PAIN
Meaning
An
unpleasant sensory and emotional experience associated with actual or potential
tissue damage or described in terms of such damage.
Pain Mechanism
Nociception is the physiological process by
which information about tissue damage is communicated to the CNS
Pain perception
consists of four processes:
1.
Transduction
2.
Transmission
3.
Perception
4.
Modulation
Transduction
·
Is
the conversion of a mechanical, thermal or chemical stimulus into a neuronal
action potential.
·
It
occurs at the level of peripheral nerves, in particular the free nerve endings
or nociceptor.
·
Noxious
stimulus causes cell damage with the release of numerous chemicals into the
area surrounding these nociceptors.
Transduction Substances
includes:
·
Prostaglandins
·
Bradykinin
·
Serotonin
·
Substance
P
·
Histamine
·
Hydrogen
ions
·
ATP
These
substances activate nociceptors and lead to generation of action potential.
Activation
results in an action potential, which is carried from the nociceptors to the spinal
cord via myelinated A-delta fibers and
unmyelinated, slowly conducting C fibers.
Transmission
Transmission
is the movement of pain impulses from the site of transduction to the brain
Action
potential continues from-
Site of injury to spinal cord
↓
Dorsal Horn processing
↓
Spinal cord to brain stem to
thalamus
↓
Thalamus to cerebral cortex for
processing
Perception
·
Conscious
experience of pain
·
Perception
occurs when pain is recognized, defined and responded to by the individual
experiencing pain.
·
Pain
perception involves several brain structures.
Modulation
·
Modulation
involves the activation of descending
pathways that exert inhibitory or facilitatory effects on the transmission
of pain.
·
Depending
on the type and degree of modulation, pain is perceived.
·
Modulation
of pain signals can occur at the level of periphery, spinal cord, brainstem and
cerebral cortex.
·
Descending
modulatory fibers release chemicals - serotonin, norepinephrine, GABA,
endogenous opioids that inhibit pain transmission.
Types of pain
·
Nociceptive
·
Neuropathic
pain
·
Acute
& chronic pain
Nociceptive pain
·
Nociceptive
pain is caused by damage to somatic or visceral tissue.
·
Somatic pain: It is characterized as deep,
aching or throbbing that is well localized, arises from bone, joint, muscle,
skin or connective tissue.
·
Visceral pain: which may result from stimuli such
as tumor involvement or obstruction, arises from internal organs such as the
intestine & bladder.
Neuropathic pain
·
Neuropathic
pain is caused by damage to peripheral nerves or CNS
·
Common
causes are trauma, inflammation, DM, tumors, toxins and neurological disorders
·
Pain
is typically described as numbing, burning, shooting, stabbing or electrical in
nature.
·
Neuropathic
pain can be sudden, intense, short lived or lingering
Difference between acute & chronic pain
|
Characterstics
|
Acute pain
|
Chronic pain
|
|
Onset
|
Sudden
|
Gradual or sudden
|
|
Duration
|
< 3 months
|
> 3 months
|
|
Severity
|
Mild to severe
|
Mild to severe
|
|
Cause of pain
|
Surgery
|
May not be known
|
|
Course of pain
|
Goes away as recovery
occurs
|
Typically pain does not
go away
|
|
Goals of treatment
|
Pain control
|
Pain control to the extent
possible
|
Pain Assessment
Pain
characteristics:
·
Pattern
of pain: onset and Duration
·
Area
of pain: Precise location, Radiating
·
'Intensity
of pain; use pain scale - no pain to
worse pain.
·
Nature
of pain: burning, shooting, stabbing, sharp, aching, throbbing and cramping.
Management
Drug therapy
Non-opioid Analgesics
·
Acetaminophen
·
Salicylates:
E.g.- Aspirin
·
NSAIDS:
Ibuprofen, Diclofenac, COX-2 inhibitors (cyclooxygenase).
Opioid analgesics
·
Morphine
·
Fentanyl
Adjuvent drugs for
pain
·
Corticosteroids
- for inflammation
·
Antidepressants
(Imipramine) - Neuropathic pain
·
Antiepileptic
drugs (Tegretol) - Neuropathic pain
·
Muscle
relaxant (Baclofen) - Neuropathic pain and muscle spasm.
·
Alpha
2 Adrenergic agonist (Clonidin) - Neuropathic pain, given intrathecally.
·
Anesthetics
(Lidocaine 2.5%)
Administration Routes
·
Oral
·
Sublingual
·
Rectal
- Suppository
·
Transdermal
- Applied on non- hairy skin.
·
Parenteral
- IV, 1M
·
Intra
spinal - Involves insertion of a catheter into the subarachnoid space (Intra
thecal) or epidural space (epidural).
·
Patient
controlled analgesia
·
Intervention
therapy: Therapeutic nerve block - local anesthetics administered to reduce pain.
Non-pharmacologic
therapy
·
Massage
·
Vibration
·
Transcutaneous
electrical nerve stimulation (TENS)
·
Percutaneous
electrical nerve stimulation (PENS)
·
Acupuncture,
exercise
·
Heat
therapy
·
Cold
therapy
Cognitive therapies
·
Distraction
·
Hypnosis
·
Relaxation
Find The Other Common Signs And Symptoms Notes Here
Find The Other Common Signs And Symptoms Notes Here
Click ME
COMMENTS