The number of women with serious (non-obstetric) systemic diseases achieving pregnancy and requiring obstetric anaesthetic management is increasing. The conditions that are most likely to cause maternal morbidity and mortality are cardiac disease, respiratory disease, neuromuscular disease, haematological disease, connective and metabolic diseases and psychiatric conditions including substance abuse. This article discusses the anaesthetic management of the pregnant mother with such serious systemic diseases.
The achievements of modern medicine and surgery have improved the prognosis for many congenital and acquired systemic diseases that were previously untreatable or fatal. This has had the effect that more girls with severe non-obstetric diseases are surviving to child-bearing age. Many of these women wish to have children and hence there has been an increase in the requirement for obstetric anaesthetic management in this challenging group of patients.
It is important that women with severe non-obstetric disease have appropriate counselling before considering pregnancy. The additional physiological burdens of pregnancy and delivery can be considerable for both the mother and the fetus, and may convert a stable and well-controlled systemic condition into a deteriorating or even fatal one. This early counselling should ideally be multidisciplinary, including input from obstetricians and relevant medical or surgical specialties, and must include anaesthetic input. The latter is important not just in guiding the choice of analgesia and/or anaesthesia for labour and delivery for these patients. With their background in intensive care medicine and familiarity with techniques of organ system support and physiological manipulation, anaesthetists can also contribute greatly in the non-anaesthetic management of women with severe non-obstetric disease. For severe conditions, involvement of an intensivist may also be appropriate.
The rest of this article discusses the anaesthetic management of mothers with non-obstetric systemic disease. Prominence has been given to conditions that have been shown to be responsible for the most maternal morbidity and mortality, in developed countries.
National or local registries/databases and published case series of admissions to intensive care, high-dependency units or obstetric units are the main sources of information about the spectrum of pre-existing conditions that result in severe morbidity in pregnancy. These suffer from differences in, and imprecision of, definitions, making comparisons between them difficult. In the UK, information about mortality comes from registries of maternal death such as the Confidential Enquiries into Maternal and Child Health (CEMACH), or from individual case series. Based on these sources the conditions that are most likely to cause maternal morbidity and mortality are shown in Table 1 . It can be seen that the spectrum of conditions that lead to mortality is different from that of those leading to morbidity.
| Major cause of mortality | Major cause of morbidity | |
|---|---|---|
| Cardiac disease | ++ | + |
| Respiratory disease | +/− | +/− |
| Neurological and muscular disease | + | +/− |
| Haematological disease | +/− | + |
| Connective tissue and metabolic disease | +/− | ++ |
| Psychiatric disease and substance abuse | + | + |
Cardiac disease
Cardiac disease is a major cause of maternal death in the UK, killing more women than haemorrhage and hypertensive disease combined.
Over the past 30–50 years there has been a change in the spectrum of cardiac conditions seen, as acquired conditions (mainly rheumatic heart disease) have become less common whilst improvements in cardiac surgery have resulted in female babies with previously fatal congenital conditions surviving to reach sexual maturity. Approximately 25% of UK maternal cardiac deaths in the past 30 years have been due to congenital heart disease, which is becoming increasingly commonly seen in maternity departments. More recently, there has been an increase in acquired cardiac disease, due partly to the presence of valve lesions in women from countries where rheumatic heart disease is more common, and partly to ischaemic heart disease resulting from increased obesity, older maternal age and smoking.
The risk of death or severe morbidity resulting from certain cardiac lesions in pregnancy varies according to the lesion ( Table 2 ).
| Level of risk | Risk of mortality/severe morbidity | Lesion |
|---|---|---|
| Low | ≤ 1% | Most repaired lesions; uncomplicated left-to-right shunts; mitral valve prolapse; valve lesions except those below |
| Intermediate | 1–5% | Metal valves; single ventricle/systemic right ventricle/switch procedure; unrepaired cyanotic lesions; mitral (any), aortic (mild-moderate) or pulmonary (severe) stenosis |
| High | 5–30% | Severe symptoms at minimal extertion or at rest; severe systemic ventricular dysfunction; severe aortic stenosis; Marfan’s syndrome with aortic involvement |
| Very high | 30–50% | Pulmonary hypertension |
Physiology and pathophysiology
The most important physiological changes that occur during pregnancy with relevance to cardiac disease are the increased blood volume and cardiac output, the reduction in systemic vascular resistance and the susceptibility to aortocaval compression. Cardiac output increases by up to 40–50% by 20 weeks’ gestation, increasing further by up to 50% during a painful labour. This may precipitate cardiac failure, arrhythmias or ischaemia. Reduced systemic vascular resistance may lead to cardiac failure and a worsening of right-to-left shunt and hypoxaemia. In patients with severe cardiac disease, even the slightest aortocaval compression (including in the first trimester and even post partum) may cause a catastrophic fall in cardiac output.
Ante-partum management
The mainstay of ante-partum care of women with cardiac disease is regular assessment throughout pregnancy. Initial electrocardiography, chest X-ray and echocardiography (depending on the lesion/severity) can be repeated as required according to progress through pregnancy. Echocardiographic measurement of valve areas is usually preferred to flow gradients in the initial assessment since the latter can be expected to increase in pregnancy as a result of the increased cardiac output (though a failure to increase may suggest developing cardiac failure). Pulse oximetry may be used to monitor the degree of right-to-left shunt during pregnancy.
The main aims of management are to reduce cardiac workload, for example, by reducing activity, and treating complications such as arrhythmias/cardiac failure. Admission to hospital has the dual benefit of facilitating assessment of the mother as an inpatient and reducing her activity.
Prophylaxis against thrombo-embolism should always be considered, especially if bed rest is encouraged. Both heparin and warfarin have been used for patients with prosthetic heart valves; heparin has a better safety profile for the fetus but carries a greater risk of thrombosis in the mother, while warfarin is more effective in preventing maternal thrombosis but has a greater risk of fetal complications.
Peripartum management
Common peripartum problems in women with pre-existing cardiac disease include:
Arrhythmias
All pregnant women, and especially those in labour, are prone to tachycardia and arrhythmias; in most cases, symptoms are absent or mild but in women with pre-existing cardiac disease they may be profound and severe. Drugs that may cause tachycardia (such as oxytocin and ephedrine) should be avoided if possible. If arrhythmias occur, the treatment options are influenced by the underlying lesion.
Cardiac failure/pulmonary oedema
Careful fluid balance is required to avoid excessive intravenous fluids and double- or quadruple- strength solutions should be considered in severe disease. Pulmonary oedema may the first indication of insidious pre-eclampsia. Furusemide in small doses (5 mg) may be useful around the time of delivery, especially caesarean section, to counter the effects of rapid fluid transfer between body compartments.
Thrombo-embolism
Increased haematocrit (in cyanotic disease), impaired circulation and prolonged bed rest combine with the prothrombotic state of pregnancy itself to increase the risk of deep vein thrombosis and pulmonary embolism – or systemic embolism in right-to-left shunt. The latter may also occur with air, so meticulous care must be taken to prevent air bubbles in intravenous lines, etc.
Bacterial endocarditis
Infective endocarditis is a rare condition, but people with structural cardiac conditions are at increased risk. Despite advances in diagnosis and treatment, infective endocarditis remains a life-threatening disease with significant mortality (up to 33% ) and morbidity.
Antibiotics have been offered routinely as a preventative measure to patients at risk of infective endocarditis undergoing interventional procedures. However, there is little evidence to support this practice. Antibiotic prophylaxis has not been proven to be effective and there is no clear association between episodes of infective endocarditis and interventional procedures. As a result, new USA and UK guidelines recommend that antibiotic prophylaxis is no longer offered routinely for defined interventional procedures, including vaginal or caesarean delivery. However, given the potentially catastrophic results should endocarditis occur, and the relatively low risk of giving antibiotics, many practitioners would advocate their use around delivery in women with significant structural cardiac disease.
Haemorrhage
Bleeding may be related to anticoagulant therapy, polycythaemia (in cyanotic disease) or uterine atony if oxytocic drugs are withheld. Women with a fixed cardiac output (e.g., aortic stenosis) have a reduced capacity to compensate for hypovolaemia, as do those who are dependent for their cardiac output on venous return (e.g., Fontan circulation). Cardiac drug therapy may also impair their ability to compensate for acute blood loss (e.g., beta blockers). If bleeding occurs, rapid infusion of intravenous fluid may readily lead to pulmonary oedema, so caution is required along with careful monitoring.
Acute reductions in systemic vascular resistance
A decrease in systemic vascular resistance may lead to profound hypotension for which the compromised cardiovascular system is unable to compensate, especially if the cardiac output is fixed. It may also increase right-to-left shunting, reducing pulmonary blood flow further and potentially leading to worsening hypoxaemia, pulmonary vasoconstriction and yet further hypoxaemia.
The most common iatrogenic causes of acute vasodilatation and reduced systemic vascular resistance are oxytocin therapy and regional anaesthesia. Standard doses of oxytocin (5–10 u), if given rapidly, may decrease mean arterial pressure and systemic vascular resistance by ∼30–50%, whilst increasing cardiac output by ∼50% and heart rate by ∼20–30%. It is now acknowledged that these cardiovascular effects can be especially dangerous in women with pre-existing cardiac disease, and oxytocin should be avoided or used with extreme caution in these cases. However, withholding oxytocin may lead to haemorrhage, which is also dangerous. Alternatives include the use of other uterotonics such as ergometrine and misoprostol or the use of physical methods such as uterine massage, inter-uterine balloons and uterine compression/brace (B-Lynch) sutures. Ergometrine may cause vasoconstriction and is contraindicated in pulmonary hypertension.
Regional anaesthetic techniques have traditionally been avoided in cardiac disease since they inevitably reduce systemic vascular resistance via sympathetic blockade. However, there is now extensive experience suggesting that spinal and epidural techniques can be used safely in fixed cardiac output conditions, if used appropriately – that is, with due care and attention, including avoidance of large bolus doses, use of invasive monitoring and vasoconstrictors.
Traditional management for women with cardiac disease has been elective caesarean section under general anaesthesia, but in the past ∼10–15 years, this has changed towards vaginal delivery with effective epidural analgesia unless caesarean section is indicated for obstetric indications.
Vaginal delivery is felt to be less stressful and with fewer complications than caesarean section in most cases, especially if the labour pain is controlled with low-dose epidural regimens, for example, using 0.1% bupivacaine with opioids (in the UK usually fentanyl). Combined spinal–epidural (CSE) or continuous spinal methods have also been used. The second stage of labour is often curtailed to avoid prolonged pushing; for example, for mild-to-moderate cases 30 min of pushing is often allowed, but an elective instrumental delivery, without any pushing, may be recommended in severe cases. Elective caesarean section may occasionally be advised in severe cases where the risks from an emergency delivery are felt to outweigh those of elective surgery (e.g., when adequate personnel/equipment cannot be mobilised fast enough), although, in general, any unit managing such cases should be able to provide the resources required even at short notice. Both general and regional anaesthetic techniques have been successfully used should operative delivery be required.
Monitoring depends on the nature and severity of the cardiac lesion. Arterial cannulation is usually well tolerated by mothers during labour and straightforward to set up, but may cause problems if the midwifery staff are not used to it. Central venous cannulation may be more difficult in late pregnancy, especially if the mother is unable to lay head down. The antecubital fossa may be a more comfortable site for central venous access than the neck, although less reliable for placement of the catheter. Air must be avoided at all times in case of systemic embolism.
Postpartum complications
After delivery, potential problems include obstetric (e.g., postpartum haemorrhage and infection) and cardiac (e.g., cardiac failure and arrhythmias) complications. If a general high-dependency unit/intensive care unit is felt appropriate, it is important that those caring for the mother are familiar with the physiological differences between her and their usual patients.
Respiratory disease
The most common respiratory diseases causing morbidity and mortality in pregnancy are asthma, cystic fibrosis and pneumonia.
Asthma
Asthma is the most common respiratory condition encountered in pregnancy, present in ∼3–8% of pregnancies. There is little evidence of an association between asthma in pregnancy and increased maternal mortality, although there is a significantly higher risk of maternal and neonatal morbidity.
Specific data are lacking on the optimal anaesthetic management of mothers with asthma, recommendations being based on the extrapolation of experience with the non-obstetric patient combined with expert opinion.
Women should be seen regularly throughout their pregnancy and have their medications optimised in conjunction with input from a respiratory physician. They should be advised to attend labour ward promptly when their labour begins since it is thought that early effective analgesia and hydration can avoid triggering bronchospasm. Lumbar epidural analgesia reduces minute ventilation during the first and second stages of labour, which benefits mothers with asthma. If caesarean section is required, regional anaesthesia is thought to reduce the risk of postoperative pulmonary complications, although objective evidence is lacking. Care is required, for if regional anaesthesia extends too high, ventilation and the ability to cough may be impaired. Additional concerns regarding general anaesthesia are mostly related to intra- and postoperative respiratory complications.
Prostaglandin E 1 or E 2 can be used for induction of labour, management of spontaneous or induced abortions or postpartum haemorrhage, although the mother must be closely monitored for development of bronchospasm. By contrast, carboprost (15-methyl prostaglandin F 2α ) and ergometrine are more likely to trigger bronchospasm and should be avoided, if possible.
Cystic fibrosis
Cystic fibrosis is relatively rare (affecting about 1 in 1800 Caucasians). Pregnancy is thought not to increase mortality in women with mild disease, but those with a pre-pregnancy forced expiratory volume in 1 s (FEV 1 ) <50–60% of predicted, with colonisation with Burkholderia cepacia , and with pancreatic insufficiency, are most at risk. The overall mortality rate is about 5–20% within 2–10 years of pregnancy. Antepartum monitoring and surveillance, with prompt treatment of infective exacerbations and regular physiotherapy, are thought to be the most important components of care.
Supplemental oxygen should be given in labour, although humidification is required to avoid excessive drying of secretion. A lumbar epidural can reduce the increased oxygen requirements during labour, and is usually indicated. If caesarean delivery is needed, then regional anaesthesia is the method of choice, taking care to avoid excessively high blocks with the risk of respiratory impairment.
Pneumonia
Pneumonia complicates 0.15–0.25% of pregnancies. Despite the fact that mortality rates have decreased substantially with the use of modern antibiotic therapy, pneumonia is still the most frequent non-obstetric infection causing maternal mortality, and is associated with increased morbidity and mortality when compared with the non-obstetric population.
Community-acquired pneumonia is the most common form of pneumonia in pregnancy, with a similar spectrum of organisms to non-pregnant patients. Complications in the pregnant patient include septic shock, cardiac arrhythmias, respiratory failure, pre-term labour and an abnormal cardiotocography (CTG) trace
Peripartum management is similar to that for cystic fibrosis, that is, supplemental oxygen in labour with epidural analgesia and regional anaesthesia, if not contraindicated by systemic sepsis, for caesarean section.
Respiratory disease
The most common respiratory diseases causing morbidity and mortality in pregnancy are asthma, cystic fibrosis and pneumonia.
Asthma
Asthma is the most common respiratory condition encountered in pregnancy, present in ∼3–8% of pregnancies. There is little evidence of an association between asthma in pregnancy and increased maternal mortality, although there is a significantly higher risk of maternal and neonatal morbidity.
Specific data are lacking on the optimal anaesthetic management of mothers with asthma, recommendations being based on the extrapolation of experience with the non-obstetric patient combined with expert opinion.
Women should be seen regularly throughout their pregnancy and have their medications optimised in conjunction with input from a respiratory physician. They should be advised to attend labour ward promptly when their labour begins since it is thought that early effective analgesia and hydration can avoid triggering bronchospasm. Lumbar epidural analgesia reduces minute ventilation during the first and second stages of labour, which benefits mothers with asthma. If caesarean section is required, regional anaesthesia is thought to reduce the risk of postoperative pulmonary complications, although objective evidence is lacking. Care is required, for if regional anaesthesia extends too high, ventilation and the ability to cough may be impaired. Additional concerns regarding general anaesthesia are mostly related to intra- and postoperative respiratory complications.
Prostaglandin E 1 or E 2 can be used for induction of labour, management of spontaneous or induced abortions or postpartum haemorrhage, although the mother must be closely monitored for development of bronchospasm. By contrast, carboprost (15-methyl prostaglandin F 2α ) and ergometrine are more likely to trigger bronchospasm and should be avoided, if possible.
Cystic fibrosis
Cystic fibrosis is relatively rare (affecting about 1 in 1800 Caucasians). Pregnancy is thought not to increase mortality in women with mild disease, but those with a pre-pregnancy forced expiratory volume in 1 s (FEV 1 ) <50–60% of predicted, with colonisation with Burkholderia cepacia , and with pancreatic insufficiency, are most at risk. The overall mortality rate is about 5–20% within 2–10 years of pregnancy. Antepartum monitoring and surveillance, with prompt treatment of infective exacerbations and regular physiotherapy, are thought to be the most important components of care.
Supplemental oxygen should be given in labour, although humidification is required to avoid excessive drying of secretion. A lumbar epidural can reduce the increased oxygen requirements during labour, and is usually indicated. If caesarean delivery is needed, then regional anaesthesia is the method of choice, taking care to avoid excessively high blocks with the risk of respiratory impairment.
Pneumonia
Pneumonia complicates 0.15–0.25% of pregnancies. Despite the fact that mortality rates have decreased substantially with the use of modern antibiotic therapy, pneumonia is still the most frequent non-obstetric infection causing maternal mortality, and is associated with increased morbidity and mortality when compared with the non-obstetric population.
Community-acquired pneumonia is the most common form of pneumonia in pregnancy, with a similar spectrum of organisms to non-pregnant patients. Complications in the pregnant patient include septic shock, cardiac arrhythmias, respiratory failure, pre-term labour and an abnormal cardiotocography (CTG) trace
Peripartum management is similar to that for cystic fibrosis, that is, supplemental oxygen in labour with epidural analgesia and regional anaesthesia, if not contraindicated by systemic sepsis, for caesarean section.
Neurological and muscular disease
Neuromuscular diseases are not the most common encountered in the obstetric population, but when they occur, they have important implications for the obstetrician and anaesthetist. It is difficult to base clinical decisions on the existing literature because information in this area is limited mainly to case reports and series.
Epilepsy
Epilepsy is one of the more common neurological diseases encountered in the parturient, with a reported incidence of approximately 1 in 200 mothers attending antenatal clinics. Seizure frequency generally increases during pregnancy due to altered drug pharmacokinetics, and deaths have occurred as a result of poor therapeutic control.
Most anti-epileptic drugs are teratogenic and individual decisions need to be made on a case-by-case basis to balance the increased risk of birth malformations and other adverse pregnancy outcomes if anti-epileptic therapy is continued during pregnancy, against the increased maternal and fetal risk from poorly controlled seizures, were it to cease. Seizure control may include blood analysis to ensure therapeutic levels of anti-epileptic drugs.
Multiple sclerosis
Patients with multiple sclerosis tend to suffer a deterioration of symptoms in the immediate postpartum period, as after surgery. There has been controversy in the past regarding the safe use of regional anaesthesia in patients with multiple sclerosis, but previous fears about an increased relapse rate following regional anaesthesia have fortunately not been borne out by large prospective series. Most authorities therefore consider regional anaesthesia not to be contraindicated in these patients, and many would recommend its use in labour to reduce fatigue. Rarely, patients who suffer from the severe spinal form of the disease may be susceptible to autonomic hypereflexia, which requires special consideration (see below).
Myasthenia gravis
The principal problems posed to the anaesthetist by myasthenia gravis concern adequacy of ventilation, ability to cough and increased airway secretions resulting from the use of anti-cholinesterase therapy. These patients exhibit unpredictable response to suxamethonium, are extremely sensitivity to the effects of nondepolarising neuromuscular blocking drugs and are at increased risk of requiring postoperative ventilation. Due to these problems, general anaesthesia is best avoided if possible.
Regional anaesthesia is usually advised to reduce fatigue in labour and allow instrumental delivery without needing general anaesthesia. Other drugs thought to worsen muscle weakness in myasthenics should also probably be avoided or used with caution – these include the aminoglycosides, clindamycin, beta blockers and magnesium sulphate.
Muscular dystrophy
The muscular dystrophies are a heterogeneous group of disorders characterised by progressive degeneration of skeletal muscle with intact innervations. Anaesthetic complications include sensitivity to neuromuscular blocking drugs, opioids and other sedative and anaesthetic drugs, a liability to respiratory infections and an increased need for postoperative ventilation.
Regional anaesthesia can be used successfully for both labour and caesarean delivery, but may be difficult if severe disease has resulted in spinal deformities. Patients with these disorders are at increased risk of malignant hyperthermia, and triggering agents should be avoided if general anaesthesia is required. Patients may also be at risk of profound hyperkalaemia after the administration of suxamethonium.
Myotonic disorders
Myotonic disorders are inherited muscle diseases characterised by the prolonged contraction of certain groups of muscles after stimulation. Problems affecting anaesthetic management include respiratory muscle weakness, cardiomyopathy and conduction defects and skeletal muscle spasm.
Regional anaesthesia is suitable for labour and delivery and both spinal and epidural anaesthesia have been successfully used. General anaesthesia presents a higher risk and careful respiratory evaluation is required. Suxamethonium and anti-cholinesterases can cause myotonic spasms in patients with myotonic dystrophy and myotnia congenita and are best avoided. Malignant hyperthermia is not associated with myotonic dystrophy, but has been reported in patients with myotonia congenita.
High spinal cord lesions
Although mothers with a lesion above T10 may not experience labour pain, the absence of central inhibition of the sympathetic neurons in the spinal cord can result in autonomic hyper-reflexia. Noxious stimuli such as uterine contractions can precipitate massive release of catecholamines from the sympathetic chain. In severe cases this can lead to death from hypertensive cerebral haemorrhage or cardiac arrhythmias.
Because uterine contractions can precipitate autonomic hyper-reflexia, the use of regional anaesthesia – usually epidural – is advised during labour for any patient with an injury at T7 or higher. Regional anaesthesia can also be used for caesarean section, or other operative interventions. If general anaesthesia is used, suxamethonium should be avoided during the period of denervation injury (24 h after the injury to 1 year), as it can result in extreme hyperkalaemia.
Brain neoplasms
Although the incidence of brain tumour is unaffected by pregnancy, pathophysiological changes during pregnancy can significantly affect tumour growth and symptomatology. Fluid retention and increases in blood volume can worsen the effects of an intracranial space occupying lesion.
The choice of analgesia/anaesthesia for labour and delivery in mothers who have raised intracranial pressure is controversial. Decisions should be made in partnership with the mother’s neurologist, and will be in part based around the size and location of the tumour and the presence/severity of raised intracranial pressure. In general, either elective caesarean delivery or a labour with effective analgesia and assisted delivery to avoid pushing is preferred.
If labour is chosen, the risk of dural puncture (causing coning) in the presence of increased intracranial pressure must be weighed against that of labour and vaginal delivery without effective analgesia. Rapid epidural injection may be associated with increases in intracranial pressure. For caesarean section, measures to avoid acute increases in intracranial pressure are required as for general neuro-anaesthesia.
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