Intrapartum care including anaesthesia
Delivery is a particularly risky time for any woman, and is additionally risky for women with significant heart disease. This is because the stress of labour adds to the strain on her heart, and during the birth there can be major cardiovascular stressors such as postpartum haemorrhage.
The general approach to managing intrapartum care is to aim for a birth which is as non-stressful as possible, and consequently it is usual to hope for a spontaneous onset of labour at term (presuming that maternal decompensation has not indicated delivery before this), with a vaginal birth (avoiding the stress and potential haemorrhage/infection from a caesarean section). At one time it was common for women with heart disease to be advised to have a caesarean section because of a common perception that this was less stressful than labour. In fact, the stress of labour can be effectively reduced by the use of regional (epidural) anaesthesia, using slow incremental top-ups of low-dose Marcaine to avoid any sudden changes in blood pressure, and vaginal delivery avoids both the increased haemorrhage and infection risk of caesarean section. Moreover, it is beneficial for the baby (45) because it avoids the respiratory difficulties associated with elective caesarean delivery (46). In cases with more severe cardiac impairment it is common to recommend the avoidance of prolonged bearing down (which is in effect repeated Valsalva manoeuvres, which can compromise venous return) and instead assist the birth of the baby using a vacuum extractor, although there are no prospective studies which show this to be necessary. The delivery is commonly straightforward because the baby tends to be smaller than average.It is particularly important to avoid acute emergencies, as these will always increase the risk in women with compromised cardiac function.
Induction of labour when necessary is therefore preferably carried out using artificial rupture of membranes and a low-dose oxytocin infusion, because the use of prostaglandins is associated with a 3-5% risk of uterine hyperstimulation. If hyperstimulation occurs, the usual tocolytics such as ritodrine or salbutamol are contraindicated because they induce maternal tachycardia. When oxytocin is used as a prophylactic against postpartum haemorrhage, it should be given as a bolus of no more than 2 units given slowly over 10 minutes (47) because acute administration can cause marked hypotension (48). Ergometrine is generally avoided because it causes vasoconstriction and hypertension, and can also cause spasm of the coronary arteries (49).Careful planning of clinical management during labour is essential, and is commonly undertaken at about 34-36 weeks of pregnancy, when the woman's ability to cope with the stress of pregnancy has become apparent, and preterm birth is no longer likely. Planning should be done by the multidisciplinary team, and the recommendations for care are best entered onto a pro forma of the sort illustrated in Figure 12.5.