anaesthetics and perioperative care

Question 1

complications of aspiration of gastric contents during anaesthesia?

Answer 1

aspiration pneumonitis

aspiration pneumonia

Question 2

what does fasting for an operation typically involve?

Answer 2

• 6hrs of no non-clear fluids/food or feeds before the operation
• 2hrs of no clear fluids as well,ie, fully nil by mouth

Question 3

what is preoxygenation

Answer 3

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)`

Question 4

what are premedication?

Answer 4

Medications are given before the patient is put under a general anaesthetic to relax them, reduce anxiety, reduce pain and make intubation easier. These may include:

Benzodiazepines (e.g., midazolam) to relax the muscles and reduce anxiety (also causes amnesia)
Opiates (e.g., fentanyl or alfentanyl) to reduce pain and reduce the hypertensive response to the laryngoscope
Alpha-2-adrenergic agonists (e.g., clonidine), which can help with sedation and pain

Question 5

what is rapid sequence induction

Answer 5

Rapid sequence induction/intubation (RSI) is used to gain control over the airway as quickly and safely as possible where a patient is intubated in an emergency scenario and detailed pre-planning is not possible. It is also used in non-emergency situations where the airway needs to be secured quickly to avoid aspiration, such as in patients with gastro-oesophageal reflux or pregnancy.

The biggest concern during RSI is the aspiration of stomach contents into the lungs. The bed can be positioned so the patient is more upright to reduce the reflux of contents up the oesophagus. Cricoid pressure (pressing down on the cricoid cartilage in the neck) may be used to compress the oesophagus and prevent the stomach contents from refluxing into the pharynx (this is somewhat controversial and should only be done by someone trained and experienced).

Question 6

triad of general anaesthesia

Answer 6

hypnosis
analgesia
muscle relaxation

Question 7

what are hypnotic agents?

Answer 7

hypnotic agents are used to make the patient unconscious and can be given either IV or INH

Question 8

IV options for GA

Answer 8

Propofol (the most commonly used)
Ketamine
Thiopental sodium (less common)
Etomidate (rarely used)

Question 9

INH options for GA

Answer 9

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)

Question 10

what are the 2 ways of giving someone GA?

Answer 10

in GA, there is induction and maintenance.

1. Commonly, an intravenous medication will be used as an induction agent (to induce unconsciousness), and inhaled medications will be used to maintain the general anaesthetic during the operation.
2. Total intravenous anaesthesia (TIVA) involves using an intravenous medication for induction and maintenance of the general anaesthetic. Propofol is the most commonly used. This can give a nicer recovery compared with inhaled options.

Question 11

muscle relaxants mechanism of action and purpose?

Answer 11

muscle relaxants block the neuromuscular junction from working. Ach is blocked from stimulating a response on the muscle.

muscle relaxants are given to relax and paralyse the muscles which makes intubation and surgery easier.

Question 12

give types and examples of muscle relaxants

Answer 12

depolarizing - suxamethonium

non-depolarizing - rocuronium and atracurium

Question 13

what medications are used to reverse the effects of muscle relaxants?

Answer 13

cholinesterase inhibitors like neostigmine can reverse the effects of NMJ blocking medications
Sugammadex is used specifically to reverse the effects of certain non-depolarizing muscle relaxants

Question 14

what analgesics are used commonly in anaesthesia?

Answer 14

opiates. - fentanyl, alfentanil, remifentanil, morphine

Question 15

what additional medication is given at the end of the procedure to prevent post-op N/V. give eg

Answer 15

antiemetics.

ondansetron (5Ht3 antagonist) - avoided in pts at risk of prolonged QT interval
dexamethasone (corticosteroid) - caution in pts with diabetes or immunocompromised pts
cyclizine (H1 receptor antagonist)- caution in elderly pts and pts with heart failure

Question 16

what is a train of four stimulation?

Answer 16

before waking, the muscle relaxant needs to have worn off.
train-of-four (TOF) stimulation is used where the nerve is stimulated four times using a nerve stimulator (usually ulnar nerve watching for thumb movements or facial nerve watching for movement in the orbicularis oculi) to see if the muscle responses remain strong (indicating it has worn off) or whether they get weaker with additional stimulation (indicating it has not fully worn off).

Question 17

when are pts extubated

Answer 17

Once the muscle relaxant has worn off, the inhaled anaesthetic is stopped. The concentration of the anaesthetic in the body will fall, and the patient will regain consciousness. They are extubated at the point where they are breathing for themselves.

Question 18

risks of GA?

Answer 18

sore throat and post op N and V are the most common adverse effects

some significant risks of GA include - 
accidental awareness
aspiration pnuemonitis and pneumonia
dental injury
anaphylaxis
malignant hyperthermia
CV events eg MI, arrhythmias, strokes
death

Question 19

what is malignant hyperthermia

Answer 19

rare but potentially fatal hypermetabolic response to anaesthesia. the risk is mainly with volatile anaesthetic agents (sevodlurane, desflurane etc) and suxamethonium.

there are genetic mutations which inc risk of malignant hyperthermia which are inherited in an autosomal dominant pattern

Question 20

what does malignant hyperthermia cause incl signs and symptoms

Answer 20

hyperthermia
muscle rigidity
tachycardia
acidosis
increased CO2 exhalation
hyperkalaemia

Question 21

treatment for malignant hyperthermia?

Answer 21

ABCDE aproach

datrolene - muscle relaxant which interferes with movement of Ca2+ ions in skeletal muscle

Question 22

in general what tests would you perform pre-op in an elective case?

Answer 22

FBC, U&Es, LFTs, clotting, group and save
urine analysis
pregnancy test
sickle cell test
ECG/CXR
plan DVT risk management

Question 23

potential complications of poorly managed diabetes during surgery

Answer 23

undetected hypoglycaemia whilst under GA
increased risk of wound and resp infections
inc risk of post op AKI
inc length of stay in hospital

Question 24

in general, for an elective surgery, how shd blood glucose be controlled in patients on insulin

Answer 24

1. pts on insulin with good glycaemic control (hba1c <69 mmol/mol) and undergoing minor surgery can be managed during the operative period by adjustment of their usual insulin regimen
2. pts on insulin with surgery requiring long fasting period of more than 1 missed meal or whose diabetes is poorly controlled will usually require variable rate insulin infusion (VRII)

Question 25

in general, for an elective surgery, how shd blood glucose be controlled in patients on oral antidiabetic medications

Answer 25

most patients can be managed by manipulating medication on the day of the surgery (eg missing 1 dose, etc.) depending on the particular drug and time of surgery. the exceptions to this are -
1. if more than 1 meal is to be missed
2. poor glycaemic control
3. risk of renal injury (eg low eGFR or contrast being used)
In such cases, VRII is used.

Question 26

imp points to remember about propofol

Answer 26

GABA receptor agonist
pain on injection
Rapid onset of anaesthesia
Rapidly metabolised with little accumulation of metabolites
Proven anti emetic properties
Moderate myocardial depression eg hypotension

Question 27

imp points to remember about sodium thiopental

Answer 27

Extremely rapid onset of action

cardio respiratory depression may occur

Question 28

imp points to remember about sodium thiopental

Answer 28

Extremely rapid onset of action

cardio respiratory depression may occur

Question 29

ketamine imp points

Answer 29

NMDA receptor antagonist
May be used for induction of anaesthesia
has moderate to strong analgesic properties
produces little myocardial depression making it a suitable agent for anaesthesia in those who are haemodynamically unstable
May induce state of dissociative anaesthesia resulting in nightmares

Question 30

etomidate

Answer 30

Has favorable cardiac safety profile with very little haemodynamic instability
Unsuitable for maintaining sedation as prolonged (and even brief) use may result in adrenal suppression