1-KNOWLEDGE ABOUT Labour pain Flashcards
how is it portrayed in the mass media?
- it is a self-evident, indisputable fact
- unavoidable except through pain meds
- so bad it makes you want to die
it make women and their mothers go mad… and sometimes turn violent on men
how is labour pain portrayed in alternative media
only ONE of the many sensations during labour!!
other sensations:
- bliss
- joy
- satisfaction
- ecstacy
- excitement
can be more powerful than the pain!
what is the source of the big differences in perspectives on birth?
are NOT between female and note…
is more between people who have experienced and/or been present during a natural, intervention-free childbirth versus those who have not
what is the primary source of this collective view of labour pain?
culture!!
what is information?
sensory data we obtain with its context and meaniing
- stories
- imaged
- numbers
- words
- visceral sensations
- feels
what is knowledge?
inferences we draw and theories we construct from our interpretations of the information we have
two ways in which new information can fail to change our knowledge
- it’s credibility is assessed as low – information is discarded
- credibility is assessed as acceptable, but it clashes with our pre-existing knowledge – info retained but but integrated into knowledge
issue with childbirth simulations
the muscles that cause contractions DO NOT EXIST in men
the type of muscle is different
- myometrium of the uterus only contains smooth muscle fibres
skeletal muscles vs smooth muscles
skeletal muscles
- attached to the bones
- help us move around
- can be willingly controlled
- part of the somatic nervous system
smooth muslces
- found in most of the internal organs
- canNOT be willingly controlled
- part of the autonomic nervous system
when does the non-pregnant uterus contract?
- all the time, spontaneously
- during menstruation
- during orgasm
what happens to the nerves in the uterus during pregnancy
at term there is almost complete DENERVATION of the uterus
- loss of nerve supply
pregnancy-induced hypoalgesia
- decreased sensitivity to painful stimuli
Motor denervation in the pregnant uterus
- orchestrated by ovarian hormones
- helps in maintaining uterine quiescence
- inhibition is relative rather than absolute
- uterine tone (to do with how taut the uterus is) maintenance remains, but there is resistance to coordinated contractions
- control of contractility becomes predominantly hormonal
Myometrium
uterine muscle
- innervated through autonomic nerve fibres
- denervated during pregancy
- middle and most prominent layer
- mostly of smooth muscle fibres united by connective tissue with many elastic fibres
endometrium
uterine lining
- glands and tiny blood vessels
- release of hormones
- innermost layer
sensory denervation in the pregnant uterus
- not very well understood or appreciated
-could serve to reduce contractility (stretch sensations can induce contraction of the myometrium and other muscles) - may be selective to the uterine muscle
- stretch sensations from the myometrium would be essentially undetectable
common explanations of pain associated with normal labour contractions
- stretching of the cervix
- contraction of uterine muscle
issue with common explanations of labour pain according to scientific knowlegde
- stretch receptors in the uterus disappear during pregnancy
- stretch receptors in the cervix disappear at the onset of labour
- muscle fibres in the cervix are almost completely replaced by connective tissue
Stages of labour
Stage 1: the uterus contracts and stretches the cervix to open to approx. 10cm diameter
stage 2: the baby passes through the “birth canal” and is born
stage 3: the placenta is born (‘expelled’)
post partum: uterus contracts in order to return to its original shape
when is the longest, hardest, and potentially most painful part of giving birth?
getting to full dilation (10 cm diameter) at the end of stage 1, beginning of stage 2
when is pain during labour felt?
- only during contractions
- spaced 2 mins apart, 30 sec duration - strongest sensations come from the inside of the body
back labour
exception to when pain during labour is felt!
it’s oriented in a way that is unusual
- pain may continue to be felt in between contractions
- the strongest sensations are felt at the lower back
some potential explanations for labour pain that are not currently contradicted by scientific knowledge
- vasoconstriction of uterine blood vessles
- release of chemicals from muscle exertion
- inflammation
- reduced oxygen delivery to tissues (schema)
why does intense physical exertion hurt?
injecting muscle metabolites evokes sensations of muscle fatigue and pain
vasoconstriction of uterine blood vessels
- contractions reduce blood flow to the uterus (and the baby)
- the contrasting myometrium compresses the blood vessels that course through it
- some hypoxia (low oxygen) happens during each contraction - innervation of blood vessels and the endometrium remains during pregnancy and childbirth
what is the modern Western cultural view of pain
very hedonic!!
“pain is BAD”
benefits of normal labor pain
- guides the birthing woman through the birth process
- how to move, how to stand, what to do - focuses the woman’s mental and physical resources on the birth process
- can regulate the strength of contractions
- greatly benefits the baby and mother
transport of oxygen, nutrients, and waste products in the placenta
placenta is like. LIVER!
Baby blood circulation is separate from mom – there’s a lil bit of transfer but its really small
some of the fetus’s blood vessels are containing in a tiny hairlike projections (VILLI) of the placenta
the mother’s blood passes through the space surrounding the VILLI (intervillous space)
only a thin membrane (PLACENTAL MEMBRANE) separates the mother’s blood in the intervillous space from the fetus’s blood in the villi
what does pain release and suppress?
the release of:
- stress-related hormones and neurotransmitters
- endogenous opioids
suppress:
- oxytocin, the hormone that causes labour contractions
pain can reduce the strength and duration of contractions, esp. during stage 1 of labour
Nociception
encoding and processing of harmful stimuli in the nervous system, leading to a body’s ability to sense potential harm
difference between NOCICEPTION and PAIN
NOCICEPTION = the sensory process that produces the nerve signals that trigger pain
PAIN = subjective experience (aching sensation)
Pain =/= harm
they can occur in absence of each other!!
what is pain hugely dependent on?
CONTEXT!!!
- our own mind and the conceptual framework with which we interpret the experience
- the people around us, with their own conceptual frameworks that determine what these people say to us and how they view us
- pain = useful indication of wellbeing?
- OR pain = unnecessary suffering?
how does warm water affect birth?
reduces pain significantly
- vascular vessels
- relaxes uterine muscles
standing up for birth vs laying down on back for birth
standing up is majorly more comfortable and less painful than lying on one’s back
why?
- veins on back -> reduce cirulation
- harder to move!! more restrictive! it is now an unnecessary pain
subdivisions of nociceptive input
VISCERAL
NON-VISCERAL (SOMATIC)
What Carries Visceral nociceptive input
internal organs of the body
carried largely by C Fibres
What carries Non-visceral (somatic) nociceptive input
from body parts that are not internal organs
carried largely by A-delta fibres
Noxious sensory input carried by
carried by A-delta and C-fibres ascending nociceptive fibres
A-delta nerve fibre
- evolutionarily new!
- fast pain!
- myelinated sheath
- 1-5 micrometer diameter
C nerve fibre
- evolutionarily old!
- slow pain
- non-myelinated sheath
70% of all nociceptive fibres :o
exteroception
perception of things that are external to su
proprioception
the sense of where one’s own body is in space
signals from joints, tendons, muscles
visceroception
the sense of the physiological condition of the body (specifically internal organs)
signals from inner organs
interoception types
proprioception
visceroception
Placebo analgesia
when positive expectations reduce pain
nocebo hyperalgesia
when NEGATIVE expectations INCREASE pain
algesia
sensitivity to pain
hyperalgesia
extreme sensitivity to pain
analgesia
the inability to feel pain (in practice, often partial)
expecting pain creates a state of anticipatory anxiety, which:
increases muscle tension and any related pain
increases stress and weakens the body’s own ability to cope with pain
suppresses endogenous optiods
baby skull
the bone is NOT fused together!
- allows for movement, and can overlap
there is an opening in the skull!
moulding of the baby skull during labour
- lets the baby fit more easily through the pelvis
- allowed by the softness of the bones and their loose connections at the sutures
- within a few days after birth, the shape of the head returns to normal
how do we know whether a baby is in pain?
- crying
- facial expressions
- body movement
- physiological stress response
early beliefs about babies’ sensitivity to pain
- newborns were not sensitive to pain
- experiments with painful stimulation on newborns found little reaction at day 1, but increased reactions by day 12
- concluded that:
- newborns had limited sensitivity to pain
- first week to 10 days was a period of hypoesthesia (abnormally weak sense of pain, heat, cold, or touch)
early beliefs about newborn reactions to painful stimuli
- a local reflex — did not go to brain
- had no mental/emotional importance
- brain at birth is highly immature bc it is still largely unmyelinated
ancient view of the uterus
used to be considered the cause of female ailments by the greek and egyptians
- greeks believes it moved around the body
perimetrium
outer connective tissue of the uterine wall
uterus = layers of interlacing smooth muscle fibres?
many resources describe 3 separate layers going in different directions.. but is controversial and something that scientific knowledge doesn’t have a clear answer to yet
in late pregnancy, thick muscle fibres merge and intertwine to form an interlacing network
Enteric Nervous system
motility of esophagus, stomach, and intestines, as well as the secretion of digestive enzymes and acids
opioid
any substance that acts on the opioid receptors of the body
narcotic
any psychoactive compound with sleep-inducing properties and is a CNS depressant
cocaine
naturally occuring local anesthetic
procaine
1st synthetic derivation of cocaine
followed by the development of lidocaine
bupivacaine
most common local anesthetics found in epidurals
fentanyl
most common opioids found in epidurals
topical anesthesia
most common
applied externally
rapid onset with high concentration
dentistry!
infiltration anesthesia
applied through injection
used for minor surgical procedures
dentistry!
diffusion of drugs depends mainly on:
far solubility!!!
congenital analgesia
people born with inability to experience pain
factors that influence the experience of pain
cultural factors
- philosophical and religious beliefs
cognitive/psychological factors
meaning that people ascribe to their pain
visceral pain
activation of nociceptors of the internal organs
- innervated by c fibres
sensitive to distension, ischemia, inflammation
tends to be vague, deep, dragging
associated with nausea and changes in heart rate and most importantly it can also evoke emotional responses
effect of oxytocin
causes the calm reaction
key role in human sexual behaviour – orgasm increases a flood of oxytocin into the bloodstream
important for mother-baby bond
non-pregnant vs pregnant uterus physiology
uterus at term:
heavier, larger volume, larger height, larger width
smooth muscle fibres at term:
larger length and larger width
uterine quiescence
state of quieting
takes more hormonal release to trigger contractions
not absolute – DECREASE in spontaneous contractions
nerves in the non-pregnant uterus vs pregnant
in non-pregnant:
ends of axon dendrites of the PNS end very close to the muscle
- muscle receives influence of release of NT
during pregnancy:
- disconnection between neurons and muscle fibres
- nerve endings almost disappear in pregnant uterus!
motor vs sensory denervation
Motor – if the neurons that produce contractions move away from the muscle
sensory – neurons that carry up sensations has moved away (sensory is not felt as much)
motor INnervation in the non-pregnant uterus
autonomic control over contractility
- neural fibres exit the spinal cord, innervating all pelvic cavity organs, including the uterus, bladder, and rectum
- sympathetic fibres exit at higher levels along the spinal cord (T10-L2) than parasympathetic fibres (S2-4)
How does autonomic control over smooth muscles work
nerve fibres release NT onto muscle cells through autonomic varicosities
sensory innervation in the uterus vs cervix and vagina
sensory nerves from the uterus enter the spinal cord at higher levels (T10-L1) than those from the cervix and upper part of the vagina
types of visceral sensations
distension/stretch
inflammation
ischemia – a part of your body isn’t getting enough blood
density of nerves to smooth muscle fibres in uterus?
in comparison to other smooth muscles of the body (which tend to be richly innervated) the uterus has a relatively low density of nerves to smooth muscle fibres
during pregnancy, under the influence of ovarian hormones, this density decreases even further:
- hypertrophy (increase and growth of muscle cells) of uterin myocytes
- decrease in number of nerve fibres
what happens to the pregnant uterus in terms of uterine quiescence
- enters into a special state of uterine quiescence
- in late pregnancy (37-40 weeks) it starts becoming active again
- spontaneous ongoing contractions
- “practice” (braxton hicks) contractions
when does the pregnant uterus contract strongly?
- orgasms in pregnancy
- labour and birth
- the post-partum period
post-partum
uterus contracts in order to return to its original shape
