pain understanding

1. PHYSIOLOGY OF PAIN IN
LABOUR
ELIZABETH CHODZAZA

2. LEARNING OUTCOMES
 Define pain
 Describe of types of pain in labour
 Explain the gate theory and its relationship to
labour pains
 Explain non-pharmacological and pharmacological
management of pain in labour

3. PAIN
 Pain is whatever the person says it is.
 Pain's an unpleasant sensation which may
be associated with actual or potential tissue
damage and which may have physical and
emotional components
 Pain is very subjective and the degree
varies in
 Different women
 Same woman in successive labours
 Same woman at different time in the same labour

4. PAIN
 Pain is describe by individual as being
 Throbbing
 Slicing
 Burning
 Crushing
 Squeezing
 Cutting
 Pounding
 Pricking e.t.c

5. PAIN THRESHOLD AND TRANSMISSION
 Pain threshold refers to the lowest level at
which the brain perceives pain.
 Nociceptors are free nerve endings that
generate pain impulses
 Nociception refers to causative factors for
pain impulses i.e. somatic or visceral
 Pain pathway or ascending sensory tract
originates at the site of trauma and travels
along the sensory nerve to the dorsal root
ganglion of the relevant spinal nerve into the
posterior horn of the spinal cord

6.  This is known as the first neuron.
 The second neuron arises at the posterior
horn, crosses over within the spinal cord and
transmits the impulse via the medulla
oblongata, pons varolii and the mid-brain to the
thalamus.
 From here it transmits to the third neuron to
the sensory cortex.
 In case of acute pain sensations travel through
Aδ fibers (A delta fibers) which are large
diameters and is perceived as pricking and
localised pain.
 Chronic pain travels through smaller diameters
called C fibers and is often described as
burning pain and difficult to localise

7. TYPES OF PAIN IN LABOUR
 There are two different kinds of labour pains
 Somatic pain: related to pressure on and
stretching of the birth canal as descent
occurs
 Visceral pain: generally is experienced
during active dilatation and is related to
cervical stretching and uterine contraction
intensity

8. VISCERAL PAIN
 This pain is transmitted slowly through
unmyelinated fibers and is felt as dull,
diffuse, persistent or aching sensation
 Pain sensation transmitted thorough
myelinated nerve fibers travel more rapidly
and are perceived as localised sensations.
 During first stage nerve impulses enter the
sympathetic chain at L1 to L5 then travel to
the posterior roots of the X, XI, XII thoracic
nerves up the spinal cord to the thalamus

9.  They may also be referred to the dermatomes of the
same nerves and pain is felt in the skin, thighs, lower
back and hips as well as hot spots of generalized aching.
 Some pain is pressure induced, some may be caused by
fatigue and hypoxia of uterine muscles
 During labour areas of referred pain change location and
if prolonged uterine fatigue may increase pain sensation
A dematome is an area of skin supplied by nerves
orginating from a single spinal nerve root.

10. SOMATIC PAIN
 Usually begins during the transition phase because
descent is speeded
 Pressure of the fetus on the cervical, vaginal and
perineal tissues is intense; first felt as need to bear
down and this sensation may become
overpowering
 These pain sensation travel through the pudendal
nerves through the dorsal roots of the II, III, IV
sacral nerves

11.  Pain is felt as contractions intensity rises 15 to
20mmHg above the resting tonus (above 25mmHg
pressure on monitor strips).

12. GATE-CONTROL THEORY
 This is important for understanding the approaches
used in pain management. It was developed by Ron
Melzack and Patrick Wall in 1962.
 Gate control theory asserts that activation of nerves
which do not transmit pain signals, called
nonnociceptive fibers, can interfere with signals from
pain fibers, thereby inhibiting pain.

13.  Afferent pain-receptive nerves bring signals to the brain
and comprise at least two kinds of fibers –
 a fast, relatively thick, myelinated "Aδ" fiber (delta fibers) that
carries messages quickly with intense pain,
 and a small, unmyelinated, slow "C" fiber that carries the
longer-term throbbing and chronic pain.
 Large-diameter Aβ fibers are nonnociceptive (do not
transmit pain stimuli) and inhibit the effects of firing by Aδ
and C fibers.
Myelinated (Myelin is a fatty white substance that
surrounds the axon of some nerve cells, forming an
electrically insulating layer. It is essential for the proper
functioning of the nervous system)

14.  The peripheral nervous system has centers at which pain
stimuli can be regulated. Some areas in the dorsal horn
of the spinal cord that are involved in receiving pain
stimuli from Aδ and C fibers, called laminae, also receive
input from Aβ fibers.
 The nonnociceptive fibers indirectly inhibit the effects of
the pain fibers, by 'closing a gate' to the transmission of
their stimuli. In other parts of the laminae, pain fibers also
inhibit the effects of nonnociceptive fibers, thus 'opening
the gate'.

15.  depending on the relative rates of firing of C and
Aβ fibers, the firing of the nonnociceptive fiber
may inhibit the firing of the projection neuron and
the transmission of pain stimuli
 The pain seems to be lessened when the area is
rubbed because activation of nonnociceptive
fibers inhibits the firing of nociceptive ones in the
laminae. For example in transcutaneous
electrical stimulation (TENS), nonnociceptive
fibers are selectively stimulated with electrodes
in order to produce this effect and thereby lessen
pain.

16.  One area of the brain involved in reduction of pain
sensation is the periaqueductal gray matter that
surrounds the third ventricle and the cerebral aqueduct
of the ventricular system. Stimulation of this area
produces analgesia (but not total numbing) by activating
descending pathways that directly and indirectly inhibit
nociceptors in the laminae of the spinal cord.It also
activates opioid receptor-containing parts of the spinal
cord.

17. PHYSIOLOGICAL RESPONSE TO PAIN IN
LABOUR
 Several body systems are affected with labour.
 Respiratory
 Pain is associated with increased respiration which may
cause decrease in PaCO2 corresponding with increase
in pH.
 The fetus is the affected with subsequent drop in
PaCO2 causing late decereletations.
 Alkalosis may affect diffusion of oxygen across the
placenta leading to fetal hypoxia
 cardiac
 Cardiac output increases during first and second stage
by 20% and 50% respectively

18.  Pain apprehension and fear may cause
a sympathetic response thereby
producing a greater cardiac output.
Both systems are affected by
catecholamine release. Epineprhine /
adrenaline reduces uterine blood flow
and this may lead to reduction in
uterine activity.

19. FACTORS AFFECTING PAIN PERCEPTION
 Worry and anxiety
 Insecurity
 Fear
 Ignorance
 Fatigue
 Intense heat or cold
 Poor general physical condition
 Malnutrition and starvation
 Infection
 Continuous pain or severe pain experienced over
an extended period (hypertonic contraction or in
prolonged labour

20.  Culture
 Parity
 Education
 Marital stability
 Childbirth preparation/knowledge of childbirth
 Past experiences
 Race
 Unplanned or planned pregnancy
 Support during labour
 Language of childbirth (terms pain and labour suggestive
of difficulty and trouble)

21. NON-PHARMACOLOGICAL PAIN MANAGEMENT
 Touch: most women respond positively to touch.
 Effleurage refers to light rhythmic stroking over the
womans abdomen in rhythm with breathing during
contractions and aids in relaxing muscles
 Counter pressure against the sacrum
 Backrub over the sacral area and buttocks every two
hours or less
 Foot massage
 Acupressure for additional endorphin response and
relief of painful sensation

22.  Warm bath or shower for relaxation
 Breathing techniques
 Dilatation less than 3cm: woman feels for onset of
contraction and takes a deep breath through the
nose and out through pursed lips. She should
focus on slow chest breathing (6 to 9 per minute).
When contraction is over she takes a final deep
breath in and “blows the contraction away through
pursed lips. She may focus on an object or close
her eyes
 Dilatation 4 to 7cm: change to shallower, lighter
breaths (no more than 16/min). Ask her to slowly
raise her abdomen when breathing in (this moves
the abdomen away from the contracting uterus

23.  Cervical dilatation 8 to 10:women has difficulties
concentrating on breathing. Ask the woman to breath 3
times and then puff (as if blowing out a candle) out to
blow away the contraction (breath, breath, breath, puff)
NB. avoid hyperventilation which can result in alkalosis,
discourage early pushing
 Do not leave the woman alone. A support
person: husband or close relation may be used.
Talk with support person and give them
reassurance, nourishment, rest elimination.
Remember they need to be comfortable for them
to provide adequate support.
 Minimize adverse environmental stimuli: control
glaring lights, decrease traffic flow and noise in
birth setting

24.  Remind mother that to select the best position in
which she feels comfortable. Encourage walking
in early labour. The mother can also stand, lean
against the wall or over a chair or support
person, sit on a chair.
 Provide privacy and space with adequate room
temperature and ventilation
 Talk of contractions and not pains
 Relax and get as near to the womans level as
possible. Sit by the bedside. Do not tower over
her

25.  Adjust the labour bed to provide comfortable
position i.e. semi fowlers. The woman should
never be flat on her back. Use pillows to support
all dependent parts.
 Use comfort measures such as cold cloths, ice
chip, backrubs, baths or shower
 Chat with the woman in-between contractions.
Do not distract her during a contraction. WAIT.
 Assure the mother that she is doing well with
kind voice
 Remind mother to urinate frequently

26.  Encourage rest in between contractions
 Keep her bedding clean, dry without wrinkles or kinking
 During actual birth trust and work with the woman. The
goal is pelvic floor release and relaxation it is not an
athletic contest. Encourage series of quick breaths
holding for five seconds while pushing with grunting
sounds or expiratory vocalizations. Give her verbal
support i.e. ‘beautiful”, “go with it”, “you are doing fine”.

27. PHARMACOLOGICAL MANAGEMENT
 Pharmacological pain management includes use of
 Analgesia: brings loss of pain sensation by raising pain
threshold for pain perception. Analgesics are the agent
used and they relieve pain without causing
unconsciousness
 Anesthesia: use of agents to bring loss of sensation

28.  Systemic analgesia
 narcotic analgesic compounds: meperedine,
morphine, pethidine. Make sure that naloxone is
available incase neonate exhibits respiratory
depression, hypotonia, lethargy, and delay in
temperature regulation
 Analgesic potentiator: i.e. phenobarbitone,
promethazine. These may be given together with the
narcotic to reduce the risk of narcotic effects from high
doses
 Nerve block analgesia and anesthesia: chemically
related to cocaine i.e. 0.5-1% lidocaine, bupivacaine,
e.t.c. in case of depressive effects atropine, oxygen
and supportive measure should be available

29.  Local infiltration anesthesia: used with episiotomy i.e. 1%
lidocaine, chloroprocaine. Epinephrine can be added to the
solution to control bleeding
 Pudendal block: useful in second stage and administered 20 to
30 minutes before perineal anesthesia is needed, but may
result into loss of the bearing down reflex.
 Spinal anesthesia: local anesthetic used for C/S.
 Epidural block: relieves pain of uterine contractions and
delivery both vaginal and abdominal by injecting anesthetic in
the epidural (peridural) space

30.  Paracervical block: relieves pain from
cervical dilatation and distension of LUS
Inhalation analgesia

31. WHEN TO GIVE NARCOTICS IN LABOUR
 Maternal assessment
 Mother should be willing
 Vital signs should be stable
 Fetal assessment
 FHR between 120 and 160 and reactive
 Fetus is term (may vary)
 Meconium staining not present
 Labour assessment
 Contraction pattern well established
 Cervix less than 6cm (4-5 in prims and 3-4 in multips,
however it may also vary in different settings)
 Fetal presenting part engaged (may also vary)
 Progressive descent of presenting part with no complication

32. THANK YOU!