Post Op Pain Relief Flashcards

1
Q

Define pain

A

An unpleasant sensory emotional experience associated with actual or potential tissue damage or expressed in terms of such damage

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2
Q

What is chronic pain

A

Duration exceeding 6 months or persisting beyond the time for tissue healing

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3
Q

What are the 3 aspect to pain

A

Physical - damage
Emotional
Rational- makes to sense to avoid painful things

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4
Q

Which spinal pathway is the pain pathway

A

Spinothalamic
1st Order neurone - periphery to spiral cord
2nd order is spinohalamic tract to the thalamus
3rd order thalamus to the cortex

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5
Q

What are the somatosensory pain transmitting neurons

A
A delta - 12-30m/sec- mechorecptors and nociceptors 
C fibres (0.5-2m/sec) mechanorecptors and nociceptors 
B fibres sympathetic preganglionic fibres 
A beta (30-70m/sec) cutaneous touch and pressure
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6
Q

What is somatosensory pain

A

Cutaneous, well localised, sharp, pain from deeper structures, less well localised

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7
Q

What is visceral pain

A

Poorly localised, often referred to surface are innervated By the same spinal segment
MI radiated to arm/neck

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8
Q

What is sympathetically maintained pain

A

Difficult to mx excessive sympathetic stimulation is interpreted or augmented painful stimuli

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9
Q

What do A beta fibres do

A

Normally they are no involved in signalling noxious stimuli but can do under abnormal conditions
They are more resistant to local anaesthetic blockaded that A delta and C fibres
This explains how patient under spinal or epidural analgesia may sense touch and movement but not pain and temperature. When all fibres but A alpha motor neurones are blocked patients move toes on command but will be unaware of doing so

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10
Q

What do A delta fibres do

A

Transmit faster
Are more readily injured by pressure and ischaemia
- sciatica

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11
Q

What are C fibres

A

More easily blocked by local anaesthetics so it is possible to remove sensation of pain and temperature leaving light touch/movement intact

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12
Q

Chemostry of pain - acute tissue trauma causes the release of what

A

Tissue injury factors
Inflammation
The contents of cells injury can be extruded and other inflammatory signalling pathways activated
K+, H+, bradykinins, ATP, prostaglandins, 5-HT, histamine, cytokines IL1,6,8 and TNF alpha, NGF

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13
Q

Neurochemistry of sensory neurones

Neuro peptides and neurotransmitters

A

Substance P, excitatory amino acids, glutamate and aspartate
Na+, K+ and Ca2+ channels are of major importance

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14
Q

What is the gate theory of pain

A

Noxious stimuli sensed by C fibres these are projected to the spinothalamic tract
A alpha and A beta fibres are stimulated by non-noxious mechanoreceptors
There act as an inhibitor interneurone to the C fibre reducing transmission to the spinothalamic tract reducing nociception

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15
Q

Examples of gate theory of pain in clinical practise

A

TENS machine

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16
Q

What is preemptive analgesia

A

Theory - preventing noxious stimuli from reaching the spinal cord and CNS, central sensitisation will not occur this minimises neuronal changes, reducing post op pain
In practice LAnfiltation in to tissues prior to incision, block of peripheral nerves or nerve plexus should epidural or spinal injury LA with or without opioids
In major studies a reduction in post op pain has been seen and faster discharge etc

17
Q

What are NSAIDS

A
They are cycloxygenase inhibitors 
Good in body wall and orthopedics 
Excellent opioid sparing effect 
SE
Peptic ulcers 
Broncospasm
Renal failure  - block prostaglandin renal failure if you become hypotensive then the renal arteries cant respond 
Interstitial nephritis
18
Q

Opioids what are they

A

Good visceral analgesics poor somatic analgesic
Analgesia by the mu receptor
All except bu[renorphine have the same effects
Toxicity manifest as slow resp rates and large tidal volume
Shift in CO2 response curve upwards

19
Q

Undesirable affects of opioids

A
Tolerance
Dependence 
Dysphoria
N/V
Smooth muscle spasm
Constipation
Resp depression 
Depress cough reflex (desirable in palliative care)
Muscle rigidity