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RAT course > Advanced anaesthesia > Flashcards

Advanced anaesthesia Flashcards

1
Q

What is considered prolonged anaesthesia?

A

Anaesthesia that is longer than 15 minutes.

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2
Q

When does ASPA require the use of an anaesthetic (unless…)?

A

Unless the application of anaesthetic would be more traumatic than the procedure, or if it would be incompatible with the study

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3
Q

What is the anaesthetic triad?

A

Unconsciousness, analgesia, muscle relaxation

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4
Q

What details should be known before anaesthetising an animal?

A

The weight, date they arrived in the unit, strain/genotype, results of a clinical examination, haematology/biochemistry results, health screening results from animals and from the unit that supplied them

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5
Q

Why might it be useful to check rodents’ heartbeats even though they are too high to count?

A

May be able to detect an abnormally low rhythm

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6
Q

What is the definition of MAC50?

A

Prevents movement response to a specified noxious stimulus in 50% of animals.

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7
Q

What is an ideal gas flow into a face mask?

A

50-100 ml/min, but to obtain a margin of safety, can use 100-200 ml/min.

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8
Q

What are dis/advantages of inhalational anaesthetics?

A

+ depth can be easily varied
+ recovery is rapid
- complex to operate
- high cost
- regular maintenance

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9
Q

What are dis/advantages of injectable anaesthetics?

A

+ minimal cost and effort
- reducing depth is not possible in most cases
- resuscitation is not possible unless O2 is used

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10
Q

What is the preferred method for injectable anaesthetics, and why?

A

Intravenous.
Intramuscular may cause pain in rodents, intraperitoneal may not be delivered correctly
Sub-cutaneous may take longer to develop

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11
Q

What is the most widely used injectable anaesthetic regimen (intraperitoneal) in rodents?

A

Ketamine/medetomidine, or Hypnorm (fent/fluanisone)

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12
Q

What is the most widely used injectable anaesthetic (intravenous) in rodents?

A

Propofol or alphaxalone

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13
Q

Is pentobarbital an anaesthetic or analgesic?

A

An anaesthetic with NO analgesic properties

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14
Q

What anaesthetic regimen can cause high glucose levels?

A

Ketamine/medetomidine

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15
Q

What drug is used to reverse medetomidine in the ketamine/medetomidine anaesthetic regimen?

A

Atipamezole

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16
Q

What drugs are used to reverse fentanyl and midazolam?

A

Butorphanol and flumazenil

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17
Q

What are some effects of anaesthesia?

A

Blink reflex is lost, cornea will dry and ulcerate.
Increased urine production and fall in blood pressure
Hypothermia, respiratory arrest (due to depressed cardiac function)
Depressed cardio output

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18
Q

What should be monitored during anaesthesia?

A

Depth of anaesthesia
Respiratory function
Cardiovascular function
Body temperature

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19
Q

How can you check depth of anaesthesia?

A

Applying noxious stimuli
Pedal withdrawal reflex
Tail/ear pinch
Respiration
Eye position (cannot be used in rodents)

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20
Q

How can you check depth of anaesthesia with neuromuscular blockers?

A

Assess changes in electrical activity in the brain. Can measure onset using a peripheral nerve stimulator - applies an electrical stimulus to electrodes placed over a peripheral nerve supplying skeletal muscles

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21
Q

What degree of heat loss can result in severe hypothermia?

A

5-10C

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22
Q

What temperature should heat pads be set to during anaesthesia?

A

39-41 C

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23
Q

How to prevent heat loss when preparing animals for anaesthesia?

A

Shave only the area required, raise ambient temperature, and warm fluids that may be administered.

24
Q

How can you check respiratory function during anaesthesia?

A

Clinical observation - look at the colour of mucus membranes
Pulse oximeters - measure % saturation of haemoglobin

25
Q

What do capnograms measure, and how does a typical capnograph look?

A

Measures change in CO2 content in each breath.
A normal capnograph reaches a plateau before inspiration starts, causing a rapid fall in CO2.
Expiration causes a rise in the trace, then plateau, then inspiration causes a fall in the trace.

26
Q

What info can be gathered from a capnograph?

A

Can detect inadvertent placement of an endotracheal tube in the oesophagus, disconnection from the anaesthetic breathing machine, changes in respiratory pattern, inadequate fresh gas flow, changes in cardiac output, obstruction of the airway

27
Q

How can you prevent re-breathing during anaesthesia?

A

Increase the fresh gas flow rate

28
Q

What could cause a loss of waveform, or a notched waveform in a capnograph?

A

Loss of waveform - animal could be disconnected from the anaesthetic machine, or it has stopped breathing, or the machine is performing a calibration
Notched waveform - may indicate the animal is making respiratory efforts that are not synchronised with the ventilator

29
Q

What are typical arterial blood gas values and end-tidal carbon dioxide concentrations in lab animals?

A

pO2 = 90 mmHg
pCO2 - 34.5 mmHg

30
Q

What are some ways of checking cardiovascular function?

A

Palpating a pulse
Capillary refill - press down on the gums - slow refill indicates a reduction in peripheral perfusion
In small animals: look at the colour of mucus membranes

31
Q

What are some typical heart rates in lab animals?

A

Mouse: 450-650
Rat: 350-400

32
Q

How can blood pressure be monitored in small animals, and what is a typical mean blood pressure?

A

A cuff is placed around the tail so that it occludes one of the main arteries.
80-100 mmHg.

33
Q

How can blood loss be monitored following a procedure?

A

Measure swabs

34
Q

What % of a rodent’s body weight is blood, and what % of blood loss is considered minor?

A

7% of the animal’s weight
10% is considered minor, 20% could lead to cardiovascular disturbance

35
Q

How is peripheral oxygen saturation measured?

A

The pulse oximetry probe is placed over a pulsating vascular bed

36
Q

What is the difference between sidestream and mainstream capnographs?

A

Sidestream: samples gas from the airway and sends it to an external monitor for analysis. Has a slight delay but is good for small animals.

Mainstream: Measures CO2 directly in the airway with a sensor. Provides realtime information, but is not good for small animals.

37
Q

What are the components of an anaesthetic machine?

A
  • source of carrier gas
  • pressure regulator (reduces gas from compressed cylinders to lower pressure)
  • flowmeters (control gas flow)
  • vaporisers (produce anaesthetic vapour from liquid anaesthetic)
  • outlet port (connects to the breathing system)
  • emergency oxygen supply
38
Q

What should the pressure of the anaesthetic machine be, and how much oxygen can an E cylinder hold?

A

137 bar
680 litres

39
Q

What does fresh gas flow have to be to prevent re-breathing?

A

3x the minute volume

40
Q

Why is it important to make sure the endotracheal tube is not too long, and how many attempts can be made at placing it?

A

It may pass into one brochus and only ventilate one lung. 2 attempts only.
The main purpose of having an inflatable cuff on an endotracheal tube is that it provides a seal between the tube and the wall of the trachea

41
Q

What are the differences between Ayre’s T piece and the Bain (co-axial system)?

A

They are both re-breathing systems.
The Bain’s has an outer tube that removes excess gases (it is more compact).
The Ayre’s T-piece is better for small rodents, but it is less compact

42
Q

What is the circle breathing system?

A

This has gas flowing in a circle through a soda lime cannister (unidirectional flow maintained by valves).
The Co2 absorber is not present in other systems. It has higher resistance so is not suitable for small rodents.

43
Q

What can positive pressure ventilation help avoid?

A

tissue acidosis
hypoxaemia
hypercapnia

44
Q

What are non-polarising and depolarising NMBs?

A

Depolarising agents cause muscle activity before paralysis of the muscles, non-depolarising don’t.
Succinylcholine is the only depolarising agent in use, for when a short period of paralysis is required.
Non-depolarising: pancuronium, vecuronium, atracurium.

45
Q

What should be checked if the animal continues breathing but the O2 saturation falls below 80%?

A

If the tube has become blocked

46
Q

Why do intravenous/intraperitoneal routes have a slower recovery time?

A

They have to be administered at a higher dose rate

47
Q

When should the tube be removed if an animal is intubated, and surgery is ending?

A

Once laryngeal/pharyngeal reflexes return

48
Q

What can be done post-surgery to speed up recovery

A

Provide supplemental oxygen, maintian a warmer environmental temperature, provide softened/soaked diet (20-100ml/kg/24 hours), administer analgesics and anaesthetic drug antagonists

49
Q

Why are short acting drugs goof for anaesthesia?

A

You can control the dgeree of anaestehsia more easily by giving continuous infusion of a short acting drug. Buprenophrine is the most widely used opioid analgesic

50
Q

What are some side-effects of NSAIDs?

A

Blood clotting time can be prolonged - can be avoided by administering COX-2 selective antagonists
Can interefere with autoregulation of kidney blood flow
Gastrointestinal ulceration

51
Q

Why are analgesics not given in food/water?

A

Msay not dissolve or be stable ins olution, the animals may not like the taste, they may eat/drink at different imes

52
Q

What are side effects of opioids

A

decreased urine output
decreased heart rate
eating of cage bedding

53
Q

Pain in rats

A

orbital tightening
cheek and nose flattening
ear position (curl inwards and angle forwards)
whisker change (angle back along the head)

54
Q

Pain in mice

A

Staggering, twitching, belly press, orbitlal tightening
nose bulge (opposite to rats)
Cheek bulge
ear position (pulled back)
whiskers are pulled forwards

55
Q

What % of animals will recieve effective pain relief?

A

50-75

56
Q

What is neuroleptanalgesia?

A

Combination of a powerful opioid analgesic and a tranq to achieve anaesthesia (e.g. fent + medazolam + medetomidine)

RAT course (11 decks)

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