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Pain management
 

Pain management

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Pain management

Pain management

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    Pain management Pain management Presentation Transcript

    • Pain Management
    • Objectives
      • Minimize severity of post surgical pain.
      • Improve the animals ability to cope with that pain.
      • Decrease suffering & hasten return to normal function.
    • Definition An unpleasant sensory or emotional experience associated with actual or potential tissue damage or is described in terms of such damage-(IASP) Pain
    • Classification of Pain
      • Acute pain
      • Chronic pain
      • Tumour pain
      • Neuropathic pain
    • Pathophysiology
      • Nociceptor – unencapsulated peripheral termini of primary afferent neurons. A receptor preferentially sensitive to a noxious stimulus or to a stimulus that will become noxious if prolonged.
      Each nociceptor has a detection threshold potential which must be exceeded before an impulse travels from the peripheral receptor site to the CNS.
    • Nociception Physiological process which involves transduction , transmission , modulation and perception of the noxious stimuli. Pain is the subjective interpretation of nociceptive input.
      • Types of nociceptors
        • High threshold mechanoceptors (HTM)- Adelta
        • Low threshold mechanothermal (LTM) receptors associated with A- beta nerve fibers.
        • Myleinated mechanothermal (MMT)- A delta heat nociceptors.
        • C-Polymodal receptors (CPM) associated with C nerve fibers.
    • Different types of stimuli
      • Chemical stimuli
      • Exogenous
      • Endogenous
      • Thermal
      • Mechanical
    • Different types of nerve fibers concerned with the impulse transfer
      • A- delta nerve fibers
      • “ Fast fibers”
      • First acute, fast, sharp pain associate with injury.
      • Receptive area is very discrete
      • Help to localize the pain to the site of stimulus. Eg HTM, MMT.
      • C- nerve fibers
      • Slow fibers
      • Second, dull, aching, burning, throbbing pain associated with injury.
      • Their receptive area is large.
      • They limit the localization of the site of stimulus to general body areas.
      • A- beta nerve fibers
      • Lower stimulation threshold than A- delta & C fibers
      • Transmit innocuous tactile sensations such as vibration, tickling, tingling etc.,.
      • Close the gate
      • Stimulating A beta nerve fibers seems to diminish A- delta & C nerve fiber nociceptor input.
      A- delta or C nerve fibers carry nerve impulse from the periphery to the dorsal or ventral spinal root and then to the dorsal horn of the spinal cord after nociceptor threshold has been reached.
    • Different Types of pain and their conduction
      • Somatic Pain
      • Both A- delta & C fibers.
      • Discretely localizable.
      • Visceral pain
      • C fibers only.
      • Poorly localized.
      • Broad stimulation of visceral nerve endings by ischemia, smooth muscle spasm of hollow organs or ducts, or distention of viscera and ligaments.
      • Parietal surfaces of thorax and abdomen and retroperitoneal organs are richly supplied by A- delta and C fibers.
    • Pain tolerance Greatest level of pain that a subject will tolerate. Varies widely among both individual and species.
      • Hyperalgesia
      • Occurs when a nociceptor is stimulated and then respond to subsequent noxious stimuli more vigorously and at a low pain detection threshold.
      • Primary hyperalgesia
      • Secondary hyperalgesia
    • Central sensitization
      • An activity dependant increase in the excitability of the spinal neurons.
      • Hypersensitisation of post synaptic ascending spinal neurons.
      • Magnitude and duration of response to the subsequent noxious stimuli will increase.
      • Clinically significant-post operative analgesia.
    • Pain Pathway
      • The first order neuron originates in the periphery and projects to the spinal cord.
      • The second order neuron ascends the spinal cord.
      • The third order neuron projects into the brain.
    • SPINAL CORD STRUCTURE
      • Nociceptive Afferent Nerves
      • A-delta – laminae I,II,V,X.
      • C-fiber – laminae I,II,V.
      • C-fiber mediating visceral nociception – laminae I,V.
      • Neurotransmitters involved – Glutamate, Aspartate, Somatostatin, vasoactive intestinal peptide, cholecystokinin, angiotensin II, dynorphin, enkephalin etc..
      • Dorsal Horn Cells
      • Nociceptive Specific cells (NS) are in high concentration in lamina I & V – receive excitatory input from HTM,MMT and CPM.
      • Some NS cells receiving input only from HTMs.
      • Wide Dynamic Range (WDR) neurons in lamina V – Receive convergent input.
      • Glutamate and Aspartate are the major excitatory neurotransmitters of CNS.
    • Ascending Pathways
      • Bundles of nerve fibers whose cell bodies are located in the gray matter of spinal cord or brain stem and terminate by synapsing with cells in the brain, usually in the reticular formation or in the thalamus.
      • Also known as relay or transmitter cells.
      • Divided into Lateral and Medial groups.
      • Lateral group- (a) Neospinothalamic tract, (b) spinocervical tract, (c) dorsal column postsynaptic tract.
      • Medial group- (a) paleospinothalamic tract, (b) spinoreticular tract, (c) spinomesencephalic tract, (d) Propriospinal system.
    • Neospinothalamic tract
    • Descending System
      • Each structure below the brain that projects to the cortex receives descending fibres from the cortex that can influence transmission in the thalamus, reticular formation, trigeminal system and spinal cord.
      • Four tiered
      • Cortical & diencephalic systems.
      • Mesencephalic periaqueductal grey matter (PAG) & periventricular grey matter (PVG)- rich in enkephalins and opiate receptors.
      • Parts of rostroventral medulla- the nucleus raphe magnus (NRM).
      • The spinal and medullary dorsal horn.
      • These axons are prominently seratonergic terminating on cells in the laminae I,II & V and selectively inhibit nociceptive neurons and interneurons.
    • Descending anlagesic system
    • Assessment and recognition of pain
      • Most important step.
      • Absence of verbal communication
      • Inconsistent interpretation.
      • Key source- Interpretation of behavioural and physiologic responses.
      • Latest - Power Spectral Encephalogram analysis.
    • Physiologic Signs of pain
      • Result of catecholamine release and activation of the sympathetic nervous system.
      • Systemic Changes
      • Cardiovascular system - heart rate & BP.
      • Pulmonary sys - resp. rate, shallow breathing.
      • Musculoskeletal sys - tense muscles, M. tremors.
      • Immune sys - resistance, stress leukogram.
      • Neuroendocrine sys - catabolism, anabolism.
      • Digestive sys - Inappetence, vomiting, diarrhoea.
    • Behavioural response
      • Vocalization
      • Facial expression
      • Body posture
      • Activity
      • Attitude
      • Appetite
      • Urinary and bowel habits
      • Grooming
      • Guarding and self-mutilation
    • Degree of Pain
      • Mild pain.
      • Moderate pain.
      • It is the common degree of pain that is treated.
      • Severe pain
        • it is intolerable
        • unprovoked vocalization
        • chance of self mutilation
    • Pain Management
      • Why pain management ?
      • Feel better
      • Physiologic changes that accompany pain
      • Should be able to eliminate pathologic pain
      • Pain free sleep
      • 12 – 24 hr post operative pain management is important.
    • Non pharmacologic approach
      • Keep patient clean & dry.
      • Keep the patient warm.
      • Room with moderate temperature and humidity.
      • Well padded place to sleep.
      • Patients surrounding should be pleasant & quiet.
      • Human contact
      • Acupressure, acupuncture, massage, manipulation stimulate A-beta nerve fibers.
    • Non pharmacologic approach
      • Cryotherapy
      • Thermotherapy
      • Actinotherapy
      • Ultrasound therapy
      • Low Level Laser Therapy (LLLT)
      • Transcutaneous Electrical Neuro-stimulation (TENS)
      Continued
    • Pharmacologic approach
      • Preemptive approach
      • Balanced approach
          • Multiple drugs for maximal effects – Customized Multimodal Therapy.
          • Multiple site.
      • Local Anaesthetics, NSAIDs, Opioids – alone or in combination.
      • Phenothiazine tranquilizers, Benzodiazepine tranquilizers & α 2 agonists.
    • Transduction Noxious Stimulus Transmission Modulation Perception LAs, NSAIDs LAs Opiods, α 2-agonists General Anaesthetics, Opiods, α 2-agonists
    • Local Anaesthetics
      • Used in perioperative and postoperative pain.
      • Application
        • Infiltration of surgical site
        • Direct nerve blocks
        • Regional Infiltration
        • Intra-articular infiltration
        • Epidurals
      • Mainly used – Lidocaine & Bupivacaine.
    • Nonsteroidal antiinflammatory drugs(NSAIDs)
      • Inhibition of prostaglandin synthesis by inhibiting cyclooxygenase enzyme (COX).
      • NSAIDs vary in their ability to inhibit COX 1 & 2
      • COX 2 inhibition will provide enhanced analgesia.
      • Eg. Ketoprofen, Meloxicam, Flunixin meglumine.
    • Opioids
      • Bind at specific receptor sites in brain and spinal cord by mimicking the actions of endogenous peptides modulating pain recognition.
      • Interfere with calcium influx.
      • Opioid agonists include morphine, hydromorphine, codeine, meperidine, fentanyl, carfentanil, etorphine and methadone.
      • Fentanyl patches are used recently in animals.
    • Principles of Postoperative pain management
      • Prevent or limit pain
      • Use analgesics pre-emptively to control pain.
      • Do not wait until behavioural changes are observed.
      • Do not ignore patient behaviour.
      • Never as a method of restraint.
      • Do not stop analgesic therapy abruptly.
      • Try to provide a calm environment.
    • Thank You….