DR. MANSOOR AQIL B.Sc., M.B.B.S., F.C.P.S ASSOCIATE PROFESSOR, KING SAUD UNIVERSITY & CONSULTANT KING KHALID UNIVERSITY HOSPITAL, RIYADH. PAIN PATHOPHYSIOLOGY & MANAGEMENT DR. MANSOOR AQIL B.Sc., M.B.B.S., F.C.P.S ASSOCIATE PROFESSOR, KING SAUD UNIVERSITY & CONSULTANT KING KHALID UNIVERSITY HOSPITAL, RIYADH.
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DR. MANSOOR AQIL B.Sc., M.B.B.S., F.C.P.S ASSOCIATE PROFESSOR, KING SAUD UNIVERSITY & CONSULTANT KING KHALID UNIVERSITY HOSPITAL, RIYADH. PAIN PATHOPHYSIOLOGY.
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DR. MANSOOR AQIL B.Sc., M.B.B.S., F.C.P.S
ASSOCIATE PROFESSOR, KING SAUD UNIVERSITY &CONSULTANT KING KHALID UNIVERSITY HOSPITAL,RIYADH.
PAIN PATHOPHYSIOLOGY
& MANAGEMENT
DR. MANSOOR AQIL B.Sc., M.B.B.S., F.C.P.S
ASSOCIATE PROFESSOR, KING SAUD UNIVERSITY &CONSULTANT KING KHALID UNIVERSITY HOSPITAL,
RIYADH.
PAINPAIN
Word pain is derived from
Latin word “Poena”, meaning penalty, suffering or punishment
PAIN
PAIPAINN
An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.(International association of study of pain)
CLASSIFICATION OF PAIN
S U P E R F IC IA L D E E P
S O M A TIC
TR U E V IS C E R A L TR U E P A R IE TA L R E F E R E D V IS C E R A L R E F E R E D P A R IE TA L
V IS C E R A L
A C U TE
D E A F F E R E N TA TIO NP A IN
S Y M P A TH E TIC A L L YM E D IA TE D P A IN
C H R O N IC
P A IN
TYPES OF PAINTYPES OF PAINAccording to durationAccording to duration
Acute
Chronic
TYPES OF PAINTYPES OF PAINAccording to According to
EtiologyEtiology
Postoperative
OR Cancer pain
TYPES OF PAINTYPES OF PAINAccording to Type of the organ According to Type of the organ
affectedaffected
ToothacheEaracheHeadacheLow backache
TYPES OF TYPES OF PAINPAIN
(According to Pathophysiology)(According to Pathophysiology)
Nociceptive; Due to activation or sensitization of peripheral
nociceptors.
Neuropathic: Due to injury or acquired abnormalities of
peripheral or CNS.
ACUTE ACUTE PAINPAIN
Caused by noxious stimulation due to injury, a disease process or abnormal function of muscle or viscera
It is nearly always nociceptive Nociceptive pain serves to detect, localize and limit the
tissue damage.
PHYSIOLOGICAL PROCESSES PHYSIOLOGICAL PROCESSES IN NOCICEPTIONIN NOCICEPTION
TransductionTransmissio
nModulationPerception
400 years ago Reneé Descartes described pain transmission: The flame that burns the hand is transmitted along the nervous system to the brain as a stimulus, where it torments man as a small flame
Frequently associated with sympathetic or parasympathetic activity – Nausea – Vomiting– Sweating – Changes in HR and BP.
PARIETAL PARIETAL PAINPAIN
Sharp (stabbing sensation) either localized or referred to a distant site.
Phenomenon of visceral pain or parietal pain referred to cutaneous area results from embryologic development and migration.
PATTERNS OF REFERRED PAINPATTERNS OF REFERRED PAIN
Lungs T2 – T6
Heart T1 –T4
Aorta T1 –L2
Esophagus T3 – T8
Pancreas & Spleen T5 –T10
Stomach, liver and gall bladder T6 –T9
Adrenals T6 – L1
Small intestine T6 – T9
Colon T10 – L1
Ureters T10 – T12
Uterus T11 – T12
Bladder and prostate S2 – S4
Urethra & Rectum S2 – S4
Kidneys, Ovaries & Testis T10 – L1
REFERRED PAINREFERRED PAIN
PAIN PATHWAY
FIRST ORDER FIRST ORDER NEURONNEURON
Reach the spinal cord through dorsal spinal root.– Some through ventral root
– Trigeminal N Gasserian ganglion
– Facial N Geniculate ganglia
– Glossopharyngeal N Superior and Petrosal ganglia
– Vagus Ganglion Nodosum and Jugular ganglia
Nociceptive pathways: peripheral sensory nerves
Dorsal Root Ganglion
Blood vessels
Skeletal muscle
Muscle and skin receptors
Tendon bundle
Peripheral nerve Sympathetic ganglion
Viscera
Spinothalamic tract
Dorsal horn of spinal cord
Nociceptive terminals
C and A fibres
Nociceptive sensory fibres are C-fibres and A fibresC-fibres umyelinatedA myelinatedSlow conduction velocitySignal variety of noxious stimuli - polymodal
SPINOTHELAMIC TRACTSPINOTHELAMIC TRACT
Axons of the second order neurons cross the midline form spinothalamic tract Thalamus, Reticular formation, Nucleus Raphe Magnus and Periaquaductal gray matter.
1. Medial tract Medial Thalamus
2. Lateral tract: Ventral Posterolateral Nucleus of Thalamus
THALAMIC THALAMIC NUCLEINUCLEI
ALTERNATE ALTERNATE PATHWAYSPATHWAYS
1. Spinomesencephalic
2. Spinoreticular
3. Spinohypothalamic
4. Spinotelencephalic
5. Spinocervical
6. In the dorsal column
THIRD ORDER THIRD ORDER NEURONNEURON
Located in Thalamus. Send projections to sensory area 1 &II and
Superior wall of Sylvian fissure.
Interlaminar and medial nuclei Anterior Cingulate Gyrus.
Polymodal mechanoheat nociceptors: Excessive pressure, Extremes of Temperature and Alogens like Bradykinin, Serotonin, Histamine, H, K, Prostaglandins and ATP.
Types of Peripheral Fibers
A. B.C.
Pain Fibers and C
Classification & Function of Peripheral Nerve Fibers
A. Myelinated A- Fibers: : Motor , Proprioception (afferent) Motor, Touch (afferent) Muscle spindles (efferent) Pain, Temperature (afferent)
B. Myelinated B-Fibers: Pre-ganglionic Sympathetic Fibers
C. Non-Myelinated C- Fibers: Pain, Temperature.
PHYSIOLOGY OF PHYSIOLOGY OF NOCICEPTIONNOCICEPTION
Fast pain (First pain)
Slow pain (Second pain)
Peripheral Terminal Activation in Acute pain: Phase 1
Second pain - dull, burning, aching, not localised, diffuse
C-fibres umyelinated slow conduction (0.5 - 2 m/s
First pain - sharp, pricking, localisingA fibres myelinated (12-30 m/s)
Time
Pai
n In
tens
ity
MODULATION
MODULATION OF MODULATION OF PAINPAIN
Peripheral Modulation
Central modulation
PERIPHRAL PERIPHRAL MODULATIONMODULATION
Primary Hyperalgesia
Secondary Hyperalgesia
1. Decrease threshold
2. Increase in frequency of response
3. Spontaneous discharge
PRIMARY PRIMARY HYPERALGESIAHYPERALGESIA
Low intensity stimulation High intensity (noxious) stimulation
Innocuous sensation
State of normosensitivity
PAIN
State of Normosensitivity Response proportional to stimulus
Stimulation of A fibers segmental inhibition of small primary pain afferents and reduce response to painful stimuli in dorsal horn secondary afferents
MECHANISM OF ACTION Exact mechanisms of actions are as yet unknown and certainly
unproven 1965- Melzack and Wall proposed the Gate Theory of Pain
– Nociceptive A delta/C fibres project in SC to second-order projection neuron but also send fibres to inhibit an inhibitory interneuron
– Large myelinated A alpha neurons in DC send collaterals to activate these same interneurons thereby inhibiting (closing the gate) the pain sensory action potentials
GATE THEORY OF PAIN
Glycine and GABA are inhibitory transmitters. GABA A and GABAB Muscimol and Beclofen.
GABAB increases K conductance GABAA increases Cl conductance Glycine also increases Cl conductance Strychnine and Tetanus toxide are Glycine receptor antagonists Glycine is facilitatory on NMDA receptors
Adenosine has two types of receptors A1 and A2 A1 inhibits adenyl cyclase and A2 stimulates adenylcyclase. A1 mediate antinociceptive action.
Pharmacological or anatomic differential neural blockade has been advocated as a method of distinguishing somatic, sympathetic, and psychogenic pain mechanisms.
The pharmacological approach relies on the differential sensitivity of nerve fibers to local anesthetics
Preganglionic sympathetic (B) fibers are reported to be most sensitive, closely followed by pain somatosensory C and A delta fibers and finally motor fibers (Aa).
By using different concentrations of local anesthetic, it may be possible to selectively block certain types of fibers while preserving the function of others.
Pharmacological interventions in pain management include – COX inhibitors, – Opioids, – Antidepressants, – Neuroleptic agents, – Anticonvulsants, – Corticosteroids, – Systemic administration of local anesthetics – Alpha 2 agonists– Botulinum toxin
THERAPEUTIC ADJUNCTSTHERAPEUTIC ADJUNCTS
PSYCHOLOGICAL INTERVENTIONS
PHYSICAL THERAPY
Heat and cold
ACUPUNCTURE
THERAPEUTIC ADJUNCTSTHERAPEUTIC ADJUNCTS
ELECTRICAL STIMULATION
– Transcutaneous Stimulation
– Spinal Cord Stimulation (SCS) Proposed mechanisms include activation of descending modulating systems and inhibition of sympathetic outflow
– lntracerebral Stimulation Deep brain stimulation may be used for intractable cancer pain (periaqueductal and periventricular gray areas for nociceptive pain)
Percutaneous radio-frequency ablation relies on the heat produced by current flow from an active electrode that is incorporated at the tip of a special needle. The needle is positioned under fluoroscopy.
Electrical stimulation A z (2'Hz for motor responses and 50 Hz for sensory responses) via the electrode and impedance measurement prior to ablation also help confirm correct positioning.