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Anaesthetics Flashcards

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1
Q

What is general anaesthesia?

A

Produces insensibility in the whole body, usually unconsciousness
Centrally acting drugs

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2
Q

What is regional anaesthesia?

A

Produces insensibility in an area or region

Local anaesthetics applied to nerves supplying area

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3
Q

What is local anaesthesia?

A

Produces insensibility in only relevant part of body

Applied directly to tissues

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4
Q

What is the triad of anaesthesia?

A

Analgesia
Hypnosis
Relaxation

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5
Q

What drugs tend to be used to cause analagesia in surgery?

A

Opiates

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6
Q

What agents are used to cause hypnosis in surgery?

A

General anaesthetic agents

Lectures…

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7
Q

What agents are used to cause relaxation in surgery?

A

Muscle relaxants

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8
Q

What is balanced anaesthesia?

A

Using different drugs to do different jobs
Titrating each drug separately
Avoids overdose
Gives flexibility

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9
Q

What are the problems with muscle relaxants?

A

They create the need for:
Artificial ventilation
A means of airway control

Awarness
Incomplete reversal = airway obstruction

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10
Q

How do general anaesthetic agents work?

A

They interfere in neuronal ion channels

Hyperpolarise neurone cells making it less likely to send impulses

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11
Q

How do inhalational agents work?

A

They dissolve in membranes

Gives a direct physical effect

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12
Q

How do IV agents give their effect?

A 
Through allosteric (enzyme) binding
GABA receptors open choloride channels
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13
Q

What function is lost in general anesthesia? What is retained?

A

Cerebral function “from top down” lost
Most complex first
More primative lost later

Reflexes relatively spared
As primitive with small number of synapses

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14
Q

What are the downsides of general anaesthesia?

A 
Long drawn out resus
Mandates airway management
Impact on resp function + control of breathing
CVS impact
Care of unconcious patient
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15
Q

What are the benefits of IV anaesthesia?

A

Rapid onset of unconciousness
>arm-brain circulation time
Rapid recovery
>however drug not necessarily out of system, just distributed

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16
Q

What are the inhalational agents?

A

Halogenated hydrocarbons

Main one sevoflurane (halothane)

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17
Q

What is MAC?

A

Minimum alveolar concentration
Measure of potency
Low number=high potency

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18
Q

What are the benefits/downsides to inhaled anaesthetics?

A

Slow induction
However, very flexible duration
And quick to come back round

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19
Q

What is the generic way of adminstering anaesthesia in surger?

A

Induction with IV

Maintain with inhalation

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20
Q

What is general anaesthesia’s effect on the cardiovascular system?

A

Depresses central cardiovascular centre
>Reduces sympathetic outflow
>Negative iontropic effect on heart
>reduced vasoconstriction -> vasodilation

Causes decreased peripheral resistance
Causes venodilation (Decreased venous return = decreased Cardiac Output)
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21
Q

What is the effect of general anaesthesia on the respiratory system?

A 
Respiratory depressant
Reduce hypoxic drive
Decreased tidal volume, increases rate
Paralyse cilia
Causes VQ mismatch, which may be prolonged
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22
Q

What are the indications of muscle relaxants?

A

Ventillation + incubation
When immobility essential
Body caivty surgery

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23
Q

Why is analgesia used intraoperatively?

A

To prevent arousal
Opiates contribute to hypnotic effect of GA
Supression of reflexes to painful stimuli (tachycardia, hypertension)

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24
Q

What are the benefits of local/regional analgesia?

A

The patient retains awareness/consciouness (pregnancy)
Lack of global effects
Derangement of CVS proportional to affected area
Relative sparing of resp function

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25
What are the limitations of local anaesthetics?
Toxicity High plasma concentration due to IV Absorption faster than metabolism They vasoconstrict
26
Why do local anaesthetics cause a differential cascade?
Due to different penetration of nerve types Motor fibres are thicker + myelinated so are relatively spared Whereas pain fibres as thinner and so affected first Allows for no paralysis but analgesia
27
What are the main IV anaesthetic drugs?
Propofol | Thiopentone (used less, but still in maternity hospital)
28
What are the downsides to IV induction?
Easy to overdose Apnoea very common Generally rapid loss of airway reflexes
29
When would you normally use gas induction?
In young children
30
What are the planes of anaesthesia?
Analgesia/sedation Excitation Anaesthesia (light-> deep) Overdose
31
What is the light/deep "sleep" of inhaled anaesthesia dependant on?
Responsivness to stimuli
32
How is conciousness monitored when a patient is under anaesthesia?
``` Loss of verbal contact Movement Respiratory pattern Processed EEG Stages/planes of anaesthesia ```
33
What is the triple airway manoeuvre?
Head tilt Chin lift Jaw thrust
34
What simple apparatus are used for airway maintenance in anaesthesia?
``` Face mask Oroopharyngeal aiway (guedal) Nasopharyngeal airway (less used) ```
35
Why should you wait for a patient to be in deep anaesthesia before using a oropharyngeal/ guedal airway?
As insertion in light patient may cause vomitting or laryngospasm Only tolerated by unconcious patient
36
What is the laryngeal mask airway?
A cuffed tube with a mask sitting over glottis | Maintains but does not protect airway (aspiration)
37
What is a laryngospasm?
Forced reflex adduction of vocal cords May result in complete airway obstruction Caused by airway simulation in light planes of anaesthesia Often not relieved by simple manoeuvres
38
What can cause obstruction?
Innefective triple airway manoeuvre Airway device malposition/kink Laryngospasm
39
What are the possible complications with the airway
Obstruction | Aspiration
40
What is endotrachieal intubation?
Placement of cuffed tube in trachea Laryngeal reflexes must be abolished >Possible in awake patient using local anaesthetic + fibre optic scope
41
Why are people intubated?
To protect airway from gastric contents Need for artificial ventilation after muscle relxants Shared airway with risk of blood contamination Need for tight control of blood gases If restricted access to airway
42
What are the risks to an unconcious patient?
``` Airway Temperature Loss of other protective reflexes - conreal, joint position VTE risk Concsent/identification Pressure areas ```
43
What is the process to emergence
``` Muscle relaxation reversed Turn off anaesthetic agents Resumption of spontaneous respiration Return of airway reflexes/control Extubation ``` Can be quick or slow
44
What are the signs in someone who is euvolaemic (has the right amount of fluid in body)
``` Not thirsty Veins well filled Warm extermities Mild sweat Normal BP/HR Normal urine ```
45
What are the signs of someone who is hypovolaemic?
``` Feels nauseous/thirsty Flat veins Cool peripheries No sweat Low/postural BP High HR Concentrated urine Response to SLR ```
46
What are the needs of someone who is hypovolaemic?
Resuscitation fluids (If low BP) Rehydration fluids Find the cause and stop it
47
What are the signs of hypervolaemia?
``` Breathless, not thirsty Distended veins Warm /oedematous extermities Sweaty High BP/HR Dilute urine ```
48
How do you manage someone who is hypervolaemic?
Stop any fluids Possibly diuretics Haemofiltration if anuric
49
What is resuscitation fluid?
IV fluids to restore circulation with hypovolaemia >Reassess after! (BP) In shock!
50
What is routine maintenance fluid?
IV fluids if cannot take orally ot enterally to meet patient maintenance requirements If cannot eat >Limited as if cannot eat not getting any nutrients Reassess after (fluid balance every day)
51
What are the 5 Rs of fluid?
``` Resus Routine maintenance Replacement Redistribution reassessment ```
52
What is replacement resuscitation?
``` Don't need urgent IV resuscitation but do need additional IV to maintenance to correct existing deficit or ongoing abnormal external losses Reassess after (bloods - did it work?) ```
53
What is redistribution resuscitation?
Patients with abnormal internal fluid redistribution/abnormal fluid handling Particularly with sepsis/major illness, cardiac, liver or renal disease etc
54
When is dextrose useful?
Chronic dehydration | Hypernatreamia
55
When is dextrose not useful?
Resuscitation | Or low albumin
56
What are the properties of dextrose fluid?
Moves through all compartments >Not useful for blood volume expansion No sodium so depletes sodium, isotonic
57
When are crystalloids useful?
acute dehydration AKI Resuscitation
58
When is crystalloids not useful?
Long term maintainence | Hypernatraemic patient
59
When are plasma expanders useful?
Liver patients | Select intraopertative
60
How do you work out how much fluid they need?
Work out fluid balance (input/output charts)
61
What are the properties of crystalloids?
Remain in ECF High sodium load, which can cause problems over time Lots of different types
62
What are colloid expanders?
Colloids | >Examples such as Blood and TPN, Albumin
63
What are teh ASA grades?
``` ASA1: healthy patient ASA2: Mild-moderate systemic disturbance ASA3: severe systemic disturbance ASA4: Life threatening disease ASA5: Moribund patient ASA6: organ retrieval ```
64
What are some potenital anaesthetic problems?
Airway Spine Reflux Obesity
65
What are METs?
A measure of exercise tolerance
66
What are the classifications of pain?
``` Duration >Acute/chronic/ Acute on chronic Cause >Cancer/non cancer Mechanism >Nociceptive >Neuropathic ```
67
What is chronic pain?
Pain lasting more than 3 months Pain lasting after normal healing Often no identifiable cause
68
What is cancer pain?
Progressive pain | Mix of acute and chronic
69
What is nociceptive pain?
Obvious tissue injury/illness "Physiological"/"inflammatory" pain Protective function Sharp +/- dull pain >Often well localised
70
What is neuropathic pain?
Nervous system damage/abnormality Injury may not be obvious No protective function Burning, shooting +/- numbness/parasthesia >Not well localised
71
What fibres carry nerve pain?
A delta | C nerve fibres
72
What pathway carries nerve pain?
Spinothalamic tract >Dorsal root synapse >Thalamus synapse >Cortex destination
73
What are the pathological mechanisms causing neuropathic pain?
Increased receptor numbers Abnormal sensations of nerves Chemical changes in dorsal horn Loss of normal inhibitory modulation
74
What are the advantages for paracetamol?
Cheap and safe Oral, rectal or IV administrations Good for mild pain by itself, and moderate-severe pain with others
75
What are the advantages of NSAIDs?
Cheap and gernally safe (GI/renal side effects) | Good for nociceptive pain
76
What are teh advantages/disadvantages of codein?
Cheap/safe Good for mild-moderate acute nociceptive pain However, constipation and not good in chronic pain
77
What does tramadol do?
Weak opoid effect + inhibition of serotonin/noradrenaline uptake
78
What are the advantages/disadvantages of tramadol?
Less respiratory depression than with other opoids Can be used with opoids/other analgesics Not a controlled drug However, can cause nasuea/vomitting
79
What are teh advantages of morphine?
``` Cheap + generally safe Oral, IV, IM + Subcut administration Effective if regular Good for mod-severe acute nociceptive pain Chronic cancer pain ```
80
What are the disadvantages of morphine?
Constipation Respiratory depression in high dose Misunderstandings about addiction Controlled drug Oral dose 2-3 x IV/IM/SC
81
What is amitriptyline?
Trycyclic antidepressant | Increases descending inhibitory signals
82
What are the advantages of Amitriptyline?
Cheap, safe in low dose Good for neuropathic pain Also treats depression, poor sleep However, anticholinergic side effects
83
What are some examples of anticonvulsant drugs?
Carbamazepine (Tegretol) Sodium valproate (Epilim) Gabapentin (Neurontin)
84
What are the delivery routes for local anaesthetics?
``` Epidural (+/- Opiates) Intrathecal (+/- Opiates) Wound Catheters Nerve Plexus Catheters Local Infiltration of wounds ```
85
What scoring systems can be used to rate pain?
``` Verbal Rating Score Numerical Rating Score Visual Analogue Scale Smiling faces Abbey Pain Scale (for confused patients) ```
86
What non-pharmaceutical treatments can be used for pain?
RICE Surgery Acupuncture, massage, physio Psychological meassures - explanation, reassurance, counselling
87
What is the pain ladder?
Step 1: >Non-opoids (Aspirin, NSAIDS, paracetamol) Step 2 >Mild opoids (codeine) w/ or w/o non-opoids Step 3 >Strong opoinds (morphine) w/ or w/o non-opoids
88
Where do you start/stop someone on the pain ladder?
Mild Pain: Start at Bottom of Pain Ladder Moderate Pain: Bottom of Pain Ladder plus Middle Rung Severe: Bottom of Pain Ladder plus Top of Ladder. Miss out the middle To stop, move down one rung at a time
89
What is the RAT approach?
Recognise >Do they have pain (ask/look) Assess Treat
90
How do you assess in RAT?
What is pain score (rest/movement) How does pain affect patient (can they move, cough work?) Type >Look for neuropathic features >Burning/shooting pain, phantom limb, parasthesia Other factors >Physical/psychological (other illness, anger, anxiety etc)
91
How do you treat neuropathic pain?
``` Traditional drugs may not be useful Use other drugs early >Amitriptylline >Gabapentin >Duloxetine Don’t forget non-drug treatments ```

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