Maternal collapse is defined as: “An acute event involving the cardiorespiratory systems and/or brain, resulting in reduced or absent conscious level (and potentially death)” - RCOG It is considered at any stage during pregnancy, and up to six weeks after delivery.
This is difficult to be clear on, despite the regular review of maternal deaths (now via MBRRACE - https://www.npeu.ox.ac.uk/mbrrace-uk). The rate of maternal collapse is estimated as between 14 and 600 per 100,000 births.
These are varied and may relate to the pregnancy or deterioration of pre existing disease e.g. cardiac disease. The mnemonic of the Resuscitation Council for arrest (4 H’s and 4 T’s) can be usefully applied to maternal collapse too. More specifically, causes of maternal collapse may include:
Amniotic fluid embolism
Haemorrhage is the most common cause, including antepartum and postpartum haemorrhage (these are considered in detail elsewhere). In many cases here the cause will be obvious, but it is important to remember that concealed haemorrhage can still result in significant hypovolaemia. This may include ectopic pregnancy.
Cardiac disease is a significant cause of death in mothers, and many patients do not have pre existing disease. Causes can include myocardial infarction, cardiomyopathy and aortic dissection.
Some causes of maternal collapse may come from anaesthetic interventions. This includes high spinal and local anaesthetic toxicity.
Magnesium toxicity is possible in patients who are being treated for preeclampsia. Calcium (gluconate or chloride) is the antidote.
A number of the physiological changes of pregnancy impact on the management of maternal collapse:
Aortocaval Compression From about 20 weeks gestation the uterus will increasing compress the inferior vena cava and (to a lesser extent) the aorta, when the mother is in the supine condition. This notably reduces venous return and results in a subsequent decrease in cardiac output (30-40%). This in itself can lead to maternal collapse and significantly contribute to CVS deterioration. It can be offset by left lateral position, manual uterine displacement, or wedges underneath the mother to provide tilt.
Respiratory Changes The hormonal and physical changes of pregnancy lead to negative respiratory changes. The increased metabolic demands of the foetus are coupled with a cephalad displacement of the uterus and a reduced functional residual capacity. This leads to more rapid desaturation and greater difficult in ventilation.
Airway Management Intubation is recognised as being more difficult in mothers from a combination of large breasts, weight gain and mucosal swelling. In addition, reduced lower oesophageal sphincter tone and increased intraabdominal pressure increase the risk of aspiration.
Circulatory Changes In many ways the circulatory changes are physiological beneficial for the collapse scenario. Mother’s have increased circulating volume and reduced afterload with and increased cardiac output. However, these may be disadvantageous in the sense of resulting in more rapid exsanguination from bleeding. In addition, young fit mother’s can compensate impressively with hypovolaemia before reaching a decompensation point, potentially delaying treatment. The gravid uterus receives around 10% of the cardiac output and so can result in very rapid blood loss.
Much of the management will follow an approach that is similar for other acutely ill patients (ABCDE or ALS algorithms) However, there are key changes that are advised in Advanced Life Support (ALS) management of maternal collapse. In summary these are
Aggressive volume replacement
Aortocaval Decompression Aortocaval compression in mothers beyond 20 weeks gestation will significantly impede resuscitation efforts due to reduced venous return. A left lateral tilt of 15 degrees will relieve this compression in many cases. The use of a wedge or pillows can achieve this, or the uterus can be manually displaced to the left. A wedge is prefered as soft material will be less effective with chest compressions and manual displacement will need to be removed for defibrillation.
Early intubation Whilst the emphasis on intubation has been removed in other cases of cardiac arrest, the increased risk of aspiration in maternal collapse means it is important. It will also facilitate more optimal oxygenation and ventilation, which will be more important in these patients due to the physiological changes.
Aggressive Volume Resuscitation With haemorrhage being the most common cause of maternal collapse, significant thought must be given to it, and volume resuscitation will often be warranted. Caution is needed in cases of preeclampsia.
Perimortem C-Section This is part of the resuscitation of the mother (a.k.a. Resuscitative hysterotomy). The gravid uterus is taking significant blood flow, oxygen and causing physical restrictions on the cardiovascular and respiratory systems. As such, delivery of the foetus may be enough to allow reversal of the arrest. It should be considered at any stage beyond 20 weeks. Whilst in may be beneficial for the foetus as well, the goal is to optimise resuscitation of the mother. The benefits may include:
Improved venous return
Reduced oxygen demand
Improved ventilator mechanics
More effective chest compression
The goal is to have delivered the foetus within 5 minutes of collapse. In general this will require a decision a 4 minutes e.g. after 2 cycles of CPR. The rationale is that this time frame allows optimal chances of recovery for both mother and foetus (but primarily mother) before devastating hypoxia begins to set it (particularly cerebral). This will mean that the procedure will need to be performed at the site of the collapse. It may be that it is still beneficial after a longer period of arrest (perhaps up to 10-15 mins), but it seems likely that outcomes will deteriorate rapidly with time.
Although the data are sparse, the outcomes are not as bleak as might be initially thought. One study described 38 procedures, with 13 women surviving (and 18 of the arrests thought to be irreversible). 30 of these procedures resulted in surviving babies too.
It is recommended that the clinician present with the most relevant experience perform the procedure with their preferred technique. Whilst for obstetricians this may be a common lower segment C-section incision, a midline approach may be more comfortable for others (and may be better).