Introduction
Pain is an unpleasant but most useful sensation developed early in
evolution as a protective mechanism. In the context of labour, pain is a symptom
of labour and alerts the mother to seek timely help for labour and delivery. The
pain of labour gets progressively severe and it is often aggravated by anxiety,
fear and ignorance.
In a civilized society, freedom from pain is one of the basic rights of a
person. This is often ignored, in the developing world, when it comes to a
labouring woman. The reason for this cruelty is tradition, ignorance and plain
lack of resources. In the developed world, when some form of analgesia is always
available, a few women are brainwashed into equating pain relief in labour with
personal failure. More often than not, these women not only suffer needlessly,
but also reduce their chance of a normal delivery. Unrelieved maternal pain
leads to a series of metabolic changes in the mother, which may adversely affect
the foetus (Jones CM, Greiss FC. 1982).
Fig. 1.
Labour Pain
As the labour progress,
the intensity and distribution of pain changes. (Fig. 2-4).
Fig. 2.
Early First stage
Fig. 3. Late First and
Early Second stage
Fig. 4. Late Second stage
and Delivery
Distribution of pain and
its intensity during labour
(Redrawn from Beisher NA,
Mackay EV, and Colditz PB).
Pain in labour is multifactorial in origin. Early in
the first stage, the pain is due to contraction of the upper segment of the
uterus (ischaemic), distension of the lower segment and dilatation of the cervix
(stretching). Late in the first stage and early second stage, pressure of peri
uterine tissue adds to this pain. Late in second stage and at delivery, the pain
is the result of severe distension of the vagina, vulva, perineum and adjoining
structures (Fig 4).
Fig. 5. Pain in
labor – causes, location and neural pathways (after Crawford JS,1984)
Pain Relief in Labour
Researchers Melzak and others, after investigating
serious pain for fifteen years, reported that labour pain was the most severe
pain that they assessed (Melzak R et.al. 1981).
Selwyn Crawford says, “Because labour pain serves no useful function in
the human female (except possibly to expiate primeval feeling of guilt), a
positive refusal to utilize available measures to alleviate it borders on the
unethical (Crawford JS, 1985).
The total pain of labour is not simply the physical pain that can be
explained on the basis of physiological, chemical and neurological phenomena.
The level of anxiety, fear and ignorance influence labour pain as mentioned
before. Melzak and others showed that mothers that entered labour with good and
sympathetic childbirth preparation had a pain score 30 percent lower than those
who entered labour with no such preparation (Melzak R. 1984).
Principles of Pain Relief in
Labour
Anticipating pain and providing pain relief is much
more successful than chasing after established pain.
There are two (or more-in the case of multiple
pregnancies) people in every labour - mother and baby.
Labour pain affects the mother primarily but also
affects the baby by release of the stress hormones of the mother when pain is
not relieved.
Treatment modalities also
affect both mother and baby.
An ideal analgesic in labour is one, which provides
total pain relief to the mother without adversely affecting the labour process
or cause unwanted side effects in the mother or baby. It should also be freely
available, easy to use and inexpensive. Unfortunately, such an analgesic is not
available at present.
Methods
of Pain Relief in Labour (not mutually exclusive)
a)
Psycho prophylaxis-
prepared childbirth, breathing exercises.
b)
Environmental modifications-
birthing room, support person(s), music, incense.
c)
Physical treatment-
massage, heating pads, warm bath.
d)
Electrical- TENS (Transcutaneous Electrical Nerve Stimulation).
e)
Pharmacological-
1.
Intermittent inhalation of a mixture of 50% Nitrous Oxide and 50% Oxygen (Entonox).
2. Systemic
narcotic injections-nurse or patient controlled-Demerol, nalbuphine HCL (Nubain)
and Fentanyl.
3.Regional
nerve blocks-paracervical, pudendal, extra dural (lumbar epidural, caudal)
and spinal.
f)
Others-hypnosis,
acupuncture.
Advantages, Disadvantages and
Complications of Labour Analgesia
Psycho prophylaxis, environmental modifications
and physical treatments are always helpful and complementary but usually
inadequate as the only methods of labour analgesia. These methods are not fully
utilised due to financial constraints and shortage of staff.
TENS electrodes placed on either side of the spine at
the level of T 11-L 1 nerve roots provide adequate pain relief to twenty
percent of labouring women in the first stage (Robson JE, 1979).Even this modest
claim is now questioned and TENS is now out of favour.
It is claimed that about twenty-five percent of selected labouring women can be
hypnotized to a depth at which the appreciation of pain is abolished or greatly
reduced (Moya F, James LS, 1960). Usually this requires the presence of a
skilled hypnotherapist with the selected, previously trained labouring woman.
Even then, the result may be only a partial success or even a total failure.
Acupuncture may provide adequate analgesia to a small group of labouring women
in the first stage of labour. Of these, only a fraction will get satisfactory
pain relief in the second stage. Unfortunately, one cannot predict which patient
will respond to this form of analgesia (Waldron BA, 1985).
The methods discussed so far have no adverse effects
for the mother or the baby and only hypnosis and acupuncture need specific
skilled providers.
Self-administered Entonox, if used properly, provides
good analgesia in the first stage, and is a good supplement in the second stage
(Arthurs GJ, Rosen M, 1969). Forty-five seconds of continuous slow and deep
inhalation is necessary for maximal analgesia. This should start at the initial
painless phase of uterine contraction and should continue until the end of the
contraction. The relatively insoluble nitrous oxide builds up a partial pressure
rapidly providing analgesia and the gas is rapidly exhaled and excreted. This is
a very safe form of analgesia as long as the Entonox cylinder is properly
maintained at room temperature. At minus seven degrees Celsius, the nitrous
oxide liquefies and remains at the bottom of the cylinder leaving the oxygen at
the top. A patient inhaling from such a cylinder, will receive pure oxygen first
and then pure nitrous oxide making her drowsy. Even then, the demand valve in
the Entonox apparatus provides safety. The drowsy patient, unable to hold the
mask tight, cannot create the negative pressure required to release the gas.
Systemic opiate, Demerol (and occasionally Nubain) is
the most common analgesic used in labour. It provides adequate analgesia for
fifty to sixty percent of labouring women. It causes nausea and vomiting,
drowsiness, delay in gastric emptying and respiratory depression and hypotension
(at higher doses) in the mother. It crosses the placenta rapidly and the foetal
and maternal blood levels are almost equal within two minutes of an intravenous
injection into the mother. Demerol accumulates in the baby and it takes three
days for a baby to metabolize and excrete it. It takes even longer for a
premature baby. Narcotic antagonist, naloxone HCL (Narcan) should be available
to reverse the respiratory depression of Demerol in the baby. Since Demerol has
a long half-life in the baby, respiratory depression, failure to suck and other
neuro behavioural problems may arise several hours later. Bearing these in mind,
one should seriously entertain a regional block if more than two doses of
Demerol are required (Waldron BA, 1985).
Of the regional blocks, Para cervical block gives relief from pain of cervical dilatation. It is rarely used now, as
it is associated with foetal bradycardia, and potential death (Rosen M, 1977).
This is probably due to spasm of uterine vessels (Fishburne JI, 1979). Pudendal
block is useful for vacuum or low forceps delivery. These are blocks used by the
obstetrician. Injection of large amounts of the local anaesthetic or accidental
injection into the vessels may cause serious central nervous system toxicity
(light headedness, dizziness, tinnitus, slurred speech and convulsions) or
cardiac toxicity (hypertension and tachycardia to hypotension and arrhythmias).
Severe foetal bradycardia maybe associated with such complications. However,
resuscitation of the foetus is best done in-utero by resuscitation of the
mother.
The technique of caudal block analgesia involves injecting a local anaesthetic
into the extra dural space through the sacral hiatus. Although it may be useful
for an instrumental delivery, it is rarely used now for fear of accidentally
puncturing the foetal head. Further more, there is considerable variation in the
anatomy of the bony sacrum, the capacity of the sacral canal and the extent of
the dural sac (Trotter M, 1947).
Lumbar epidural analgesia provides complete pain
relief for eighty-five percent and partial relief in a further twelve percent of
labouring women. Only three percent have no relief at all (Crawford JS, 1979). A
continuous infusion maybe started early in the first stage and can be continued
for anaesthesia if a caesarean section is required.
A well-trained anaesthesiologist with an interest in obstetric analgesia is
needed to provide an epidural analgesia service. Ideally, a twenty-four hour
obstetric analgesia service should be in operation. The labouring woman should
have had an informed discussion about the procedure, benefits and risks of
epidural analgesia in the prenatal period. The epidural catheter should be
inserted early in labour when the patient is more co-operative and the epidural
veins are not dilated.
The patient should be preloaded with intravenous fluids before the epidural
insertion. The anaesthetic technique of the epidural catheter insertion is well
described in the textbooks on obstetric anaesthesia (Glosten B, 1994). The
anaesthesiologist who inserts the epidural catheter is obliged to stay with the
patient until it is established that the epidural analgesia was working
satisfactorily. The anaesthesiologist must also leave contemporaneous notes in
the chart on the procedure, regimen for the infusion and emergency measures for
possible complications and contact person in case of emergency. Occasionally,
serious complications may result from an epidural analgesia. Central nervous
system toxicity and cardio-respiratory arrest (from intravenous injection),total
spinal blockade and hypotension may occur. The patients with epidural analgesia
should have one to one nursing care by specially trained nurses. The epidural
infusion rate should be titrated and the position of the patient altered to
achieve sensory block without motor block. Monitoring
devices, infusion pumps and resuscitation equipment must be readily available.
In the absence of the above safety
features, it would be malpractice to provide epidural analgesia. One has to
sacrifice patients’ comfort for their safety.
Late in the first stage of labour or in the early second stage, where the
patient is very distressed and unable to sit still for any length of time and
the extra dural space is made smaller by the dilated epidural plexus, insertion
of epidural catheter is more difficult and requires more time. Often times, the
patient has delivered by the time an epidural is established. Spinal analgesia
using a fine spinal needle, is quick, effective and most appropriate under these
circumstances (Crawford JS, 1984)
Conclusion:
1.
Labour is almost always painful.
2.
Pain does not confer any benefit to the labouring woman or her baby.
3.
An ideal analgesic in labour is one which is inexpensive, easy to use
and effective with no adverse affects for the mother or baby. Such an
analgesic is not available at present.
4.
Psycho prophylaxis, environmental modifications and physical treatments
are very useful complementary methods that should be available to all mothers.
5.
A systemic opiate, Demerol (Pethidine), is the most frequently used
analgesic in labour worldwide. It is safe and satisfactory for a multi-gravid
where a short labour is expected and epidural service is not available.
6.
The lumbar epidural and spinal analgesia provide the most satisfactory
labour analgesia. However, in the absence of specially trained personnel,
equipment and protocols, the potential for major complication is high.
Reference:
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Arthurs GJ, Rosen M:
Self-administered intermittent nitrous oxide for labour. Anaesthesia 1979;
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Beisher NA, Mackay EV Colditz
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Crawford JS:
Continuous lumbar epidural analgesia for labour and delivery.
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Crawford JS:
Relief from pain and anxiety in labour, in Obstetric analgesia and
anaesthesia. Churchill Livingston. Ch2: 47, 1984.
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Crawford JS:
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Copyright © 1999 [Dr. Kalaichandran]. All rights reserved.
Revised: May 12, 2003
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