Pain and analgesics Flashcards
Review of Pain
Pain acts as a signal, it tells us that we have encountered something potentially dangerous that may lead to tissue damage, and so it enables us to respond to potentially protect ourselves from further pain and injury.
The term Nociception
term used to describe the transmission of information related to pain along the peripheral and central nervous systems once a pain receptor has been activated. Skin is densely innervated with pain receptors (called nociceptors) and they are also present in bone, muscle and joints
What are the four major physiological processes associated with pain?
transduction, transmission, perception and modulation
Transduction
Transduction refers to the process by which painful or noxious stimuli activate peripheral nerve endings.
These noxious stimuli are physical or chemical and are tissue-damaging.
The trauma from the noxious stimuli causes the release of a number of neurotransmitters (i.e. prostaglandins, bradykinin, serotonin, substance P, histamine), in effect converting the stimulus event into a chemical tissue event which will facilitate further action of the nociceptors.
Transmission
Transmission refers to the process that occurs when the signal generated by the neurotransmitters, is carried by afferent pathways to the spinal cord then along to the central nervous system (brainstem and higher cortical levels).
Some afferent nerve fibres are large diameter and myelinated, allowing the fast conduction of pain-related impulses. These fibres are called A fibres and transmit sharp, localised pain signals.
Conversely, C fibres are small diameter, unmyelinated fibres that have a relatively slower conduction rate. They transmit dull, aching pain signals.
Perception
Perception occurs when the person becomes consciously aware of pain.
This is the subjective experience of pain where cognitive and behavioural aspects of the individual are activated, and the experience interpreted.
Modulation
Modulation is when the body facilitates or inhibits pain impulses.
The pathways involved in modulation are referred to as descending fibres because they involve neurons originating in the brain stem that descend to the spinal cord.
Descending fibres release substances such as endogenous opioids, serotonin, and norepinephrine, which bind to opioid receptor sites through the body - inhibiting the transmission of pain impulses.
Modulation helps to explain the wide variation in perception of pain seen from one person to the next.
Conditions associated with symptomatic pain
Pain is typically categorised by duration (acute or chronic) and underlying mechanism (e.g. nociceptive, neuropathic, visceral, somantic)
Acute pain
An important biological protective mechanism of the body to warn of injury or disease.
It lasts for a short time and occurs following surgery or trauma or other condition.
It acts as a warning to the body to seek help.
Chronic non-cancer pain
Pain that persists constantly or intermittently and beyond the time of normal healing – usually 3 months.
Chronic pain is a major cause of physical and psychosocial disability and poor quality of life
Cancer pain
Pain from cancer can be acute and chronic, persisting for long durations with acute episodes.
It is caused by the impact of neoplastic cells on the normal anatomy of a person
Nociceptive pain
Sometimes called physiological pain, it is pain that is sustained by ongoing activation of the sensory system that serves the perception of noxious stimuli
Neuropathic pain
Pain that is sustained by injury or dysfunction of the peripheral or central nervous system.
It is associated with remodelling of neural connectivity caused by chronic disease or injury
It is more common in disease that affect the nervous system such as diabetes mellitus or multiple sclerosis but may also result from surgery or trauma to nervous tissue
Somatic pain
Pain that emanates from the muscles and tissues in the musculoskeletal system, common in patients with cancer
Visceral pain
Pain that emanates from the internal organs and involuntary tissues of the torso.
Cardiovascular conditions
Example
Angina pectoris - Crushing or searing acute chest pain that spreads to neck, jaw or arms. May also be described as a heaviness or pressure.
Urinary / renal conditions
Example
Renal calculi - Acute pain associated with passing kidney stones.
Musculoskeletal conditions
Examples
Arthritis - swelling and tenderness of one or more joints. Pain is a common symptom.
Osteoporosis - caused by loss of bone tissue resulting in weak, brittle bones. May be associated with hormonal changes (e.g. loss of oestrogen at menopause), calcium or vitamin D deficiency. If vertebra collapse, may cause back pain.
Musculoskeletal injuries - injuries of the muscles, nerves, tendons, joints, cartilage, and spinal discs. Risk factors (e.g. for back pain) may include poor posture, and muscular strain.
Neurological conditions
Example
Migraines – usually characterised as intense, throbbing or pulsing headaches. May be preceded by an aura and associated with nausea and vomiting.
Fibromyalgia - a condition characterised by general muscle pain, often accompanied by fatigue and interrupted sleep. Primarily affects the central nervous system so now considered a nervous system disorder (was previously classified as a musculoskeletal condition).
Reproductive conditions
Example
Endometriosis – cells similar to the endometrium, grow outside the uterus and respond to female hormonal changes in the same way as endometrial tissue. Results in local swelling, pain and unusual bleeding.
Gastrointestinal conditions
Example
Abdominal pain – associated with digestive diseases e.g. diverticulitis, irritable bowel syndrome (IBS) or constipation.
What are analgesic medications?
Analgesics include both non-opioid and opioid medications. Common non-opioid medications with which you are likely familiar include non steroidal anti-inflammatories (NSAIDs) and paracetamol. Opioid medications are commonly known as narcotics. They are Schedule 8 medications that have regulations regarding their use.
Non-opioid analgesics
Analgesia is the inability to feel pain. Analgesics are medications used to relieve pain and are sometimes called ‘painkillers’.
Non Steroidal Anti-inflammatory Drugs (NSAIDS)
NSAIDs are prostaglandin inhibitors that inhibit the activity of the COX enzyme. NSAIDs result in analgesia, as well as a reduction in inflammation. Some NSAIDs are non-specific COX inhibitors (eg. Aspirin, Ibuprofen, Indomethicin, Diclofenac) while others are specific COX inhibitors. Some preparations are enteric-coated
Paracetamol
Paracetamol is not a true NSAID as it does not have any anti-inflammatory properties and its mechanism of action is not entirely understood. Paracetamol has analgesic and antipyretic properties
Aspirin
Analgesic group
NSAIDS, non specific COX inhibitors
Trade names
Disprin
Solprin
Aspro
Important nursing knowledge
May be used as analgesic or anti-thrombotic (prevents clots)
May cause gastric irritation and hence gastric bleeding
Stop taking a week before surgery due to risk of bleeding
Avoid use for children
Low dose aspirin (e.g. 100mg) may be enteric coated to resist absorbing in the stomach, instead it absorbs in the small intestine. As an enteric medication, it should not be crushed.
Ibuprofen
Analgesic group
NSAIDS, non specific COX inhibitors
Trade names
Nurofen
Rafen
Advil
Brufen
Important nursing knowledge
Useful for arthritis, migraines, dysmenorrhoea (painful periods), any acute or chronic pain with an inflammatory component
May cause gastric irritation.
Celecoxib
Analgesic group
Specific COX inhibitors
Trade names
Celebrex
Important nursing knowledge
Useful for arthritis.
Paracetamol
Analgesic group
Specific COX inhibitors
Trade names
Panadol
Dymadon
Febridol
Panamax
Important nursing knowledge
Analgesic for mild to moderate pain
Several brands of paracetamol are available
Need to exercise care in checking the strength and combinations with other medicines.
Opioids (narcotic analgesics)
Opioid or narcotic analgesics are opioid agonists that act on the opioid receptors in the brain, depress the respiratory centre, stimulate vomiting, cause pupil constriction, and reduce gastrointestinal tract peristalsis. Narcotic analgesics can also cause physical dependence and there is a risk of accidental overdose and death
Morphine sulphate
Analgesic group
Opioid analgesic
Trade names
Morphine
Kapanol
MS Contin
Ordine
Mist Morph
Important nursing knowledge
Administration and storage as per schedule 8
Potential side effects of respiratory depression, vomiting, constipation, tolerance over time
Concerns around physical dependence have prevented RNs from administering previously but when used appropriately not an issue.
Codeine phosphate
Analgesic group
Opioid analgesic
Trade names
Codeine
Panadeine
(in combination with paracetamol)
Important nursing knowledge
May be schedule 4 (if combined with paracetamol) or schedule 8
Much less potent than morphine.
Analgesic activity of codeine potentiates the analgesic activity of paracetamol and therefore panadeine and panadeine forte are used.
Oxycodone
Analgesic group
Opioid analgesic
Trade names
Endone
Oxycontin
Oxynorm
Prolodone
Important nursing knowledge
Administration and storage as per schedule 8
May come in slow release formulations which can contribute to medication errors
Potential side effects of respiratory depression, vomiting, constipation, tolerance over time.
Opioid side effects
Nausea and Vomiting, Constipation, Respiratory depression, Opioid dependence
Nausea and vomiting
This occurs particularly when opioids are administered as anaesthesia for surgery.
The nurse can support the patient by ensuring a legal order is written for an anti-emetic and ensuring regular administration as ordered.
Post-operatively, nurses should ensure emesis bags are readily available for patients
Constipation
The nurse can support the patient by encouraging mobility, fluid intake and adequate diet.
Chewing gum has also been found to be effective!
Nurses can advocate for legal orders to be written for stool softeners (e.g. senna, docusate) and osmotic laxatives should stool softeners be ineffective
Respiratory depression
Opioid-induced respiratory depression is often feared, however is actually an uncommon side effect.
Respiratory depression is preceded by increasing sedation, and as such, the nurse should monitor patient’s level of consciousness (using a sedation scale) and respiratory rate.
It is helpful to know that an alert patient will not suddenly succumb to respiratory depression. As a result, respiratory depression can be prevented by evaluating sedation levels and decreasing opioid doses before respiratory depression ensues
Opioid dependence
Nurses have a responsibility to educate patients about the therapeutic use of opioids. For hospitalised patients who may be discharged with opioid prescriptions, the nurse should discuss the need to:
not take opioids for reasons other than those prescribed;
not take opioids in doses other than those prescribed;
not share opioids with others (and safely store them);
not keep leftover opioids (rather, return them to a local chemist)
