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a13. Specialities: Anaesthetics (Medical knowledge) > Zero to Finals : General anaesthesia > Flashcards

Zero to Finals : General anaesthesia Flashcards

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USMLE® Step 1 flashcards
1
Q

What are the 2 main categories of anaesthesia?

A
  • General
  • Regional
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2
Q

Define general anaesthesia

A

Making the patient unconcious

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3
Q

Define Regional anaesthesia

A

Blocking feeling to an isolated area of the body

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4
Q

What type of respiratory support is in place during general anesthesia for an operation?

A
  • Intubation / Supraglottic airway device
    breathing suppoerted by ventilator

Patient is continuously monitored at all times immediately before, during and after general anaesthesia

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5
Q

Prior to general anaesthesia, what type of preperation must be done?

A

If possible:
* Fasting (reduce risk of reflux and spiration)

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6
Q

What are the possible consequences of a patient not fasting prior to undergoing general anaesthesia?

Preperation

A
  • Aspiration of gastric contents into airway -> inflammitory response (pneumonitis)

Highest risk before and during intubation and during extubation

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7
Q

What are the 2 major causes of morbidity and mortality in general anaesthetics?

Preperation

A
  • Apiration pneumonitis
  • Pneumonia

Although rare in non-emergency planned procedures

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8
Q

How long is the fasting period typically?

Preperation

A
  • 6hrs (no food/feeds) prior to op
  • 2 hrs of no clear fluids (NBM)

NBM: nil by mouth

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9
Q

Why is it important to preoxygenate the patinet prior to undergoing general anaesthesia?

Preperation

A

To provide 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)

Patinet breathes 100& O2 for several mins prior to going under

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10
Q

What medications may be given to a patient prior to the undergoing general anaesthesia?

Preperation

A
  • Benzodiazepines (e.g. midazolam): muscle relaxant/reduce anxiety, causes amnesia
  • Opiates (e.g. fentayl/alfentanyl): pain management/reducehypertensive response to laryngoscope
  • Alpha-2-adregenic agonist (e.g. clonidine): sedation/pain
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11
Q

When is RSI performed?

What is RSI?

A

RSI= Rapid Sequance Induction/Intubation

  • Gain control over the airway (quickly/safely) in emergency situations
  • Non-emergency situations where the airway needs to be secured quickly to avoid aspiration (e.g. GORD/Pregnancy )
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12
Q

How may the risks associated with performing RSI be minimised?

A

Risk: Aspiration of stomach contents
Minimised by:
* Bed positioned upright
* Cricoid pressure (compress oesophagus/prevent reflux- ONLY used by trained/experinced health professionals)

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13
Q

Whta is the triad of General Anaesthesia?

A
  • Hypnosis
  • Muscle relaxation
  • Analgesia
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14
Q

What 2 modes may hypnosis be induced in patients?

Hyponsis

A
  • IV
  • Inhalational
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15
Q

List some hypnotic IV agents used in GA?

A
  • Propofol (the most commonly used)
  • Ketamine
  • Thiopental sodium (less common)
  • Etomidate (rarely used)
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16
Q

What are some adverse effects of propofol?

A
  • Pain on injection (due to activation of the pain receptor TRPA1)
  • Hypotension
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17
Q

What is an adverse effectof thiopental?

A

Laryngospasm

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18
Q

What are some adverse effects of etomidate?

A
  • Primary adrenal suppression (secondary to reversibly inhibiting 11β-hydroxylase)
  • Myoclonus
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19
Q

In cases of hameodynamic instability, what IV hypnotic agent is used and why?

A

Etomidate
Causes less hypotension than propofol and thiopental during induction

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20
Q

What are some adverse effects of Ketamine?

A
  • Disorientation
  • Hallucinations
21
Q

What IV hyponitic agent is useful in trauma situations and why?

A

Ketamine
Doesn’t cause a drop in blood pressure

22
Q

What is the most commonly used IV Hypnosis agent in GA?

Hyponosis

A

Propofol

Used extensively in intensive care for ventilated patients

23
Q

List some Inhalational hypnotic agents used in GA?

Hypnosis

A

Volatile Liquid anaetshtics:
* Sevoflurane (the most commonly used)
* Desflurane (less favourable as bad for the environment)
* Isoflurane (very rarely used)

Other:
* Nitrous oxide (combined with other anaesthetic medications – may be used for gas induction in children)

24
Q

What are some adverse effects of volatile liquid anaesthetics?

A

e.g. isoflurane, desflurane, sevoflurane

  • Myocardial depression
  • Malignant hyperthermia
  • Halothane (not commonly used now) is hepatotoxic

Used for both induction and maintenance of GA

25
Q

What is the most commonly used inhalational hypnotic agent in GA?

Hypnosis

A

Sevoflurane

26
Q

What inhalational hypnotic agent is used in GA in children?

A

Nitrous oxide (combined with other anaesthetic medications – may be used for gas induction in children)

27
Q

Waht conditions that patients may have CI use fo NO for general anaesthesia?

A

Pneumothorax
May diffuse into gas-filled body compartments → increase in pressure

Used for maintenance of anaesthesia and analgesia (e.g. during labour)

28
Q

What devices are used for inhaled volatile agents? How do these work?

Hypnosis

A

Vaporiser:
* The liquid medication is poured into the machine.
* The machine then turns it into vapour and mixes it with air in a controlled way.
* During the anaesthesia, the concentration of the vaporised anaesthetic medication can be altered to control the depth of anaesthesia.

29
Q

a) What mode of administartion is most commonly used for induction of GA?
b)What mode of administartion is most commonly used for maintenance of GA?

Why is this?

Induction

A

a) IV: infused directly into the blood and so can quickly reach an effective concentration

b) Inhalational: need to diffuse across the lung tissue and into the blood, where it takes a while for them to reach an effective concentration. Convcentration can be controlled easier

30
Q

What is TIVA?

A

Total intravenous anaesthesia (TIVA):

  • involves using an intravenous medication for induction and maintenance of GA
    Propofol is the most commonly used. This can give a nicer recovery (as they wake up) compared with inhaled options.
31
Q

How do muscle relaxants work?

Muscle relaxants

A

Block the neuromuscular junction from working

Acetylcholine (the neurotransmitter) is released by the axon but is blocked from stimulating a response from the muscle (msucle is relaxed/paralysed)

32
Q

What are the 2 categories of muscle relaxants used in GA?

Muscle relaxation

A
  • Depolarising (e.g., suxamethonium)
  • Non-depolarising (e.g., rocuronium and atracurium)
33
Q

What medications can reverse effects of neuromuscular junction blocking medications?

Muscle relaxants

A

Cholinesterase inhibitors (e.g., neostigmine)
Sugammadex is used specifically to reverse the effects of certain non-depolarising muscle relaxants (rocuronium and vecuronium).

34
Q

What medication category is most frequently used for analgesia?

Analgesia

A

Opiates

35
Q

List some common analgesic agents used in GA?

Analgesia

A
  • Fentanyl
  • Alfentanil
  • Remifentanil
  • Morphine
36
Q

What medications are administered at the end of the ooperative procedure?
What are most common types given to patients?

A

Antiemeteics: prevent post-operative nausea and vomiting

  • 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
37
Q

What antiemetic medication should be avoided in pts with risk of prolonged QT interval?

A

Ondansetron (5HT3 receptor antagonist)

38
Q

What antiemetic medication should be used with caution in diabetic or immunocompromised patients?

A

Dexamethasone (corticosteroid)

39
Q

What antiemetic medication should be used with caution in heart failure and elderly patients?

A

Cyclizine (histamine (H1) receptor antagonist)

40
Q

What must be done prior to emergence from GA?

A
  • Reversal of muscle relaxants (prevent awareness under anaesthesia)- can be tested with nerve stimulators to ensure muscle relaxant effects have ended (done on ulnar n./facial n using TOF stimualtion)

TOF Stimulation : Train of four stimulation (nerve stimualted 4 times to check for appropriate response

41
Q

What does the anaesthetist control during the emergence phase of GA?

A
  • Switches off anaesthetics (concentration of anaesthetic in the body falls, the patient regains concioussness)
  • Extubation
42
Q

What are the most common side effecst of GA?

A
  • Sore throat
  • Post-op nausea/vomiting
43
Q

What are some significant risks of general anaesthesia?

A
  • Accidental awareness (waking during the anaesthetic)
  • Aspiration
  • Dental injury, mainly when the laryngoscope is used for intubation
  • Anaphylaxis
  • Cardiovascular events (e.g., myocardial infarction, stroke and arrhythmias)
  • Malignant hyperthermia (rare)
  • Death
44
Q

What agents increase risk of malignant hypothermia during GA?

A
  • Volatile anaesthetics (isoflurane, sevoflurane and desflurane)
  • Suxamethonium
45
Q

What increases risk of malignant hyperthermia?

A

Genetic mutation (autosomal dominant)

46
Q

What does malignant hyperthermia cause?

A
  • Increased body temperature (hyperthermia)
  • Increased carbon dioxide production
  • Tachycardia
  • Muscle rigidity
  • Acidosis
  • Hyperkalaemia
47
Q

How is malignant hyperthermia treated?

A

Dantrolene (interrupts the muscle rigidity and hypermetabolism by interfering with the movement of calcium ions in skeletal muscle)

48
Q

Waht conditions that patients may have CI use fo NO for general anaesthesia?

A

Pneumothorax
May diffuse into gas-filled body compartments → increase in pressure

Used for maintenance of anaesthesia and analgesia (e.g. during labour)

a13. Specialities: Anaesthetics (Medical knowledge) (7 decks)

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