1. Presented by- Dr Neha kumari
First Year MD Student
Moderator- Dr Mumtaz Hussain
Associate Professor,
Dept Of Anesthesiology And Critical Care
IGIMS, Patna
3. Pain
International Association for study of Pain(IASP)-
Unpleasant sensory and emotional experience
associated with actual or potential tissue damage or
described in terms of such damage.
Pain is redefined as a perception instead of a
sensation because it is a psychological state.
Latin word "peona " meaning punishment
• Pain is always subjective
• It is differently experienced by each individual.
4. Anatomy of Pain-Pathway
Nervous system & pain-
Somatosensory system has 3-components-
1.Brain-Somatosensory cortex,Thalamus
2.Spinal cord-Dorsal & ventral root
3.PNS-Afferent & Efferent neurons,
A-delta fibre,C fibre
Spinal cord has following parts-
Gray matter
White matter
Gray commissure
Central canal
Dorsal & Ventral nerve root
6. Pain pathway
Perception of pain
Transduction of pain
Signal formation-chemical signal- inflammatory
mediators
Electrical activity-Recognises by neurons
Transmission-transmitted through PNS
A-delta-Fast,small,myelinated,acute pain
C-fiber-Slow,large,unmyelinated,chronic pain
Modulation-Signal processing in spinal cord(dorsal horn)
& other endogenous system
7. Pathway
First-order neurons have their cell bodies in the dorsal horn and synapse
on thermoreceptors & nociceptors in the skin.
The first-order neurons synapse on second-order neurons in the spinal
cord.
In the spinal cord, the second-order neurons “decussate” cross the line
and ascend to the contralateral thalamus (ventral posterolateral nucleus).
Decussation usually occurs 1-2 spinal nerve segments above the point of
entry.
In the thalamus, second-order neurons synapse on third-order neurons,
which ascend to the somatosensory cortex and synapse on fourth-order
neurons.
10. Anterolateral system
Spinothalamic tract (lateral and
anterior): destined for
thalamus; important in the
localization of painful or
thermal stimuli.
Spinoreticular tract: destined for
reticular formation;
causes alertness and arousal in
response to painful stimuli.
Spinotectal tract: destined for
tectum; orients the eyes
and head towards the stimuli.
11. Cortical pain processing
Sensory aspects of pain seem to be processed in
somatosensory area
Emotional distress(Empathy) associated with pain seem to
be processed in Anterior Cingulate Cortex(ACC)
12. Subsystem
Direct-Direct conscious appreciation of pain
Indirect-Affective or arousal impact of pain via-
-Spino-reticular-thalamic-cortical pathway -
Spino-mesencephalic pathway(affective impact of
pain)
13. Types of pain
1.Somatic pain-It is a nociceptive pain that arises from
skin,tissue,muscle,bone.
Superficial-skin & subcutaneous
tissue,eg-cuts,burns
deep-muscle,bone,periosteum,fascia
eg-fracture,arthritis,muscle belly rupture
2.Visceral-It is another type of nociceptive pain that
arises from internal organ, eg.Angina pectoris
renal colic,intestinal colic
14. Pain
Nociceptive pain-Tissue damage
Neuropathic pain-Nerve damage
Acute pain-It typically comes on suddenly and has a limited
duration
eg-Damage of tissue such as bone,muscle,organ
Chronic pain-Lasts longer than acute pain & is
generally resistant to medical T/t
eg-Osteoarthritis,Fibromyalgia
Breakthrough pain-often happens in between regular
interval
15. pain
Fast pain-is carried on A-delta,group ΙΙ & ΙΙΙ fibers,has rapid
onset & offset and is precisely located.eg-pin-prick
Slowpain-is carried on C-fibers & is characterized as
aching,burning or throbbing pain that is poorly localized.eg-
Burn
Referred pain-is of visceral origin
According to the dermatomal rule –Sites on the skin are
innervated by nerves arising from the same spinal cord segment
as those innervating the visceral organs
Eg-Ischemic heart pain reffered to chest & shoulder
Gallbladder pain is referred to abdomen
Kidney pain is referred to lower back
17. Pain
Adaptive-Normal response-Tissue damage
Protects from further injury,Inflammation is a large
component
Maladaptive-Abnormal response
Stimulus is gone but pain persists.eg-inappropriate
managed adaptive pain
Allodynia-Not typically painful
Hyperalgesia-Exaggerated response
Hyperesthesia-Increase loss of sensation
18. Pain - Receptors
Specialized naked nerve endings found in almost every tissue
of the body.
Activated by stimuli (mechanical, thermal, chemical)
Distinguished from other receptors by
their higher threshold, and
they are normally activated only by stimuli of noxious
intensity-sufficient to cause some degree of tissue damage.
Aδ: Myelinated
C: Unmyelinated
19. Characteristic features of
Aδ & C fibres
Feature Aδ fibre C fibre
Number Less More
Myelination Myelinated Unmyelinated
Diameter 2-5 µm 0.4-1.2 µm
Conduction
velocity
12-30 m/s 0.5 -2 m/s
Specific
stimulus
Most sensitive to
pressure
Most sensitive
for chemical
agents
Impulse
conduction
Fast component of
pain
Slow component
of pain
20.
21.
22. Nociception
Coined by Sherrington
Latin: noxa means injury
it means the ´perception of noxious stimuli
Pain is termed nociceptive and nociceptive means
sensitive to noxious stimuli
-Noxious stimuli are stimuli that elicit tissue damage and
activates nociceptors
-Nociceptors are free(bare) nerve ending,found in the
skin,muscle,joints,bone & viscera
-A nociceptor is a type of receptor at the end of a sensory
neuron´s axon that responds to damaging or
Potentially damaging stimuli by sending possible threat signals
to the spinal cord and brain
23.
24. Location of nociceptors
Pain detecting
receptors,found through out
the body-
Superficial skin layers
Deeper tissues
Periosteum, joints, arterial
wall, liver capsule, pleura
Other deeper tissues
Sparse pain nerve endings
But wide spread tissue
damage results in pain
25. Types of Nociceptors
Somatic
Free nerve endings of Aδ & C fibres
Visceral
Wide spread inflammation, ischemia, mesentric
streching , spasm or dilation of hollow viscera produces
pain
Probably strech receptors
26. Pain stimuli
Mechanical / thermal stimuli
Fast pain: Sharp well localized , pricking type
Chemical stimuli
Slow pain: poorly localized, dull, throbbing
Bradykinin, histamine
Serotonin, Prostaglandins
Substance P
27. Neurochemicals of pain
Pain initiators-
central-Glutamate,Substance P
Peripheral-Bradykinin,Prostaglandins
Pain inhibitors-
Serotonin,Endorphin,enkephalin,
Dynorphin
29. Gate control system
Gate control theory of pain was proposed by Ronald
Melzack and Patrick Wall in 1965
According to this theory, painful information is
projected to the supraspinal brain regions if the gate is
open, whereas painful stimulus is not felt if the gate is
closed by the simultaneous inhibitory impulses.
30. Usually, rubbing the skin of painful area seems to somehow
relieve the pain associated with a bumped elbow.
In this case, rubbing the skin activates large-diameter
myelinated afferents (A beta), which are “faster” than A
delta fibers or C fibers conveying painful information.
These A-beta fibers deliver information about pressure and
touch to the dorsal horn and override some of the pain
messages (“closes the gate”) carried by the A-delta and
C fibers by activating the inhibitory interneurons in the
dorsal horn
This hypothesis provided a practical theoretical basis for
some approaches such as massage, transcutaneous nerve
stimulation, and acupuncture to treat pain in patients.
33. Pain assessment tool
For young infant-1.PIPP-Premature Infant Pain Profile
1.three behavioural-facial action-brow buldge,eye
squeez & nasolabial furrow and two physiological
heart rate,oxygen saturation
2.FLACC SCORE
3-7 yrs old child-FACES scale,CHEOPS scale
Children>8yrs-VAS score ,numerical rating scale
34.
35.
36. Opioid Receptors
Found in the brain, spinal cord and
peripheral nervous system as:
Mu (μ)
Kappa (k)
Delta (δ)
Nociceptin/Orphanin (N/OFQ)
37. RECEPTOR ENDOGENOUS LIGAND EFFECT ON RECEPTOR
STIMULATION
Mu(μ) Endorrphin Supraspinal analgesia
(μ1)
Dependance (μ2)
Respiratory depression
(μ2)
Constipation (μ2) ,
miosis (μ2)
Kappa(ĸ) Dynorphin Spinal analgesia
Sedation
Miosis
Delta(δ) Enkephalins Respiratory depression
Sigma(σ) Unknown Dysphoria
OPIOID RECEPTORS, THEIR ENDOGENOUS
LIGANDS AND EFFECT PRODUCED ON
RECEPTOR STIMULATION
38. μ -Receptor
μ1
Located outside
spinal cord
Higher affinity for
morphine
Supraspinal
analgesia
Selectively blocked
by naloxone
μ2
Located throughout
CNS
Responsible for
spinal analgesia,
Respiratory
depression,
constipation
physical dependence,
and euphoria
39. Kappa Receptor
Only modest analgesia(spinal κ1 and supraspinal
κ3)
Little or no respiratory depression
Little or no dependence
Dysphoric effects
Miosis
Reduced GI motility
40. Delta Receptor
High affinity for enkephalins endogenous ligands.
The δ mediated analgesia is mainly spinal
Affective component of supraspinal analgesia
appears to involve δ receptors as these receptors
are present in limbic areas—also responsible for
dependence and reinforcing actions.
The proconvulsant action is more prominent in δ
agonists.
Editor's Notes
Pain is unpleasant sensation which only sufferer casn appraise as such is not capable of any satisfactory objective definition
The word unpleasant comprises whole range of disagreeable feelings from being merely inconvinienced to misery, anguish, anxiety, depression
Because pain is universally accepted as signal of disease it is most common symtom that brings the patient to doctor
Thuis this topic is important
Causalgia
Conduct impulses only in response to noxious stimuli
Conduct impulses in response to to thermal and mechanical stimuli
Pain can occur without nociception merely by its expectation and
Nociception does not invariably cause pain
Accompaniment of fast pain: withdrawl reflex, symp response
Accompaniment of slow pain: emotional perception, autonomic symptoms, skeletal muscle tone
An emotional state characterized by anxiety, depression, or unease.