PAIN By Dr. Cuong Ngo-Minh Back to Basics April 14th 2010
Objectives • To differentiate between Nociceptive from Neuropathic types of pain on neural basis • To make a differential diagnosis of causes of pain. • To clinically assess pain and it’s impact on daily function by history and search for most likely cause • To create an individualized plan of management for patients with acute or chronic pain. Use multiple modalities to relieve pain. • Select clients appropriately for referral to pain specialist, interdisciplinary approach.
Definitions 1 • PAIN: « an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage » by the International Association for the Study of Pain. • A) Nociceptive pain is cause by DIRECT stimulation of peripheral nociceptors. It is usually associated with TISSUE DAMAGE as well asinflammation processes. Nociceptive pain is sub-categorized into A1) somatic which can be superficial (skin) or deep pain (eg tumor infiltration, arthritis) A2) visceral (eg. Pancreatitis, Crohn’s disease). Pathophysiology: SOMATIC pain signal start with the AFFERENTMYELINATED A-delta fibers (sharp pain) then goes to the C fibers (delayed dull pain). Visceral pain (eg endometriosis): the afferent travel with sympathetic and parasympathetic fibers.
Definitions 2 • B) Neuropathic pain is caused by an injury to the peripheral or central nervous system or is due to sensitazation of central pain neurons. B1) Sympathetic via maintained sympathetic Efferent activity eg Complex regional pain syndrome type 1 – Reflex sympathetic dystrophy Pain wildly out of proportion to soft tissue or bone injury but no nerve injury. Nerve block may help. - Type 2 causalgia where pain wildly out of proportion to nerve injury (by EMG-NerveConductionStudy). B2) Non-Sympathetic via damage to peripheral nerve (eg. Mechanical herniated disc, Neuroma of Morton, Infectious: post-herpetic neuralgia) C) Central via Central nervous system Deafferation pain: no need for peripheral stimulus eg. Post stroke, spinal cord injury, Phantom Limb)
History for Pain 1 • Use systematic questionnaire to find the cause of pain. A) Where : point to area(s), localized/generalized, radiating B) When/frequency: Acute vs chronic (more than 6 weeks) Specific triggering factor/acute event vs progressive. C) Intensity: scale 1-10, Visual Scale/facial expression, mild-moderate-severe, Relieving and worsening factors D) Type: constant vs intermittent , superficial vs deep, sharp/dull, burning, electric shock E) Context: Work-related, MVA accident, F) Functional impairement: Work, Home, sleep, quality of life, FIFE =Feelings Ideas Function Expectation-Emotions. Socio-economic support.
History for Pain 2 • Past Medical History: Cancer, Accident, Surgery, medical illness (Diabetes, CVA, Neurological illness eg Multiple sclerosis, neuropathy, Arthritis), Mental illness (depression, anxiety, somatization,...). Drug users and addiction history. • List of medications prescribed (acetaminophen, Nsaids, narcotics, co-analgesic (amitriptilline, neurontin, pre-gabelin,...), psychotropes eg Effexor) and overcounter medications. • Review of system to look for « red flags » Systemic symptoms of weight loss, diaphoresis, asthenia, neurological symptoms
Physical examination for Pain Antalgic gait? Is pain intensity change with distraction? Reproductibiliy of pain? (use of PROVOCATIVE manoeuvers is KEY) • Facial expression, vitals signs • Complete physical exam with more attention to painful structures, according to clinical hypothesis coming from history and r/o sign of cancer (localized or with metastasis), Range of motion, Trigger points, guarding, rebound • Muscolo- Neurological exam, ? Swelling ? Redness ? Allodynia-Hyperesthesia search for signs to decide if nociceptive vs neuropathic • Mental status r/o sign of co-morbid mental illness • « perform complete physical examination regardless of complain »
Investigations and management for pain 1 • Investigation are done to confirm or infirm hypothesis of diagnosis (eg Imaging, MRI L-Spine for Low back pain) eg If suspect cancer of pancreas : CT abdomen For neuropathy: EMG-NCS Refer to specialists appropriately to treat the cause of pain (eg oncologist if cancer). For advise on pain relief for non-cancer pain, refer to pain specialists (re: Chronic Pain Management clinic) who can offer Injections (nerve blocks, epidural...) and interdisciplinary team approach
Investigations and management for pain 2 • For pain symptom relief, use multimodal (non-pharmacologic and pharmacologic) approach. • Holistic approach, especially for total pain/ suffering. • Experience of pain differs from individuals affected by same disease/condition so treatment is in case by case basis. Even for the same person, pain changes over time. Approach differs depending if Acute vs Chronic, Cancer pain vs Non-cancer pain.
Investigations and management for pain 3 • Non-pharmacologic includes: physiotherapy-exercice, TENS, Adjustement of work activities, Acuponcture, Massotherapy, psychotherapy, surgery ... • Pharmacologic:1) Non- opioids: Acetaminophen, NSAIDS, steroids Opiods (codeine, tramadol, morphine, oxycodone, hydromorphone, fentanyl, methadone), ADJUVANT Tricyclic (eg amitryptilline), Anticonvulsant as adjuvant therapy (gabapentin, pregabelin, ...). Cannabinoids eg nabilone Always assess Benefice vs Risk/side effects ratio. • Use combination eg opioid long-acting, PRN short acting opioid and adjuvant (eg pre-gabelin). Treat comorbid conditions: eg. Antidepressant. Use laxatives with narcotics.
Investigations and management for pain 4 • Narcotic use principles: 1) Try non-narcotic treatment first, up to their maximum dose tolerated 2) Goal is NOT pain= 0 but pain relief to allow Functional status in daily activities 3) Progressive titration of dose of narcotic. Use minimal dose that relieve pain/ assure function. Titrate with short acting opiods eg hydromorphone. Once stable dose (not frequent PRN), use total daily dose and convert to long acting meds eg Hydromorphone Contin. Manage side effects: constipation, nausea, confusion 4) Tolerance effect: Same dose not as efficient to relieve pain so need to increase dose. Tolerance is different than addiction! « Explain that the correct use of morphine is more likely to prolong a more rested, pain free life » 5) Narcotics can be used for non-cancer pain: need narcotic contract to avoid abuse.
Investigations and management for pain 4 • Third party issues: Employer, Worker’s Comp or WSIB, Private Insurance and objective assessment of functional status. • Quality of life eg Palliative care. Capacity issues in end-stage disease. Caregiver stress. Euthanasia and Physician assisted suicide are illegal in Canada. No maximum dose, use necessary dose of narcotics to relieve pain (but document reasoning and monitor) and assure quality of life. Counsel care givers.
Summary for pain management • History and physical to search for cause of pain. Management differs from Acute vs Chronic pain, Cancer vs Non-Cancer pain. Goal is to improve functional status. • Use multiple approach non-pharmacologic and pharmacologic modalities to relieve pain and co-morbid conditions (eg depression). Set action plan with client and caregivers. • Refer appropriately for diagnosis and management. Eg pain specialist can do epidurals, nerve block or neurolysis
Consent, capacity, controversial ethical issues (Cleo 4.3, 4.10) • Capacity: ability to decide with understanding and appreciate consequence (pro-cons) of decision. Capacity for health is different from financial capacity • Capacity is affected by factors: severity of physical and psychological illness, effect of medications/ delirium, religious belief and values, fear of death. • Issues of Euthanasia and Physician Assisted Suicide (illegal in Canada) “ The candidate will be aware that they may be asked to comment on unresolved or controversial ethical issues and will be able to name and describe relevant key issues and ethical principles” “Contrast resp. depression caused by opioids to resp rate 6-8bpm of dying patient in which resp depression is not caused by opioids but a natural part of dying process”. Titrate Rx to provide appropriate pain control.
Ressources 1) Managing pain. The Canadian Healthcare Professional’s Reference by the Canadian Pain Society, Dr Jovey Editor 2) Practice Based Learning program from McMaster University, Module on Chronic Non Cancer Pain, Vol 11(10), August 2003