Pain

Question 1

What is the definition of pain?

Answer 1

• an unpleasant sensory and emotional experience associated with actual or potoential tissue damage.
• pain is a protective mechanism

Question 2

What is dysethesia?

Answer 2

any abnormal sensation described as unpleasant by the patient

Question 3

Hyperalgesia

Answer 3

• Exaggerated pain response from a normally painful stimulus
  
  • usually additive of repeated stimulus of constant intensity and aftersensation

Question 4

hyperesthesia

Answer 4

exaggerated perception of touch stimulus

Question 5

allodynia

Answer 5

• abnormal perception of pain from a normally non-painful mechanical or thermal stimulus
  
  • usually has elements of delay in perception

Question 6

hypoalgesia

Answer 6

decreased sensitivity and raised threshold to painful stimuli

Question 7

anesthesia

Answer 7

reduced perception of all sensation, mainly touch

Question 8

analgesia

Answer 8

Reduced perception of pain stimulus

*warn pts to expect some pain after surgery, analgesia can only reduce it, not fully eliminate it

Question 9

paresthesia

Answer 9

• spontaneous abnormal sensation that is not necessarily unpleasant
• usually described as “pins and needles”
  
  • ex. diabetic patients

Question 10

Causalgia

Answer 10

• burning pain in the distribution of one or more peripheral nerves (wherever the affected nerve(s) innervates)
  
  • ex: shingles

Question 11

What is the overview of how pain perception works?

Answer 11

• perception depends on the specialized neurons that function as receptors
• neurons detect a stimulus
• stimulus is transduced and conducted to the CNS
• sensation is then felt

Question 12

Are neurons adaptive?

What are the two types of sensation?

Answer 12

• Neurons are non-adaptive- you never “get used” to pain like you might get used to a noxious smell
• Two types of sensations
  
  • protopathic- noxious
  • epicritic- non-noxious
    
    • pressure, light touch, temperature discrimination

Question 13

What are the two types of pain?

Answer 13

• Fast pain
  
  • myelinated A delta fibers
  • felt 0.1 sec after stimulus
  • felt on surface of body (sharp, pricking, electric pain)
  • easy to localize
• slow pain
  
  • unmyelinated type C pain fibers
  • felt 1 sec after stimulus
  • felt in deeper tissue and surface tissue (slow burning, aching, throbbing, chronic)

Question 14

What are the different types of painful stimuli?

Answer 14

• mechanical
  
  • fast and slow pain
• thermal
  
  • fast and slow pain
• chemical- uses bradykinin, Ach, prostaglandins, substance P, and proteolytic enzymes to increase permeability to ions like potassium
  
  • slow pain only

Question 15

What are the four steps of nociception?

Answer 15

• Transduction- the noxious stimuli is converted to electric activity at the sensory nerve endings
• transmission- propagation of impulses through the sensory nervous system
• Modulation- process of transmission modified by neural influence
  
  • may be up-regulated or down-regulated
• perception- the signal interacts with the psychology of the pt to create what is perceived as pain

Question 16

What is the transduction process?

list the chemicals (5)

Answer 16

• Mechanical, thermal, and chemical receptors convert to electrical action potential by opening and closing Na and K ion channels
• A noxious stimuli that causes cell damage which release sensitizing chemicals
  
  • prostaglandins
  • bradykinin
  • serotonin
  • substance P
  • histamine

Question 17

What is the route of action potential transmission?

Answer 17

• site of injury to spinal cord
• spinal cord to brainstem and thalamus
• thalamus to cortex for processing

Question 18

What is the pathway for most pain sensation?

Answer 18

• First order neuron- from site of problem to spinal cord via dorsal (sensory) root
  
  • may synapse with interneurons, sympathetic neurons, and ventral horn (motor) neurons
• second order neuron- in gray matter of ipsilateral dorsal horn
  
  • most cross midline and go up the spinothalamic tract to the thalamus, reticuar formation, nucleus raphe magnus, and periaqueductal grey
• third order neuron- send message from thalamus to somatosensory areas I and II in the parietal cortex and the superior wall of the sulvian fissure
  
  • where pain is localized

Question 19

Where does the spinothalamic tract lie?

Answer 19

anterolaterally in white matter of the spinal cord

Question 20

What are the three (four) alternate pain pathways?

Answer 20

• Spinoreticular tract-Causes insomnia due to pain
• spinomesencephalic tract- activates anti-nociceptive descending pathways
• spinohypothalamic and spinotelencephalic tracts- activate the hypothalamus and evoke emotional behaviour

Question 21

Details about the neospinothalamic tract (fast pain):

Where do first order neurons enter?

Where do second order neurons cross midline?

Where do most travel to?

Answer 21

• First order neurons (via A delta fiber) enter lamina I and V (lamina marginalis) of the dorsal horn of SC.
• Second order neurons cross the midline through the anterior white commissure and pass upwards in the spinothalamic tract
• Few terminate in reticular formation (affecting sleep cycle)
• MOST travel to Ventrobasal Complex of Thalamus
• Third order neurons comminicate to somatosensory cortex

Question 22

What is the other name for the Spinothalamic tract?

Answer 22

anterolateral column

Question 23

Details of the Paleospinothalamic pathway (slow pain):

Where to first order neurons enter lamina?

Where do second order neurons connect?

Where do the third order neurons terminate?

Answer 23

• First order neurons (C fibers) enter via laminae II and III of the dorsal horns (aka substantia gelatinosa)
• Second order neurons connect in laminae IV-VIII and go up without crossing over
  
  • most join fibers from the fast pathway, crossing to the other side and saking the STT
• 1/10th of fibers stop in thalamus
• the rest terminate in the medulla, pons, and tectum of midbrain mesencephalon periadueductal grey
• B/C these fibers do not go beyond the thalamus to the somatosensory cortex, these sensations are not localized

Question 24

When can fast pain be easily localized?

Answer 24

If the A delta fibers are stimulated together with tactile receptors

Question 25

What three components mediate the analgesia system?

Answer 25

* the periaquaductal grey matter (in the midbrain) * the nucleus raphe magnus (in the medulla) * the nociception inhibitory neurons within the dorsal horns of the spinal cord

Question 26

What is the periaquaductal grey matter?

Answer 26

* the epicenter of analgesia * it plays a role in the descending modulation of pain and in defensive behavior * has enkephalin producing cells

Question 27

What is the Nucleus Raphe Magnus?

Answer 27

* afferently stimulated from axons in the spinal cord and cerebellum * main function: **pain mediation** * sends projections to the dorsal horn of the spinal cord to directly inhibit pain

Question 28

What are the chemical mediators of pain? Which one is released slowly? Which one is released instantly?

Answer 28

* Substance P- slow release, builds over a few minutes for slow, chronic pain * Glutamate- acts instantly; only lasts a few milliseconds- fast pain * CGRP- calcitonin gene related peptide

Question 29

Where can pain moculation happen?

Answer 29

* peripherally at the nociceptors * in the spinal cord * in supraspinal structures * \*modulation can suppress or aggravate pain

Question 30

What is the cellular physiology of acute pain? Mechanism? fibers?

Answer 30

* **Peripheral mechanism** * Information about noxious stimuli arrives from the periphery along A-delta and C fibers * Substance P and excitatory amino acids (EAA) i.e. glutamate are released * **Substance P**- activates neurokinin-1 (NK-1) receptors * EEAs activate amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors

Question 31

What is the cellular physiology of pain in the chronic state? (not chronic pain, but chronic barrage of signals) mechanism?

Answer 31

* **Central mechanism**- the information is relayed to higher brain areas * normally the NMDA-linked channels are inoperative b/c they always have the Mg ion "plug" * the Mg gets bumped off due to intense and prolonged barrages of nociceptive info * the neurons become sensitized and over respond to subsequent incoming nociceptive signals * The loss of Mg results in Ca ions influxing in and activating nitric oxide synthase (cNOS), converting L-arginine to nitric oxide * This NO acts **presynaptically** to cause exaggerated release of substance P and EAAs * **Postsynaptically** NO causes the neurons to become hyperexcitable and releasing Substance P, ACh, etc

Question 32

What is the neuroendocrine responses to acute pain?

Answer 32

* Neuroendocrine response * increased secretion of catabolic hormones * stress response * decrease anabolic metabolism * insulin, testosterone * ACTH release * hyperglycemia

Question 33

What are the cardiac responses to acute pain?

Answer 33

* Increased HR, BP, SVR, CO * MI, CHF, dysrhythmias * decrease myocardial oxygenation- d/t pulmonary dysfunction/atelectasis * Coronary artery constriction d/t high catecholamines * release of serotonin may induce coronary vasospasm * increased plasma viscosity * platelet induced occlusion

Question 34

What are the pulmonary responses to acute pain?

Answer 34

* Increased total body O2 consumption * increased CO2 production * increased MV * decreased TV, VC * decreased FRC- most detrimental change in post surgical lung volume. As FRC decreases, resting lung volume approaches closing volume, continues on to atelectasis, V/Q mismatch, and hypoxemia ensues * Pulmonary function decreases with abdominal or throacic incision (splinting)

Question 35

What are the other physiologic responses to acute pain?

Answer 35

* Vascular system- stress mediated due to platelet adhesion and hyper-coagulability * DVT, pulmonary edema * Visceral pain is referred to somatic sites * GI and urinary systems have increased sympathetic done (sphinctor); decreased gastric motility * promoting N/V, ileus, urinary retention * Muscle spasms- periosteal and somatic irritation initiates reflex motor response leading to muscle spasm * Anxiety and anger

Question 36

What should you consider regardings the different methods of pain relief?

Answer 36

* Duration of pain relief * patient history * goals of management * acute vs chronic pain

Question 37

What is the BEST postoperative pain management?

Answer 37

* Preemptive analgsia! * opioids and NSAIDS in GA * regional blocks * local infiltration at the surgical site

Question 38

What are the benefits of regional anesthesia? Where does a block need to be to have a significant effect on the neuroendocrine response to surgery?

Answer 38

* Pts do better overall * less morbidity * less CV ailure * less infections * less urinary cortisol- means less of a stress response * lower overall post-op complication rate * \*\*higher than L1 has a significant effect on the neuroendocrine response to surgery

Question 39

What is the current COX concept?

Answer 39

* COX 1- Constitutive * homeostatic funtions- GI tract, renal, platelet function, macrophage differentiation * **Inhibition undesirable** * COX 2- Induced * Inflammation * **Inhibition desireable**

Question 40

What are the advantages of patient controlled analgesia? Features?

Answer 40

* Advantages? * Cost effective * higher degree of pt satisfaction * total drug consumption is less than IM * harder to overmedicate self * Features * Reservoir * infusion controller- pushbutton to be controlled **by the patient only** * delivers a specific dose * lockout * basal infusion

Question 41

What do PCAs prevent? What are the findings regarding PCAs?

Answer 41

* prevents the "pain no pain cycle" * findings * patients consume less drug * male use more than females * shortens hospital stays

Question 42

What are nearly all PCA overdoses attributed to? Other side effects?

Answer 42

* errors in the programming of the parameters * N/V, constipation, pruritis

Question 43

What is the definition of chronic pain?

Answer 43

* pain which persists **one month** longer than expected * Originally defined as pain that lasted 6 months or longer * Now it is the "disease of pain" * What is chronic pain often associated with? * musculoskeletal disorders * chronic visceral disorders * lesions of peripheral nerves * nerve roots * dorsal root ganglia (including causalgia, phantom limb pain) * lesion of the CNS and cancers invading the nervous system

Question 44

What are the most common forms of chronic pain? What can chronic pain trigger?

Answer 44

* low back pain * HA * recurrent pacial pain * cancer pain * arthritic pain * can have a psychosomatic or psychogenic cause * Chronic pain can trigger multiple psychological problems that confound both patient and health care provider, leading to feelings of helplessness and hopelessness

Question 45

What are some causes of chronic pain? (7) \*there is another card with 3 others.....sorry \*hint: physical

Answer 45

* C**hronic pathology** in somatic or visceral structures * **peripheral mechanisms** * chronic pain syndromes associated with chronic inflammation--respond to aspirin and NSAIDS which prevent synthesis of prostaglandins * **reflex role**- chronic pain can create excessive muscle tension and tendon stretch * sympathetic hyperactivity can create local ischemia and persistent disruption of the microcirculation * **Lesions** of peripheral nerves, dorsal roots or dorsal ganglion cells * found in causalgias and other reflex sympathetic dystrophy, phantom pain * **The circle mechanism**- intense stimulation of nerve fibers in the cord activate internuncial neurons creating an abnormal reverberatory activity in a closed loop * **chronic nerve compression** * **Central pain mechanisms**- lesions to the thalamus and spinal cord injury, such as paraplegia

Question 46

Whart are some other causes of chronic pain? (3) \*hint: psych (kinda)

Answer 46

* **Psychological mechanisms** * **psychophysiologic mechanisms-** * severe stress- chronic tension HA, muscle spasms in the shoulder, back and chest * **Learned mechanisms-** Secondary gain * these patients frequently develop reactive depression and hypochondriasis

Question 47

What are the effects of chronic pain?

Answer 47

* Serotonin and endorphins become depleted, so minor injuries become intolerable * psychologic profiles * chronic pain pt shows significant differences on the MMPI, neuroticism * When the pain is relieved, the neurotic features dissipate * the longer the pain, the greater the psychological changes

Question 48

Chronic pain treatment goal examples

Answer 48

* Must remove pain and the cause of pain * also rehabilitate the pt and family psysically, psychosocially and psychologically * Examples: * steroid epidural injection (with or without trigger point injections) * peripheral nerve blocks with neurolytics, acupuncture * Note: chronic pain patients often require more analgesics