404154
Anaesthesia
- General
- Loss of
consciousness
and sensitivity to
pain
- Either IV or
inhalation
- IV: Induction with propofol, thiopental or etomidate. Pt is
pre-oxygenated and monitored. Maintenance with oxygen +
nitrous oxide + continuous propofol with
additional muscle relaxants when required.
- Inhalation: Either for induction
or maintenance. Potency
calculated by MAC (minimum
alveolar concentration): the
amount of gas required in the
lungs to prevent 50% of
humans moving when given a
painful stimulus. Isoflurane,
sevoflurane, desflurane. For
maintenance they are given
with O2, muscle relaxants and
analgesia.
- Preferably IV for
induction and inhaled
for maintenance.
- IV: Induction with propofol, thiopental or etomidate. Pt is
pre-oxygenated and monitored. Maintenance with oxygen +
nitrous oxide + continuous propofol with
additional muscle relaxants when required.
- Rapid sequence induction
- For emergency situation: rapidly
acting muscle relaxant given
immediately after induction
agent. Risk of inability to intubate
and ventilate pt.
- For emergency situation: rapidly
acting muscle relaxant given
immediately after induction
agent. Risk of inability to intubate
and ventilate pt.
- Acts on the brain
- Effect on cardio and respiratory systems: CVS:
reduced myocardial contractility, reduced cardiac
output, hypotension, arrythmias, increased
myocardial sensitivity to catecholamines. RS:
reduced ventilation, laryngospasm/airway
obstruction, reduced ventilatory response to
hypoxia and hypercapnia, bronchodilation.
- Risks: PONV, acid
aspiration syndrome,
allergic reactions,
respiratory arrest, pt
awareness, slow
recovery
- Loss of
consciousness
and sensitivity to
pain
- Regional
- Epidural
- Local anaesthetic into epidural space
either via single dose, intermittent
top-up or continuously via a pump.
Unlike a spinal it can be topped-up so
prolongued action, but slower onset (up
to 45 mins). Can also be used as a
PCA system. Must monitor ECG, BP,
RR & O2 sats. May become
hypotensive.
- Risks: respiratory
depression, toxicity,
failure, total spinal
effect from dural
puncture, CSF/dural
puncture causing
spinal headache
- Local anaesthetic into epidural space
either via single dose, intermittent
top-up or continuously via a pump.
Unlike a spinal it can be topped-up so
prolongued action, but slower onset (up
to 45 mins). Can also be used as a
PCA system. Must monitor ECG, BP,
RR & O2 sats. May become
hypotensive.
- Caudal
- Blocks sacral and lumbar
nerve roots. Mainly in children.
- Blocks sacral and lumbar
nerve roots. Mainly in children.
- Spinal
- Solution directly into CSF. Complete sensory
block, may also be loss of power. Usually lower
body, can extend from nipples (T10) to toes. Level
measured using ice/light touch. Fast onset lasting
1-4 hrs. Must monitor ECG, BP, RR & O2 sats.
May become hypotensive (sympathetic blockade)
so may need fluid.
- Effect on cardio and respiratory
systems: reduced ventilation (if
opiates) , bradycardia,
hypotension (vasodilation caused
by anaesthetic blocking
sympathetic nerves to blood
vessels)
- Risks: Failure, localised bruising/pain, infection, respiratory
depression with opiates, PONV, bladder distension,
bradycardia, hypotension, high spinal block (depression of
cervical spine and brainstem, spinal headache.
- Solution directly into CSF. Complete sensory
block, may also be loss of power. Usually lower
body, can extend from nipples (T10) to toes. Level
measured using ice/light touch. Fast onset lasting
1-4 hrs. Must monitor ECG, BP, RR & O2 sats.
May become hypotensive (sympathetic blockade)
so may need fluid.
- Epidural
- Local
- Blocks
conduction
of nerve
impulses
along
nerve
axons
- Topical (skin/mucous membranes ie
before injection), local infiltration (for
minor procedures ie suturing),
regional/conductional anaesthesia
(minor/major nerve blockade ie
ulnar/brachial plexus). Can also be
used for treatment of pain in combi
with opioids, NSAIDS etc.
- Vasodilator effect so often given with vasoconstrictor to increase potency. But
do not use adrenaline around end-arteries (ie penis/finger ring-block) - can
cause ischaemia
- Risks: Toxicity -
coma, circulatory
collapse, cardiac
arrest, apnoea
- Blocks
conduction
of nerve
impulses
along
nerve
axons
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