Acute Pain Basics - Exam 2 Flashcards
What are examples of superficial somatic pain?
- skin
- subQ tissue
- mucous membranes
What are examples of Deep Somatic Pain?
- muscles
- tendons
- joints
- bones
What is Parietal Visceral pain?
- pain localized to the area around the organ
- ex: acute appendicitis pain
What is referred visceral pain?
- cutaneous pain
- comes from patterns of embryological development & migration of tissues
- convergence of visceral & somatic afferent input to CNS
What are 4 goals of pain control?
- pt comfort
- attenuate adverse physiologic responses to pain
- prevent chronic pain syndrome
- control anxiety & agitation
What 2 main things can be done to reach the pain goals?
- preemptive/preventative analgesia
- multimodal approach (diff. receptors)
What are the 3 phases of pain?
- acute pain
- chronic nociceptive pain
- neuropathic pain (DM)
not exclusive
What are some examples of disease states that cause pain?
- Degenerative joint and disc disease
- spinal stenosis
- DM
- CVD
- osteoporosis
- cancer
- heart disease
- polymyalgia rheumatica
- wounds
- PAD
- end of life
What are 3 things that cause pain r/t immobility?
- loss of functional status (dementia, stroke, DJD, fx, amputation)
- neuropathy
- PVD (edema/pain)
What are 6 red flags of pain?
- new loss of bowel/bladder
- pain that wakes pt up
- immunosuppression (malignancy)
- severe/progressive neuro deficit
- cold, pale, mottled, cyanotic limb
- severe abd. pain/shock peritonitis
The Specificity theory states that pain has —-
Who proposed this theory?
its own pathway not involving any other senses
Rene Descartes (French philospher)
Who introduced the intensity theory of pain?
What does the theory state?
- Plato
pain is an emotional experience not a sensory one
Who proposed the Gate Control Theory of Pain?
What is the idea of theory?
- Ronald Melzack and Patric Wall (1965)
pain transmission is modulated by balance of impulses transmitted to spinal cord
* inhibitory interneurons in substantia gelatinosa & cells function as a gate
* regulating transmission of impulses to CNS
What is the physiologic pathway of pain?
1. initial insult:
2. activates:
3. releases:
- initial insult: thermal, mechanical, & chemical tissue damage
- activates: afferent nerve endings of myelinated a-delta and unmyelinated C fibers
- releases: histamine & inflamm. mediators
What are the nerve fibers involved in acute pain?
- a-delta
- C fibers
what are the inflammatory mediators released in response to pain?
- peptides: bradykinin, substance P
- lipids: PGs
- neurotransmitters: serotonin, Ach
1st order neurons:
periphery to spinal cord
* tissue receptors of skin & proprioceptors (muscle, joints, tendons)
* synapse in spinal cord w/ 2nd order
2nd order neurons:
spinal cord to thalamus
* 1st order neurons in dorsal horn
* crosses to contralateral side of spinal cord
* ascends in spinothalamic tract
3rd order neurons:
thalamus to post-central gyrus in cerebral cortex
* 2nd order neurons in thalamus
* ascends through internal capsule
* post-central gyrus
How are nerve fibers characterized?
- myelination status
- diameter
- velocity of impulse conduction
What are the characteristics of A-fibers?
A-beta?
A-delta?
fast, myelinated, large
- A-beta: pressure, touch, proprioception
- A-delta: fast pain, touch, heat
What are the characteristics of C-fibers?
slow, non-myelinated, small
- slow pain, heat, touch
Elements of Pain Processing
Transduction:
- what meds work on transduction?
- thermal, chemical, mechanical tissue damage
- release of inflammatory mediators
- activate nociceptor
noxious stimuli converted into APs
Meds: LA, NSAIDs
Elements of Pain Processing
Transmission:
What meds work on transmission?
AP conducted through nervous system
* A-delta & C fibers
* meds: LAs
Elements of Pain Processing
Modulation:
What meds work on modulation?
pain transmission alters afferent neural transmission
* happens in dorsal horn of spinal cord
* Meds: LAs, opioids, ketamine, alpha 2 agonists
Elements of Pain Processing
Perception:
What meds work on perception?
integration of painful input into somatosensory & limbic cortices (post-central gyrus) - S1/SII
* in the frontal cortex
* meds: alpha 2 agonists, opioids, general anesthetics
Neuropathic Pain
What is allodynia?
pain response to something that is normally not painful
ex: DM neuropathy
Neuropathic Pain
What is hyperalgesia?
exaggerated response to a normally painful stimulus
* release of local inflammatory mediators that can produce augmented sensitivity to stimuli
Neuropathy
What is primary hyperalgesia?
- augmented sensitivity to painful response
- OR allodynia misinterpretation of non-painful stimuli
Neuropathy
What is secondary hyperalgesia?
- increased excitability of neurons in CNS
- from Glutamate activation of NMDA receptors
Neuropathy
What is a drug we give that can cause hyperalgesia?
- Remifentanil
give w/ Ketamine or something long acting
Neuropathy
What happens w/ central hypersensitivity?
- there is no or minimal & undetectable tissue damage required to induce pain
What is the hallmark of neuropathy?
- complete denervation of a body part resulting in numbness
- negative symptom
What is the paradoxical part of neuropathic pain?
- from nerve trauma and disease
- associated w/ postive symptoms
What are the postive symptoms of neuropathic pain?
- burning
- lancinating
- electric
- raw skin like
- shooting
- deep/dull
- aching
Elderly & Pharmacology
What physiologic changes affect absorption of drugs?
- decreased GI motility & blood flow
- gastric acid secretion decreased (elevated pH)
- use of meds alters gastric pH more
Elderly & Pharmacology
What 5 things have an overall effect on distribution of drugs?
- protein binding
- pH - PK/PD
- molecular size
- water
- lipid solubility
Elderly & Pharmacology
What physiologic changes affect the distribution of drugs?
- decreased muscle mass
- increased proportion of body fat (Vd)
- decreased total body water
- decreased albumin - PB drugs
Elderly & Pharmacology
What physiologic changes affect the metabolism of drugs?
- decreased hepatic blood flow
- decreased liver mass & intrinsic metabolic activity
Elderly & Pharmacology
What physiologic changes affect the elimination of drugs?
- decreased renal blood flow
- decreased GFR
- decreased kidney mass & # of functioning nephrons
WHO pain relief step 1:
- non-opioids
- adjuvant (PT, massage, heat, braces)
WHO pain relief step 2
- opioids for mild-mod
- non-opioids
- adjuvant
WHO pain relief step 3
- stronger opioids
- non-opioids
- adjuvant
Opioid Analgesics
* Act ________.
* addiction/dep/tolerance: y or n
* controlled?
* AE: 3
* anti-inflammatory: y or n
* ceiling effects: y or n
- act centrally
- yes addiction/dep/tolerance
- schedule II, III controlled
- AE: sedation, resp. depression, constipation
- anti-inflammatory: no
- ceiling effects: no (can keep giving more and more)
non-opioid analgesics
* act ________.
* addiction/dep/tolerance?
* controlled?
* AE: (3)
* anti-inflammatory: y or n
* ceiling effects: y or n
- act peripherally
- not habit forming
- not controlled
- AE: gastric irriation, bleeding, renal toxicity
- yes anti-inflammatory
- yes ceiling effects (increasing dose does not increase analgesia - causes more SE)
Mu receptor effects:
- analgesia
- resp. depression
- euphoria
- decreased GI motility
Kappa receptor effects
- analgesia
- dysphoria
- psychosis
- delirium/delusions
- miosis
- resp. depression
Delta receptor effects
- analgesia
Do opioids act peripherally or centrally?
centrally
* dorsal horn - lamina II
* somatosensory cortex in brain
