Incidence: Cardiac arrest is rare in pregnancy, but it is estimated that it happens to 1 : 7692 women from pregnancy to one year after birth. Approximately half are due to substandard care (CEMACH 2004).
Risk factors: The most common cause of maternal cardiac arrest, regardless of aetiology, is hypovolaemia and hypotension (Morris and Stacey 2003).
The factors that increase the requirement for maternal resuscita- tion vary, but include those identifi ed by CEMACH (2004) as being the leading causes of direct maternal death (due to pregnancy), shown in Figure 6.1.
Certain physiological changes that occur in pregnancy may have an impact on maternal resuscitation. These include:
• Increase in cardiac output by 30–40 per cent. This starts as early as four weeks’ gestation to promote maternal adaptation to preg- nancy, as well as the blood supply to the enlarging uterus.
Amniotic fluid embolism Anaesthesia Other Direct Sepsis Hypertensive disease of pregnancy Deaths in early pregnancy including ectopics Haemorrhage
0 2 4 6 8 10 12
Rate per million maternities 14 16 Thrombosis and thromboembolism
Figure 6.1 Mortality rates per million maternities of leading causes of direct deaths; United Kingdom 2000–2002 (CEMACH, 2004)
• Increase in blood volume by up to 50 per cent. The uterine blood fl ow increases from 100 ml/min at the end of the fi rst trimester to 500 ml/min by term (Stables 1999). It results in a fall of haemo- globin due to the effect of haemodilution.
• Increased oxygen consumption of 20 per cent.
• Decreased peripheral resistance. This is due to both the develop- ment of the uteroplacental circulation, and the relaxation of the peripheral vascular tone.
• Decreased residual capacity of the lungs of 25 per cent.
• Delayed emptying of stomach contents. This leads to an increase in volume and acidity of the gastric contents.
• The weight of the pregnant uterus. This can lead to aortocaval com- pression when a woman is lying in a supine position, particu- larly after 20 weeks’ gestation. The weight presses on the aorta and vena cava, restricting blood fl ow to vital organs such as the brain and heart, causing a reduction in cardiac output and hypo- tension.
The Resuscitation Council (UK) currently sets the standard for maternal resuscitation in the United Kingdom and produces train- ing aids and literature. These are available to health care profession- als and lay people through resuscitation trainers. The aim is to establish and maintain standards for resuscitation and to foster good working relations between all disciplines involved. Figure 6.2 shows the algorithm for basic adult resuscitation.
In pregnancy physiological changes can complicate the resuscita- tion procedure, and particular attention should be made to minimise aortocaval compression. The uterus needs to be tilted to the left by 25–30º. This can be achieved by:
• Using a fi rm triangular wedge present in many maternity units, or a pillow
• Using a human wedge, i.e. knees
• Using a tipped up chair
• Performing manual uterine displacement. This is when an atten- dant (who may be the midwife or another helper, e.g. doctor, health care assistant or partner) manually lifts the weight of the uterus to the left, off the woman. Aortocaval compression will be relieved by this method and cardiac output increased by 20–25 per cent, but it may interfere with effective chest compressions. It is important to remember that cardiac output is reduced to approximately 30 per cent of the normal output during effective cardiopulmonary resuscitation and its effective- ness depends on the effi cacy of external chest compressions (Ueland et al. 1972; Lee et al. 1986; Resuscitation Council (UK) 2005).
• Perimortem (near the time of death) (Webster’s New World Medical Dictionary 2003) caesarean section may have to be undertaken early in the resuscitation attempt in order to relieve aortocaval compression, increase venous return and increase cardiac output. If it is done within 4–5 minutes, the likelihood of maternal and neonatal survival is increased. Due to the length of time it may take to get a theatre ready, it may be appropriate to undertake the procedure on the spot. The only vital equip- ment required for this is a scalpel. In a hospital setting, equip- ment to enable intravenous access, administration of fl uids, endotracheal intubation, a method for closure of the wound and neonatal resuscitation should be immediately available.
In all cases it is imperative that staff with the appropriate experi- ence are present when dealing with a cardiac arrest in a pregnant
UNRESPONSIVE ?
Shout for help
Tilt uterus to the left
Open airway
Early airway intervention
Call 999
30 chest compressions
2 rescue breathes 30 compressions NOT BREATHING NORMALLY ?
Figure 6.2 Algorithm for basic adult resuscitation (Reproduced by kind permis- sion of the Resuscitation Council (UK) 2005)
woman as soon as possible. These are an obstetrician, anaesthetist and neonatologist. Particular attention should be made to effective cardiac compressions. A rate of 30 compressions to 2 breaths is recommended.
Once expert help arrives:
• Incorporate early advanced airway intervention
• Apply pressure to the cricoid cartilage to occlude the upper end of the oesophagus against the vertebrae and prevent the acid gastric contents from being aspirated
• Treat causative factors such as hypovolaemia, toxicity
• Communicate with relatives
• Maintain record keeping and documentation
If the situation occurs in an out-of-hospital setting, then the emergency services need to be mobilised and basic resuscitation must continue with the woman tilted to the left until expert help is available.