the gold standard in the treatment of chronic
pain. So, we're going to move over to another
area completely. This is the treatment of obstetric
pain. And the reason that I place obstetric
pain separate from acute pain or from
chronic pain is that, it truly is unique.
It's the only condition in humans
that results in intermittent,
very severe pain, and intermittent
periods of relaxation and loss of pain.
It's really quite unique. It can be
very intense, but
unlike most pain, it's intermittent. When we provide
pain relief, we have to take into account the fact that
it's intermittent pain. And we must also take
into account that we're dealing with a mother
and a baby. And that anything that we provide
to mom, may very well make it to baby and may not
be a good thing for baby to receive. So, there are
two areas of innovation for the uterus
that come into play during labour
and delivery. The first
occurs in segments T10, thoracic 10,
to the first lumber segment. And this
is the pain that women feel during actual
labour. This is the abdominal pain they feel.
And it, as we've already mentioned, is intermittent,
severe, and it tends to become more severe
as labour goes on. So, it starts with a few
fairly mild little pains, and then it slowly builds
up over time and becomes extremely
intense. The pain of delivery is served
by nerves from S2, Sacral 2 to Sacral 4.
And this is pain in the perineum
area of the body. It's also intermittent
and is related to the labour
pain, to the contraction of the uterus, but it's
a different kind of pain and it tends to occur later
in the labour phase. So in early
labour, the pain is largely
in the abdomen, above the pubis. And epidural
analgesia works like a dream. And you
use low concentrations, you can completely remove
the sensation of pain, but the woman will
often continue to be aware that she's contracting
and that's the ideal situation. However, in late
labour the pain spreads over the entire
abdomen and into the perineum, and becomes
much more severe. And at that point, we use
higher concentrations of local anesthetic
in the epidural to provide pain relief
in that area. The local anesthetics
are not transferred across the placenta to the baby.
So there's no concern about fetal toxicity
from local anesthetics. However,
opiates are transferred to the baby.
So, we usually have very low doses of opiates
included in our epidural, but you must be
very careful not to rise
with the pain, rise the opiate
level, because that is transmitted to the baby and it may
cause respiratory depression in the newborn.
There are lots of other modes of obstetric
pain relief. But I can say with some
certainty that nothing works as well as epidurals.
But other conditions such as, or other modes such as
psycho-prophylaxis, which is usually mom
plus her partner working on breathing,
certainly can help in the earlier stages
of labour. And certainly, mom and
the partner, dad in many cases, feel like they're
participating in something together and they
can work as a team. Massage, baths
and acupuncture have all been used
to varying degrees of success. Nitrous oxide,
which is breathe through a demand valve,
so it only goes to the patient when she takes
a breath in, is also used. So,
the patient has to be taught how to use it. She has to be told
that as soon as she starts to feel the contraction developing,
she should take a big breath of nitrous oxide
or a couple of breaths. And this will produce quite
effective analgesia, but only
of intermediate potency. So later
in the labour it's probably not going to be
terribly useful. Can cause sedation
and confusion. And it should never be delivered
by the partner. In other words, if mom's lying there
and contracting, the husband should not put
the mask on and hold it in place. It's important
that the patient control it, takes her breaths and drops
the mask so she doesn't have an overdose of
the nitrous oxide. Intravenous narcotics are sometimes
given, but remember what I said, they do
transfer to the baby and there's a potential
for respiratory depression in the newborn. Ketamine
is used primarily, if it's used at all,
early in labour in small doses.
And it produces good analgesia, it is transferred
to the baby, so you can have a baby
that's anesthetized and you don't want that. So it's
only used early in labour and in very small doses.
And intramuscular narcotics have been used.
They're not effective, generally because they
don't, they're not absorbed quickly enough to be effective.
But they're longer lasting, they do go to the baby
and they can cause all the problems in the baby that
you just don't want to see. So the goal of obstetric
analgesia is to provide the patient with as much
comfort as possible without affecting the fetus.
Many drugs can cross the placenta and have
an effect upon the baby, but local
anesthetics, asI've mentioned, do not. Care must be
given when opiates are given because they
do cross. And labour, the good news, is labour
is not delayed by epidural analgesia,
nor is the rate of C-section increased
by epidural labour analgesia.
These are both statements that are commonly
made and there's a vast amount of evidence
that says that they're simply incorrect.
That labour is not affected, nor is a C-section
rate affected. So this is the International Association
for the Study of Pain. If you have further interest in this subject,
you should look at this website. It's a very
good website. So in summary, in this lecture
we've talked about a number of drugs that are used
in the management of pain, both their usefulness
and their side-effects. We've had three
very short case presentations.
And an appreciation, I hope, of how pain is managed
in different conditions. And we've ended
with that unique form of pain, obstetrical
pain, and how we use epidural
and other forms of pain management to safely
care for the mother and for the baby.