After studying this chapter you should be able to:
Knowledge criteria
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Describe the mechanisms, diagnosis and management of normal and abnormal labour
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Describe the methods of induction and augmentation of labour including the indications, contraindications and complications
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Describe the aetiology and management of cord prolapse
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Discuss the impact and management of preterm labour, prelabour rupture of membranes and precipitate labour
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Summarize the methods of assessment of fetal wellbeing used in labour, e.g. meconium, fetal heart rate monitoring and fetal scalp blood sampling
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Explain the options available for pain relief and anaesthesia in labour
Clinical competencies
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Participate in the management of normal labour
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Interpret the results of fetal heart rate monitoring in labour
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Assess the progress of labour including the use of partograms and explain the findings to the labouring woman
Professional skills and attitudes
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Demonstrate respect for cultural and religious differences in attitudes to childbirth
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Demonstrate empathy by effective communication and providing reassurance to women in labour
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Demonstrate awareness of importance of multi-professional working in the care of women in labour (communicate findings and management plans with midwives and doctors)
Labour or parturition is the process whereby the products of conception are expelled from the uterine cavity after the 24th week of gestation. About 93–94% deliver at term, i.e. between 37 to 42 weeks, while about 7–8% develop preterm labour and deliver preterm from 24 to 37 weeks. Preterm labour is defined as labour occurring before the commencement of the 37th week of gestation. Prior to 24 weeks this process results in a previable fetus and is termed miscarriage. Prolonged labour is defined as labour lasting in excess of 24 hours in a primigravida and 16 hours in a multigravida. Prolonged labour is associated with increased fetal and maternal morbidity and mortality.
Stages of labour
The early preparation (prelabour phase) goes on for days and weeks, while the onset of painful uterine contractions and delivery is shorter and the process is called parturition or labour. The cervix ripens by becoming softer, shorter and dilating, which takes a greater speed with onset of uterine contractions.
For purposes of clinical management, ‘observed’ labour is a continuum that is divided into three stages:
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The first stage commences with the onset of regular painful contractions and cervical changes until it reaches full dilatation and is no longer palpable. The first stage is divided into an early latent phase when the cervix becomes effaced and shorter from 3 cm in length and dilates up to 3 cm, and an active phase when the cervix dilates from 3 cm to full dilatation or 10 cm.
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The second stage is the duration from full cervical dilatation to delivery of the fetus. This is subdivided into a pelvic or passive phase when the head descends down the pelvis, and an active phase when the mother gets a stronger urge to push and the fetus is delivered with the force of the uterine contractions and the maternal bearing down effort.
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The third stage is the duration from the delivery of the new born to delivery of the placenta and membranes.
Onset of labour
It is often difficult to be certain of the exact time of onset of labour because contractions may be irregular and may start and stop with no cervical change, i.e. ‘false labour’. The duration of labour for management purposes is based on the observed progress of the contractions and cervical changes along with the descent of the head. This concept may have to be judged based on the place of practice, as in some remote areas a mother may be brought in after a day of labour with no progress. Her general condition and findings of the maternal and fetal conditions should dictate management. In the rare cases of cervical stenosis that can occur after surgery to the cervix, normal contractions of labour may produce thinning of the cervix without cervical dilatation.
The clinical signs of the onset of labour are:
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Regular, painful contractions that increase in frequency and duration and that produce progressive cervical dilatation.
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The passage of blood-stained mucus from the cervix called the ‘show’ is associated with but not on its own an indicator of the onset of labour.
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Similarly, rupture of the fetal membranes can be at the onset of labour, but this is variable and may occur without uterine contractions. If the latent period between rupture of membranes (ROM) to onset of painful uterine contractions is greater than 4 hours it is called prelabour rupture of membranes (PROM) and this can occur at term or in the preterm period when it is called preterm prelabour rupture of membranes (PPROM).
Labour is one of the commonest clinical conditions and yet the diagnosis may need time and sequential vaginal examination to assess cervical changes unless the mother is admitted in advanced labour.
Accurate diagnosis of labour is important so as to avoid unnecessary interventions such as artificial rupture of membranes (ARM) or the use of oxytocin infusion.
The initiation of labour
The onset of labour involves progesterone withdrawal and increases in oestrogen and prostaglandin action. The mechanisms that regulate these changes are unresolved but likely involve placental production of the peptide hormone corticotrophin-releasing hormone (CRH).
During pregnancy, painless irregular uterine activity is present. It is minimal in early pregnancy and greater with advancing gestation. There is a cascade of events regulated and controlled by the fetoplacental unit. At the end of gestation, there is gradual downregulation of those factors that keep the uterus and cervix quiescent and an upregulation of procontractile influences.
Placental development across gestation leads to an exponential increase in the number of syncytiotrophoblast nuclei in which transcription of the CRH gene occurs. This maturational process leads to an exponential increase in the levels of maternal and fetal plasma CRH. The CRH has direct actions on the placenta to increase oestrogen synthesis and reduce progesterone synthesis. In the fetus the CRH directly stimulates the fetal zone of the adrenal gland to produce dehydroepiandrosterone (DHEA) the precursor of placental oestrogen synthesis. CRH also stimulates the synthesis of prostaglandins by the membranes. The fall in progesterone and increase in oestrogens and prostaglandins leads to increases in connexin 43 that promotes connectivity of uterine myocytes and changes uterine myocyte electrical excitability, which in turn leads to increases in generalized uterine contractions:
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The uterine myocytes contract and shorten, unlike the process in striated muscle, where cells contract but then return to their precontraction length.
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Ion channels within the myometrium influence the influx of calcium ions into the myocytes and promote contraction of the myometrial cells.
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Other hormones produced in the placenta directly or indirectly influence myometrial contractility, e.g. relaxin, activin A, follistatin, human chorionic gonadotrophin (hCG) and CRH, by influencing the production of cyclic AMP that causes relaxation of myometrial cells.
Reduced cervical resistance (i.e. release of the brakes in a car) and increasing frequency, duration and strength of uterine contractions (i.e. accelerator of the car) are needed for the progress of labour. The first stage of labour that starts from onset of painful uterine contractions to full dilatation is divided into a slow latent phase when the cervix becomes shorter, i.e. effaced and dilated to 3–4 cm (an average of 6-8 hours in nulliparae and 4-6 hours in a multiparae) and an active phase of labour when the cervix dilates at an average of 1 cm per hour from 3–4 cm to full cervical dilatation.
Uterine activity in labour: the powers
The uterus exhibits infrequent, low-intensity contractions throughout pregnancy. As full term approaches, uterine activity increases in frequency, duration and strength of contractions. By palpation or external tocography one can identify the frequency and duration of contractions, but intrauterine pressure catheters are needed to assess the strength of contractions. It is likely that labour is established if two contractions each lasting for >20 seconds are observed in 10 minutes. Normal resting tonus in labour starts at around 10–20 mmHg and increases slightly during the course of labour ( Fig 11.1 ). Contractions increase in intensity with progress of labour which in some ways are characterized by the duration of contractions. WHO recommends contraction recording on the partograph based on the frequency and duration of contractions.
In late pregnancy, strong contractions can sometimes be palpated that do not produce cervical dilatation, and hence do not constitute true labour.
A pacemaker for the uterus has never been demonstrated by anatomical, pharmacological, electrical or physiological studies. The electrical contraction impulse starts in one or the other uterine fundal region and spreads downwards through the myometrium. Contractions are stronger and last longer in the fundus and upper segment than in the lower segment. This fundal dominance is essential for progressive effacement and dilatation of the cervix. As the uterus and the round ligaments contract, the axis of the uterus straightens and pulls the longitudinal axis of the fetus towards the anterior abdominal wall in line with the inlet of the true pelvis.
The realignment of the uterine axis promotes descent of the presenting part as the fetus is pushed directly downwards into the pelvic cavity ( Fig. 11.3 ).
The passages
The shape and structure of the bony pelvis has already been described (see Chapter 6 ). The size and shape of the pelvis vary from woman to woman and not all women have a gynaecoid pelvis; some may have platypelloid, anthropoid or android pelvis thus influencing the outcome of labour. Softening of the sacroiliac ligaments and the pubic symphysis allow expansion of the pelvic cavity, and this feature along with the dynamic changes of the head diameter brought about by flexion, rotation and moulding facilitate normal progress and spontaneous vaginal delivery.
The soft tissues of the pelvis are more distensible than in the non-pregnant state. Substantial distension of the pelvic floor and vaginal orifice occurs during the descent and birth of the head. The distensible nature of the pelvic soft tissues, vagina and perineum help to reduce the risk of tearing of the perineum and vaginal walls during descent and birth of the head.
The mechanism of labour
The pelvic inlet offers a larger lateral than an anteroposterior diameter. This promotes the head to normally engage in the pelvis in the transverse position. The passage of the head and trunk through the pelvis follows a well-defined pattern because the upper pelvic strait is transverse, the middle pelvic strait is circular and the outer pelvic strait is anteroposterior. The fetal head presents by the vertex in 95% of the cases and hence is called normal presentation. With the vertex presentation the head is well flexed in 90% of the cases and the head rotates to an occipitoanterior position and presents the shortest diameters, i.e. anteroposterior suboccipito bregmatic (9.5 cm) and lateral biparietal (9.5 cm) diameters, hence occipitoanterior position where the occiput is in the anterior half of the pelvis is called normal position. A deflexed or extended head presents as an occipitoposterior or transverse position and with further extension as a brow or face presentation. Labour with an occipitoposterior position is prolonged as a larger anteroposterior diameter of occipitobregmatic or occipitofrontal diameter (11.5 cm) presents to the pelvis. With the brow presentation, entry of the head into the pelvic brim is difficult as it presents the largest anteroposterior–mento vertical diameter (13.5 cm). The brow presentation can flex to a vertex or extend to a face presentation. If there is no progress the baby is best delivered by caesarean section in a term brow presentation.
The process of normal labour therefore involves the adaptation of the fetal head to the various segments and diameters of the maternal pelvis and the following processes occur ( Fig. 11.4 ):
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Descent occurs throughout labour and is both a feature and a prerequisite for the birth of the baby. Engagement of the head normally occurs before the onset of labour in the majority of primigravid woman, but may not occur until labour is well established in a multipara. Descent of the head provides a measure of the progress of labour.
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Flexion of the head occurs as it descends and meets the medially and forward sloping pelvic floor, bringing the chin into contact with the fetal thorax. Flexion produces a smaller diameter of presentation, changing from the occipito-frontal diameter, when the head is deflexed, to the suboccipitobregmatic diameter when the head is fully flexed.
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Internal rotation: The head rotates as it reaches the pelvic floor and the occiput normally rotates anteriorly from the lateral position towards the pubic symphysis. This is due to the force of contractions being transmitted via the fetal spine to the head at the point the spine meets the skull which is more posterior and due to the medially and forward sloping pelvic floor. Occasionally, it rotates posteriorly towards the hollow of the sacrum and the head may then deliver as a face–to–pubis delivery.
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Extension: The acutely flexed head descends to distend the pelvic floor and the vulva, and the base of the occiput comes into contact with the inferior rami of the pubis. The head now extends until it is delivered. Maximal distension of the perineum and introitus accompanies the final expulsion of the head, a process that is known as ‘ crowning’ when the head is seen at the introitus but does not recede in between contractions.
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Restitution: Following delivery of the head, it rotates back to be in line with its normal relationship to the fetal shoulders. The direction of the occiput following restitution points to the position of the vertex before the delivery.
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External rotation: When the shoulders reach the pelvic floor, they rotate into the anteroposterior diameter of the pelvis. This is accompanied by rotation of the fetal head so that the face looks laterally at the maternal thigh.
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Delivery of the shoulders: Final expulsion of the trunk occurs following delivery of the shoulders. The anterior shoulder is delivered first by traction posteriorly on the fetal head so that the shoulder emerges under the pubic arch. The posterior shoulder is delivered by lifting the head anteriorly over the perineum and this is followed by rapid delivery of the remainder of the trunk and the lower limbs.
The occiput normally rotates anteriorly but, if it rotates posteriorly, it deflexes and presents a larger diameter to the pelvic cavity. As a result, the second stage may be prolonged and the damage to the perineum and vagina is increased.
The third stage of labour
The third stage of labour starts with the completed expulsion of the baby and ends with the delivery of the placenta and membranes ( Fig. 11.5 ).
Once the baby is delivered, the uterine muscle contracts, shearing off the placenta and pushing it into the lower segment and the vault of the vagina.
The classic signs of placental separation include trickling of bright blood, lengthening of the umbilical cord and elevation of the uterine fundus within the abdominal cavity. The uterine fundus becomes firm to hard and smaller and rounded instead of being broad and globular and sits on top of the placenta as it descends into the lower segment.
The duration of placental separation may be compressed by the use of oxytocic drugs administered at the delivery of the anterior shoulder.
As the placenta is expelled, it is accompanied by the fetal membranes, although the membranes often become torn and may require additional traction by using a sponge forceps to grasp them. Uterine exploration is rarely needed to complete their removal.
The whole process lasts between 5 and 10 minutes. If the placenta is not expelled within 30 minutes, a diagnosis of retained placenta is made and the third stage should be considered to be abnormal.
Most complications of labour and delivery such as postpartum haemorrhage, pelvic or perineal haematoma and any deterioration of the maternal or newborn condition takes place within the first few hours of delivery and hence in most settings the mother and baby are closely examined with periodic observations in the delivery unit for up to 2 hours before the mother and baby are sent to the postnatal ward. The observations are continued for 6 hours if the mother is to be discharged home from the delivery unit.
Pain in labour
Contractions in labour are invariably associated with pain, particularly as they increase in strength, frequency and duration with progress of labour. The cause of pain is uncertain but it may be due to compression of nerve fibres in the cervical zone or to hypoxia of compressed muscle cells. Pain is felt in the lower abdomen and as lumbar backache when the intrauterine pressure exceeds 25 mmHg.
The management of normal labour
The primary aim of intrapartum care is to deliver a healthy baby to a healthy mother. The preparation of the mother for the process of parturition begins well before the onset of labour. It is important for the mother and her partner to understand what actually happens during the various stages of labour. Strategies to deal with pain in labour, including mental preparation with controlled respiration, should be introduced during antenatal classes, as well as educating the mother about the regulation of expulsive efforts during the second stage of labour.
Antenatal classes should also include instructions about neonatal care and breastfeeding, although this is a process that requires reinforcement in the postdelivery period.
The mother should be advised to come into hospital, or to call the midwife in the event of a home birth, when contractions are at regular 10–15 minute intervals, when there is a show or if and when the membranes rupture. If the mother is in early labour, she should be encouraged to take a shower and to empty her bowels and bladder. Shaving of the pubic hair or abdomen is no longer considered necessary and is likely to cause abrasions with some bleeding that may become the nidus for bacterial proliferation and subsequent infection.
The home birth rate in the UK is about 2–3% but it is common practice to organize ‘domino’ ( dom iciliary in and o ut) deliveries, whereby the mother is discharged home 6 hours after delivery, provided that the delivery is uncomplicated.
Examination at the commencement of labour
On admission, the following examination should be performed:
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Full general examination , including temperature, pulse, respiration, blood pressure and state of hydration; the urine should be tested for glucose, ketone bodies and protein.
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Obstetrical examination of the abdomen: Inspection is followed by palpation to determine the fetal lie, presentation and position, and the station of the presenting part by estimating fifths of head palpable. Auscultation of the fetal heartbeat is by a stethoscope or by using a Doptone device which enables the mother and her partner to hear.
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Vaginal examination in labour should be performed only after cleansing of the vulva and introitus and using an aseptic technique with sterile gloves and an antiseptic cream. Once the examination is started, the fingers should not be withdrawn from the vagina until the examination is completed.
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The position, consistency, effacement and dilatation of the cervix.
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Whether the membranes are intact or ruptured and, if ruptured, the colour and quantity of the amniotic fluid.
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The fetal presentation (e.g. vertex, breech), position (e.g. LOA, ROA, ROP, etc.) of the presenting part and its relationship to the level of the ischial spines (e.g. station −1 or +1 etc.).
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Assessment of the bony pelvis at the upper, middle and lower pelvic strait and the pelvic outlet.
General principles of the management of the first stage of labour
The guiding principles of management are:
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Observation of the progress of labour and intervention if it is slow.
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Monitoring the fetal and maternal condition.
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Pain relief during labour and emotional support for the mother.
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Adequate hydration and nutrition throughout labour.
Observation: the use of the partogram
The introduction of graphic records of progress of cervical dilatation and descent of the head was a major advance in the management of labour. It enables the early recognition of a labour that is non-progressive. The partogram ( Fig. 11.6 ) is a single sheet of paper on which there is a graphic representation of progress in labour. On the same sheet other observations related to labour can be entered. There are sections to enter the frequency and duration of contractions, fetal heart rate (FHR), colour of liquor, caput and moulding, station or descent of the head, maternal heart rate, BP and temperature. The partogram should be started as soon as the mother is admitted to the delivery suite and this is recorded as zero time regardless of the time at which contractions started. However, the point of entry on to the partogram depends on a vaginal assessment at the time of admission to the delivery suite. The value of this type of record system is that it draws attention visually to any aberration from normal progress in labour.
The use of partograms at an applied level was first introduced in remote obstetric units in Africa, where recognition that progress in labour is becoming abnormal enables early transfer to specialist units before serious obstruction occurs.
This has led to a major reduction in maternal mortality due to avoidance of uterine rupture, sepsis and postpartum haemorrhage and reduction in severe morbidity of vesico or recto vaginal fistula. Earlier recognition of obstructed labours and immediate attention by caesarean delivery where indicated prevents such tragedies.
Fetal condition
The fetal heart rate is charted as beats/min and decelerations of heart rate that occur during contractions are recorded by an arrow down to the lowest heart rate recorded on the partogram. These records are an adjunct to the actual recording of auscultated FHR in the notes and/or electronic fetal monitoring (EFM) by continuous cardiotocography (CTG).
The time of rupture of the membranes and the nature of the amniotic fluid, i.e. whether it is clear or meconium-stained, are also recorded. Moulding of the fetal head and the presence of caput are also noted as they provide an indicator of obstructed labour. The suture lines meeting is moulding +, over riding but reducible with gentle pressure is ++, and overriding and not reducible with gentle pressure is +++. The soft tissue swelling of the scalp called caput is also marked from + to +++ but is based on relative impression formed by the clinician.
Progress in labour
Progress in labour is measured by assessing the rate of cervical dilatation and descent of the presenting part. The progress is assessed by vaginal examination on admission and every 3 to 4 hours afterwards during the first stage of labour. Cervical dilatation is plotted in cm along the scale of 0–10 of the cervicograph. The cervix is expected to efface and dilate from 0 to 3 cm (latent phase) in 6 hours in a multipara and 8 hours in a nullipara, followed by approximately 1 cm per hour from 3 to 10 cm dilatation (active phase) in nulli and multipara although multipara tend to dilate faster. The expected progress recorded on the chart at a rate of 1 cm per hour from admission dilatation in the active phase of labour is called the alert line which helps to identify those who are progressing slowly. A line 2 hours parallel with the alert line called the action line can be drawn to decide on when to actively intervene with artificial rupture of membranes or oxytocin infusion to augment labour in the absence of malpresentation, disproportion or concern for fetal condition.
If the progress of cervical dilatation lags more than 2 hours behind the expected rate of dilatation, it will cut the action line indicating the poor progress in the active phase of labour. The UK National Institute for Health and Clinical Excellence guidelines suggest that when encountered with slow progress of <1 cm in 3 hours with no other changes such as cervical effacement or descent of the head in the presence of ruptured membranes, cephalopelvic disproportion should be excluded and labour augmented with an oxytocin infusion. Descent of the station of the head is charted on the partogram based on the palpable portion of the head above the pelvic brim in fifths, i.e. whether it needs 5, 4, 3, 2 or 1 finger to cover the head.
The station of the head is plotted on the 0–5 gradation of the partogram.
Descent is also recorded by assessing the level of the presenting part in cm above or below the level of the ischial spines and marked as −1, −2, and −3 when it is above the spines and +1, +2, and +3 if it is below the spines.
The nature and frequency of the uterine contractions are recorded on the chart by shading in the number of contractions per 10 minutes. Dotted squares indicate contractions of less than 20 seconds duration, cross-hatched squares are contractions between 20 and 40 seconds duration, while contractions lasting longer than 40 seconds are shown by complete shading of the squares. Frequency and duration of contractions can be measured by clinical palpation or external tocography. The intensity of contractions cannot be assessed by the degree of pain felt by the mother or by palpating the uterus abdominally and can only be determined by intrauterine pressure catheters. However intrauterine catheters are not used routinely in management of labour because their use has been shown not to improve the outcome of labour.
Fluid and nutrition during labour
In most maternity units in the developed world, caesarean section rates now exceed 20%. The issue of what can be taken by mouth therefore becomes particularly important. If there is a likelihood that the mother will need operative delivery under general anaesthesia, then it is clearly important to avoid oral intake at any significant level during the first stage of labour. Delayed gastric emptying may result in vomiting and inhalation of vomitus if general anaesthesia for operative delivery is needed. On the other hand, most operative deliveries are now achieved under regional anaesthesia and therefore there is a case for giving some fluids and light nutrition orally if labour is progressing normally and a vaginal delivery can be anticipated. Recent clinical trials have suggested little concern with feeding the mother with soft easily digestible solid nutrition in addition to fluids. Intravenous fluid replacement should be considered after 6 hours in labour if delivery is not imminent. The major cause of acidosis and ketosis is dehydration, and urine should be checked for ketones in addition to sugar and protein whenever mother passes urine. Administration of normal saline or Hartmann’s solution is preferred and the fluid input and output should be monitored not to over or under hydrate the mother.
The classic signs of dehydration in labour include tachycardia, mild pyrexia and loss of tissue turgor. Remember that labour can be hard physical work and that the environmental temperature of delivery rooms is often raised to meet the needs of the baby rather than the mother, leading to considerable insensible fluid loss.
Pain relief in labour
There are a number of strategies used in labour for the relief of pain and these should be discussed with the pregnant mother in the antenatal period. Essentially, these techniques are aimed at reducing the level of pain experienced in labour whilst invoking minimal risk for the mother and baby.
The level of pain experienced in labour varies widely, some experience very little whilst others suffer from abdominal and back pain of increasing intensity throughout their labour. Thus, any programme for pain relief must be tailored to the needs of the individual. The care giver may be able to advise the best mode of pain relief based on whether the mother is nulliparous or multiparous, the current cervical dilatation, the rate of progress of labour and the extent to which the mother is feeling the pain. The mode of pain relief is best decided by the mother based on the advice given. Often this may result in a combination of methods, starting from the least to most effective method to alleviate her pain. The only technique that can provide complete pain relief is epidural analgesia.
Narcotic analgesia
Pethidine has traditionally been the most widely used narcotic agent but has been replaced in many centres in the UK and Australia by morphine. The common side effects for all the opiates are nausea and vomiting in the mother and respiratory depression in the baby. The effect on the neonate is particularly important when the drug is given within 2 hours of delivery. Opiates are often administered with anti-emetics to reduce nausea.
Remifentanil is used in some centres as this is an ultra-short-acting opioid that produces superior analgesia to pethidine and has less of an effect on neonatal respiration.
Because some mothers are unsuitable for regional analgesia, e.g. those on anticonvulsants, opiates are likely to continue to play a significant role in pain relief in labour.
Inhalational analgesia
These agents are used in early labour until the mother switches to much stronger analgesics. It is best for short-term pain relief in the late first and second stage of labour. The most widely used agent is entonox, which is a 50/50 mixture of nitrous oxide and oxygen. The gas is self-administered to avoid overdosing when they drop the mask off and is inhaled as soon as the contraction starts. Entonox is the most widely used analgesic in labour in the UK and provides sufficient pain relief for the majority.
Nitrous oxide has been shown to have adverse effects on birth attendants if exposure is prolonged; these effects include decreased fertility, bone marrow changes and neurological changes. Forced air change every 6–10 hours is effective in reducing the nitrous oxide levels and should be mandatory in all delivery rooms.
Non-pharmacological methods
Transcutaneous electrical nerve stimulation (TENS) involves the placement of two pairs of TENS electrodes on the back on each side of the vertebral column at the levels of T10–L1 and S2–S4. Currents of 0–40 mA are applied at a frequency of 40–150 Hz. This can be effective in early labour but is often inadequate by itself in late labour. For the technique to be effective, antenatal training of the mother is essential.
Other non-invasive methods include acupuncture, subcutaneous sterile water injections, massage and relaxation techniques: the effectiveness of which are debated.
Regional analgesia
Epidural analgesia is the most effective and widely used form of regional analgesia. It provides complete relief of pain in 95% of labouring women.
The procedure may be instituted at any time and does not interfere with uterine contractility. It may reduce the desire to bear down in the second stage of labour due to lack of pressure sensation at the perineum and reduced uterine activity due to loss of ‘Ferguson reflex’: which is an increased uterine activity due to reflex release of oxytocin due to the presenting part stretching the cervix and upper vagina.
A fine catheter is introduced into the lumbar epidural space and a local anaesthetic agent such as bupivacaine is injected ( Fig. 11.7 ). The addition of an opioid to the local anaesthetic greatly reduces the dose requirement of bupivacaine, thus sparing the motor fibres to the lower limbs and reducing the classic complications of hypotension and abnormal fetal heart rate.
The procedure involves:
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Insertion of an intravenous cannula and preloading with no more than 500 mL of saline or Hartmann’s solution.
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Insertion of the epidural cannula at the L3–L4 interspace and injection of the local anaesthetic agent at the minimum dose required for effective pain relief.
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Monitor blood pressure, pulse rate and fetal heart rate and adjust maternal posture to achieve the desired analgesic effect.
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Hypotension: this can be avoided by preloading and the use of low-dose anaesthetic agents and opioid solutions.
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Accidental dural puncture: occurs in fewer than 1% of epidurals.
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Postdural headache: about 70% of mothers will develop a headache if a 16 or 18 gauge needle is used. A postdural headache that persists for more than 24 hours should be treated with an epidural blood patch.
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maternal refusal
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coagulopathy
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local or systemic infection
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uncorrected hypovolaemia
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inadequate or inexperienced staff or facilities.
Many women set out in labour without requesting any form of pain relief. However, as labour progresses, the realization that labour can be painful will change the requirements of the mother. It is therefore essential to have an epidural service that can be readily available so that the labour is not too far advanced before the epidural can become established.
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