Pain,Shangrong Li, MD Anesthesiology department Third hospital Sun Yat-sen University,2018/10/1,2,Content,Definitions Basic of Pain Categories and Assessment Medicine Nerve block Acute pain Chronic pain,2018/10/1,3,Definition of Pain,Pain is whatever the experiencing person says it is, existing whenever the experiencing person says it does. McCaffery M. (1968),2018/10/1,4,“Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.” IASP (1979),Definition of Pain,Implies emotional component,can exist without tissue damage.,2018/10/1,5,Content,Definitions Basic of Pain Type and Assessment Medicine Nerve block Acute pain Chronic pain,2018/10/1,6,TRPV 辣椒素受体 TREK 钾离子通道 ASIC 酸敏感离子通道 DRASIC ACIC3 MDEG退化蛋白通道 TRPM8 冷受体8,2018/10/1,7,Somatosensory nerve fibers,2018/10/1,8,Somatosensory nerve fibers,2018/10/1,9,2018/10/1,10,2018/10/1,11,Pain Pathways,2018/10/1,12,Content,Definitions Basic of Pain Categories and Assessment Medicine Nerve block Acute pain Chronic pain,2018/10/1,13,Categories of Pain,Somatic pain Examples: acute postoperative pain, bone fractures aching, gnawing, and/or sharp in quality, well localized initiated by nociceptor activation in cutaneous and deep tissues. Visceral pain Examples: abdominal pain due to constipation dull and aching in quality and poorly localized associated with tissue injury, specifically infiltration, compression, and distention of viscera. . Neuropathic pain examples: trigeminal neuralgia，postherpetic neuralgia (PHN) shooting, electrical, or burning pain often is superimposed on a chronic background of burning and aching sensations. results from injury to the peripheral or CNS.,2018/10/1,14,Trigeminal neuralgia,2018/10/1,15,Acute or Chronic,Acute pain:Can be resolved quickly, less than 3-6 months Highly correlated to damage Example: Postoperative pain, Bone fractureChronic pain:last long time, more than 3-6 months “pain that extends beyond the expected period of healing” Arise from injury to disease to visceral, somatic or neural structures Often no correlated to damage Example: Headache, Low back pain, Cancer pain,2018/10/1,16,Measuring Pain,Physiological Symptoms, Signs Unreliable Self-report Behavioral observations Rankings Pain questionnaires Psychological tests,No one tool is suitable for all situations,2018/10/1,17,Visual analogue scale(VAS),2018/10/1,18,Visual analogue scale(VAS),The feeling of pain is subjective, and individual difference VAS are of most value when looking at change within individuals, and are of less value for comparing across a group of individuals at one time point. researchers prefer to use a method of analysis that is based on the rank ordering of scores rather than their exact values, to avoid reading too much into the precise VAS score.,2018/10/1,19,Content,Definitions Basic of Pain Type and Assessment Medicine Nerve block Acute pain Chronic pain,2018/10/1,20,Opioids,(Narcotics, Narcotic analgesics),2018/10/1,21,Blooming poppy flower,2018/10/1,22,2018/10/1,23,Opioid Receptor Subtypes,Mu receptors: Mu1 and Mu2 receptors Kappa receptors: Kappa1, and Kappa3 receptors Delta receptors: Delta1 and Delta2 receptors,2018/10/1,24,Agonist and antagonist,Agonists: Morphine(吗啡）,Codeine(可待因）， Meperidine（度冷丁）, Fentanyl（芬太尼） Antagonists: Naloxone（纳洛酮） Agonist-Antagonists: Butorphanol（布托诺啡），Buprenorphine（丁丙诺啡）,2018/10/1,25,Pharmacological Effects of Morphine,Central Analgesia Sedation euphoria Pupillary constriction Cough suppression Depression of respiration Main cause of death from opioid overdose Combination of opioids and alcohol is especially dangerous,2018/10/1,26,Other properties,Tolerance: need more doses to keep the effect Toxicity: especially respiratory depression Dependence: Physiological and psychological,2018/10/1,27,Naloxone,no agonist activity displaces morphine from all receptors, reverses all of the effects of morphine effects are immediate (3-5 min) duration is 30-45 minutes,2018/10/1,28,NSAIDs,2018/10/1,29,Pharmacological Effects,Antipyretic Analgesia Antiinflammatory(higher doses) Antirheumatic Anti-platelet aggregation,2018/10/1,30,Mechanism,inhibiting the cyclooxygenase(COX) pathway(COX-1,COX-2)stops the production of various prostaglandins that can sensitize free nerve endings to painful stimuli.,2018/10/1,31,Charataristics,limited of analgesic effect (Ceiling effect) do not produce tolerance or physical dependence A good adjuvant (with opioid) no superior NSAID for pain control,2018/10/1,32,classiify,Salicylates Salicylates Aspirin(水杨酸阿斯匹林）, Choline Magnesium trisalicylate（三柳胆镁） Salicylate-Like Drugs Ibuprofen(布洛芬）, Naproxen（萘普生）, Ketoprofen（酮洛芬）, Indomethacin（消炎痛）, Celecoxib(COX 2) （塞来昔布）,2018/10/1,33,2018/10/1,34,Content,Definitions Basic of Pain Type and Assessment Medicine Nerve block Acute pain Chronic pain,Nerve block,Injection of local anesthetic onto or near nerves for temporary control of pain Indentify specific nerves as a pain generators For permanent block by destruction of nerve tissue Can be used to: lower back pain, neck pain, sciatica (from a herniated disc), spinal stenosis, reflex sympathetic dystrophy (a complex regional pain syndrome), cancer, and painful peripheral vascular disease Temporary nerve blocks: a local anesthetic (such as lidocaine) with epinephrine, a steroid (corticosteroid), and/or opioids.,