Y3 Anaesthetics Flashcards
What is pain?
pain is the unpleasant sensory and emotional experience associated with actual or potential tissue damage
What are the 3 durations of pain?
acute, chronic and acute on chronic
What are the two broad causes for pain?
Cancer and non-cancer
What are the 2 pathway mechanisms of pain?
nociceptive and neuropathic
What is acute pain described as?
pain of recent onset and probable limited duration
What is chronic pain defined as?
pain lasting more than 3 months, pain lasting after normal healing, often no identifiable cause
What is cancer pain defined as a?
Progressive, may be a mixture of acute and chronic
Nociceptive pain is caused by what happening?
Obvious tissue injury or illness
Is nociceptive pain sharp/dull and well/poorly localised?
Can be sharp or dull and is well localised
What causes Neuropathic pain?
Nervous system damage or abnormality.
What is often used to describe neuropathic pain and is it well/not well localised?
burning, shooting +/- numbness, pins and needles
not well localised
What occurs in the periphery that causes pain?
Tissue injury
release of chemical e.g. prostaglandins, substance P
Stimulation of pain receptors (nociceptors)
What nerves does pain travel in?
Ad or C nerve fibres
Where do these pain fibres enter the spinal cord?
The dorsal horn
What side of the spinal cord does the second nerve travel up?
the opposite side
What is the second relay station for the pain?
the Thalamus
Where does pain perception occur in the brain?
Occurs in the cortex
What is modulation and does it increase/ decrease pain signal?
A descending pathway from brain to dorsal horn. Usually decreases pain signal
What are some examples of neuropathic pain?
nerve trauma, diabetic pain, fibromyalgia, chronic tension headache
What are some of the simple analgesics?
Paracetamol, non steroidal anti inflammatory- NSAIDs- diclofenac, ibuprofen
What are some opioids?
Mild- codeine, dihydrocodeine
Strong- morphine, oxycodone, fentanyl
What type of treatment would be used to deal with the peripheral injury?
Non-drug treatments= RICE
NSAIDs, local anaesthetics
What kind of tx would you use to treat the spinal cord?
non drug: acupuncture, massage, TENS
local anaesthetic, opioids, ketamine
Treatments for the brain?
non drug tx: psychological
drug tx: paracetamol, opioids, amitriptyline, clondine
What are the advantages of paracetamol?
advantages- cheap, safe, can be given orally, rectally or IV.
What are the disadvantages of paracetamol?
liver damage in overdose
What are the three most common NSAIDs?
aspirin, ibuprofen, diclofenac
What are the advantages of NSAIDs?
cheap, generally safe, good for nociceptive pain. Best given regularly with paracetamol (synergism)
What are the disadvantages in NSAIDs?
GI and renal side effects plus sensitive asthmatics
What are the advantages of codeine?
Cheap, safe, good for mild-moderate acute nociceptive pain. Best again given with paracetamol
What are the disadvantages of codeine?
Constipation, not good for chronic pain.
What are the advantages of morphine?
cheap, generally safe. Can be given oral, IV,IM, SC
Effective if given regularly.
Good for mod-severe nociceptive pain (e.g. post-op pain) and chronic cancer pain
What are the disadvantages of morphine?
Constipation, respiratory distress in high dose. Misunderstanding about addiction. Controlled drug. Oral dose is 2-3 times IV/IM/SC dose
What are some of the delivery routes available for pain relief?
oral, rectal, sublingual, subcut, transdermal, intramuscular, IV- boluses with possible for patient control.
What are some of the delivery routes for local anaesthetics?
Epidural, intrathecal, wound catheters, nerve plexus catheters, local infiltration of wounds
What are the three levels on the pain ladder?
mild to moderate pain, moderate to severe pain, severe pain
What is the name of the scoring system used in confused and/or older patients?
the Abbey Pain Scale screening
What should be given in step 1 of the ladder? mild to moderate pain
non opioids, aspirin, NSAIDs or paracetamol
What should be given for step 2? moderate to severe pain
Step 1
+ mild opioids with or without non opioids
What should be given for step 3? severe pain
Step 1 if first tx or as a build up should give-
strong opioids e.g. morphine with or without non opioids
What is the RAT approach to pain?
Recognise, assess, treat
What are the three components of the triad of anaesthesia?
Analgesia, relaxation and hypnosis
What parts of the triad does general anaesthetic influence?
relaxation and hypnosis
What is the basic action of general anaesthetic?
Interferes with neuronal ion channels. Makes them less likely to fire- it hyper polarises them. Inhalation agents dissolve in membranes. IV agents- allosteric binding on GABA receptors- open chloride channels.
In what order do your higher functions “switch off” under GA?
LOC early and then hearing is later.
How rapid an onset and recovery do IV anaesthetics have?
IV anaesthetics have a rapid onset time- one arm to brain circulation time. They also have a rapid recovery time as the drug disappears from the system very quickly due to it being fat soluble.
What is the induction rate for inhaled anaesthetics like?
The induction rate for inhaled anaesthetics is very slow. They also then have a long duration.
What is the sequence of GA in terms of induction and maintenance?
The induction of GA is mainly IV with a mix of inhalation thrown in. The maintenance of GA is then mainly inhalation with some IV options in modern centres. (IV options- propofol, opiate (remifentanil).
What part of the triad do muscle relaxants work on?
Relaxation
When are muscle relaxants indicated?
ventilation and intubation, when immobility is essential- microscopic surgery, neurosurgy. Body cavity surgery
What are the problems of muscle relaxants?
Awareness, incomplete reversal, apnoea
What is the basic action of muscle relaxants?
Competitive block of Ach receptors at NMJ.
What is the most commonly used muscle relaxant?
Suxamethonium
Which parts of the triad do analgesics work on?
Analgesia, relaxation (tiny bit hypnosis)
What are the two main types of analgesia?
Opiates and local anaesthetic
Why is it necessary to provide intraoperative analgesia?
To prevent arousal, as opiates add to hypnotic effect of GA, suppression of reflex responses to painful stimuli- tachycardia, hypertension
What part of the triad does local anaesthetics act on?
Local anaesthetics act on the analgesia and relaxation parts of the triad
What are three common local anaesthetics?
lignocaine, bupivacaine, prilocaine
What is the basic action of LA?
Na channel blockers
What is the limiting factor in local anaesthetics?
Toxicity
What are some of the most common symptoms of local anaesthetic toxicity?
circumoral and lingual numbness, light headiness, tinnitus, muscular twitching, drowsiness
What fibres are blocked by LA and what fibres are spared?
motor fibres are spared and pain fibres are blocked- luckily
What level is spinal and epidural anaesthesia injected at?
L4
What are the common medications in IV induction?
propofol and thiopentone
What are the indications for gas induction and what is the most common gas induction for GA?
Op in a young child. Sevoflurane
What does the triple airway manoeuvre involve?
head tilt, chin lift, jaw thrust
What are the levels of ASA grading?
ASA1- other wise healthy patient ASA2- mild to moderate systemic disturbances ASA3- severe systemic disturbance ASA4- life threatening disease ASA5- moribund patient (ASA 6 organ retrieval)
