Pain

• The International Association for the Study of Pain (IASP) published a definition of pain in 2020: “An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage”.
• There are two categories of pain: Acute pain, which is new onset of pain, and Chronic pain, which is pain present for 3 months or more.
• Pain has two aspects: Sensory, which is the sensory signal transmitted from the pain receptor, and Affective, which is the unpleasant emotional reaction to the pain.
• Pain is supposed to indicate underlying or potential damage to tissues, but it can occur without tissue damage.
• The physiology of pain is very complex and there is still a lot that is not fully understood about the experience of pain.
• Pain is subjective, meaning that when someone indicates they are in pain, we need to accept their experience, even when there is no apparent underlying cause.
• Pain threshold refers to the point at which sensory input is reported as painful.
• For example, different temperatures can be applied to the skin to measure the point at which the heat is interpreted as pain.
• A higher temperature indicates a higher sensory threshold for pain.
• Allodynia refers to when pain is experienced with sensory inputs that do not normally cause pain, such as light touch.
• Pain tolerance is different to pain threshold and generally refers to a person’s response to pain.
• One person may experience pain but think little of it and carry on with their activities as usual.
• Another person may experience a similar pain and worry that it indicates a serious underlying illness, take time away from work, and seek medical investigations and treatment.
• Proton pump inhibitors (e.g., omeprazole or lansoprazole) are often co-prescribed with NSAIDs to reduce the risk of gastrointestinal side effects (e.g., acid reflux, gastritis and stomach ulcers).
• NSAIDs may be inappropriate or contraindicated in patients with Asthma, Renal impairment, Heart disease, Uncontrolled hypertension, Stomach ulcers.
• The information here is from the BNF, which gives approximate conversions between different opiates, equivalent to 10mg of oral morphine.
• Medication overuse headache is a common side-effect of the long-term use of analgesic medication.
• The rescue dose is usually 1/6 of the background 24-hour dose.
• Naloxone is used to reverse the effects of opioids in life-threatening overdose (usually due to respiratory depression).
• Chronic pain refers to pain that has been present or reoccurs in one or more areas over more than three months.
• The key side effects of opioids are: Constipation, Skin itching (pruritus), Nausea, Altered mental state (sedation, cognitive impairment or confusion), Respiratory depression (usually only with larger doses in opioid-naive patients).
• Other medications may be combined with the analgesic ladder for additional effect, known as adjuvants, including antidepressants (e.g., amitriptyline or duloxetine) or anticonvulsants (e.g., gabapentin or pregabalin).
• Using opioids to control pain in palliative patients is a specific scenario where the doses are titrated and optimised over time.
• Biological, psychological and social factors contribute to the persistence and severity of pain.
• The key side effects of NSAIDs are: Gastritis with dyspepsia (indigestion), Stomach ulcers, Exacerbation of asthma, Hypertension, Renal impairment, Coronary artery disease, heart failure and strokes (rarely).
• Common causes of neuropathic pain include: Post-herpetic neuralgia from shingles is in the distribution of a dermatome and usually on the trunk Nerve damage from surgery Multiple sclerosis Diabetic neuralgia (typically affecting the feet) Trigeminal neuralgia Complex regional pain syndrome
• Chronic pain is a complex condition that can be challenging to manage.
• Part of chronic pain management aims to maintain the quality of life despite the pain.
• Physical processes that can lead to chronic pain include: Sensitisation of the primary afferent nociceptors by frequent stimulation Increased activity of the sympathetic nervous system Increased muscle contraction in response to pain
• The NICE guidelines (2021) specifically state that for chronic primary pain, patients should not be started on: Paracetamol NSAIDs Opiates Anti-epileptic drugs (e.g., pregabalin or gabapentin)
• In chronic secondary pain, analgesia may be helpful depending on the underlying cause.
• The DN4 questionnaire can be used to assess the characteristics of the pain and the likelihood of neuropathic pain.
• Treatment for complex regional pain syndrome is guided by a pain specialist and is similar to other types of neuropathic pain.
• Complex regional pain syndrome is characterised by areas of abnormal nerve functioning, causing neuropathic pain, abnormal sensations and skin changes.
• Neuropathic Pain is characterised by numbness, burning, tingling, pins and needles or an electric shock sensation.
• First-line treatments for neuropathic pain include: Amitriptyline – a tricyclic antidepressant Duloxetine – an SNRI antidepressant Gabapentin – an anticonvulsant Pregabalin – an anticonvulsant
• Chronic pain often fluctuates, with flare-ups, and may get worse over time.
• Options for managing chronic primary pain in the NICE guidelines (2021) include: Supervised group exercise programs Acceptance and commitment therapy (ACT) Cognitive behavioural therapy (CBT) Acupuncture Antidepressants (e.g., amitriptyline, duloxetine or an SSRI)
• Good communication and building a relationship is important in managing chronic pain.
• Afferent sensory nerves that transmit pain signals are part of the peripheral nervous system and are called primary afferent nociceptors.