Pain Lecture 1 PDF

Classification of Pain and Pain Assessment Kannan O. Ahmed Assistant professor, uofg Faculty of pharmacy Clinical pharmacy and pharmacy practice department 2023 learning Objectives ▪ Define pain ▪ Pathophysiology of Pain ▪ Classify p...

Classification of Pain and Pain Assessment Kannan O. Ahmed Assistant professor, uofg Faculty of pharmacy Clinical pharmacy and pharmacy practice department 2023 learning Objectives ▪ Define pain ▪ Pathophysiology of Pain ▪ Classify pain (in terms of pathophysiology & duration) ▪ Clinical Presentation and Diagnosis of Pain. ▪ Identify method of pain assessment and to select an appropriate pain assessment tool. Definition of Pain The International Association for the Study of Pain (IASP) defined pain as an “unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”. Generally pain is subjective. Affects all areas of a person’s life (sleep, thought, emotion, & activities of daily living ADLs) Epidemiology According to the American Pain Foundation, more than 76 million people in the US suffer from chronic pain, and an additional 25 million experience acute pain from injury or surgery. Approximately one-fourth of U.S. adults reported having low back pain lasting at least 1 day in the past 3 months. Pathophysiology of Pain ▪ The nociceptive system extends from the receptors in the periphery to the spinal cord, brainstem, to the cerebral cortex where pain sensation is perceived. ▪ This system is a key physiologic function that prevents further tissue damage due to the body’s autonomic withdrawal reflex. ▪ When tissue damage occurs despite the nociceptive defense system, inflammatory pain ensues. Pathophysiology of Pain ▪ Signals from these nociceptors travel primarily along two fiber types: 1. slowly conducting unmyelinated C-fibers. 2. small, myelinated, and more rapidly conducting A delta fibers. Pathophysiology of Pain ▪ Injury to tissue causes cells to break down and release various tissue byproducts and mediators of inflammation (e.g., prostaglandins, substance P, bradykinin, histamine, serotonin, cytokines) ▪ These mediators sensitize nociceptors (increase their excitability and discharge frequency). Classification of Pain Although pain classes are not diagnoses, categorizing pain helps guide treatment. Multiple systems for classifying pain exist. Pain can be classified based on: Underlying pathophysiology Pain duration In Terms of pathophysiology 1. Nociceptive pain 2. Inflammatory pain 3. Neuropathic pain 4. Functional (dysfunctional) pain Nociceptive pain 1. Transient pain in response to a noxious stimulus at nociceptors. 2. Caused by the ongoing activation of A-δ and C-nociceptors in response to a noxious stimulus(e.g., injury, disease, inflammation) 3. Serve to protect against painful stimuli. Nociceptive pain 1. Acute, localized, well described, and relieved with conventional analgesic. 2. Pain arising from visceral organs is called visceral pain, whereas that arising from tissues such as skin, muscle, joint capsules, and bone is called somatic pain. Neuropathic pain Spontaneous pain or hypersensitivity to pain associated with damage to or pathological change in the peripheral or central nervous system. Reflects nervous system injury or impairment. It serves no purpose. Common causes include: trauma, inflammation, metabolic diseases (e.g., diabetes), infections (e.g., herpes zoster), tumors, toxins, and primary neurological diseases. Neuropathic pain Pain may be continuous or episodic. perceived in many ways (e.g., burning, tingling, prickling, shooting, electric shock-like, jabbing, squeezing, deep aching, spasm, or cold).  Nociceptive Neuropathic Usually aching or throbbing Pain often describe as and well localized. tingling, shock-like, and Usually time limited (resolved burning commonly after damaged tissue heal) associated with numbness. but can be chronic. Almost always a chronic Generally respond to condition. conventional analgesic. Respond poorly to conventional analgesic. Central sensitization ▪ Under normal conditions, a balance generally exists between excitatory and inhibitory neurotransmission. Changes in this balance can occur both peripherally and centrally, resulting in exaggerated responses and sensitization, such as that observed in inflammatory, neuropathic, or functional chronic pain. ▪ Repeated or prolonged input from C-nociceptors or damaged nerves causes a longer-lasting increase in DH neuron excitability and responsiveness. ▪ This may outlast the stimulus by minutes to hours. ▪ Central sensitization is associated with a reduction in central inhibition. ▪ Clinically, these changes may manifest as: Central sensitization ▪ Hyperalgesia: ✓an increased response to a noxious stimulus (severe pain from stimulus that normally cause slight pain). ▪ Allo-dynia: ✓a painful response to a normally innocuous stimulus (pain from stimulus that normally cause no pain). ▪ Persistent pain: prolonged pain after a transient stimulus (pain with no stimulus). ▪ Referred pain: the spread of pain to uninjured tissue. Inflammatory pain ▪ Body response to tissue damage by activating pain pathway to produce inflammation. ▪ To protect the injured tissue. ▪ Examples include: appendicitis, rhaumatoid arthritis. Functional or (dysfunctional) pain ▪ Pain due to an abnormal processing or function of the CNS in response to normal stimuli. ▪ Pain in absence of tissue damage with perception of pain being very real Chronic (e.g. IBS, fibromyalgia ) ▪ Influenced by factors e.g. stress, anxiety, depression, or illness In Terms of duration Acute Pain Chronic Pain Referred to as adaptive Maladaptive, pain a pathologic function It is a symptoms. of the nervous system or pain as a disease. Acute Pain ▪ Easily identified cause (injury, illness or surgery) & location (Somatic or visceral). ▪ High levels of pathology usually accompany acute pain and the pain resolves with healing of the underlying injury. ▪ Nociceptive, but can be neuropathic or associated with inflammatory response. ▪ Acute Pain Should be Treated Aggressively Chronic Pain ▪ Chronic pain was once defined as pain that extends 3 or 6 months beyond onset or beyond the expected period of healing. ▪ Recognized as pain that extends beyond the period of healing, with levels of identified pathology that often are low and insufficient to explain the presence and/or extent of the pain. Chronic Pain ▪ Chronic pain is also defined as a persistent pain that “disrupts sleep and normal living, ceases to serve a protective function, and instead degrades health and functional capability. ▪ Nociceptive, inflammatory, neuropathic, or functional. Chronic Pain ▪ Either continuous or recurrent (episodic). ▪ Caused by injury (e.g., trauma, surgery), malignant conditions, or a variety of chronic non-life-threatening conditions (e.g., arthritis, neuropathy). ▪ In some cases, chronic pain exists de novo. Chronic Pain ▪ Chronic pain has sufficient duration and intensity to adversely affect quality of life. There are four main effects ▪ Physical function; sleep & ADLs. ▪ Psychological changes; depression, anxiety, anger ▪ Social consequences; changes in relationships, isolation ▪ Societal consequences; costs, disability, lost productivity Classification of chronic pain Associated with progressive disease Chronic e.g. cancer, AIDS, progressive malignant pain neurologic diseases, end-stage organ failure Last > 6 months beyond healing Chronic non- period malignant pain e.g. low back pain, osteoarthritis, previous bone fractures Factors affecting Chronic Pain Acute VS Chronic Pain Cancer Pain ▪ Pain associated with potentially life-threatening conditions. ▪ Includes pain caused by the disease itself (e.g., tumor invasion of tissue, compression or infiltration of nerves or blood vessels, organ obstruction, infection, inflammation) and/or painful diagnostic procedures or treatments. ▪ So it has multiple etiologies. Clinical Presentation and Diagnosis of Pain ▪ Symptoms ✓ Pain is described based on the following characteristics: ✓onset, duration, location, quality, severity, and intensity. ✓Other symptoms may include anxiety, depression, fatigue, anger, fear, and insomnia. Clinical Presentation and Diagnosis of Pain ▪ Signs ✓Acute pain may cause hypertension, tachycardia, diaphoresis, mydriasis, and pallor. ▪ Diagnosis ✓ The patient is the only person who can describe the intensity and quality of their pain. ✓There are no laboratory tests that can diagnose pain. Pain Assessment ▪ Many organization consider pain is the 5th vital sign, so routine screen for pain is highly recommended. ▪ Effective pain management begins with a thorough and accurate pain assessment ▪ Reassessment should be done as needed ▪ Lack of regular assessment and reassessment of pain remains a problem and contributes to the under treatment of pain. Method of pain assessment ▪ General history ✓Including psychological status, drug and alcohol use ▪ Pain history ✓Onset, duration, location, quality, intensity (pain scale) ✓Relieving and exacerbating factors ✓Impact on functional, behavior & psychological states ▪ Analgesics history (past & current) ✓Dose/route, duration, effectiveness, adverse effects  A common mnemonic for pain assessment is PQRST P Palliative factors What makes the pain better? Provocative or precipitating factors What makes the pain worse? Q Quality of pain Describe pain; sharp, dull, constant, aching, shooting, etc R Region or radiation Where is pain locate? S Severity/intensity How does this pain compare with other pain you have experienced? T Temporal or time related, nature Does the intensity of the pain change with of the pain time? Method of pain assessment ▪ Clinical examination ✓Observations of patient behavior (grimacing, guarding, withdrawing) ✓Physical examination and functional assessment ▪ Others ✓Other conditions such as renal or hepatic dysfunction (influence therapy choices) ✓Patient’s expectations and goals (level of pain relief, functional status, quality of life). Pain assessment tools or scales (intensity or severity) ▪ Rating scales provide a simple way to classify the intensity of pain, and they should be selected based on the patient’s ability to communicate. ▪ 1. Single-dimensional pain scales (Rating scales): ✓ Numerical Rating Scale (NRS) ✓ Visual analog scale (VAS) ✓ Categorical scale: Verbal Description Scale (VDS), Faces Pain Scale (FPS) ▪ 2. Multidimensional pain assessment tools: ▪ Obtain information about the pain and impact on quality of life, ✓ Brief Pain Inventory (BPI) ✓ McGill Pain Questionnaire (MPQ Thanks you 2023