Clin Med - Pain Mgmt Flashcards
Define pain
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
Biologists recognize that those stimuli or illnesses that cause pain are likely to damage tissue.
How is pain subjective?
each individual learns the meaning of the word “pain” through experiences related to injury in early life.
Implications of pain for clinical practice
- there is no physiological, imaging, or laboratory test that can identify or measure pain.
- pain is what the patient says it is.
- clinician must accept the patient’s report of pain.
Define nociception
- the process by which information about a noxious stimulus is conveyed to the brain.
- the total sum of neural activity that occurs prior to the cognitive processes that enable humans to identify a sensation as pain.
Nociception vs. pain
Pain is a conscious experience that results from brain activity in response to a noxious stimulus and engages the sensory, emotional and cognitive processes of the brain.
What are the 2 dimensions/components of pain?
- sensory-discriminative
2. affective-emotional
Goal of pain therapies
to relieve pain whenever possible: from nociception to the conscious experience as well as to decrease the emotional response to the unpleasant experience
Reduction of symptoms = improved quality of life
Physiology pain pathway
-4 steps
- Transduction
- Transmission via Ascending pain pathway: Spinothalamic Tract
- Perception
- Modulation via Descending pain pathway: Corticospinal Tract
Define transduction
phys process where a noxious mechanical, chemical, or thermal stimulus is converted (transduced) via specialized receptors on primary afferents into an electrical impulse (action potential)
Where does transduction occur?
nociceptors
What are nociceptors?
a subpopulation of primary sensory neurons that are activated by intense stimuli such as pressure, heat, mechanical insults (a surgical incision) or irritant chemicals (including those which are released by damaged cells)
What are some of the irritating chemicals released by cells?
bradykinin, cholecystokinin and prostaglandins, activate or sensitize nearby nociceptors.
Examples of interventions that reduce transduction
ice or NSAIDs
*recall that NSAIDs inhibit the synthesis of prostaglandins - normally produced and released at the site of injury, and which in turn make neighboring nociceptors more responsive to noxious and innocuous stimuli.
How are action potentials conducted to the CNS?
via two types of primary afferent neurons:
- thinly myelinated, faster conducting A delta fibers and
- unmyelinated, slowly conducting C fibers, both termed primary afferents.
Action potentials result from activation of specific sodium channels
Nociceptive impulses travel along…
travel along these peripheral nerve fibers (peripheral transmission) to the dorsal horn of the spinal cord where they synapse with the second order neurons (synaptic transmission)
Where is the impulse transmitted after it reaches the dorsal horn of the spinal cord and synapses with second order neurons?
the impulse is further transmitted via neurons which cross the spinal cord and ascend to the thalamus and branches to the brainstem nuclei (central transmission)
Nociceptive impulses are then relayed…
to multiple areas of the brain including the:
- somatosensory cortex
- the insula
- frontal lobes
- limbic system
Intervention action
- local anesthetics
- some epileptic drugs
Local anesthetics and some antiepileptic drugs block sodium channels and inhibit the production of action potentials along the nociceptive afferents
Intervention action
-opioids
Opioids bind to presynaptic receptors in the dorsal horn and decrease release of neurotransmitters such as glutamate
Intervention action
-peripheral and spinal nerve blocks
interfere with propagation of action potentials and pain transmission into the CNS (at the nociceptors, along the nerve, at the dorsal root ganglion and along the spinothalamic tracts)
Intervention action
- epidural
- intrathecal
may provide presynaptic and postsynaptic inhibition of receptors at the level of dorsal horn neurons and affect the transmission of nociceptive impulses
Define perception
the process by which a noxious event is recognized as pain by a conscious person
What parts of the brain are involved in perception?
- multiple areas of the brain are involved.
- there is no one location where perception occurs, although major defining components of pain are attributed to processes that take place in specific areas of the brain
What does the limbic system mediate?
the affective-emotional response to the noxious stimulus is mediated by the limbic system
Descending input from the brainstem influences…
central nociceptive transmission in the spinal cord
How does descending modulation occur?
specific brainstem nuclei send projections to the dorsal horn of the spinal cord and, when activated by ascending nociceptive impulses and other influences from the brain, result in descending modulation
Modulation results in descending inhibition of nociception through which neurotransmitters?
release of neurotransmitters such as serotonin, norepinephrine, and endogenous opioids
How is descending facilitation increased?
modulatory processes can also increase descending facilitation of nociception and consequently pain
what role do fear and anxiety play in modulatory systems?
they exert facilitatory influences through these modulatory systems
Which drugs enhance descending inhibition?
Certain antidepressants - tricyclics and selective norepinephrine reuptake inhibitors (SNRIs) that inhibit the reuptake of serotonin and norepinephrine enhance
*opioid analgesics have direct effects on descending modulation
Other therapies to modify descending modulation
cognitive behavioral therapies, spinal cord stimulation, epidural, and intrathecal delivery of drugs such as opioids
Define hyperalgesia
abnormally heightened sensitivity to pain
Define allodynia
previously non-painful stimuli is now noxious
Hyperalgesia and allodynia are the result of…
changes in either the peripheral or central nervous systems, referred to as peripheral or central sensitization, respectively
What kind of pain do nociceptors signal?
-significance
acute and chronic - when chronically sensitized, contribute to persistent pathological pain disorders from previous injury or ongoing disease
Chronic pain is characterized by…
abnormal state and function of the spinal cord neurons which become hyperactive
Spinal cord hyperactivity is a result of…
increased transmitter release by spontaneously active primary afferent neurons and an increased responsiveness of postsynaptic receptors (in part due to phosphorylation of glutamate-activated NMDA receptors)
Hyperexcitable state of synaptic transmission
- maintained by
- aggravated by
- at the dorsal horn, it is maintained by release of biologically active factors from activated glia
- aggravated by loss of inhibitory interneurons involved in the modulation of pain
Treatment aims to…
decrease the intensity of acute pain in an effort to reduce or prevent permanent changes in the nervous system that may result in chronic pain
What are the 3 types of pain?
- nociceptive
- neuropathic
- inflammatory
Nociceptive pain
- definition
- examples
-normal response to noxious insult or injury of tissues such as skin, muscles, visceral organs, joints, tendons, or bones
- somatic ex: musculoskeletal (joint pain, myofascial pain), cutaneous; often well localized
- visceral ex: hollow organs and smooth muscle; usually referred
Neuropathic pain
- definition
- examples
- pain initiated or caused by a primary lesion or disease in the somatosensory nervous system
- ex: diabetic neuropathy, post-herpetic neuralgia, spinal cord injury pain, phantom limb (post-amputation) pain, and post-stroke central pain
Inflammatory pain
- definition
- examples
- result of activation and sensitization of the nociceptive pain pathway by a variety of mediators released at a site of tissue inflammation
- proinflammatory cytokines are the key mediators
-ex: appendicitis, rheumatoid arthritis, inflammatory bowel disease, and herpes zoster
Pain intensity scale
- categorized as mild, moderate, severe
- used to identify how effective pain treatments are
Time course
-acute pain
less than 3-6 months
Time course
-chronic pain
greater than 6 months
Time course
-acute-on-chronic
acute pain flare superimposed on underlying chronic pain
When should you screen patients for pain?
regularly screen all patients for pain and perform a comprehensive pain assessment when pain is present
Diagnosis of pain
-keys
- history and physical
- understanding that it is multidimensional (affecting function, quality of life, emotional state, and general well-being
Pain history
-“QISS TAPED”
- Quality
- Impact
- Site
- Severity
- Temporal characteristics
- Aggravating – Alleviating Factors
- Past response
- Expectations
- Diagnostics – Physical Exam
What is meaningful pain relief?
33-50% decrease in intensity of both acute and chronic pain is clinically meaningful
Acute pain treatment
- goals
- mainstays
- pain control and relief
- analgesics, but nondrug methods (pt education, heat/cold, massage, distraction/relaxation, others) are essential too
Chronic pain treatment
-goals
- pain control, but more focused on quality of life and function
- also, prevention of secondary pain problems such as myofascial pain is essential
Multi-modal treatment can include
- Physical Therapy
- Acupuncture
- Chiropractic Therapy
- Interventional Pain Management
- DCS / Intrathecal Implanted Device
What are the 2 types of acute exacerbation of chronic pain?
- pain flare
2. disease progression
- Pain flare
- definition
- transient increases in pain that can last for hours to days
- flares are extremely common and generally benign although they may be perceived as harmful by the patient
Caution in pain flare
care should be used with additional short-acting analgesics since they are not appropriate from a mechanistic standpoint and may only lead to escalated use of analgesics
- Disease progression
- definition
if pain is exacerbated and does not remit with flare management techniques, look for and treat any change in the causative disease process
Define breakthrough pain (BTP)
a transitory exacerbation of pain (predictable or spontaneous) that occurs on a background of otherwise stable pain in a cancer patient receiving chronic opioid therapy
Categories for increases in pain
- incident related
- end of dose failure
- idiopathic
What are the 5 R’s of analgesics?
- Right Analgesic
- Right Dose
- Right Route of Administration
- Right Dosing interval
- Right Expectations
Interventional pain management
- examples
- epidural steroid injections
- vertebroplasty
- intrathecal drug delivery
- spinal cord stimulation
- neurolysis by radiofrequency of surgery reserved for patients with limited life expectancy
Treatment time course
-reassessment
- define an appropriate time frame for accomplishment of goals
- reassessment is crucial to ascertain whether treatment is working or needs further modification
Treatment end
treatment may end if:
- goals are not met
- treatment has not worked
- pt unable/unwilling to continue
- maximum possible progress has been achieved
When should you refer to specialist?
any provider should refer a patient to a specialist or other provider when he/she has reached the limits of comfort or competence, or when patients desire referral.
Responsible opioid prescribing
-FSMB 8 basic elements
- Evaluation of the patient
- Medication agreement / contract
- Development of a treatment plan
- Informed consent and agreement for treatment
- Periodic review
- Consultation
- Maintenance of comprehensive medical records
- Compliance with controlled substances laws and regulations
What 4 outcomes must be regularly assessed and documented?
- analgesia: pain relief
- activities of daily living (ADL): physical and psychosocial functioning
- ADRs: side effects (these are common and can affect function and adherence)
- aberrant behaviors: may indicate addiction or inadequate treatment
Define addiction
a primary, chronic, neurobiologic disease, with genetic, psychosocial, and environmental factors influencing its development and manifestations
What is addiction characterized by?
behaviors that include one or more of the following:
- impaired control over drug use
- compulsive use
- continued use despite harm
- craving
Define tolerance
a state of adaptation in which exposure to a drug induces changes that result in a diminution of one or more of the drug’s effects over time
What do you call an alligator in a vest?
An investigator
:)
