Anaesthetics Flashcards
two many categories of anaesthesia
- General anaesthesia – making the patient unconscious
- Regional anaesthesia – blocking feeling to an isolated area of the body (e.g., a limb)
triad of general anaesthesia
- Hypnosis
- Muscle relaxation
- Analgesia
since general anaesthesia involves patients becoming unconscious, patients must be
intubated or have a supraglottic airway device, and their breathing will be supported and controlled by a ventilator
- Defintiibe airway- endotracheal tube
- for high risk and long surgery
- Supraglottic airway
- most common
before general anesthesia is given patients are
pre-oxygenated
aim: replace nitrogen in the RBC with oxygen
Before being put under a general anaesthetic, the patient will have a period of several minutes where they breathe 100% oxygen. This gives them a reserve of oxygen for the period between when they lose consciousness and are successfully intubated and ventilated (in case the anaesthetist has difficulty establishing the airway)
medication which may be given before patient is put under to relax them and reduce anxiety, pain and make intubation easier
- Benzodiazepines (e.g., midazolam) to relax the muscles and reduce anxiety (also causes amnesia)
- Opiates (e.g., fentanyl) to reduce pain and reduce the hypertensive response to the laryngoscope
what is the idea behind rapid sequence induction/intuvation
successful intubation with an endotracheal tube as soon as possible after induction (when the patient is unconscious) to protect the airway.
biggest concern during rapid sequence induction/intubation
- aspiration of stomach content into the lung
hypnotic agents help which which part of the triad of general anaesthesia
hypnosis
induction agents for general anaesthesia can either be
intravenous or inhaled
intravenous options for GA
- Propofol (the most commonly used)
- Ketamine
- Thiopental sodium (less common)
inhaled options for GA
- Sevoflurane (the most commonly used)
- Desflurane (less favourable as bad for the environment)
- Isoflurane (very rarely used)
- Nitrous oxide (combined with other anaesthetic medications – may be used for gas induction in children)
what type of agents are sevoflurane, desflurance and isoflurane
volatile anaesthetic agents
- must be vaporised into a gas to be inhaled
types of maintenance of GA
- induction: IV and maintenance: inhaled
- induction: IV and maintenance : IV (total intravenous anaesthesia)
total intravenous anaesthesia
IV medication for induction and maintenace of GA
e.g. propofol
benefit of TIVA
nicer recovery when waking up than inhaled options
muscle relaxants
lock the neuromuscular junction from working
- paralyse muscles by blocking the activity of Axcetylcholine at the NMJ
why give muscle relaxants
makes intubation and surgery easier.
types of muscle relaxants
- Depolarising (e.g., suxamethonium)
- Non-depolarising (e.g., rocuronium and atracurium)
reversing the effects of neuromuscular blocking medications after surgery
Cholinesterase inhibitors (e.g., neostigmine)
analgesia
opiates are used most commonly during surgery
- Fentanyl
- Morphine
- local anaesthetic- injected near the end of the surgey to prevent post operative pain*
- lidocaine
emergence - before waking the patient …
-
muscle relaxant needs to have warn off
- can give neostigamine
- then the inhaled anaesthetic is stopped
- conc of anaesthetic in the body falls… pt regains consciousness
- they are extubated when they are breathing for themselves
after emergence many patients get
PONV
PONV
post operative nauese and vomiting
prophylaxis for PONV
- Ondansetron (5HT3 receptor antagonist) – avoided in patients at risk of prolonged QT interval
- Dexamethasone (corticosteroid) – used with caution in diabetic or immunocompromised patients
- Cyclizine (histamine (H1) receptor antagonist) – caution with heart failure and elderly patients
risks of GA
common
- sore throat
- PONV
significant
- accidental awareness
- aspiration
- dental injury
- anaphylaxis
- cardiovascular events
- malignant hyperthermia
- death
Malignant hyperthermia
is a rare but potentially fatal hypermetabolic response to anaesthesia. The risk is mainly with:
- Volatile anaesthetics (isoflurane, sevoflurane and desflurane)
- Suxamethonium
malignant hyperthermia presentation
- Increased body temperature (hyperthermia)
- Increased carbon dioxide exhalation
- Tachycardia
- Muscle rigidity
- Acidosis
- Hyperkalaemia
treatment if malignant hypertension
dantrolene
- interferes with movement of calcium ions in skeletal muscle
phases of GA
Phases of GA
- Induction
- send patients to sleep
- Maintenance
- keeping them asleep
- Emergence
- waking them up
- Recovery
- Managing them until “ward ready”
phases of GA
Phases of GA
- Induction
- send patients to sleep
- Maintenance
- keeping them asleep
- Emergence
- waking them up
- Recovery
- Managing them until “ward ready”
other types of anaesthesia
- peripheral nerve block
- epidural anaesthesia
- local anaesthetic
peripheral nerve blocks
regional anaesthesia
- patient conscious
- local anaesthetic injected around specific nerves causing distal nerves to be anaesthesised
- method: US guided with the help of nerve stimulator
- sedation may be given to help patient relax
epidural anaesthesia
involves inserting a catheters into the epidermal space in the lower back
- outside dura mater, separate from the spinal cord and CSF
- local anaesthetic are infused through he catheter into the epidural space where they diffuse to the surrounding tissues and through to the spinal cord
e.g. levobupivacaina
adverse effect from epidural
- Headache if the dura is punctured, creating a hole for CSF to leak from (“dural tap”)
- Hypotension
- Motor weakness in the legs
- Nerve damage (rare)
- Infection
- Haematoma (may cause spinal cord compression)
local anaesthesia in surgery
to numb specific areas where a procedure is being performed e..g lidocaine
