Management of chronic pain Flashcards
Define pain
An unpleasant sensory and emotional experience, associated with actual tissue damage, or described in terms of such damage
Describe the 2 main categories of pain
Acute and chronic pain
Acute pain:
- Usually obvious tissue damage
- Protective function
- Increased nervous system activity
- Pain resolves upon healing
- e.g. pain following trauma or surgery, burns pain, headache, pain of trigeminal neuralgia, pain of major cardiac events, colic pain
Chronic pain:
- This is Pain beyond expected period of healing which no longer serves a useful purpose
- Changes in pain signalling and detection
- Degrades health and function
What are some of the different scales for measuring pain ?
Verbal rating scale:
- no pain = 0, mild = 1, moderate = 2 or severe = 3
Numeric rating scales:
- 0-10 on 11 point scale (or 0-100 on 101 point scale)
- 0 = no pain 10 (100) = worse pain imaginable
Visual analogue scale:
- Analogue goes from no pain to worst pain
Other than how the patient rates/ describes the pain what are some of the other factors which might suggest someone is in pain ?
behavioral observations
- grimacing, rigid body posture, limping, frowning or crying
physiologic responses:
- increased blood pressure and pulse rate?
Note these are not sensitive nor specific
What are the 2 main types of pain?
- Nociceptive pain
- Neuropathic pain
Define nocieptive pain and state what is it caused by
This is an appropriate physiologic response to painful stimuli via an intact nervous system
It is caused by damage to body tissue and usually described as a sharp, aching, or throbbing pain.
This kind of pain can be due to benign pathology; or by tumors or cancer cells that are growing larger and crowding other body parts near the cancer site.
For example, the damaged areas could include the skin, muscles, bones, or other tissues. The nociceptors can also detect chemical and thermal damage. Chemical damage is caused by contact with toxic or hazardous chemicals. Exposure to extremely hot or cold temperatures leads to thermal damage.
Injuries that cause nociceptive pain include:
- bruises
- burns
- fractures
- pain caused by overuse or joint damage, such as arthritis or sprains
Nociceptive pain may also be caused by cancer spreading to the bones, muscles, or joints, or that causes the blockage of an organ or blood vessels.
Define and describe neuropathic pain
An inappropriate response caused by a dysfuntion in the nervous system i.e. when there is actual nerve damage.
Nutritional imbalance, alcoholism, toxins, infections or auto-immunity can all damage this pathway and cause pain. Neuropathic pain can also be caused by a cancer tumor pressing on a nerve or a group of nerves.
Common causes:
- Shingles, post herpetic neuralgia
- Surgery
- Trauma
- Diabetic neuropathy
- Amputation
- Many of unknown origin
Describe the typical presentation of neuropathic pain
Description – burning, shooting, tingling, sensitivity
Examination – sensory changes:
- Allodynia -pain from a stimulus that is not normally painful, eg. Cotton wool
- Hyperalgesia -more pain than expected from a painful stimulus, eg. Pin prick
What can nociceptive pain be subdivided into ?
Can be subdivided into somatic (affecting bones and or/soft tissues) and visceral (affecting the gut and/or organs)
Describe the WHO analgesic ladder in the management of pain ?
- Non-opioid analgesics (e.g. NSAIDs, paracetamol)
- Opioid analgesics (e.g. tramadol, codeine, morphine, oxycodone)
Adjuvants:
- Antidepressants (e.g. amytriptyline, duloxetine)
- Anticonvulsants (e.g. gabapentin, pregabalin)
- Topical analgesics (e.g. capsaicin, lidocaine 5% plaster)
What are the main types of non-opioid analgesics (NSAIDs) and what type of pain are they mainly effective for/ used in?
Aspirin, ibuprofen, paracetomol
Nociceptive pain
What type of pain is aspirin and ibuprofen mainly used for and what is their mechanism of action ?
- Mechanism of action is inhibition of cyclooxygenase (COX) and also decreases prostagladin synthesis
- Most inhibit COX-1 & 2
What are the main side effects of aspirin and ibuprofen ?
- These include GI irritation and risk of GI bleeding, renal toxicity and potential drug -drug interactions
- Some selective COX -2 inhibitors have also been found to have cardiovascular side effects such as myocardial infarction, stroke and elevation of blood pressure
NSAIDs must be used with caution in older patients and those with impaired renal function and heart failure
What is the mechanism of action of paracetamol and what is its main side effect/ risk?
- It is a central prostaglandin inhibitor, the rest of its mechanism is unknown
- It is associated with risk of toxic liver damage at high doses
What are the weak and strong opioids?
- Weak opioids e.g. tramadol and codeine
- Strong opiods e.g. morphine and oxycodone
What type of pain are opioids mainly used in and when?
- Mainly used in nociceptive pain when NSAIDs become ineffective in managing pain
- The mainstay of use of opioids is in management of postoperative and cancer pain
- They have limited use in neuropathic pain
Describe the mechanism of action of opioids
- Mainly on the central nervous system. They are predominantly agonists of morphine (mu) receptors, which are present in the brain and spinal cord.
- In the brain, receptor activation in the limbic system appears to affect the emotional response to pain - although the pain remains, it doesn’t hurt anymore. By activating receptors in other areas of the brain, opiods also affect the descending pathways
- of pain inhibition.
- Also reduce ascending pain signal transmission in the spinal cord
What are the main side effects of opioids ?
- Nausea and vomiting
- Constipation
- Dizziness or vertigo
- Somnolence
- Dry skin, puritis
What is the nice guidelines managemeant of neuropathic pain ?
For all neuropathic pain (except trigeminal neuralgia):
Offer a choice of amitriptyline, duloxetine, gabapentin or pregabalin as initial treatment for neuropathic pain (except for trigeminal neuralgia)
What are the 2 main TCA’s and their mechanism of action ?
Amitiptyline and Imiparmine
What is the mechanism of action of TCA’s?
Inhibit neuronal reuptake of noradrenaline and serotonin (5-HT)
What type of pain may TCA’s be useful in the management of ?
- Neuropathic pain
- Complex regional pain syndrome
- Tension headache
What are the side effects of TCA’s?
- Constipation
- Dry mouth
- Somnolence (sedation)
- Abnormalities in heart rate or rhythm
- Insomnia
- Increased appetite
What are the main anti-convulsant drugs used in the management of pain and what type of pain are they used for?
Carbamazepine, Gapapentin and Pregabalin
Used for neuropathic pain esp shooting neuropathic pain (e.g. trigeminal neuralgia, postherpetic and other neuralgias).
For neuropathic pain which of the first line options is prob the one to use first ?
Gabapentin
What is the mechanism of action for Carbamazepine, Gabapentin and Pregabalin ?
- Carbamazepine - blocks sodium and calcium channels
- Gabapentin - It binds to a subunit of presynaptic voltage-dependent Ca2+ channels. The binding reaction reduces release of pre-synaptic transmitters
- Pregabalin - interacting with special N-type calcium channels
What are the main side effects associated with anti-convulsants ?
- Sedation
- Dizziness
- Ataxia
- Peripheral oedema
- Nausea
- Weight gain
What are the main categories of topical analgesics ?
- Rubefacients
- capsaicin
- NSAIDs: diclofenac, felbinac, ibuprofen etc
- Lidocaine plaster
- Levomenthol
How do topical analgesics work and what are their main side effects ?
Topical analgesics reduce pain impulses transmitted by:
- A-delta-fibres
- C-fibres
Main side effects are localised application site reactions:
- Rash
- Pruritus
- Erythema
What are the non-pharmacological therapies for pain management ?
Aim to work in conjunction with and alongside conventional treatments i.e. pharmacological management, and can aid pain control
Physical therapy, where there is a direct intervention on the body
- Massage, Aromatherapy, Reflexology, Acupuncture
Mind therapy, where the focus is on the psychological aspect of disease and assisting coping mechanisms
- Relaxation, Breathing Techniques, Visualisation, Art, Music Therapies,
- Reiki, Stress and anger management, Sleep hygiene, Activity pacing,
- Hypnosis, Biofeedback, Mindfulness
Psychological therapy:
Cognitive behavioural therapy
- Helps people challenge/modify negative thoughts, feelings and behaviour
- Encourages people to take an active part in changing the outcome of a situation,
- the emotional response to a situation and the physical response to it
Solution focused brief therapy - focuses on what patients would like to achieve in the present or the future
