Pain

Pain and Pathophysiology

Theories of Pain

Classification of Pain

Pain

- Acute pain

- Malignant/cancer pain (Chronic/persistent)

- Non-cancer pain (Chronic/persistent)

Pain: An unpleasant sensory and emotional experience associated with actual or potential tissue damage. Pain is a personal experience and is best defined by the person experiencing it. The most accurate way of determining pain is by the person's self-report of it.

- Gate Control Theory: Said that there was a gate that opened or closed at the spinal cord, allowing impulse conduction of pain to the brain

- Neuromatrix Theory: Addresses the role of the brain in the perception of pain and factors that influence it. Recognizes attention, culture, expectations, & stress.

Nociceptive pain: Involves the nerves processing noxious stimuli in superficial structures of the body

- Visceral pain: Pain originating from the organs

- Somatic pain: Pain originating from a body part

Pain exists to alert us of danger and occurs through all stages of life. It depends on perception and sensory stimulation. Genetics, age, gender, and cognitive level all play a role in pain sensations.

Neuropathic pain: Caused by abnormal processing of sensory input due to injury or malfunction

Definitions

Neuropathic Pain

Physiology of Pain

Spinothalamic Tract: Sensory pathway from skin to the thalamus and reticular formation

Reticular Formation: Allow pain to reach cortex

Thalamus: Transmits pain to cortex

Cerebral Cortex: Perception and sensation of pain

Periaqueductal Grey: Blocking and modulation of pain through descending analgesic pathways

- Allodynia: Pain sensitization following stimulation

- Hyperalgesia: Abnormally heightened sensitivity to the sensation of pain

- Paresthesia: An abnormal feeling or sensation (pins and needles) due to pressure/damage to nerves

- Hypoesthesia: Reduced sense of touch or sentation

- Neuralgia: Intense, intermittent pain along a nerve, typically occuring in the head or the face

- Phantom Limb Pain: The sensation of pain in a limb that is no longer present due to removal.

- Nociceptors: Sense cellular damage due to chemicals, heat, or mechanical pressure

- Periaqueductal grey: Sends impulses to inhibit pain

- Thalamus: 2nd order neurons connect to 3rd order

- Substance P: Increases pain transmission

- Glutamate: Excitatory, sensitize nociceptors

- Prostaglandins: Excitatory, sensitize nociceptors

- Endorphins: Inhibit transmission of pain

- Neospinothalamic tract: 1st order neurons

- Cerebral cortex: Perception, interpretation of pain

Chronic Pain

Acute Pain

Physiology of Pain

Transduction: Occurs when noxious stimuli cause cells to have action potentials and release chemical mediators (histamine, bradykinin, serotonin)

Acute pain is pain that lasts less than 3 months. It serves as a protective mechanism to alert the body of harm or potential danger. It is self limiting and goes away once the tissue has healed or stimulus removed.

- Accompanied by anxiety, spasms, guarding, high blood pressure, increased breathing rate

- Pain can be referred/felt in another area

- Often treated by interrupting the stimulus through opioid and non-opioid analgesics

- Medication

Transmission: Conduction of nerve impulses along the spinal cord and to the structures of the brain

- A Delta fibres: Quick, localized, sharp,

- C fibres: Poorly localized, dull, aching, burning

Chronic pain lasts longer than the expected healing period of an injury. It often does not have a cause, and it is unproductive and doesn't have any purpose. Normal vitals are expected, and this pain often fails to respond to treatments.

Perception: Conscious awareness of pain

Modulation: Descending pathways inhibit further pain sensation. This occurs in the periaqueductal grey.

Pain Response in Infants

Untreated Pain

Pain Response in Elderly

Pain that goes untreated can have severe negative consequences such as:

Management of pain in the children and elderly is often difficult as it is easy for it to go untreated due to inability to communicate and lack of knowledge.

There are many misconceptions about pain in the elderly and older adults. The prevalence of pain increases with age and is more common in women, and pain is often underreported in the elderly.

- Babies and newborns are able to feel pain

- Exposure to pain has effects on young children

- Children are not always truthful with pain levels

- Childen can use scales to measure their pain

- Children are not at a higher risk for opiate abuse

- Children do not experience more adverse effects

- Increase in hormones (ACTH, Cortisol, Epinephrine)

- Cardiovascular problems (High HR, CO, PR)

- Metabolic dysfunction (Hyperglycemia, lipolysis)

- Depression of immune response

- Reduction in cognitive function

- Lower gastrointestinal activity

- Musculoskeletal problems (twitching, fatigue)

- Decreased quality of life

- Elderly patients don't have a decreased sense of pain

- Elderly patients can tolerate pain medication

- Pain is not a normal part of the aging process

- Those who ask for pain do not have a low tolerance

- Pain medication will not hasten death in elderly