what are some of the adverse effects of pain?
- sympathetic nerevous system activation –> increased myocardial oxygen demand
- inability to deep breath –> atelectasis, chest infections, hypoxaemia
- reduced mobility –> increased risk of DVT, PE, pressure sores
- chronic pain problems
- nausea/decreased GI motility
- anxiety, fear, insomnia
- increased catabolic hormones/decreased anabolic hormones –> hyperglycaemia
what is step 1 in WHO pain ladder?
paracetamol
what is step 2 of the WHO pain ladder?
paracetamol + codeine
what is step 3 of the WHO pain ladder?
paracetamol + morphine
name an example of local anaesthetic
- bupivacaine
- lidocaine
how long does local anaesthetic work for?
several hours
what will a nerve block do?
blockade of plexuses or peripheral nerves will provide selective analgesia in those parts of the body supplied by the plexus or nerves
what is local anaesthetic particularly useful?
- surgical anaesthesia
- post-operative pain relief
- sympathetic block when spinal or epidural contraindicated
what is the purpose of spinal anaesthesia?
- analgesia for surgery in the lower half of the body
- pain relief lasting many hours after completion of the operation
what are the side-effects of spinal anaesthesia?
- hypotension
- sensory and motor block
- nausea
- urinary retention
how does an epidural anaesthetic work?
- indwelling epidural catheter
- provides a continuous infusion of analgesic agents
what are the disadvantages of epidural anaesthesia?
- confine patients to bed
- indwelling catheter required
- epidural haematoma
when is epidural anaesthetic contraindicated?
coagulopathies
how is transverse abdominal plane block (TAP) set up?
- ultrasound is used to identify the correct muscle plane
- local anaesthetic (usually bupivicaine) is injected
- agent diffuses in the plane and blocks many of the spinal nerves
what is the preferred pain management technique for an extensive laparoscopic abdominal procedure?
transverse abdominal plane block (TAP)
what are the disadvantages of transverse abdominal plane block (TAP)?
- duration of action is limited to the half-life of the local anaesthetic agent
- some anaesthetists do not have the USS skills required to site the injections
what is patient controlled analgesia (PCA)?
patients administer their own IV analgesia and titrate the dose to their own end-point of pain relief
what drug is typically used in patient controlled analgesia?
morphine
where is morphine metabolised?
liver
clearance reduced in liver disease, elderly and debilitated
what are the side-effects of morphine?
- nausea
- vomiting
- constipation
- respiratory depression
what is pethidine?
synthetic opioid which is structurally different from morphine but which has similar actions
what is the toxic metabolite of pethidine?
norpethidine
how is norpethidine excreted?
cleared by the kidney
accumulates in renal failure or following frequent and prolonged doses
what are the signs of norpethidine build-up?
- muscle twitching
- convulsions
