs. A patient's heart rate, blood pressure, and respiratory rate will all go up in response to a release of catecholamines. Due to the increase in vitals, the patient will often get light and may even move. If not properly treated the patient may continue to have a high heart rate, blood pressure, and or respiratory rate despite a deeper plane of anesthesia. Other than the most obvious cause of intra-operative pain (surgical stimulation), large bladders, painful hips, and the positioning of the front legs (when tied forward) are also significant.

When trying to determine whether a patient may be painful under anesthesia, a look at the patient's analgesic plan is necessary. What has he gotten already? How long ago was that? Is he currently on a CRI containing analgesia? How much time is left for the surgery/procedure? If the procedure is almost finished, treatment may not be necessary until after patient is extubated.

Post-Op Pain Assessment

This section contains many pictures and videos of patient assessment post-operatively.

At Home Pain Assessment

Creating a plan for clients to assess their pet's pain is based largely upon client communication. Knowing that the client understands what is expected of them, what to expect from the animal, and when to call with concerns are just the start. Clients also need to know what the current treatment plan is, when it may be necessary to have their pet reassessed by the veterinary team, and most importantly what they are looking for.

Discussions with clients should cover what to look for in terms of their animal's positioning and posturing, and how to determine if they are painful to the touch. Owners can watch for their animal's "normal" behavior whether it's getting in and out of the car, up and down stairs, or on and off counters (for cats). Cats have a tendency to hide when they are painful, and clients should know to watch for this. Most animals will not eat as well when they are painful, clients should watch for their pet to have a "normal" appetite. Dogs being such social creatures typically want to play a lot, the owner can note whether their dog is playing like always or a little withdrawn. Explaining to a client why it is necessary for them to notice whether the drugs helped their pet or not is part of good client communication. When doctors send clients home with medications labeled "give as needed", clients will sometimes misinterpret what that means. If the only effect of the drugs is to make them zombie-like, continuation is probably not in the pet's best interest.