Acute Pain NETP: SEPTEMBER 2013 COHORT

Acute Pain NETP: SEPTEMBER 2013 COHORT

Pain & Suffering an unpleasant sensory & emotional experience associated with actual or potential tissue damage, or described in terms of such damage International Association for the Study of Pain Suffering involves the experience of pain & additionally the complex context that the individuals pain occurs within, the multiple issues that must be endured

Because of the highly subjective nature of pain it is difficult to study. There are two distinct components to pain THE PHYSICAL COMPONENT = the sensation of pain, - nociception involving peripheral and central nerve pathways. THE PSYCHOLOGICAL COMPONENT = the emotional response to pain, involving factors such as anxiety, previous experiences, meaning of pain, age, gender, culture, psychological skills i.e. mindfulness / cognitive behavioral therapy. Factors that lower pain tolerance; averse drug reactions, anxiety, communication difficulties, sleeplessness, fatigue, anger, fear, depression, discomfort, pain, previous pain, isolation, conflict, despair Factors that raise pain tolerance; symptom relief, sleep, rest, diversion, empathy, drugs adjunct therapies, anesthetics, analgesics, anti-anxiety agents, antidepressants. Intense and prolonged pain transmission as well as analgesic under-medication can increase post-surgical / traumatic morbidity, delay recovery, and lead to the development of chronic pain.

The Science of Nociception Nociceptors = detect noxious stimuli - heat - irritating chemicals - intense mechanical stimulation Signals are transmitted to the spinal cord via first order neurons - A-delta δ fibers - C-fibers Second order neurons cross over & continue upwards in the anterolateral spinothalamic tracts to the thalamus & the cerebral cortex The message is perceived as pain

Physiologic Pain Rapidly perceived nontraumatic discomfort of very short duration Alerts the individual to the presence of a potential injurious environmental stimulus: initiates withdrawal reflexes that prevent or minimise injury

Nociceptive Pain Noxious perception resulting from cellular changes following surgical, traumatic or disease related injuries

Peripheral inflammation and inflammatory mediators play major role in initiation and development of pain, pain is proportional to magnitude of tissue damage and release of inflammatory mediators. Somatic nociceptive pain = well localised and generally follows dermatonal pattern, sharp, tearing, crushing in character. Visceral nociceptive pain relates to peritoneal irritation and dilatation of smooth muscle surrounding viscous or tubular passages = poorly localised, nondermatomal, cramping or colicky (referred pain explained by convergence)

Neuropathic Pain Pain initiated or caused by a pathological lesion or dysfunction

Mechanism is not well understood but spontaneous activity in damaged sensory nerves is thought to be a factor. SNS plays a role since damaged sensory nerves can express alpha 1 adrenergic receptors & develop a sensitivity to noradrenaline that they normally don t possess Physiological & psychological stimuli that evoke sympathetic responses may produce severe pain sympathetically mediated pain Neuropathic pain may be a component of many types of clinical pain including common conditions such as back pain, cancer pain, amputation pain It may be difficult to control with conventional analgesia other drugs or treatments may be added anticonvulsants (membrane stabilizers), TCAs (prevent noradrenaline reuptake), sympathectomy, cognitive behavioral therapy. Neurological disease affecting sensory pathways can produce severe chronic pain unrelated to any current peripheral tissue injury CNS disorder related; CVA, MS. PNS disorder related; mechanical nerve injury, diabetic neuropathy, herpes zoster Constant, burning, lancing, electrical, shooting Some consider any chronic pain associated with structural remodeling or plasticity changes should be characterised as neuropathic

Pain Assessment The single most reliable indicator of the existence and intensity of pain and any resultant distress is the patients self report

If you want to know if your patient is in pain - ask them and believe what they say

Fears & Misconceptions Fear of addiction Fear of tolerance Fear of respiratory depression Underestimation of pain Misunderstanding opioid legal regulations Reserving stronger analgesia

Pain Management a Fundamental Human Right

Evidence identifies pain assessment is effective when: - it is regularly presented - uses a patient-matched tool - acknowledges variables

Treatment of Acute Pain Multimodal approach Analgesic algorithms Assessment: - frequent & regular - pain on rest & movement - sedation score - respiratory rate

Consequences of Undertreated Pain Suffering Complications Death

Adult Opioid Policy The right dose is enough Right dose is based initially on patient age and adjusted by titration based on analgesic response and side effects Integral to achieving the analgesic corridor is regularly monitoring the effect

Individualised Analgesia Regimens Dose Route Dose interval Opioid naïve patient Opioid experienced patient Addiction

Each drug regardless of the route of administration is titrated to suit each patient Pain scores at appropriate intervals is essential at least hourly, = more regular assessments/monitoring of side effects & appropriate dose and dose interval must be charted It is well established that regular analgesia rather than prn is appropriate for the first 48 hours Route; parenteral opioids are required when patients are unable to take drugs orally, i.e. nbm, ponv, severe acute pain requiring rapid aggressive analgesia titration. Oral morphine has 40-50% bioavailability (oxycodone = 80%) this relates to dose/route conversion. Morphine 10mg IV = 25mg PO T1/2 of 2-3 hours The ideal route for parenteral administration of opioids is IV. Results = rapid, predictable onset of action and step-wise approach to titration of patient pain. IV morphine in the ward setting is best used for acute or breakthrough pain. Longer term IV opioid can be achieved using a PCA. Dose interval; Q4H regimen dates back to a study from 1950 s where it was found that the time between injection of opioid and return of severe pain was found to be 4 hours. Oral doses; compared with IV the onset is a little slower and the duration of action is a little longer

OPIOID NAÏVE OR OPIOID EXPERIENCED Opioid naïve patients treated according to opioid guidelines involve APMS in cases of repeated or ineffective opioid dosing. Consider associated risks of respiratory depression and sedation. Opioid experienced patients are patients with a history of medical use MST M-Eslon Methadone oxycodone or illicit opioid use are regard as requiring increased doses of opioid due to tolerance and at reduced risk of sedation and respiratory depression. Therefore; continue regular opioid dose, add intravenous opioid and co-analgesic agents, consider PCA and involve the APMS.

Opioids, Opiates & Narcotics Both naturally occurring & synthetic molecules that produce effects by action at opioid receptors

Opioid Analgesia Foundational drug in the management of moderate severe nociceptive pain Morphine Pethidine Fentanyl Alfentanil Methadone Oxycodone Codiene

Naloxone Opioid antagonist that competitively displaces opioid analgesia from their receptor sites, thus reversing their effects Used to reverse adverse effects or overdose effects of opioid agonists

Adjuncts Tramadol Cox2 Parecoxib Paracetamol Magnesium Ketamine Gabapentin Clonidine Amitriptyline

Drug tolerance is the gradual decrease in the effectiveness of a drug given repeatedly over a period of time: if tolerance develops higher doses are required to achieve the same effect Tolerance

Dependence Manifested by withdrawal symptoms after the drug is suddenly removed May be psychological as well as physiological Symptoms include stress response signs; sweating, nausea, vomiting, tremors, mood changes

Addiction Addiction involves inseparable biological and behavioral components. It is the quintessential biobehavioral disorder The development of opioid addictive disease in the therapeutic treatment of pain is exquisitely rare.