46

Obstetric emergencies

Introduction

Worldwide, one woman dies every minute of every day from a complication of pregnancy. In developed countries, maternal death is uncommon, but evidence from the UK Confidential Enquiry into Maternal Deaths found substandard care in around two-thirds of cases. This is partly due to the fact that most obstetric emergencies are rare and often unfold with such rapidity that junior medical staff can find themselves facing potentially catastrophic conditions that they may never have seen before, let alone have ever managed.

This chapter will examine the obstetric emergencies listed below:

 unexpected collapse

 amniotic fluid embolism

 prolapsed umbilical cord

 retained placenta

 shoulder dystocia

 uterine inversion

 uterine rupture.

See also haemorrhage (Chapter 34), eclampsia (Chapter 36) and pulmonary embolism (p. 254):

Principles of management

Anticipation and preparation are essential – and they may lead to prevention. For example, if the mother has a history of postpartum haemorrhage, anticipation with i.v. access and blood sent for group and save in early labour may make an important difference to the outcome should the problem recur. If there are risk factors for shoulder dystocia, such as a presumed large fetus in a mother with diabetes and a long first stage of labour, it is important to ensure that an experienced midwife is allocated to care for her and that senior medical staff are present on the labour ward at the time of delivery.

In addition, as life-threatening emergencies are relatively rare, it is important that there should be regular ‘fire drills’ of obstetric emergencies to ensure that all staff are fully prepared, that equipment is fully functional and that supporting systems (portering, laboratory, etc.) are prepared. It should also be remembered that emergencies can arise anywhere in the unit, not just in the labour ward. There is now clear evidence of the benefits of formal team-training and use of simulation in rare obstetric emergencies. This applies to both technical aspects of delivery and non-technical (team working) aspects of care.

The principles outlined in Box 46.1 can be adapted for initial resuscitation in all obstetric emergencies which involve maternal compromise. Remember that there are often two lives at stake and in most emergencies, minutes or even seconds count. Remember too, however, that panicking is never helpful. A good principle to remember is that the fetus rarely needs to be resuscitated directly – ‘resuscitate the mother and you will resuscitate the fetus’. It should be noted that an obstetric emergency can cause profound lifelong psychological problems for both the mother and her partner. This can manifest itself as postnatal depression, post-traumatic stress syndrome and a real fear of becoming pregnant again. Counselling and debriefing after such experiences should be encouraged both while the woman is in hospital and some weeks later.

Resuscitation

Resuscitation should have a strong focus on the ABC of basic life support as noted in Box 46.1. The aim is to resuscitate the mother and then (and only then) to consider the welfare of the baby. Resuscitation in pregnancy has some differences from that in a non-pregnant person, as outlined below, but it is still essential to approach the problem by using ABC, and then consider possible causes. The 4 Hs and 4 Ts listed in Box 46.2 are helpful.

The key resuscitation differences are that:

 the aorta and vena cava are compressed by the gravid uterus, impeding venous return and reducing cardiac output

 there is an increased risk of aspiration of stomach contents due to relaxation of the oesophageal–gastric junction (progesterone effect) and the pressure of the uterus

 difficult intubation is more common in the pregnant than in the non-pregnant patient (1:300 vs 1:3000) – short neck and laryngeal oedema

 chemical pneumonitis is more likely than in the non-pregnant state, owing to the decreased pH of the stomach contents and the increased chance of inhaling the contents because of the changes outlined above.

It is therefore important, in the early stages of resuscitation, to:

 tilt the patient to the left by 15–30° (reduces aortocaval compression and increases potential cardiac output by 25%)

 apply cricoid pressure and intubate early, to avoid aspiration of gastric contents and to facilitate oxygenation

 involve a senior obstetrician and anaesthetist immediately or as early as possible (to facilitate intubation and early caesarean section where and when appropriate).

In cases of cardiorespiratory arrest, the revised Resuscitation UK guidelines (2010) should be followed. These have moved the emphasis for basic life support towards a single compression-ventilation (CV) ratio of 30:2. If the mother is not delivered, left lateral tilt can be achieved using firm support under the right hip (an assistant can be asked to kneel and use their knees to support the patient in left lateral tilt).

After about 20–22 weeks, it is essential to perform a caesarean section early if resuscitation is unsuccessful (at this gestation, the fundus of the uterus will be at or above the level of the umbilicus). The decision for perimortem caesarean section should be made by 4 min if there is no response to active resuscitation, and the delivery by 5 min (the ‘4-minute rule’). An anaesthetic is not required in order to proceed. This is primarily to save the life of the mother and forms part of the resuscitation technique. It makes CPR more efficient by:

 increasing venous return

 improving ease of ventilation

 allowing CPR to be carried out in the supine position

 reducing oxygen requirement after delivery.

Amniotic fluid embolism

Epidemiology

This is one of the most catastrophic conditions that can occur in pregnancy. It is rare, with an incidence somewhere between 1:10 000 and 1:30 000. As a precise diagnosis can be difficult, it is also difficult to establish an accurate mortality rate, but it is probably around 20–40%.

Aetiology

The exact pathophysiology remains unclear. It was believed that some breakdown occurred in the physiological barrier separating the mother and fetus, allowing a bolus of amniotic fluid to enter the maternal circulation. This bolus moved to the pulmonary circulation and produced massive perfusion failure, bronchospasm and shock. More recently, it has been suggested that the underlying mechanism may be an anaphylactoid reaction to fetal antigens entering the maternal circulation and individual variations in sensitivity to these antigens are reflected by the severity of the resulting clinical picture.

Risk factors

Amniotic fluid embolism can occur at any time in pregnancy but it most commonly occurs in labour (70%), after vaginal delivery (11%) and following caesarean section (19%). The following risk factors have been identified:

 multiparity

 placental abruption

 intrauterine death

 precipitate labour

 suction termination of pregnancy

 medical termination of pregnancy

 abdominal trauma

 external cephalic version

 amniocentesis.

Clinical features

The clinical picture usually develops almost instantaneously and the diagnosis must be considered in all collapsed obstetric patients. The mother may demonstrate some or all of the signs and symptoms listed in Box 46.3 but classically a woman in late stages of labour or immediately postpartum starts to gasp for air, starts fitting and may have a cardiac arrest. There is often a profound disseminated intravascular coagulopathy (DIC) with massive haemorrhage, coma and death. There are inevitably signs of fetal compromise.

Diagnosis

The definitive diagnosis is usually at autopsy and is made by confirming the presence of fetal squames in the pulmonary vasculature. It is also possible to confirm the diagnosis in a surviving patient, again by finding fetal squames in washings from the bronchus or in a sample of blood from the right ventricle. In the acute situation, as there is no single clinical or laboratory finding which can diagnose or exclude amniotic fluid embolism, the diagnosis is made clinically by exclusion.

Management

This is primarily supportive and should be aggressive. There is, however, no evidence that any specific type of intervention significantly improves maternal prognosis. Initial therapy is aimed at supporting cardiac output and management of DIC. If the woman is undelivered, an immediate caesarean section may be appropriate, providing the mother can be stabilized.

A chest X-ray will often show pulmonary oedema, and an increase in right atrial and right ventricular size. The ECG demonstrates right ventricular strain and there is a metabolic acidosis (reduction of pO₂ and pCO₂).

In addition to the initial management of an obstetric emergency (Box 46.1), therapy may include:

 aggressive fluid replacement

 maintenance of cardiac output with a dopamine infusion

 treatment of anaphylaxis with adrenaline (epinephrine), salbutamol, aminophylline and hydrocortisone

 treatment of DIC with fresh frozen plasma and cryoprecipitate

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