--- module: 061-01 language: en chapter: 61 title: "Pain Medicine, Analgesia, Anaesthesia, Sedation, and Procedural Safety" module_title: "Foundations" source_sha256: 31c9ae9a171f9fabace053ab51c7f9fb189c9f68f4620b729cebff2cd63752d6 --- # Pain, analgesia, anaesthesia, and sedation safety ## Orientation ### Pain protective, disabling when persistent ### Analgesia preserves breathing, circulation, cognition ### Anaesthesia and sedation alter consciousness and reflexes #### Rapid airway and haemodynamic emergencies ### Safe care: mechanism, consent, monitoring, rescue ## Pain mechanisms and assessment ### Nociceptors detect mechanical, thermal, chemical threat ### Spinal cord amplifies or inhibits signals #### Ascends through thalamic and cortical networks ### Descending pathways, fear, mood, sleep modulate ### Real without visible damage, description not mechanism ### Nociceptive: somatic or visceral tissue injury ### Neuropathic: somatosensory lesion or disease #### Burning, electric, shooting, numb, allodynic ### Nociplastic: altered processing without lesion ### Mixed in cancer, back pain, diabetes, trauma ### Scale suited to communication, not replacing function ### Impaired communication: behaviour, caregivers, trials ## Multimodal analgesia ### Treat cause, combine different pathways ### Positioning, splinting, physiotherapy, psychology ### Regional anaesthesia is opioid-sparing ### Paracetamol: analgesia, antipyresis, little anti-inflammation #### Check total dose across combination products #### Overdose causes silent early hepatic injury ### NSAIDs inhibit cyclooxygenase and prostaglandins #### Ulcer, bleeding, kidney injury, sodium retention #### Risk: age, dehydration, anticoagulation, heart failure #### Lowest dose, shortest time, topical for local pain ## Opioids ### Receptors reduce transmitter release and excitability ### Sedation, respiratory depression, constipation, itch ### Risk: sleep apnoea, frailty, naivety, co-sedatives ### Small monitored intravenous doses for rapid effect ### Oral treatment safer for stable pain ### Equianalgesic tables estimate, cross-tolerance incomplete #### Reduce calculated dose when rotating ### Long-acting unsuitable for naive rapid titration ### Respiratory depression: rate, depth, arousal fall #### Oxygen keeps saturation deceptively normal #### Stimulate, airway, ventilate, titrate naloxone #### Naloxone may wear off first ### Chronic pain: functional goals, benefit over harm #### Higher doses increase overdose, not function ### Dependence adaptation, addiction impaired control #### Avoid abrupt discontinuation ## Neuropathic and specialised analgesia ### Antidepressants, gabapentinoids, lidocaine, capsaicin #### Start low, review falls and sedation ### Ketamine #### N-methyl-D-aspartate receptor antagonist #### Analgesia with relative preservation of breathing #### Dissociation, hypertension, emergence phenomena ### Local anaesthetics block sodium channels #### Toxicity: circumoral, tinnitus, seizure, dysrhythmia #### Stop, airway, modified resuscitation, lipid emulsion ### Cancer pain: disease-directed and multimodal care #### Incident pain needs pre-emptive rescue dosing ## Pre-anaesthetic assessment ### Procedure, urgency, airway, reflux, fasting, frailty ### Records: difficult airway, malignant hyperthermia ### No single test predicts airway difficulty #### Prepare up to front-of-neck rescue ### Test only when results change care ### Optimise without delaying emergency surgery ### Excessive fasting causes dehydration ### Delayed gastric emptying, fasted patients aspirate ## General and regional anaesthesia ### Hypnosis, amnesia, analgesia, immobility, reflexes ### Agents reduce sympathetic tone, resistance, breathing ### Monitoring guides dosing and detects failure ### Preoxygenation extends safe apnoea time ### Confirm tube by sustained exhaled carbon dioxide ### Failed oxygenation: oxygen before repeated attempts ### Neuraxial blocks nerve roots and sympathetic outflow #### Hypotension, retention, headache, high block #### Antithrombotic timing prevents spinal haematoma ### Peripheral blocks: dose, monitoring, protect limb ## Procedural sedation ### Continuum from anxiolysis to unresponsiveness ### Rescue one level deeper than intended ### Dedicated monitoring clinician for deeper sedation ### Prepare oxygen, suction, bag-mask, reversal ### Capnography detects hypoventilation before desaturation ### Benzodiazepine plus opioid synergistically depress ### Propofol: apnoea, hypotension, no reversal ### Ketamine preserves reflexes, laryngospasm possible ### Nitrous oxide expands closed gas spaces ## Emergencies and recovery ### Anaphylaxis without rash: give adrenaline ### Malignant hyperthermia: carbon dioxide, rigidity, heat #### Stop triggers, dantrolene, cool ### Awareness: take reports seriously, support ### Hypothermia raises bleeding and infection ### Recovery: stable airway, circulation, consciousness ### Discharge: escort, written advice, restrictions