Pain and management of pain Henning Andreas Haga Associate professor Norwegian School of Veterinary Science Pain An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. Note: The inability to communicate verbally does not negate the possibility that an individual is experiencing pain and is in need of appropriate pain-relieving treatment. International association for the study of pain
Is there a purpose to pain? Learning Protection of harmed tissue Avoid strain What is the purpose of inflicted pain in a controlled situation? Pain vs nociception Nociception is the activity generated in the nervous system in areas where it is not processed by the consciousness.
Nociception Nociception
Nociception Transduction Peripheral nociceptors Transmission Nociceptive impulses travels along nerves to the central nervous system (CNS) Modulation Nociceptive impulses are modulated at different levels of the CNS Perception Pain is experienced, cerebral cortex Nociception Perception Modulation Transmission Transduction
Peception Pain is a subjective and emotional experience Behavioural responses Physiological responses Hard wired system?
Peripheral hypersensitisation Sensitising soup of pro inflammatory mediators High treshhold nociceptorl Low treshhold nociceptor Central hypersensitisation Repetitive nociceptive impulses can induce changes in the central nervous system that faciliate transmission of nociceptive impulses.
Hypersensitivisation may lead to: Hyperalgesia: An increased response to a painful stimulus Allodyni: Pain caused by a stimulus which normally wouldn't be painful Cathegorisation of pain Acute - chronic pain Physiological - pathological pain Somatic - visceral pain
Why is pain important? Ethical Pain induces a stress response changes in the autonomic nervous system and in hormonal secretion may induce: Catabolic state, with change in plasma metabolites Increased water and sodium level Cardiovascular system changes Respiratory system changes Changed blood viscocity and clotting time Decreased gastrointestinal activity Increased time for wound healing Increased risk of infection Evaluation of pain No single physiologic parameter can tell if an animal is in pain or not. Pain behaviour is species specific. Animals are individuals with indivdual responses. Evaluation of pain based upon several physiologic and behavioural parameters.
Evaluation of pain Assume that procedure that would be painful in humans are painful in animals, administer analgesics. Evaluate effect of analgesic, and if possible adjust medication to each individual. Types of analgetics Non Steroidal Antiinflammatory Drugs (NSAIDs) Local anaesthetics NMDA antagonists Alfa-2 agonists Opioids
Analgesics effect nociception at different levels A combination of Perception Modulation Transmission analgesics affecting different levels may increase wanted effect and minimise side effects. Transduction Inhibits the production of prostaglandins which is one ingredient in the "inflammatory soup". NSAIDs
NSAIDs Perception Modulation Transmission NSAIDs Transduction Examples of NSAIDs Acetylsalisylsyre (Aspirin, Globoid, Dispril ) Ibuprofen Ketoprofen Meloxicam (Metacam ) etc...
Precautions for NSAIDs? Caution in animals: Bleeding tendency Decreased renal function Decreased hepatic function Ulcers in the gastrointestinal tract Prior to anaesthesia in dehydrated or circulatory compromised animals Local anaesthetics Perception Modulation Local anaesthetics NSAIDs Transmission Transduction
Local anaesthetics Has the potential for complete analgesia Good for acute pain Does not inhibit wound healing Opioids
Opioids Opioids Perception Modulation Opioids Local anaesthetics Transmission NSAIDs Transduction Opioids Morphine Methadone Pethidine Buprenorphine (Temgesic ) Fentanyl (Leptanal ) Butorphanol (Torbugesic ) + mange fler
NMDA antagonists In daily use, ketamine (Ketalar ) Ketamine in subanaesthetic doses gives profound analgesia Other NMDA antagonists will propably be avaiable in the future NMDA antagonists Opioids Perception Modulation Opioids, NMDA antagonists Local anaesthetics Transmission NSAIDs Transduction
Alpha-2 agonists Sedation and analgesia Frequently used in veterinary medicine Uncommon in humane medicine Alpha-2 agonists Opioids alpha-2 agonists Perception Modulation Opioids, NMDA antagonists, alpha-2 agonists Local anaesthetics NSAIDs Transmission Transduction
Alpha-2 agonists Xylazine (Rompun ) Romifidine (Sedivet ) Detomidine (Domosedan ) Medetomidine (Domitor ) Dexmedetomidine (Dexdomitor ) Questions?