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Dog Pain Management: How to Treat Acute vs. Chronic Pain

Like humans, pets experience pain when they are injured or sick. Yet, recognising when our pet is in pain can be difficult to detect as they can’t verbalise it and different species express pain in different ways.

Pet Wellness is… Exceptional postoperative care and pain management.

For National Pet Wellness Month this October, we have teamed up with Dr Maja Drozdzynska from SASH - Small Animal Specialist Hospital to learn more about pain in our pets.

Dr Maja joined the SASH Anaesthesia team in July 2021. She works closely with the Surgery, Neurology, Sports Medicine, and Oncology departments, offering advice and alternative pain-management options based on advanced-imaging techniques to in-hospital patients suffering from acute and chronic pain conditions.

Pain management in veterinary medicine is an important part of the treatment plan. There are many types of pain, each with different treatment options. Evaluating the extent of the pain can help with the diagnosis and provide the plan for what further treatments the patient is given. Effective pain management is the key to overall better outcomes for our pets.

What are the Different Types of Pain?

Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage. To perceive pain, a series of events take place. First, painful stimuli is detected by specific nerve endings, which then passes this information onto the spinal cord and brain.

The role of the anaesthetists is to use various techniques and medications to block or decrease the intensity of these signals reaching the brain. Although evolutionarily pain has had adaptive and protective function, when it's too severe or is long lasting, it may lead to pathological states that severely affect the animal’s welfare and their quality of life.

1. Acute Pain

Acute pain is the most common type of pain; it is the noticeable and often predictable response to an adverse event. This can be in the form of a twist, burn or crush, or tissue damage in the form of a bruise, wound or surgical incisions. Typically, acute pain improves when the inflammation that follows the initial injury, subsides. Though the healing time can last up to three months.

2. Chronic Pain

Chronic pain is persistent pain that lasts beyond the expected tissue healing time.

3. Visceral Pain

Visceral pain is associated with malfunction or surgical stimulation of internal organs, for example pain in the liver, stomach, spleen or lungs. This type of pain is difficult to localise and describe. There is normally poor correlation between the degree of tissue damage and the intensity of pain.

4. Somatic Pain

Somatic pain is associated with the damage, injury or inflammation of the bones, joints, tendons, muscles, or skin. Depending on if the injury is superficial or deep, it may be well or poorly defined. However, there is always a good correlation between the degree of tissue damage and intensity of somatic pain.

5. Neuropathic Pain

Neuropathic pain is caused by a lesion in central or peripheral nervous system, and it is associated with abnormal function of the somatosensory system.

6. Cancer Pain

Cancer pain can be acute, chronic, or acute on chronic (when sudden exaggeration of pain condition appears). Depending on the localisation of the primary lesion, cancer pain can possess the components of visceral, somatic, or neuropathic pain.

What are the Signs of Pain in Pets?

As pet owners, it is important to identify the key signs to assess if our pet is in pain so that if needed, clinical intervention can be sought, and a pain management plan can be provided to prevent further distress. 

Unfortunately, physiological changes like an increased heart rate, increased respiratory rate ore increased blood pressure are not specific enough to pain itself to be unique indicators of pain in pets. Some of these changes can also be associated with anxiety, stress or infection.

Therefore, most of the pain scales in animals are based on the behavioural factors.

Behavioural signs of pain can be include:

✔️ Shaking
✔️ Loss of appetite
✔️ Reluctant to move
✔️ Lameness or limping
✔️ Reluctant to play or interact/hiding
✔️ Sullen temperament (lethargy)
✔️ Restlessness
✔️ Flattened ears
✔️ Squinted eyes
✔️ Tense muzzle
✔️ Flinching
✔️ Hunched posture
✔️ Reaction to palpation of painful area

Understanding the Veterinary Anaesthetist's role within the Specialist Hospital

Anaesthesia means controlled and temporary loss of awareness whereas analgesia means lack of pain. 

Dr Maja Drozdzynska in action
Veterinary Anaesthesia is one of very few specialities where the training is done across many veterinary species (dogs, cats, horses, exotic animals). These are veterinarians who undertook a further four years of training in anaesthesia and analgesia.

It is the anaesthetist’s role is to provide the plan for pain management while considering underlying health conditions of the patient such as heart, liver or kidney diseases as well as certain breed and species predispositions. 

Anaesthetists aim to avoid anaesthetic complications and increase anaesthetic safety. My team and I also work with the other specialist departments as they develop their treatment plans. Whilst the other departments look to treat the issue at stake, anaesthetists look at the overall wellbeing of the animal.

In my team, we conduct a clinical examination of each patient to determine the best pain management technique for their treatment. 

One of the most well-known ways to manage pain is to put the patient under general anaesthesia, otherwise known as putting the patient to sleep whilst they are undergoing treatment. 

In veterinary medicine, we may use anaesthesia and sedation for some non-invasive procedures. For example, if a patient needs a CT or MRI, it is critical that there is minimal movement otherwise the image quality is affected, and interpretation becomes difficult.

Advanced Pain Management Techniques:

SASH has a team of five Specialists in Anaesthesia,
supported by dedicated Anaesthesia Interns
 & Anaesthesia Nurses

Veterinary anaesthetists have a thorough knowledge of different techniques to manage acute and chronic pain treatment. 

With the plan prepared by the anaesthetist, these techniques can be used in insolation or combination through what is known as a multimodal approach

Multimodal techniques aim to maximise the capabilities of each of the techniques. In essence, we use more techniques at lower levels to minimise the number of drugs used (and their possible side effects) while maximising the intended outcome.

1. Ultrasound-guided and nerve-stimulation-guided locoregional techniques

We can minimise the amount of pain to a certain spot by locating it using ultrasound and putting in a nerve block to target that area specifically. These techniques allow anaesthetists the ability to get as close as possible to the target area, visualise the nerve and its roots and accurately inject the local anaesthetic, therefore reducing the dose needed.

SASH Anaesthetists using a Sonosite portable ultrasound machine

2. Epidural blocks

An epidural is an injection into the space around the spinal cord which provides temporary loss of feeling. Anaesthetists can place indwelling epidural catheters for continuous pain control. This allows the patient to receive direct constant infusions of pain relief into the central nervous system.

3. Intravenous pain relief

All patients undergoing general anaesthesia are given an intravenous (into the vein) catheter so that an infusion of direct pain medication can be given at any time.

4. Post Operative care

Another role of the anaesthetist is to stabilise patients before and during the anaesthetic period. That may include administration of the drugs that stabilise blood pressure, treat arrythmias, use of advanced ventilators or giving blood products. 
When a patient is pain free during the recovery after surgery, wound healing is optimised.
Cody's Story
Cody is a nine-year-old Labrador who was diagnosed with osteo-aggressive mesenchymal tumour of his right chest wall.

The diagnosis was made, based on the computed tomography (CT) and cytology (examination of cells under the microscope) of a needle biopsy of the mass. 

The mass was affecting the 8th, 9th, 10th and 11th ribs. The partial resection of the chest wall, including four ribs resection, was performed as a surgical treatment of choice. 

The chest wall surgeries are potentially, one of the most painful procedures because they are composed of few different types of pain like: neuropathic pain (caused by surgical manipulation of the intercostal nerves), somatic pain (from the dissection of the muscle layers), inflammatory pain (because all surgical intervention will create inflammatory process) and visceral pain. 

Moreover, the chest wall muscles must be functional during the recovery period because otherwise respiratory system will be compromised (inadequate oxygenation). 

It has been shown, both in human medicine and in experimental animal studies, that ineffective treatment of acute perioperative pain associated with chest surgeries may lead to chronic and pathological pain conditions like hyperalgesia [TH1] or allodynia [TH2]. Hence, the importance of providing effective pain control for this kind of surgery.

Perioperative analgesia (pain control) was provided by multimodal approach. Multimodal analgesia is a synergistic use of a few pain-relief medications that have different mechanisms of action. 

The aim of this approach is to maximise pain relief and minimize the dose and side effects of individual drugs. 

In Cody's case it was combined use of methadone (good for visceral pain), medetomidine (good for somatic pain), meloxicam (effective for inflammatory pain) and gabapentin (effective for neuropathic pain). 

However, the local block performed under ultrasound guidance called Erector Spinae Plane Block 
[TH3], contributed the most to Cody's good perioperative pain control. This procedure allowed for a complete blockade of pain transmission from the site of surgery to the patient’s brain. 

This is why locoregional anaesthesia is the most effective way of providing pain control.

Because Cody didn't have any reaction to surgical stimulation, the Erector Spinae Plane Catheter was placed under ultrasound guidance, after the surgery, for intermittent delivery of local anaesthetics in the postoperative period. 

That gave excellent results: Cody was eating within few hours after surgery, opioids were discontinued 24 hours after the surgery and he was discharged home on oral medications only, 48 hours after major surgery.

written by Dr Maja Drozdzynska from SASH, September 2022 for Australian Dog Lover (all rights reserved).

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About Dr Maja Drozdzynska

Dr Maja completed her veterinary medicine degree at Wroclaw University of Environmental and Life Sciences in Poland. After graduation, she worked in the Surgery department at the same University where she developed an interest and gained initial experience in Anaesthesia and Emergency Critical Care Medicine. After two years, she decided to continue her career abroad. She completed an Anaesthesia Internship at the University of Liverpool and a speciality residency training program in Veterinary Anaesthesia and Pain Management (Analgesia) at the Royal Veterinary College, London (RVC). She obtained a master’s degree in Veterinary Sciences from the RVC in 2016 and passed her European Speciality Exam in Veterinary Anaesthesia and Analgesia in 2017.

During her residency, her main research interest was effective management of acute perioperative pain by application of more advanced ultrasound-guided loco-regional techniques. During this time, together with her research colleagues, she described and developed two new ultrasound-guided blocks for dogs (Ultrasound-guided serratus plane block & subcostal approach to TAP block). During her residency at RVC, she was also part of the large research group composed of human cardio-thoracic surgeons, cardiopulmonary perfusionists and veterinary anaesthetists who were working together in order to increase the viability of hearts transplanted from the patients who suffered circulatory death. This experience enabled her to anaesthetise dogs for open heart (valve replacement surgeries) carried out at the Queen Mother Hospital for Animals at the Royal Veterinary College.

After completing her residency, Maja has had the great pleasure of working in a large and very busy private multi-disciplinary hospital (Dick White Referrals) in England where she continued her clinical research, trained and supervised a new generation of veterinary anaesthetists (residents) and further mastered her anaesthesia and teamwork skills.

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