Anaesthesia + Analgesia Flashcards

1
Q

What is full cervical dilation?

A

10 cm

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2
Q

Describe pain transmission in the first stage of labour

A

Repetitive uterine contractions

Visceral - crampy, poorly localised

Slow, unmyelinated C fibres

  • paracervical ganglion
  • lumbar sympathetic chain

Uterus: T10-L1

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3
Q

Describe pain transmission in the second stage of labour

A

Repetitive uterine contractions + distension of pelvic + perineal structures

Somatic - well localised, sharp pain

Fast, myelinated A delta fibres - lumbo-sacral plexus

  • pudendal nerves
  • ilio-inguinal
  • genito-femoral
  • perforating branch posterior cutaneous nerve of thigh

Perineum: S2-S4

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4
Q

How is pain modulated in the spinal cord?

A
  • Afferent pain neurones enter dorsal horn
  • Synapse in substantia gelatinosa
  • Interneurones effect sensitivity of secondary afferents
  • Secondary afferents cross + ascend in spino-thalamic tract
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5
Q

What role do C fibres play in spinal cord pain modulation?

A
  • C fibres stim secondary afferents
  • Inhibitory interneuron suppressed
  • Strong pain stimulus transmitted via 2nd order neurone
  • Pain gate = open
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6
Q

What role do AB fibres play in spinal cord pain modulation?

A
  • AB fibres stim inhibitory interneurones
  • Reduced transmission of pain to secondary afferents
  • Pain gate = closed
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7
Q

How is Entonox used and what are the side effects?

A
  • Gas & air
  • Analgesic, sedative, euphoric
  • Rapid on/offset
  • Nausea + vomiting
  • B12 inactivation
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8
Q

How do opiates (e.g. Naloxone) work and what are their side effects?

A
  • Widespread in CNS
  • GPC
  • Hyperpolarize neurones, reduce excitability
  • Analgesic + Euphoria
  • Nausea, Sedation, Resp depression
  • IV/IM
  • Readily cross placenta
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9
Q

What is the most commonly used opiate for labour pain management in the UK?

A
  • Pethidine
  • IM
  • Analgesic
  • Sedative
  • Nausea + vomiting
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10
Q

What are the types of neuraxial analgesia?

A

Epidural

Spinal

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11
Q

What is the route of epidural anaesthesia administration?

A

Skin > Subcut tissue > Supraspinous L > Interspinous L > L Flavum > Epidural space

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12
Q

Compare the onset of epidural vs spinal anaesthesia

A

Epidural

  • Slow as local anaesthetic outside dura
  • Catheter - prolonged effect

Spinal

  • Rapid onset
  • Dense block
  • Single injection
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13
Q

What is the route of spinal anaesthesia administration?

A

Skin > Subcut tissue > Supraspinous L > Interspinous L > L flavum > Epidural space > Dura

Below conus L1-2

Pierce dura + aspirate CSF

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14
Q

What are the contraindications for neuraxial anaesthesia?

A
  • Abnormal spinal anatomy - spina bifida + lumbar fusion
  • Impaired coagulation - risk spinal haematoma
  • Infection - risk abscess/meningitis
  • Fixed CO - severe aortic stenosis, massive haemorrhage
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15
Q

What are the complication of nauraxial anaesthesia?

A
  • Failure - incorrect placement/anatomical
  • Dural puncture headache - CSF leak, low pressure headache
  • High block - total spinal
  • Nerve damage - direct-connus, nerve root, indirect - haematoma, abscess
  • Meningitis
  • LA toxicity - wrong route administration
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16
Q

What are the labour risks associated with neuroaxial blocks?

A
  • Motor block (heavy legs)
  • Reduced urge to push (reduced sensation) - prolonged 2nd stage, increased chance instrumental delivery
  • No increase in CS rate or LT backache
17
Q

What nerves are targeted by nerve blocks?

A
  • Peripheral nerves

- Pudendal S234