Management of Pain - apt.med.ubc.ca · Management of Pain •NMDA receptor antagonists: –Reduce...
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Management of PainPCTH 325
C. Brian Warriner, MD, FRCPCProfessorUBC Department of Anesthesiology, Pharmacology and [email protected]
Management of Pain
• Agenda:
– Definitions
– Pathophysiology
– Analgesics
• Gases (N2O)
• Opiates
• NSAID’s
• Acetaminophen
• Phencyclidine – derivatives (NMDA antagonists)
• Alpha2-adrenergic agonists
Management of Pain
• Agenda (continued)– Analgesics
• Local anesthetics – combination therapy
• Modes of delivery– Oral
– Rectal
– Systemic
– Neuraxial
– Modes of Delivery – Case reports
– Obstetrics
Management of Pain
• Definition:
– Oxford Pocket Dictionary
• Strongly unpleasant bodily sensation such as is caused by illness or injury
• Mental suffering or distress
• Vulgar as in “pain in the neck” or other anatomical areas
• Great cares or troubles
• Verb (idiomatic) – to pain
Management of Pain
• Descriptors:
– Sharp, crushing, burning, cramping, gassy, throbbing, cutting, aching, dull, deep, pinching, slashing, pin-point, continuous, spasm, tearing, lancing, knifing, etc…
Management of Pain
• The Pain Team:– The patient– Nurses (nurse-clinician)– Anesthesiologist– Clinical pharmacologist– Psychiatrist– Dentist– Pharmacist– Psychologist– Physiotherapist– Occupational therapist– Radiologist– Neurosurgeon– Social worker– The family– Pastoral care– Obstetrical pain: patient, partner, coach, midwife, obstetrician
Management of Pain
• Incidence:
– Appears to be independent of race, culture, economic status
– 30% of adults have “chronic pain” at any given time
– 12% have severe pain
– 2% have disabling pain
– 80,000 British Columbians have disabling pain –more common that cancer or heart disease
Management of Pain
Pathophysiology
of Pain
Management of Pain
• Pain neurotransmission – simplified – Nociceptive receptors in periphery respond
to pH, ATP, and ligands to create afferent nerve conduction to dorsal root ganglia, dorsal horn of the spinal cord, brainstem, thalamus, hypothalamus, and cortex
– Modulation occurs at all levels and is mediated by opioid peptides, norepinephrine, glycine, and GABA
Management of Pain
• Opioid peptides inhibit synaptic transmission at several sites: beta-endorphin, enkephalins, dynorphins.
• Opiate receptors are mu, delta and kappa
Management of Pain
• Opioids produce analgesia because of their actions in the brain, brainstem, spinal cord, and peripheral terminals of primary afferent nerves.
• Brain: Alter mood in response to pain
• Brainstem: stimulate release of inhibitory signals
• Spinal cord: inhibit primary afferent activity
• Peripheral sites: inhibit afferent response
Management of Pain
• Types of Pain:– Acute – severe but usually managed with
opioids, NSAID’s, acetaminophen, local anesthetics
– Transitional: not easily diagnosed, needs aggressive treatment to prevent transition to chronic
– Chronic: long-lasting, difficult to treat, personality changes, drug seeking
Management of Pain
• Complex regional pain syndromes:– Previously called reflex sympathetic dystrophy
– Transitional to chronic in nature
– Can be initiated by relatively minor insults
– Peripheral sensitization resulting in allodynia and hyperalgesia
– Requires very aggressive team approach to therapy
– Can result in completely non-functional limb requiring amputation
Management of Pain
• Neuropathic pain:
– Injury to peripheral nerves and CNS can lead to functional and structural changes in the pathways (concept of plasticity)
– Nerve regeneration after injury can produce a nidus of intense pain
– Flitting, shock-like pain
– Often very difficult to treat
Management of Pain
• Classes of Drugs:
– Opioid receptor agonists
– Non-steroidal anti-inflammatory drugs
– Tri-cyclic antidepressants
– Anti-convulsants
– NMDA receptor antagonists
– Alpha2- agonists
– 5HT1-agonists for migraine
– Gases (N2O)
Management of Pain
• Opioid receptor agonists:– Morphine– Heroin – Meperidine– Codeine– Oxycodone– Hydromorphone– Fentanyl– Sufentanil– Remifentanil, alfentanil– methadone
Management of Pain
• Opioid receptor agonists:– Act on mu-receptors to produce both
effects and side-effects – brain, brainstem, spinal cord, and peripheral terminals
– Side effects: respiratory depression, nausea and vomiting, constipation, sedation, dizziness, euphoria, confusion, muscle rigidity, pruritus
– Physical and psychological dependence
Management of Pain
• Opioid receptor agonists:– Tolerance can develop quickly (in a matter
of minutes with remifentanil)
– Morphine is the reference opioid – used primarily for treatment of acute pain –injury, surgery, acute abdomen, etc
– Primary metabolism is in liver and oral morphine is rapidly reduced by first-pass metabolism
Management of Pain
• Opioid receptor agonists:– Many dosage forms:
• Oral, transmucosal
• Inhalation
• Subcutaneous
• Intramuscular
• Intravenous (continuous, intermittent, PCA)
• Intra-thecal
• epidural
Management of Pain
• Opioid receptor agonists:
– Codeine – methyl-morphine – rapidly converted to morphine by the liver – effective orally and intramuscularly – commonly used as antitussive and mild analgesic
– Heroin – converted to morphine by liver – no real therapeutic advantage over morphine – addicted claim it produces more euphoria than morphine but studies inconclusive
Management of Pain
• Opioid receptor agonists:
– Meperidine (Demerol) – first synthetic opioid – 1/10th potency of morphine
– Less Sphincter of Vater spasm
– Fentanyl – 100 times potency of morphine – intermediate duration – intravenous –used primarily by anesthesiologists, ER and pain physicians
Management of Pain
• Opioid receptor agonists:– Sufentanil – 1000 times potency of
morphine – intermediate duration – used only by anesthesiologists
– Remifentanil – 70 times potency of morphine – very short duration of action -metabolized by ester hydrolysis in plasma –given only by continuous intravenous infusion by anesthesiologists
Management of Pain
• Opioid antagonists:
– naloxone – very rapid reversal of opioid effects – given IV by ER physicians and anesthesiologists
– Naltrexone – longer acting antagonist used in treatment of both opioid addiction and alcoholism
Management of Pain
• Non-steroidal anti-inflammatories
– ASA and others of same class
– Ibuprofen is a relatively low potency, short acting example of the family
– Inhibit the action of cyclooxygenase enzymes (COX-1 and COX-2) and reduce the production of prostaglandins
Management of Pain
• NSAID’s :
– Analgesia by reducing prostaglandin synthesis
– Reduce the recruitment of leukocytes which produce inflammatory mediators
– Directly inhibit the release of prostaglandins in the dorsal horn
Management of Pain
• NSAID’s:– Side effects: gastric hemorrhage, platelet
dysfunction, renal toxicity
– Specific drugs:• ASA – relatively short acting, little negative
effect upon kidney
• Acetaminophen – reduces central prostaglandin synthesis – no real anti-inflammatory effect –no renal effects – overdose can cause acute liver failure
Management of Pain
• NSAID’s:
– Specific drugs:
• Ibuprofen – relatively short acting
• Naproxen, ketorolac (systemic), diclofenac, and others –relatively long acting – all have negative renal and gastric effects – likely also have cardiac effects
• COX-2 inhibitors were introduced with the expectation of fewer side effects (particularly gastric) but caused increased incidence of ischemic cardiac events and were withdrawn from the market
Management of Pain
• Antidepressants:
– Tri-cyclics
– Increase norepinephrine and serotonin activity in spinal cord
– Activate depressed chronic pain patients
– Diabetic neuropathy and post-herpetic neuralgia
– Amitriptyline, nortriptyline and imipramine
Management of Pain
• Anticonvulsants:
– Reduce neuronal excitability
– Gabapentin, carbamazepine
– Chronic pain management
– Diabetic neuropathy
– Trigeminal neuralgia
– Dizziness, somnolence, confusion, ataxia
– Pre-gabalin new member of this class – fewer side effects –heavily marketed – efficacy???
Management of Pain
• NMDA receptor antagonists:
– Reduce central sensitization due to increased NMDA
– Ketamine (phencyclidine relative) – general anesthetic agent which, in small doses, is an effective analgesic
– Used occasionally for labour analgesia and analgesia prior to surgery.
Management of Pain
• Alpha2-agonists:
– Clonidine, dextrometomodine
– Can be given orally or neuraxially
– Sedation, severe postural hypotension, very dry mouth
Management of Pain
• 5HT1-agonists: (sumatriptan)
– For the treatment of migraine headaches
– Vasoconstriction and prevention of central sensitization
– Vasoconstriction can increase risks in other vascular beds such as the cardiac
Management of Pain
• Local anesthetics as an adjunct to opiates:
– Neuraxial analgesia
• Sub-arachnoid (spinal)
• Epidural
– loss of sensation, muscle weakness, hypotension
Management of Pain
• Modes of delivery:
– Oral – most drugs
– Rectal – acetaminophen, NSAID’s, ASA
– IM or IV – opiates, ketorolac (NSAID) –patient controlled analgesia (PCA)
– Neuraxial – opiates, clonidine, local anesthetics
– Percutaneous – fentanyl patch
Management of Pain
• Case 1:
– A 27 year old male is in a fight and appears in the ER with severe abdominal pain and evidence of internal damage. He asks for pain relief. What would you do?
Management of PainPCA
Management of Pain
• Case 2:
– A 60 year old woman is admitted to the hospital with cancer of the lung. She requires a lobectomy. This is associated with very severe post-operative pain. What can be done to help?
Management of PainEpidural
Management of Pain
• Case 3:
– A 62 year old woman complains of continuous nagging, aching pain over her back and legs. Neurological and musculo-skeletal exam are essentially normal except for reduced range of motion of the back and lower limbs. How should her pain be managed?
Obstetrical Pain
• Each patient has a unique labour pain experience
• Labour pain is mediated from t10 – l1• Intermittent, increasing in intensity,
very severe
• Delivery pain is mediated from S2,3,4 and tends to be continuous or nearly so
Downloaded from: Miller's Anesthesia (on 27 November 2006 01:15 AM)
© 2005 Elsevier
Downloaded from: Miller's Anesthesia (on 27 November 2006 01:15 AM)
© 2005 Elsevier
Obstetrical Pain
• Pain varies greatly from patient to patient and pregnancy to pregnancy
• Modes:– Psycho-prophylaxis – breathing, relaxation
exercises
– Massage, baths, acupuncture
– Nitrous oxide – demand valve respirator for period during contraction only – effective analgesic but of only intermediate potency – can cause sedation, confusion
Obstetrical Pain
• Modes:– Intravenous narcotics: different effects on
Mom and babe – potential for respiratory depression in new born
– Ketamine – effective in small doses but effect short-lived and larger doses can cause neuro-psychiatric effects
– Intramuscular narcotics – same problems as IV but longer lasting
Obstetrical Pain
• Modes:– Epidural – continuous infusion of local
anesthetic (dilute) and opioid (usually fentanyl) – can cause reduced muscle strength and loss of urge to push – slows down early stages of labour but probably quickens entire labour time (controversial)
– Various potential complications associated with the procedure
Recent Developments
• May, 2008 - British Columbia 1st province to include “chronic pain” as separate disease entity under the common heading of “chronic diseases” – allows funding for research and treatment to be released by Ministry of Health
• October 31, 2008 – BC Pain Society approved by BC Legislature
• July, 2014 – start of pain residency
Management of Pain