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Principles of Science > Anaesthesia > Flashcards

Anaesthesia Flashcards

1
Q

What reasons are there for anaesthesia?

A

Restraint - Surgery - Diagnostic procedures - Therapy - Legal requirements

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2
Q

Define anaesthesia

A

Loss of sensation resulting from pharmacological depression of nerve function

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3
Q

Define general anaesthesia

A

State of unconsciousness produced by controlled reversible drug-induced intoxication of CNS - No patient recall or perception

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4
Q

Define local anaesthesia

A

Temporary block of sensory nerves

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5
Q

What are the components of general anaesthesia that mark it as successful?

A

Unconsciousness - Analgesia - Muscle relaxation - Normal oxygen delivery - Homeostasis

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6
Q

What is balanced anaesthesia?

A

Use of smaller doses of a combination of drugs to achieve various components of anaesthesia to reduce disadvantages of using large doses of one drug

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7
Q

What are the side effects of anaesthesia?

A

Excessive physiological depression - Depressed homeostatic mechanisms - Specific drug effects (eg NSAIDs reducing prostaglandin-mediated renal autoregulation)

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8
Q

What is pre-anaesthetic medication?

A

Drugs given prior to anaesthesia which contribute to the peri-anaesthetic process (prep, medication, anaesthesia and recovery)

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9
Q

Why premedicate for anaesthesia?

A

Relieve anxiety - Peri-operative analgesia - Counteract unwanted side effects - Reduce anaesthetic dose

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10
Q

What is the difference between a tranquiliser and a sedative?

A

Tranquilisers reduce anxiety (anxiolytic) whereas sedative reduce anxiety whilst causing drowsiness

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11
Q

What are the 4 main classes of sedatives?

A

Phenothiazines - Butyrophenones - Benzodiazepines - Alpha 2 agonists

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12
Q

Give an example of a phenothiazine

A

Acepromazine (ACP)

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13
Q

Give the general pharmacodynamics of Acepromazine on CNS

A

CNS - dopamine antagonism causing sedation

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14
Q

Give the general pharmacodynamics of Acepromazine on GI

A

Anti-emetic (CTZ antagonism) - Anti-spasmodic - Anti-sialagogue

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15
Q

Give the general pharmacodynamics of Acepromazine on CVS

A

Alpha1-adrenergic antagonism - Peripheral vasodilation and anti-arrhythmic effects

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16
Q

What routes can ACP be administered?

A

IM (mainly) - IV - Oral (variable absorption)

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17
Q

How is ACP distributed in the body?

A

Lipophilic and protein bound

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18
Q

Why should ACP be avoided in breeding stallions?

A

Paralysis of retractor penis muscle - May lead to penile relaxation and priapism

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19
Q

With what breed of dog should you be cautious with using ACP in? Why?

A

Brachycephalic and giant breeds - Airways and sensitivity

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20
Q

Why shouldn’t you use ACP prior to intradermal skin testing?

A

Has anti-histamine effect

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21
Q

What does ACP potentiate?

A

Opioids - Local anaesthetic - General anaesthetics - Organophosphates

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22
Q

Give two examples of Butyrophenones

A

Azaperone - Fluanisone

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23
Q

How do Butyrophenones cause sedation?

A

Dopamine antagonism

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24
Q

What are the pharmacodynamics of butryophenones?

A

CNS - Sedative, antiemetic, hallucinations (humans)

CVS - vasodilation and hypotension

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25
Q

Give two examples of Benzodiazepines

A

Diazepam - Midazolam

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26
Q

What is the mechanism of action of Benzodiazepines?

A

Potentiation of GABA (Gamma amino buteric acid) - Major inhibitor of neurotransmitter in CNS

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27
Q

What are the pharmacodynamics of Benzodiazepines in the CNS?

A

Anxiolytic action - Anticonvulsant properties (for seizures)

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28
Q

In which patients do Benzodiazepines work best in?

A

Very young, very old or sick patients

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29
Q

What kind of drug is Diazepam? Describe the properties of it

A

Benzodiazepine - Insoluble in water and irritant - Presented as solution in propylene glycol (causes discomfort on injection)

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30
Q

Why shouldn’t you draw up diazepam into a syringe early?

A

Absorbed onto plastic

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31
Q

Describe the pharmacokinetic properties of diazepam (valium)

A

Rapid onset and short duration - Highly lipid soluble and protein bound - Metabolised in liver (some metabolites active) - Excreted in urine

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32
Q

What are the pharmacodynamics of Diazepam in the CNS?

A

Central muscle relaxation - Anticonvulsant - Appetite stimulant in cats

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33
Q

Why do you have to be careful when administering Diazepam as an appetite stimulant in cats?

A

Causes hepatic failure on oral administration

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34
Q

Give an example of a water soluble benzodiaepine. How is it administered?

A

Midazolam - IM

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35
Q

Give the mechanism of action of alpha2-adrenoceptor agonists

A

Act centrally and peripherally - Pre-synaptic a2 receptors reduces release of noradrenaline (-ve feedback) - Post-synaptic a2 receptors initiates a1 type response

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36
Q

What is the a1-type response caused by a2-receptor agonists?

A

Peripheral vasoconstriction - Splenic contraction - Increase PCV

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37
Q

What are the aplha2-adrenoceptor agonist phramacodynamics in the CNS?

A

Sedation - Analgesia - Muscle relaxation

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38
Q

What are the aplha2-adrenoceptor agonist phramacodynamics in the CVS?

A

Dramatic vagally mediated bradycardia - Biphasic effect on blood pressure/vascular tone
1 - hypertension due to a1-type effect
2 - hypo/normotension because of bradycardia

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39
Q

What are the aplha2-adrenoceptor agonist phramacodynamics in the respiratory?

A

Depression especially in ruminants - Sometimes pulmonary oedema (esp. sheep)

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40
Q

What are the aplha2-adrenoceptor agonist phramacodynamics in the GIT?

A

Vomiting in dogs and cats - Depressed motility - Aerophagia

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41
Q

What are the aplha2-adrenoceptor agonist phramacodynamics in the endocrine system?

A

Inhibition of ADH (polyuric) - Inhibition of insulin release (osmotic glucose diuresis)

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42
Q

Why should Alpha2-adrenoceptor agonists be avoided in pregnant animals?

A

Cause uterine contraction

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43
Q

Give examples of a2-agonists

A

Xylazine - Detomidine - Romifidine - Medetomidine - Dexmedetomidine

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44
Q

In which species do you have to be careful with xylazine dosage? Why?

A

Ruminants - Very sensitive

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45
Q

What are the four stages of general anaesthesia?

A

Premed/Sedation - Induction - Maintenance - Recovery

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46
Q

Which stage of induction isn’t preferable? How is this skipped?

A

Signs of excitement - Administer with IV for quicker sedation

47
Q

What do anaesthetic agents generally do to a patient?

A

CV depression - drop in CO, vasodilation, reduced BP

Respiratory depression - decrease resp rate, decrease tidal volume, reduced minute volume

48
Q

During surgery, what else needs to be administered alongside anaesthetic agents? Why?

A

Analgesics (opioids) - Anaesthetic agents provide very little analgesia

49
Q

What is the ultimate goal of anaesthetic agents? What interferes with this?

A

Reach adequate blood and brain levels to provide anaesthetic effects - Blood brain barrier

50
Q

How would you generally administer dosages of anaesthetic agents?

A

Slowly and to effect

51
Q

What can propofol be used for?

A

Induction and maintenance of anaesthesia

52
Q

Describe the pharmacokinetics of propofol

A

Rapid onset - Blood levels decreased by distribution - Rapid metabolism in liver - Causes cardiovascular and respiratory depression

53
Q

Why do cats take longer to recover from propofol than dogs?

A

Cats lack the enzymes to conjugate glucuronides so slow metabolism of propofol - Problems metabolising triglycerides (lipid carrier)

54
Q

What is propofol plus?

A

Better mix of propofol - No pain on injection - Reduces anaesthetic waste as has shelf life of 28 days - Contains benzyl alcohol (preservative)

55
Q

Name and describe a steroid that can be used for anaesthetic

A

Alfaxalone - Poorly soluble - Rapid onset and short duration - Less cardiopulmonary depression than propofol

56
Q

Why can’t ketamine be solely used for anaesthetic?

A

Doesn’t provide muscle relaxation

57
Q

What is ‘triple combination’ use of ketamine? What is it used for mainly?

A

Ketamine, Medetomidine, Opioid - Aggressive cats

58
Q

How would you administer ketamine to a horse?

A

After profound sedation with a2-agonist - Combination with benzodiazepine to counteract muscle tension

59
Q

What is strange about the pharmacodynamics of ketamine?

A

CNS - reflexes are preserved, jaw tone, swallowing

CVS - stimulation of sympathetic, hypertension and tachycardia

60
Q

What agents can be used as inhalation induction of anaesthesia?

A

Sevoflurane - Isoflurane

61
Q

What is the relationship between solubility of anaesthetic gas agent and length of induction and recovery?

A

The more soluble the agent is the longer it will take for induction/recovery

62
Q

Why do we monitor during anaesthesia?

A

Ensure adequate depth - Ensure adequate perfusion & oxygenation of tissues

63
Q

What problems can you get with ET tubes?

A

Occlusion of the end - Endobronchial intubation - Compression of tube - Stretching of tracheal wall

64
Q

Why is analgesia still required during anaesthesia?

A

Prevent up-regulation of pain processing pathways

65
Q

What needs to be done to cats before inserting an ET and why?

A

Spray larynx with local anaesthetic to desensitise and reduce laryngospasm during intubation

66
Q

What local anaesthetic spray is used for cats when inserting an ET?

A

Intubeaze - Lidocaine spray

67
Q

How can anaesthesia be maintained?

A

Inhalation - Injection - Mixture of the two - Occasionally single intramuscular injection

68
Q

What are the two methods of injectable anaesthesia? Give adv. and dis. of both

A

Intermittent boluses
+ve simpler and less equipment
-ve swinging plane of anaesthesia

Continuous rate infusion
+ve minimum infusion rate
-ve more complicated

69
Q

What injectable agents for maintenance are there?

A

Propofol - Alfaxalone - Ketamine

70
Q

With gas inhalation, how do you approximate the brain concentration?

A

Approximately equal to alveolar concentration

71
Q

What does high partial pressure of anaesthetic agent in lungs mean?

A

=high partial pressure in brain

72
Q

What is MAC?

A

Minimum Alveolar Concentration required to prevent movement in response to painful stimulus in 50% animals

73
Q

Name 5 agents that can be used for inhalational anaesthetic

A

Isoflurane - Halothane - Sevoflurane - Nitrous oxide - Desflurane

74
Q

Why can’t N2O solely be used for anaesthetic?

A

MAC is ~200%

75
Q

When should you extubate?

A

When swallowing reflex returns

76
Q

When do most mortalities occur because of anaesthetic and how can this be prevented?

A

Recovery - Good monitoring

77
Q

What cranial nerve reflexes can be used to measure the depth of anaesthesia?

A

Palpebral - Ocular position - Pupil diameter - Jaw tone

78
Q

What does EEG stand for?

A

Electroencephalogram

79
Q

What methods can be used to monitor CVS function?

A

Pulse - Stethoscope - ECG - Pulse oximeter

80
Q

What does the mucous membrane colour tell you about CVS function?

A

Haemoglobin quantity - Peripheral blood flow - Respiratory adequacy - Toxaemia

81
Q

What information does an oesophageal stethoscope give you?

A

Heart rate - Respiratory rate

82
Q

What is ABP and how is it calculated?

A

Arterial blood pressure = Cardiac output x Systemic Vascular Resistance

83
Q

What indirect methods are there for monitoring ABP?

A

Doppler flow detection - Oscillometric method

84
Q

Describe how Doppler flow detection for ABP works

A

Pressure cuff around extremity - Ultrasound sensor distal to cuff - Indicates systolic pressure

85
Q

How does Oscillometric method measure ABP?

A

Automatically inflates - Senses oscillation in cuff - Max oscillation = mean ABP

86
Q

What does Pulse oximetry indicate?

A

Arterial oxygen saturation - Heart rate - Pressure wave form (peripheral circulation)

87
Q

What’s the method of action of Pulse oximetry?

A

Photodetectors detect pulsate signal of arterial blood - Differential absorption of red and infrared gives oxyhaemoglobin

88
Q

What sites do you monitor during pulse oximetry? When?

A

Peripheral (tongue, mammary, toe, etc) - During and after anaesthesia

89
Q

What homeostatic reflexes do general anaesthetics stop?

A

Baroreceptor reflex - Hypoxic pulmonary vasoconstriction - Thermoregulation

90
Q

Why is it good to measure urine output during anaesthesia?

A

If anaesthetic not deep enough then stress response will mean increased vasopressin which reduces urine output

91
Q

How do you help in cases of hypoxaemia and hypercapnia?

A

Check depth - Check airway - Increase FiO2 if possible - Ensure no rebreathing - Ventilate - Consider albuterol

92
Q

What does IPPV mean?

A

Intermittent positive pressure ventilation

93
Q

What are the effects of IPPV?

A

Intrapleural pressures remain above 0 - Decreased venous return

94
Q

How would you treat an animal that is developing haemodynamically significant VPCs and VT?

95
Q

What fluids would you give to an animal that has lost a) 10% blood b) 10-25% blood c) >25% blood?

A

a) Crystalloid
b) Colloid
c) Blood

96
Q

What does ICP stand for? What does an increase suggest?

A

Intracranial pressure - Impending death

97
Q

How do you treat increasing ICP?

A

Hyperventilate - Manitol (osmotic effects) - Hypertonic saline - Furosemide (synergistic with manitol)

98
Q

Why do you have to be very careful when anaesthetising farm animals?

A

They are much more sensitive to anaesthesia

99
Q

What are the main legislated drugs for use in farm animals in the UK?

A

Xylazine - Detomidine - Azaperone - Ketamine - Thiopentone - Isoflurane

100
Q

What specific issues are involved in anaesthesia of ruminants?

A

Regurgitation - Salivation - Bloat - Hypotension - Hypertension - Hypoventilation - Myopathy

101
Q

What can be done to reduce incidence of regurgitation during anaesthesia of farm animals?

A

Reduce rumen fill and rumen water (starve 18-24 hours pre-op - Remove water 12 hours pre-op)

102
Q

Which NSAIDs have 0 day withdrawal period for milk?

A

Ketoprofen - Carprofen

103
Q

What is Xylazine? Why is it used carefully in ruminants?

A

Alpha 2 agonist for sedation - ruminants very sensitive

104
Q

What licensed local anaesthetics are there for ruminants?

A

Procaine - Benzocaine - Tetracaine

105
Q

What licensed sedation is there for pigs?

106
Q

What is malignant hyperthermia?

A

Faulty gene - Higher affinity of a-site (opening Ca2+ channels) - Large amount of ATP used - Generates large amounts of heat

107
Q

What are the clinical signs of MH (MHP)?

A

Muscle rigidity - High CO2 and moisture production

108
Q

How do you treat MH?

A

Active cooling - Ventilate - Dantrolene injection (reduce calcium release)

109
Q

Give an example of a weak sedative in horses?

A

Phenothiazines eg. acepromazine

110
Q

Give 3 alpha 2 agonists that can be used in horses for sedation

A

Xylazine - Detomidine - Romifidine

111
Q

Why must ketamine be given in conjunction with other agents?

A

Its is a hallucinogenic and convulsant - Need other agents to counteract these side effects

112
Q

What is Guiaphenesin?

A

Centrally acting muscle relaxant

113
Q

What is the minimum monitoring horses under general?

A

Depth of anaesthesia - Heart rate and rhythm - Arterial blood pressure

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