Anaesthetics: Essential Pain Management Flashcards
What is pain?
Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage
What are the physical benefits for the patient if we treat pain?
- Improved sleep, better appetite
- Fewer medical complications (e.g. heart attack, pneumonia)
What are the psychological benefits for the patient if we treat pain?
- Reduced suffering
- Less depression, anxiety
What are the benefits for the family if we treat pain?
- Improved functioning as a family member (e.g. as a father or mother)
- Able to keep working
What are the benefits for society if we treat pain?
- Lower health costs (e.g. hospital stay)
- Able to contribute to the community
How can pain be classified?
- Duration
- Acute
- Chronic Cause
- Cancer / Non-cancer
- Mechanism
- Nociceptive
- Neuropathic
Describe nociceptive pain
- Sharp +/- dull
- Well localised
When does nociceptive pain occur?
When there is obvious tissue injury or illness
What is the function of nociceptive pain?
It has a protective function and is also referred to as inflammatory pain
When does neuropathic pain occur?
When there is nervous system damage or abnormality
Describe neuropathic pain
- Burning, shooting +/- paraesthesia
- Not well localised
- Does not have a protective function
What are the 4 steps in the physiology of pain?
- Periphery
- Spinal cord
- Brain
- Modulation
What physiology occurs in the periphery during the pain response?
- Tissue injury
- Release of chemicals e.g. prostaglandins, substance P
- Stimulation of pain receptors (nociceptors)
- Signal travels in Aδ or C nerve to spinal cord
What physiology occurs in the spinal cord during the pain response?
- Dorsal horn is the first relay station
- Aδ or C nerve synapses with second nerve
- Second nerve travels up contralateral side of spinal cord
What physiology occurs in the brain during the pain response?
- Thalamus is the second relay station
- Connections to many parts of the brain including cortex, limbic system and brainstem
- Pain perception occurs in the cortex
What physiology occurs during modulation in the pain response?
- Descending pathway from brain to dorsal horn
- Usually decreases pain signal
What is the gate theory?
Stimulation by non-noxious input is able to suppress pain by closing the ‘gate’ to painful input preventing pain sensation from travelling to the cortex
Give examples of neuropathic pain
- Nerve trauma, diabetic pain (damage)
- Fibromyalgia, chronic tension headache (dysfunction)
What is the pathology behind neuropathic pain?
- Increased receptor numbers
- Abnormal sensitisation of nerves (peripheral and central)
- Chemical changes in the dorsal horn
- Loss of normal inhibitory modulation
What non-drug treatments can be used to act at the periphery?
- Rest
- Ice
- Compression
- Elevation
What drugs can be used to act at the periphery?
- NSAIDs
- Local anaesthetics
What non-drug treatments can be used to act at the spinal cord?
- Acupuncture
- Massage
- TENS
What drugs can be used to act at the spinal cord?
- Local anaesthetics
- Opioids
- Ketamine
What non-drug treatment can be used to act at the brain?
Psychological therapies
What drugs can be used to act on the brain?
- Paracetamol
- Opioids
- Amitriptyline
What route of drug delivery is preferred?
Oral
What are the advantages of paracetamol?
- Cheap, safe
- Can be given orally, rectally or intravenously
What is the disadvantage of paracetamol?
Liver damage in overdose
What is paracetamol good for?
Mild pain (by itself) or moderate to severe pain (with other drugs)
Give examples of NSAIDs
- Aspirin
- Ibuprofen
- Diclofenac
What are the advantages of NSAIDs?
- Cheap
- Generally safe
What is the disadvantage of NSAIDs?
- GI and renal side effects
- Can cause exacerbation of asthma
What are NSAIDs good for?
Nociceptive pain
What are the advantages of codeine?
- Cheap
- Safe
What is codeine good for?
Mild to moderate acute nociceptive pain
What are the disadvantages of codeine?
- Can cause constipation, drowsiness
- Not good for chronic pain - addictive
What are the advantages of morphine?
- Cheap, generally safe
- Can be given IV, IM, SC
- Effective if given regularly
What is morphine good for?
- Moderate to severe nociceptive pain (i.e. post-op pain)
- Chronic cancer pain
What are the disadvantages of morphine?
- Constipation
- Respiratory depression in high dose
- Misunderstandings about addiction
- Controlled drug
How does the oral dose of morphine differ from the IV/IM/SC dose?
Oral dose is 2-3 times that of IV/IM/SC dose
What is amitriptyline?
Tricyclic antidepressant
How does amitriptyline work?
Increases descending inhibitory signals
What are the advantages of amitriptyline?
- Cheap, safe in low dose
- Good for neuropathic pain
- Also treats depression and poor sleep
What are the disadvantages of amitriptyline?
Anti-cholinergic side effects (i.e. glaucoma, urinary retention)
Give examples of anticonvulsants that can be used for pain.
- Gabapentin (neurotonin)
- Carbamazepine (tegretol)
- Sodium valproate (epilim)
Why are anticonvulsants also known as membrane stabilisers?
They reduce abnormal firing of nerves
What type of pain are anticonvulsants good for?
Neuropathic pain
What are the steps in the WHO pain ladder?
- Step 1 -Paracetamol +/- NSAIDs
- Step 2 Paracetamol (+/- NSAIDs) + Codeine/alternative
- Step 3 Paracetamol (+/-NSAID) + Morphine
How should the pain ladder be used as pain resolves?
- Move from top to middle of WHO ladder
- Continue bottom rung drugs at all times
- Lastly stop NSAIDs, then paracetamol as more adverse side effects with NSAIDs
What is the RAT approach to pain?
- Recognise
- Assess
- Treat
How do you assess pain severity?
- Verbal scale (mild, mod, severe)
- Numerical rating scale
- Visual analogue scale
- Faces scale
What other factors can influence the severity of a patient’s pain?
Physical factors
- Other illnesses
Psychological and social factors
- Anger, anxiety, depression
- Lack of social support
What drugs are used in neuropathic pain?
- Amitriptyline (tricyclic antidepressant)
- Gabapentin (anticonvulsant)
- Duloxetine (selective serotonin noradrenaline reuptake inhibitor - SNRI)
