Pain - N111 Pathopharmacology 1 - Samuel Merritt University

Pain N111 Pathopharmacology 1 Samuel Merritt University  5 Vital Sign th “unpleasant sensory and emotional experience associated with active or potential tissue damage” (IASP) What the patient says it is (The Joint Commission)  Reason for Pain To pr...

Pain N111 Pathopharmacology 1 Samuel Merritt University  5 Vital Sign th “unpleasant sensory and emotional experience associated with active or potential tissue damage” (IASP) What the patient says it is (The Joint Commission)  Reason for Pain To protect the body – Alert the body to a dangerous situation Allow the body to remove itself from the situation  Types of pain Nociceptive Pain – OTC analgesics NSAIDS Tylenol – Prescription analgesics: opioids Morphine Neuropathic Pain: Anticonvulsants – Neurontin – Lyrica Nociceptive Pain  Neuroanatomy of Pain Nociception – Nociceptors: pain receptors Nociceptive pain: pain that occurs as a result of actual/perceived tissue injury  Nociceptive Pain Pathway Transduction Transmission Perception Modulation  Transduction Process of converting painful stimuli to action potentials – Nociceptors transduce Chemical mediators – Prostaglandins NSAIDs – Lactate – Kinins – K+, H+ – Histamine, Serotonin Transmission  Transmission Spinal nerves → anterolateral tract/ thalamus Sensory fibers, ascending Aδ (10%) C (90%) Myelinated Unmyelinated Fast/Large Slow/Small Sharp, Dull, aching stinging Highly Poorly localized pain that  Spinal Neurotransmitters Excitatory Neurotransmitters Substance P Glutamate Histamine Inhibitory Neurotransmitters Endorphins Norepinephrine GABA Serotonin  How does the brain localize pain? Nociceptor pathways are organized in anatomic order in the spinal cord and then in the somatosensory cortex – Dermatome map Primary sensory cortex Dermatome Map Perception  Perception Neural processing of pain sensation Influenced by – Awareness – Emotion/mood – Prior experience – Expectation – Culture – Physical status – Sex/gender (Racine et al., 2012)  Perception Concepts Pain threshold Pain tolerance – Tolerable pain Pain expression – Quantity of pain: pain rating – Quality of pain  Kappa Mu Delta Sigm (κ) (μ) (δ) a (σ) Analge Yes Yes No No sia Agents Morphine Morphine, meperidine, Other that bind Naloxone hydromorphone, less to Endorphi methadone, fentanyl common receptor ns Naloxone pain s Endorphins meds Manifest- Diuresis N/V N/V Tachypn ations Sedation Urinary ↓ RR ea ↓ RR retention Pruritis Hallucin- Pupil Sedation ation constrictio ↓ RR Paranoia n Pupil Delirium  Nociceptive Pain Etiology Injury to tissue stimulates nociceptors – Visceral – Somatic Deep Superficial 22  Nociceptive Pain CM: – Deep, squeezing, dull, poorly localized  visceral pain – Dull, aching, throbbing, poorly localized  deep somatic pain – Sharp, well-defined, well localized  superficial somatic pain TI: Maintain functionality and heal underlying injury – Opioids – OTC analgesics NSAIDs Tylenol 23  Neuropathic Pain E: Possible tissue injury to the nerves P: – Nerve damage or dysfunction – Altered central processing of nociceptive input 24  Neuropathic Pain CM: – Shooting – Burning – Electric/ shock like – Tingling/ pins & needles TI: maintain functional ability and quality of life – Anticonvulsants – Antidepressants (TCAs) 25  Acute Pain E: tissue injury P: – Pain resolves when injury heals – 6 months – ↑ peripheral transduction sensitivity – Abnormal central responsiveness Synaptic plasticity – Breakthrough pain: lowered pain threshold 28  Chronic Pain CM: non-SNS – Mood disturbances – Inability to function – Hyperglycemia chronic – Fatigue & sleep disturbance – Weakened immune system TI: Maintain functional status & quality of life – Multimodal – Long acting meds: opioids, antidepressants, anticonvulsants 29  Referred Pain E: Injury to a different site P: – Referred to tissue in the same sensory dermatome – Visceral nociceptor activity with primary somatic afferent nerves in the posterior horn of the spinal cord CM: Various clinical manifestations TI: Relief of the underlying injury 30 Referred Pain Treatment Implications  Interrupt Peripheral Transmission Thermal treatment –  inflammation/swelling Local anesthetics –  pain stimulus Splinting –  further tissue injury/inflammation NSAIDs –  prostaglandins   inflammation/ pain 33  Altering the perception & integration Opioids/Non-opioids Anticonvulsants/ Antidepressants Non-medication – Distraction – Imagery – Relaxation – Biofeedback – Hypnosis 34  Opioids Side effects – N/V – Respiratory depression ↓ RR – Constipation Addiction, dependence, and tolerance 35