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Anaesthesia and analgesia for specific obstetric conditions 

Anaesthesia and analgesia for specific obstetric conditions
Chapter:
Anaesthesia and analgesia for specific obstetric conditions
Author(s):

Sarah Harries

DOI:
10.1093/med/9780199572144.003.0019
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Key points

  • The obstetric anaesthetist is requested to deal with a variety of problems on a busy delivery suite each day

  • An understanding of the common obstetric problems is essential to safely provide the appropriate anaesthetic management

  • Teamwork and prompt, effective communication between anaesthetists, anaesthetic practitioners, midwives, and obstetricians are vital in each situation

  • It is important for all professionals involved to understand their own role and the factors affecting the decision-making of other disciplines.

19.1 Intra-uterine death

The unexpected death of a fetus after 20 weeks gestation may be detected by a prolonged period of absent fetal movements and confirmed by the absence of a fetal heart-beat on Doppler or preferably ultrasound scanning. The underlying maternal or fetal cause is frequently not found.

19.1.1 Key issues

Intra-uterine death is a devastating event for parents and the management of the subsequent delivery is emotionally difficult and stressful for all staff involved. There are major obstetric consequences: deranged clotting, sepsis, postpartum haemorrhage.

Labour is usually induced as soon as feasible after the diagnosis has been confirmed, with the aim to deliver the fetus vaginally. Labour may be prolonged and difficult, especially if the fetus is near term gestation and may require assisted delivery.

19.1.2 Management

The mother should be assessed for signs of a coagulapathy or sepsis prior to discussion of pain relief available for delivery. You should record: serial temperature, pulse rate and blood pressure, and check FBC and clotting. Any clotting abnormalities should be corrected. Any signs of infection should be treated with broad spectrum antibiotics, e.g. IV penicillins and metronidazole. Regional techniques are contra-indicated if a coagulopathy is present or uncorrected.

19.2 Breech presentation

The position of the fetus at term is defined by its lie i.e. the relationship of the longitudinal axis of the fetus to that of the mother, and the nature of the presenting part foremost in the pelvis, e.g. cephalic (head), breech (buttock), compound or abnormal lie.

19.2.1 Key issues

Breech presentation and abnormal lie are both associated with grand multiparity, polyhydramnios, placenta previa, and other obstructive lesions in the pelvis, e.g. large uterine fibroids. There is an increased risk of cord prolapse and consequently fetal compromise. If a mother presents with a mal-presentation, early anaesthetic assessment of the mother is important because of the high incidence of intervention often required. Effective teamwork between obstetrician, anaesthetist, and midwife is essential to ensure a safe delivery and best outcome for mother and baby.

19.2.2 Management of breech presentation

Vaginal breech delivery has been shown to be associated with greater intrapartum hypoxia than a vaginal, cephalic delivery, due to prolonged compression of the umbilical cord during the second stage of labour. If a breech presentation persists until term, it is now recognized that perinatal mortality, neonatal mortality and serious neonatal morbidity are significantly lower following a planned caesarean section (CS) compared to a planned vaginal breech delivery. As a result, many women opt for an external cephalic version (ECV), where the aim is to turn the fetus around to a cephalic position before labour starts, or a planned CS if an ECV fails.

19.2.2.1 Labour management

Continuous fetal monitoring is essential throughout labour, with the facilities available to proceed to emergency CS if required. The anaesthetist should remain near to the delivery room to deal swiftly with any complications.

19.2.2.2 Caesarean section

There are many situations when a CS may be required for breech presentation: planned CS, emergency CS following a known or undiagnosed breech presenting in labour or if there is severe fetal distress during a planned vaginal breech delivery. Regional anaesthesia confers significant benefits over GA for CS and should be attempted if time allows. If an emergency CS is required during the second stage of labour, extraction of the fetus may be very difficult at CS. Additional uterine relaxation may be required, e.g. 50–100mcg IV glyceryl (GTN) or sublingual GTN spray.

19.3 Vaginal delivery after CS (VBAC)

If a woman has undergone a transverse incision caesarean section for a previous delivery, subsequent vaginal delivery is possible (VBAC).

19.3.1 Key issues

VBAC is safe and effective in carefully selected mothers and has a success rate of 72–76%. Repeat elective CS is also safe, but does carry additional risks e.g. haemorrhage, thromboembolism, bladder damage and adhesions. Contraindications to VBAC include: previous classical incision CS, extensive uterine surgery, previous uterine rupture, 3 or more CS. The main risk is uterine dehiscence or rupture during labour. Extreme caution is advised with the use of induction agents, e.g. prostaglandins and oxytocics.

19.3.2 Complications

The main complication is uterine scar rupture, which can present with: severe abdominal pain which is continuous in nature, intra-partum bleeding, maternal tachycardia, hypotension or collapse, fetal distress, or demise. Management includes immediate delivery by CS and prompt resuscitation of the mother.

19.4 Fetal distress

The most important thing to appreciate when dealing with cases of ‘fetal distress’ is that this term covers a wide range of degrees of risk to the fetus. The diagnosis of intra-partum fetal distress usually indicates that the obstetrician considers the fetus needs early or immediate delivery and the timing of delivery is graded according to the following categories for CS:

  • Category 1: ‘Decision to delivery’ time 15–30 minutes

  • Category 2: ‘Decision to delivery’ time less than 1 hour

  • Category 3: ‘Decision to delivery’ time less than 24 hours

  • Category 4: ‘Decision to delivery’ time to suit staff.

19.4.1 Key issues

Effective teamwork and communication is essential. Discuss the patient with the obstetrician, midwives and obstetric theatre team.

Ascertain the degree of urgency immediately. The mother is your first priority and as her anaesthetist, her safety is your prime concern. In difficult situations, everyone else will be focused on the baby and you may be the sole voice for the mother. Don't be afraid to speak up for her.

During transfer to theatre, every effort should be made to improve the fetal condition and provide ‘intra-uterine resuscitation’, which includes: position the mother in full left lateral to reduce aorto-caval compression, administer oxygen by face mask, treat hypotension with increments of vasopressor, e.g. IV ephedrine or adrenaline, stop oxytocic drug infusions, consider tocolytic drugs, e.g. IV terbutaline 100–250mcg, IV GTN 50mcg or sublingual GTN 200–400mcg. Always reassess the situation with the obstetrician after transfer to theatre. Reapply the CTG monitor—if fetal heart is more reassuring, the options for the anaesthetic technique for delivery should be discussed again.

19.4.2 Management of delivery

The management of ‘fetal distress’ depends on the stage of labour and the degree of concern. It is essential to establish immediately with the obstetrician the required ‘decision to delivery’ time.

19.4.2.1 First stage of labour

‘Fetal distress’ during first stage almost always necessitates delivery by emergency CS. General anesthesia is usually required for a Category 1 section when the mother’ s life is in danger or the ‘decision to delivery’ time is less than 15 minutes. An experienced anaesthetist may decide to have ONE attempt inserting a spinal anaesthetic, whilst the woman is being pre-oxygenated via a tight-fitting mask and the fetus monitored continuously. If the attempt is successful, the caesarean section may proceed; however, there must be a low threshold for stopping and no time lost before converting to a GA. The degree of urgency following the decision for CS can change in either direction, therefore it is vital that the fetal heart is monitored closely.

19.4.2.2 Second stage of labour

Fetal distress in the second stage occurs not infrequently when the vertex is visible. This is often successfully managed with experienced midwifery care. If fetal distress occurs in the second stage of labour, when the fetus is below the ischial spines, an emergency assisted ventouse or outlet forceps delivery in the delivery room may be appropriate. This can be performed under a pudendal nerve block: 10 mls of 1% lidocaine is injected just below and medial to the ischial spines bilaterally and it should be supplemented with perineal infiltration for the episiotomy. If the obstetrician considers a ‘trial of instrumental delivery’ to be appropriate, the woman should be transferred rapidly to theatre with fetal monitoring in place. If the decision to delivery time is less than 15 minutes, the most appropriate decision is an emergency CS. It is essential that the degree of urgency for CS is discussed before deciding on a particular anaesthetic technique.

19.4.3 Recognition of the ‘at risk’ fetus

Regular communication with the midwives and obstetricians is of paramount importance to enable you to spot the ‘At Risk’ fetus and form an early management plan of ‘what to do if…’ in your mind. Attend staff handover rounds and have regular updates on new admissions. Watch out for: slow labour, induced or augmented with syntocinon, pre-eclampsia, intrauterine growth retardation (‘small for dates’), meconium staining of liquor.

19.5 Placental abruption

Placental abruption is premature separation of a normally implanted placenta.

19.5.1 Key issues

There are many associated risk factors: pre-eclampsia, eclampsia or chronic hypertension, premature rupture of membranes, increased uterine size, e.g. multiple pregnancy, polyhydramnios, multi-parity. Classical signs include: abdominal pain, haemorrhage, uterine tenderness or irritability, coagulopathy or fetal distress, or demise. The presence of abdominal pain often differentiates an abruption from bleeding secondary to a placenta previa. It may present with either profound revealed or concealed bleeding, requiring rapid resuscitation of the mother. Blood loss with a concealed retro-placental haemtoma is frequently under-estimated. Close observation of the mother is required as cardiovascular stability is often maintained until >40% of the circulating blood volume is lost (2–3 L).

Clotting abnormalities occur early following an abruption. Prompt correction of a coagulopathy is necessary to minimize further bleeding. Stabilization of the mother and immediate delivery can be life-saving for the mother and fetus. The perinatal mortality rate following a major placental abruption can be as high as 50%.

19.5.2 Management

Establish IV access with 2 large bore cannulae and commence fluid resuscitation, administer oxygen by face mask and send blood for urgent FBC, clotting studies and cross-match 2–4 units of blood, depending on the degree of concern. Rapid assessment of the cardiovascular status of the mother, and viability and gestational age of the fetus is important, as this will determine the ultimate obstetric management of delivery.

19.5.2.1 Viable fetus

If bleeding is continuing and/or the fetus demonstrates signs of distress, immediate delivery by CS is indicated. CS should not be delayed until blood results, cross-matched blood or blood products are available if the mother or fetus remains compromised in any way.

General anaesthesia is the technique of choice for the mother who is cardiovascularly compromised, or a coagulopathy is present. Regional anaesthesia is not contra-indicated provided the mother is not hypovolaemic and there is no evidence of clotting abnormalities. A single-shot spinal technique would be appropriate. Despite the urgency, it is important to complete a rapid pre-operative anaesthetic assessment and not forget to administer antacid prophylaxis.

19.5.2.2 Dead fetus

If the placental separation has caused intra-uterine death, vaginal delivery is the preferred mode of delivery, provided there is no ongoing catastrophic maternal haemorrhage. Following resuscitation, any coagulopathy should be corrected.

19.5.2.3 Postoperative complications

Always exclude co-existing pre-eclampsia when faced with a placental abruption. The fluid management can be difficult to manage effectively and the mother can rapidly develop pulmonary oedema. The risk of uterine atony following delivery is increased. At CS, all blood clots should be fully evacuated from the uterus and the uterus massaged to aid contraction. Additional uterotonics may be required to maintain uterine contraction, e.g. IV/IM ergometrine, IV oxytocin infusion or misoprostol PR. Disseminated intravascular coagulation (DIC) complicates ~10% of all abruptions but is more common if fetal death has occurred. Acute renal failure may result if DIC or hypovolaemia remains uncorrected.

19.6 Cord prolapse

Cord prolapse occurs when the umbilical cord lies in front of or beside the presenting part, in the presence of ruptured membranes.

19.6.1 Key issues

Cord prolapse is an obstetric emergency, as compression of the umbilical cord will severely compromise the fetal bood supply and precipitate immediate fetal distress. Delivery by CS must be performed extremely quickly, i.e. within minutes, to ensure no hypoxic damage to the fetus. Predisposing factors include: high/ill fitting presenting part, breech, high parity, prematurity, multiple pregnancy, polyhydramnios, high head at the time of either spontaneous or instrumental membrane rupture.

19.6.2 Management

Although speed is essential, the situation should not prevent a rapid pre-operative assessment prior to CS and antacid prophylaxis. Oxygen must be administered via a tight fitting face mask. For transfer to theatre, the presenting part must be pushed out of the pelvis with manual upward pressure by the obstetrician or midwife. If fetal blood supply remains compromised, general anaesthesia is the only option and a standard technique is applied with the usual safety precautions. The drugs required for a GA should always be prepared in advance and refrigerated, ready for a Category 1 CS. Simulated drills of cord prolapse involving the delivery suite and theatre team should be performed regularly and any weak points from the drills addressed.

19.7 Twins and other multiple pregnancies

The incidence of twin pregnancies is 1 in 80, triplets 1 in 8000 and quads 1 in 800,000.

19.7.1 Key issues

Multiple pregnancies are associated with a number of major obstetric complications, placing them at increased risk during pregnancy and delivery: pre-eclampsia, anaemia, intrauterine death, malpresentations, premature labour, prolonged labour, malpresentation of second twin following delivery of first twin, postpartum haemorrhage secondary to uterine atony. Aorto-caval compression is much more severe.

19.7.2 Management

In a twin pregnancy, if the first twin is cephalic presentation and there is no evidence of other co-existing problems, there is often no reason why these women cannot labour. In triplet and quadruplet pregnancies, a planned CS between 34–36 weeks gestation is the preferred mode of delivery, before preterm labour is threatened.

19.7.2.1 Labour

The labour may be long, and the second fetus may present abnormally, necessitating instrumental delivery, cephalic version, or immediate CS. The anaesthetist should be aware at all times of the progress of labour in twin births, and be present during the second stage of labour to respond and treat appropriately if the decision is made to transfer to theatre or for emergency CS.

19.7.2.2 Caesarean section

The usual choices for anaesthetic technique apply. The subarachnoid space may be compressed increasing the risk of a high spinal block, therefore the dose of intrathecal local anaesthetic should be reduced by 20%. Aorto-caval compression is greater and hypotension following a spinal block is likely to be more severe, therefore maintain left lateral position for as long as possible following insertion of the regional technique. Large-bore venous access, close observation and additional oxytocics are recommended to treat uterine atony.

19.8 Premature fetus

The premature fetus is defined as a delivery between 20 and 37 weeks gestation.

19.8.1 Key issues

Risk factors for pre-term delivery include: previous pre-term delivery, multiple pregnancy, infection (e.g. chorio-amnionitis, pyelonephritis), abnormal placentation (e.g placenta previa, extremes of age). To improve fetal lung maturity, two doses of steroid, e.g. beta-methasone, 12 hours apart, are beneficial if administered to the mother when the gestational age is less than 34 weeks. If possible, delivery should be delayed until 24 hours after the first dose.

19.8.2 Management

Labour may progress rapidly but if a CS is required, a ‘Classical’ CS with a vertical incision in the uterus may be necessary if the gestational age is less than 28 weeks, as the lower segment of the uterus has not developed at this stage. A regional anaesthetic technique is appropriate for either a Classical or lower segment CS; however, the dose of local anaesthetic required to provide an adequate block will be greater than that required for a term CS by about 20%. In the extreme pre-term situation, syntocinon may not be fully effective in promoting uterine contraction as the receptors are not fully developed. Ergometrine is more suitable post delivery to prevent uterine atony.

19.9 Placenta praevia

Placenta praevia occurs when the placenta either completely or partially covers the internal cervical os, or is implanted at its margin. It is associated with considerable morbidity and mortality. The incidence is approximately 1 in 200 pregnancies, but is higher with previous uterine scars, multiparity and increasing maternal age.

19.9.1 Key issues

Placenta previa can present with painless insidious vaginal bleeding, catastrophic obstetric haemorrhage or be asymptomatic. The differential diagnosis is placental abruption, which is usually associated with abdominal pain and uterine tenderness or irritability. An ultrasound will differentiate these two diagnoses.

Postpartum haemorrhage is a major risk. Early use of ergometrine, continuous syntocinon infusion, misoprostol PR, and carboprost should be considered. If bleeding is uncontrolled following delivery, early use of a B-Lynch suture +/- an intra-uterine balloon device may avoid the need for a caesarean hysterectomy.

19.9.2 Management

19.9.2.1 Initial resuscitation

Following presentation with a vaginal bleed, an urgent ultrasound will confirm the diagnosis and the position of the previa. In the event of major haemorrhage, two large bore cannulae should be inserted and fluid resuscitation commenced. Blood should be sent for FBC, clotting studies and cross-matched blood requested.

19.9.2.2 Elective CS

Whenever possible, elective caesarean section is delayed until 38 weeks to reduce neonatal morbidity. Traditionally, regional anaesthesia has been relatively contra-indicated for an elective CS for major previas, particularly anterior placenta previas, and general anaesthesia advocated because of the risk of uncontrolled bleeding. A senior anaesthetist and obstetrician should be present for the CS. Two large bore cannulae should be inserted prior to starting surgery and invasive BP monitoring is recommended for a major anterior previa. Major haemorrhage during surgery should be anticipated. Cross-matched blood should be available in theatre or in the delivery suite fridge prior to surgery. Resuscitation of the mother will be optimized by the use of rapid infusion devices, with the facility to warm all infusion fluids.

19.2.2.3 Emergency CS

General anaesthesia should be performed in any mother with uncontrolled bleeding despite resuscitation, any cardiovascular instability, coagulopathy, or fetal distress. Ideally, an experienced anaesthetist and obstetrician should take responsibility for the surgery.

Resuscitation should continue throughout transfer to theatre and preparation for general anaesthesia. It is not advisable to start surgery before blood is available for rapid infusion at the time of uterine incision.

19.10 Suturing the perineum

Perineal trauma may occur spontaneously during vaginal birth or by surgical incision, i.e. episiotomy, where an incision is intentionally made to increase the diameter of the vulval outlet to facilitate delivery. 1st and 2nd degree tears involve the skin and perineal muscles, 3rd and 4th degree tears involve the anal sphincter and epithelium and require expert repair.

19.10.1 Key issues

There are a number of recognized risk factors for perineal trauma: fetal birth weight >4000g, prolonged 2nd stage of labour, instrumental delivery, direct occipito-posterior position, nutritional status. Perineal trauma can be associated with significant post-delivery haemorrhage, which is often under-estimated. Continuing vaginal bleeding should always be investigated. High vaginal or cervical lacerations may be missed and continued bleeding falsely attributed to uterine atony. Perineal trauma causes significant pain and discomfort in the early post-delivery period and in the longer term, with urinary and faecal incontinence. Examination and suturing should be performed as soon as possible to reduce bleeding, pain and the risk of infection.

19.10.2 Management

Assess the mother for signs of hypovolaemia, establish IV access, check FBC +/– clotting studies, and request cross-matched blood early. Superficial suturing of the perineum is usually performed with local infiltration instilled by the obstetrician or midwife. More extensive suturing of the perineum usually requires transfer to the operating theatre for further assessment and both anaesthetic and surgical management.

A low spinal is required (e.g. 1.5–2 ml heavy 0.5% bupivacaine +/– short-acting opioid). Site the spinal with the mother in the lateral position if she is uncomfortable, and sit her up or with 45 º head up tilt as soon as possible thereafter. General anaesthesia may be necessary to achieve adequate muscle relaxation and visualisation for surgical repair of severe or complex lacerations, or for delayed or revision of suturing. General anaesthesia is also best for the haemodynamically unstable mother or if a coagulopathy prevents a regional technique. Antacid prophylaxis should be given and a rapid sequence induction performed on all mothers requiring general anaesthesia within 24 hours of delivery. Beware of opioid analgesia causing constipation and straining at defaecation. A regular laxative should be prescribed with all opioids.

19.11 Retained placenta

The third stage of labour involves the separation, descent and delivery of the placenta. The placenta is considered retained if it fails to deliver within 60 minutes of birth.

19.11.1 Key issues

Retained placenta is a common cause of postpartum haemorrhage, with an incidence of ∼2%. It is a significant cause of maternal morbidity and mortality world-wide. Potential complications include: primary and secondary (delayed) postpartum haemorrhage, ‘cervical shock’ (i.e. profound bradycardia and hypotension precipitated by increased vagal tone when the placenta sits in the open cervix) and uterine inversion.

19.11.2 Management

19.11.2.1 Early management

Initial management may be conservative. Empty the bladder and wait for signs of spontaneous separation and delivery of the placenta.

Early initiation of breast-feeding may assist placental separation. Active management of 3rd stage involves use of available uterotonics with controlled cord traction after uterine contraction. A second dose of uterotonic may be required. Blood loss may be concealed and close observation for maternal pallor, tachycardia and hypotension must be maintained. Establish IV access with a large bore cannula, estimate amount and rate of blood loss and cardiovascular stability, and check FBC +/– clotting studies and arrange for cross-matched blood. If the placenta has not been expelled after an hour or there is significant bleeding +/– haemodynamic instability, the placenta must be removed manually.

19.11.2.2 Manual removal of placenta

Manual removal of placenta should be performed in the theatre environment, preferably under regional anaesthesia, provided no contra-indications exist, e.g. uncorrected hypovolaemia or coagulopathy. A sensory block to T6 is required for pain-free manual removal of placenta as the uterine fundus is often manipulated (e.g. 2.5 ml heavy 0.5% bupivacaine +/– short-acting opioid). Site the spinal with the mother in the lateral position if she is uncomfortable. Continuous monitoring of ECG and pulse oximetry, and intermittent BP should always be performed.

General anaesthesia may be required for the haemodynamically unstable mother or if a coagulopathy prevents a regional technique. Antacid prophylaxis should be given and a standard rapid sequence induction performed. A volatile agent will assist placenta removal by providing greater uterine relaxation but may also increase bleeding.

On placental delivery, administer available uterotonics, e.g. 5 IU oxytocin IV bolus (caution if patient is hypotensive) followed by an infusion of 40 IU oxytocin in 500 ml normal saline over 4 hours.

19.12 Uterine inversion

Puerperal uterine inversion is the displacement of the fundus of the uterus usually occurring during the 3rd stage of labour. Although rare, it is a serious, life-threatening emergency due to associated blood loss and cardiovascular instability.

19.12.1 Key issues

The classical presentation of uterine inversion is an obviously displaced uterus during placental delivery, postpartum haemorrhage, severe pain and clinical shock, which appears out of proportion to the blood loss. Shock is thought to be due, in part, to the parasympathetic response to traction on the uterine suspensory ligaments and often accompanied by profound bradycardia. This is an emergency and there should be no delay in instituting treatment.

19.12.2 Management

Simultaneously treat haemorrhagic shock (i.e. high flow oxygen, aggressive IV fluid resuscitation), give atropine for bradycardia, and replace the uterus. Any delay in replacement will increase uterine oedema, impeding later replacement and exacerbate cardiovascular instability. Immediate general anaesthesia is usually required to facilitate uterine replacement. The uterus may be replaced manually or by hydrostatic correction, pouring warm saline into the vagina. Tocolytic drugs can be given to increase cervical relaxation:

  • β‎2 receptor agonists—Salbutamol 0.25mg i.v. bolus

  • Magnesium sulphate—4 g i.v. over 10 minutes.

  • Glyceryl trinitrate—50–100mcg i.v. bolus.

Volatile general anaesthetic agents will cause uterine and cervical relaxation. Severe cases may require laparotomy and combined abdominal-vaginal correction.