Anaesthetics Flashcards
what are the 2 types of anaesthesia?
- general
- regional
what is true NBM pre-operatively?
- 6h no food
- 2h no clear fluids
which medications can be offered pre-op? give the indication for each one
- BDZ, e.g. midazolam (anxiolytic)
- opiates, e.g. alfentanil (reduces pain and HTN in response to laryngoscope)
- alpha-2-adrenergic agonists, e.g. clonidine (sedation and pain relief)
why and when is rapid sequence induction used?
- to gain airway control as quickly and safely as possible
- emergencies
- GORD
- pregnancy
key complication in RSI? how can this be avoided?
- aspiration of stomach contents into lungs
- apply cricoid pressure
what is the triad of GA?
- hypnosis
- muscle relaxation
- analgesia
what is the role of hypnotic agents in GA?
to make the pt unconscious
hypnotic agents which can be administered IV?
used to induce LOC:
- propofol
- ketamine
- thiopental sodium
- etomidate (rare)
hypnotic agents which are inhaled?
mostly used to maintain LOC
volatile:
- sevoflurane
- desflurane
- isoflurane
non-volatile:
- nitrous oxide
where do muscle relaxants act?
NMJ
name a depolarising muscle relaxant
suxamethonium
name a non-depolarising muscle relaxant
- rocuronium
- atracurium
how can a muscle relaxant’s actions be reversed?
- neostigmine
- sugammadex (only for non-depolarising ones)
give examples of analgesic agents used in GA?
all opiates:
- fentanyl
- alfentanil
- remifentanil
- morphine
which antiemetics are used prophylactically post-op?
- ondansetron
- dexamethasone
- cyclizine
drug class of ondansetron?
5HT3 (serotonin) receptor antagonist
drug class of dexamethasone?
corticosteroid
drug class of cyclizine?
H1 (histamine) receptor antagonist
who should cyclizine be used with caution in?
- pts with HF
- elderly
who should dexamethasone be used with caution in?
- pts with DM
- immunocompromised pts
how can you test if the muscle stimulant has worn off?
- train-of-four stimulation
describe train-of-four stimulation
- try to stimulate a nerve 4 times
- if the muscle responses get weaker with each stimulation, it means the relaxant has not yet worn off
what is malignant hyperthermia?
rare but dangerous hypermetabolic response to anaesthesia
which agents carry a risk of malignant hyperthermia?
- volatile anaesthetics (isoflurane, sevoflurane, desflurane)
- suxamethonium
presentation of malignant hyperthermia?
- increased body temp LMAO
- increased CO2 exhalation
- high HR
- muscle rigidity
- acidosis
- high K+
management of malignant hyperthermia?
dantrolene
how is a peripheral nerve block carried out?
- LA injected under ultrasound guidance
- pt remains conscious
- usually done to numb a single limb
indications for a spinal block?
- C-sections
- TURP
- hip fracture repairs
how is a spinal block carried out?
- LA injected into subarachnoid space in CSF
- anywhere between L3 and L5
- all nerves below level of injection are numbed
- cold spray used to test if it has worked
typical indication for an epidural?
woman in labour with vaginal delivery
how is an epidural carried out?
- catheter inserted into epidural space (OUTSIDE of CSF and spinal cord)
- levobupivacaine inserted +/- fentanyl
key risks of using epidural in labour?
- prolonged second stage of labour
- increased chances of needing instrumental delivery
why is it important that a pt is able to do a straight leg raise under epidural anaesthesia?
- if not, catheter may be in subarachnoid space
- needs urgent anaesthetic review
example of LA?
lidocaine
examples of indications for LA use?
- skin sutures in A&E
- dental procedures
- carpal tunnel syndrome surgery
- inserting central line
- PCI
indications for a tracheostomy?
- resp failure where long-term ventilation will be needed (e.g. following brain injury)
- prolonged weaning from mechanical ventilation
- upper airway obstruction
- to manage resp secretions
- to reduce risk of aspiration (in unsafe swallow)
what can an arterial line be used for?
- measuring BP
- getting ABG samples
- NEVER to give drugs
where might a central venous catheter (central line) be inserted?
- internal jugular vein
- subclavian vein
- femoral vein
define chronic pain
pain that has been present for 3+ months
what is allodynia?
when pain is experienced with sensory inputs which should not cause pain, e.g. light touch
features of neuropathic pain?
- burning
- tingling
- pins and needles
- electric shocks
- loss of touch sensation in affected area
what are the 3 steps of the WHO analgesic ladder?
- non-opioids (paracetamol, NSAIDs)
- weak opioids (codeine, tramadol)
- strong opioids (morphine, oxycodone, fentanyl, buprenorphine)
which adjuvants can be used to treat neuropathic pain?
- amitriptyline
- duloxetine
- gabapentin
- pregabalin
- capsaicin cream
common side effects of NSAIDs?
- indigestion
- stomach ulcers
- asthma exacerbations
- HTN
- renal impairment
- CAD, HF strokes (rare)
in which pts are NSAIDs inappropriate / contraindicated?
- asthma
- CKD
- heart disease
- uncontrolled HTN
- pts with stomach ulcers
which drugs are co-prescribed with NSAIDs?
PPIs (e.g. omeprazole)
key side effects of opioids?
- constipation
- pruritus
- nausea
- altered mental state
- resp depression
how is opioid overdose reversed?
naloxone
how are opioids prescribed in palliative care?
- background opioids
- plus rescue doses for breakthrough pain
how is the rescue dose of an opioid calculated for palliative care?
rescue dose = 1/6 of total background dose over 24 hrs
how is bradycardia secondary to patient-controlled analgesia overuse managed?
atropine
common areas affected by chronic pain?
- headaches
- lower back pain
- neck pain
- knee / hip pain
describe the analgesic ladder for treating pain secondary to OA
- PO paracetamol + topical NSAIDs
- add PO NSAIDs (+PPI)
- consider opioids
which 4 medications are used first-line in the treatment of neuropathic pain?
- amitriptyline
- duloxetine
- gabapentin
- pregabalin
1st line treatment for trigeminal neuralgia?
carbamazepine (different to other neuropathic pain conditions!)
describe the different “levels” of patient care needs in a hospital
- level 1 = ward-based care
- level 2 = HDU
- level 3 = ICU (highest level of support needed)
common reasons for ICU admission?
- following major surgery, e.g. AAA repair
- severe sepsis
- major trauma
- following CPR
- acute resp / renal / liver failure
how can enteral nutrition be given in the ICU setting?
- orally
- NG tube
- PEG
why is TPN given via central line rather than a cannula?
- it irritates peripheral veins
- causes thrombophlebitis
complications of mechanical ventilation?
- alveolar damage from over-inflation
- barotrauma
- pneumonia
- cor pulmonale
which drug can be administered to treat agitated pts with delirium in ICU setting?
dexmedetomidine
