Pain Relief in Labour
Stages of Labour
- Stage 1: from regular uterine contractions to full cervical dilatation.
- Stage 2: from full cervical dilatation to delivery of the infant
- Stage 3: from delivery of the infant to delivery of the placenta
Stage 1 Mechanisms
- Associated with contractions
- Progressive dilatation of the cervix / lower uterine segment
- (Ischaemia of the cervical wall)
o Is the restriction of blood supply to the cervical wall which causes pain
o When a muscle contracts its blood supply need increases, but due to the
contractions it begins to restrict itself and this causes pain
- Mostly visceral in nature
o Transmitted by unmyelinated c fibres
o Dull / poorly localized (but still very severe)
- T10 to L1 nerve roots – supply the wall of the uterus
- somatic pain is sharp
- Visceral pain is dull and poorly localised
Stage 2 Mechanisms
- Associated with contractions
- Stretching of pelvic floor, perineum and vagina
- (Perineal / vaginal injury - tears etc)
- Mostly somatic in nature
o Transmitted by myelinated a-delta fibres
o Sharp and easily localized
- Predominantly S2-S4 nerve roots
o Pudendal nerve – if this were
blocked anesthesia may be
provided for delivery
Mechanisms
- Pain nerve impulses pass to dorsal horn
cells.
- Processed (see later)
- Transmitted to brainstem / brain via
spinothalamic tracts.
, Pain management approaches
- Systemic analgesics:
o e.g. opioids, nitrous oxide
- Regional techniques:
o e.g. epidural
- Pain modulation:
o e.g. TENS
- Psychological approaches
o e.g. Hypnobirthing
Systemic analgesics
- e.g. opioids – morphine and diamorphine (heroin)
o used a lot in labour analgesia
o admission through intramuscular injection – lasts for a few hours
o travels throughput the body and targets opioid receptors in spinal cord and brain
- e.g. nitrous oxide
o part of laughing gas
o breathed in through lungs
o acts on receptors in CNS
Regional techniques
- e.g. epidural
o targets nerves as they enter and leave the spinal cord
Pain Modulation
- looks at the processing function of pain to treat it
- TENS – transcutaneous electrical nerve stimulation
- A TENS stimulator sends electrical impulses through the skin kickstart body’s pain killers
o The electrical impulses release endorphins and other substances to stop pain signals
in the brain
Psychological approaches
- Hypnobirthing – hypnosis/distraction/taking control of pain and working with it
- Less side effects than medicalised pain relief
Nitrous Oxide
- Given as a 50:50 mix with oxygen ‘Entonox’ – ‘gas and air’
- Antagonist at NMDA receptors – switches them off, which therefore makes it harder for the
pain nerve cells to be activated
- Analgesia (pain relief) and sedation
- Many years of experience
- DNA damage under long exposure
- Pollution
o Local
o Environmental
Stages of Labour
- Stage 1: from regular uterine contractions to full cervical dilatation.
- Stage 2: from full cervical dilatation to delivery of the infant
- Stage 3: from delivery of the infant to delivery of the placenta
Stage 1 Mechanisms
- Associated with contractions
- Progressive dilatation of the cervix / lower uterine segment
- (Ischaemia of the cervical wall)
o Is the restriction of blood supply to the cervical wall which causes pain
o When a muscle contracts its blood supply need increases, but due to the
contractions it begins to restrict itself and this causes pain
- Mostly visceral in nature
o Transmitted by unmyelinated c fibres
o Dull / poorly localized (but still very severe)
- T10 to L1 nerve roots – supply the wall of the uterus
- somatic pain is sharp
- Visceral pain is dull and poorly localised
Stage 2 Mechanisms
- Associated with contractions
- Stretching of pelvic floor, perineum and vagina
- (Perineal / vaginal injury - tears etc)
- Mostly somatic in nature
o Transmitted by myelinated a-delta fibres
o Sharp and easily localized
- Predominantly S2-S4 nerve roots
o Pudendal nerve – if this were
blocked anesthesia may be
provided for delivery
Mechanisms
- Pain nerve impulses pass to dorsal horn
cells.
- Processed (see later)
- Transmitted to brainstem / brain via
spinothalamic tracts.
, Pain management approaches
- Systemic analgesics:
o e.g. opioids, nitrous oxide
- Regional techniques:
o e.g. epidural
- Pain modulation:
o e.g. TENS
- Psychological approaches
o e.g. Hypnobirthing
Systemic analgesics
- e.g. opioids – morphine and diamorphine (heroin)
o used a lot in labour analgesia
o admission through intramuscular injection – lasts for a few hours
o travels throughput the body and targets opioid receptors in spinal cord and brain
- e.g. nitrous oxide
o part of laughing gas
o breathed in through lungs
o acts on receptors in CNS
Regional techniques
- e.g. epidural
o targets nerves as they enter and leave the spinal cord
Pain Modulation
- looks at the processing function of pain to treat it
- TENS – transcutaneous electrical nerve stimulation
- A TENS stimulator sends electrical impulses through the skin kickstart body’s pain killers
o The electrical impulses release endorphins and other substances to stop pain signals
in the brain
Psychological approaches
- Hypnobirthing – hypnosis/distraction/taking control of pain and working with it
- Less side effects than medicalised pain relief
Nitrous Oxide
- Given as a 50:50 mix with oxygen ‘Entonox’ – ‘gas and air’
- Antagonist at NMDA receptors – switches them off, which therefore makes it harder for the
pain nerve cells to be activated
- Analgesia (pain relief) and sedation
- Many years of experience
- DNA damage under long exposure
- Pollution
o Local
o Environmental
