pain management

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  1. 1. AFFIRA NASIR 4TH YEAR MBBS STUDENT PAIN MANAGEMENT
  2. 2. CONTENTS Defination of PAIN Types of pain Nociceptors :Locaton & Types Pathway of Pain Mechanisam of Action of NSAID & Opoid as Analgesic
  3. 3. PAIN Pain is an unpleasant sensory & emotional experience arising from actual or potential tissue damage. It is often described in terms of peneterating or tissue destructive process(eg.,stabbing,burning,tearing) or of a bodily or emotional reaction(eg.,nauseating,terrifying)
  4. 4. Classification of pain Pain can be classified on the base of intensity ,duration, physiology and syndrome Intensity (mild,moderate & severe) Duration(acute,choronic) Physiology(nociceptive,inflammatory) Syndrome(cancer,migraine & other)
  5. 5. Pain Threshold The point at which a stimulus, usually one associated with pressure or temperature, activates pain receptors and produces a sensation of pain. Individuals with low pain thresholds experience pain much sooner and faster than those with higher thresholds Pain Tolerance amount of pain a person is willing or able to tolerate
  6. 6. Allodynia :mean a painfull response to a normaly innocuous stimuls. Hyperalgesia: is an increased sensitivity to pain, which may be caused by damage to nociceptors or peripheral nerves.
  7. 7. Neuroanatomy of Pain The portion of the nervous system responsible for the sensation & perception of the pain is devided into three areas. i. Afferent pathway ii. CNS iii. Efferent pathway
  8. 8. Afferent portion is composed of Nociceptors (pain receptor) Afferent nerve fiber Spinal cord network
  9. 9. Primary afferent nerves Primary afferent nerve fibres that transmit electrical impulses from the tissues to the spinal cord via the ascending nerve tracts. The cell bodies of primary sensory nerves are located in the dorsal root ganglion in the vertebral foramina It has two branches: i. one projects centrally into the spinal cord ii.other projects peripherally to innervated tissues.
  10. 10. Classification of primary afferent nerves Primary afferents are classified by their diameter,degree of myelination and conduction velocity Basically divided into 3 classes i. The largest diameter afferent fibers A- beta(responsd maximally to light touch or moving stimuli) ii.The small diameter myelinated A-delta iii.The small diameter unmyelinated C fiber axons
  11. 11. NOCICEPTORS Primary afferent nociceptors are specialized free nerve endings of primary afferent nerves (A-delta and C fibres). They are generally the first structures to be involved in the nociceptive process and are located in various body tissues including skin, muscle, connective tissue, blood vessels and thoracic and abdominal viscera
  12. 12. NOCICEPTION The peripheral nervous system includes primary sensory nerves specialized to detect mechanical ,thermal or chemical condition associated with potential tissue damage The signals,when these nociceptors are activated,must be transduced & transmited to the spine & brain where signal are modified before they are ultemately understood or "felt"
  13. 13. Transduction During this stage,noxious stimuli trigger the release of biochemical mediator that sensitize nociceptor. Noxious or painfull stimulation also cause movement of ions across cell membrane,which excite nociceptor
  14. 14. Transmition includes 3 segments First segment -pain impulse travels from the peripheral nerve fiber to thr spinal cord Second segment- transmission from the spinal cord & ascension via spinothalamic tract ,to the brain stem and thalamus
  15. 15. Third segment - involves transmission of signals between thalamus to the somatic sensory cortex where pain perception occur
  16. 16. Modulation Often discribed as "Descending System" occur when neurons in the thalamus and the brain stem send signal down to the Dorsal horn of the spinal cord
  17. 17. Perception Transduction,Transmission & Modulation intrect to create subjective emotional experience of pain
  18. 18. Pain pathways Anterolateral or spinothalamic pathway
  19. 19. Anterolateral pathway Pain & Temperature 3 neuron pathway. Its primary neurons axons enter the spinal cord and then ascend one to two levels before synapsing in the substantia gelatinosa. After synapsing, secondary axons decussate and ascend in the anterior lateral portion of the spinal cord as the spinothalamic tract. This tract ascends all the way to the thalamus, where it synapses on tertiary neurons. Tertiary neuronal axons then travel to the primary sensory cortex
  20. 20. MECHAINISM OF ACTION OF NSAID
  21. 21. NSAIDS Nonsteroidal anti-inflammatory drugs are a class of drugs that provides analgesic (pain-killing) and antipyretic (fever-reducing) effects, and, in higher doses, anti-inflammatory effects. The most prominent members of this group of drugs are aspirin, ibuprofen and naproxen.
  22. 22. Most NSAIDs act as nonselective inhibitors of the enzyme cyclooxygenase (COX), inhibiting both the cyclooxygenase-1 (COX-1) and cyclooxygenase- 2 (COX-2) isoenzymes. COX catalyzes the formation of prostaglandins and thromboxane from arachidonic acid
  23. 23. PGs directly stimulate pain receptors and increase sensitivity of pain receptor to bradykinin etc to produce pain . NSAIDs relieve pain via inhibition of PGs biosynthesis.
  24. 24. MECHAINISM OF ACTION OF OPOIDS AS ANALGESIC
  25. 25. Opioids Opioids are act directly on the CNS to relive the pain they produce analgesia by binging to specific G protein coupled receptors in brain & spinal cord
  26. 26. They open K+ channels Prevent opening of Ca++ channels This results in hyperpolarization and a reduction in neuronal excitability Inhibit the release of other neurotransmitters