Neuraxial anaesthesia in parturient with cardiac disease.

Parturient with corrected or uncorrected cardiac problem may undergo neuraxial anaesthesia for several reasons and in different trimesters. The altered physiological state in a parturient is further deranged in the presence of a cardiovascular lesion, producing the added risk to the parturient undergoing a neuraxial block. A detailed evaluation, knowledge regarding cardiovascular disease state, more vigilant monitoring, and a team approach can lead to a successful outcome.

INTRODUCTION

Heart disease is the third most common cause of maternal death, and 20% of the patients suffering from cardiac disease have severe haemodynamic instability related to the underlying cardiac problem.[1] Parturients with cardiac disease often undergo surgery and neuraxial anaesthesia for various reasons and in different trimesters. There are few reports in the literature describing the management of parturients with cardiac disease during neuraxial anaesthesia. This article reviews current data and discusses important aspects of heart disease in relevance to neuraxial anaesthesia in a parturient. As labour and delivery are the most important aspect of pregnancy, the major focus of this article is on this segment.

The physiological changes occurring in the cardiovascular system due to pregnancy are exaggerated in the presence of a cardiac lesion.[23] These cardiovascular changes along with coagulation abnormalities may discourage the use of neuraxial blockade due to the sympathetic blockade produced with the resulting haemodynamic changes. The author searched electronic databases including the following: MedLine, PubMed, and the Cochrane Central register of controlled clinical trials (until June 2018) and applied the following search terms: neuraxial block, spinal and epidural anaesthesia (EA), heart disease, surgery, and pregnant patient. Only the relevant English literature reports are considered in this review.

Approximately 60%–80% of parturients suffering from cardiac disease have congenital heart disease.[3] The commonest ones are tetralogy of Fallot, septal defects, and Eisenmenger's syndrome. Valvular heart disease comprises 15% cases, of which rheumatic mitral stenosis is the most common. Table 1 lists the common cardiac diseases in which successful use of neuraxial anaesthesia has been performed.

Table 1

Common cardiovascular conditions in a parturient

PHYSIOLOGICAL CHANGES DURING PREGNANCY THAT CAN HAVE IMPACT ON NEURAXIAL BLOCK

The four major changes that are important in the presence of cardiovascular disease are as follows:

Normal pregnancy is associated with a 30%–50% increase in blood volume, corresponding increase in plasma volume, and increase in cardiac output (CO). There is dilutional anaemia in spite of an increase in red cell mass over the third trimester because of an increase in plasma volume.[2] Stroke volume (SV) normally increases by 25%–35% with the remaining increase in CO being accounted for rise in heart rate (HR). Cardiac compromise with pulmonary oedema or biventricular failure may present in parturients earlier making the management of neuraxial anaesthesia more difficult. The early signs of cardiac compromise may become apparent in the first trimester and peak during second trimester, around 24 weeks when CO reaches the maximum and remains high till delivery

There is a progressive decrease in systemic vascular resistance (SVR) throughout gestation, and hence mean arterial pressure (MAP) is preserved at normal values despite an increase in CO. This has importance in patients with aortic stenosis and those with right to left shunt lesions

During labour, CO further increases by 10%-20% due to pain, anxiety, and autotransfusion during uterine contractions. SV and HR increase and decrease with each contraction, with peaks as high as 50% above the prelabour values. In the immediate postpartum period, CO peaks as the evacuated uterus contracts and blood from myometrial veins is autotransfused into the systemic venous system and gradually decreases thereafter. After vaginal delivery, the increase in CO and SV persists for 60–90 min, whereas HR decreases and blood pressure remains unchanged. After caesarean delivery, MAP remains unaltered and CO increases by 30%–50%, compared with predelivery values. These changes usually persist for 10–15 min and may precipitate pulmonary oedema in a decompensated heart

Hypercoagulability associated with pregnancy and the possible need for anticoagulation (e.g., patients in chronic atrial fibrillation (AF), prosthetic heart valve, and pulmonary thromboembolism) increase the risk of thrombosis or bleeding during neuraxial block. Table 2 represents the major haemodynamic changes in different cardiac conditions.

Table 2

Haemodynamic state in different cardiac diseases

Apart from the physiological responses towards pregnancy and delivery, the other factors that affect haemodynamic status during neuraxial block include gestational age, intravascular fluid status, positioning of the patient, and the route, dose, and choice of uterotonic agents.

INDICATIONS AND CONTRAINDICATIONS OF NEURAXIAL BLOCK

Not all the parturients suffering from cardiac disease are fit to undergo a neuraxial block. The following lines depict some indications and contraindications of neuraxial anaesthesia in parturients with cardiac disease.

Indications

Patient's demand

Associated preeclampsia

Breech delivery or multiple pregnancy

Trial of pregnancy and labour after previous caesarean delivery

Obese parturient.

Contraindications

Patient refusal

Expected severe bleeding when on anticoagulant treatment

Uncontrolled haemorrhage

Severe hypovolemia

Severe spinal deformity.

PREANAESTHETIC COSIDERATIONS

Parturient may require neuraxial anaesthesia during labour, delivery, or during the second trimester for procedures such as appendicectomy and ovarian cyst removal. Many reports have been published of successful administration of neuraxial blockade in parturient with cardiac disease coming for these procedures.

A detailed evaluation of the underlying cardiac problem including risk stratification is essential to consider for extensive monitoring/switch over to general anaesthesia and need for the help of a specialised team with experience of cardiovascular anaesthesia and intraoperative echocardiography. Pertinent cardiac testing (angiography, computerised tomography, or magnetic resonance imaging) apart from the routine echocardiography can determine the disorder that can affect the anaesthesia management. If available, serum β-type natriuretic peptide can be done for the parturient with the potential to develop heart failure during additional stress of surgery or anaesthesia. Patients with coartation of aorta are at increased risk of hypertension and ecampsia and neuraxial block should be avoided. Bleeding at the time of surgery/delivery is more common in patients having cyanotic heart disease and/or on anticoagulation.

Infective endocarditis (IE) prophylaxis is needed in parturient with highest risk of IE, for example, those with prosthetic heart valve, history of IE before, and with some complex congenital lesions. In high-risk parturient, the preferred regime is ampicillin 1.5 mg/kg (maximum 120 mg) given intravenously 30 min before neuraxial block followed by ampicillin 1 g given intravenously/intramuscularly or amoxicillin 1 g given orally 6 h later.[4] The parturient needs to undergo some risk assessment scores, for example, CARPREG or ZAHARA and KHAIRY score to predict maternal cardiovascular events.[4] Patients with NYHA class >II, with a prior cardiac event (heart failure, stroke, or arrhythmia), critical mitral or aortic stenosis, severe left ventricular dysfunction, presence of a valve prosthesis or severe pulmonary regurgitation, and smoking history have an increased risk of both maternal and neonatal events during the course of pregnancy, labour, and delivery.

MONITORING

The extensiveness of monitoring depends on the severity of disease. In case of mild disease, monitoring includes noninvasive blood pressure measurement, electrocardiography (ECG), tocodynamometry, and foetal HR monitoring. In moderate to severe disease, the following additional monitoring aids may be applied depending on the availability. External defibrillator paddles should be placed before surgery in patients especially prone to intractable tachyarrhythmia. Filter in all intravenous lines in patients with shunt lesion to prevent paradoxical air embolism.

Pulse oxymetry: For rapid detection of desaturation, for example, tetralogy of Fallot's patient developing hypercyanotic spell.

ECG: Continuous five lead monitoring and ST segment monitoring is required for the detection of myocardial ischemia in patients with aortic stenosis (AS), coronary artery disease (CAD), or hypertrophic obstructive cardiomyopathy (HOCM) or arrhythmia in other patients.

Intra-arterial catheter: In moderate to severe disease patients for minute-to-minute monitoring of arterial pressure, arterial blood gas sampling, and management of vasoactive drugs, if any.

Central venous pressure (CVP): In high-risk patients especially those who are prone to hypotension, pulmonary oedema, or peripartum haemorrhage, a CVP line is a guide to fluid therapy and administration of inotropes and vasodilators.

Pulmonary artery catheter: Rarely used, for example, in a patient with severe pulmonary hypertension in which it guides titration of pulmonary vasodilators.

Echocardiography: Have some role in assessment of ventricular function both pre and post surgery or delivery and direct visualisation of the ventricles to know the volume status.

NEURAXIAL ANAESTHESIA

Neuraxial anaesthesia [Table 3] is the preferred technique if (a) the surgery is nonemergent and (b) the cardiac disease is mild to moderate. The indications are (1) in the second trimester: torsion ovarian cyst, hysterotomy, lower limb surgeries, etc; (2) and most importantly for conduct of labour and delivery. It is preferred over general anaesthesia for the following reasons:

Table 3

Types of neuraxial anaesthesia, advantages and disadvantages, drug, and doses

Attenuates pain

Decreases the release of catecholamines

Allows a passive stage 2 of labour

Provides adequate surgical anaesthesia.

Mitral stenosis is the commonest lesion in pregnancy in our country. The symptoms depend on the severity of stenosis. However, the usual features are breathlessness, palpitation, chest pain, haemoptysis, pulmonary oedema, and thromboembolism. Knowing the severity of mitral stenosis (MS) is of paramount importance [Table 4] to manage neuraxial block during labour and delivery. AF is common in parturients. An increase in HR decreases left ventricular filling time and thereby a fall in CO. This in combination with an increase in plasma volume as well as increase in preload (due to autotransfusion) following delivery may lead to pulmonary oedema.[5] The anaesthetic goals in these parturients are as follows: maintenance of acceptable HR, immediate treatment of acute AF, avoidance of aortocaval compression, maintenance of adequate venous return and normal blood pressure, adequate analgesia, as well as avoidance of hypoxia, hypercarbia, and acidosis.

Table 4

Gradation of severity of mitral stenosis

Management of labour

Combined spinal epidural with intrathecal opioid such as fentanyl in the first stage followed by titrated dose of local anaesthetic (LA) in the second stage is beneficial to prevent stress-related tachycardia. The addition of fentanyl to dilute LA mixture enhances the quality of analgesia without contributing to the sympathetic blockade. The fall in SVR in this stage is managed with small bolus (50–100 μg) of phenylephrine. Ephedrine is avoided unless there is relative bradycardia (HR <70/min). For a critically ill parturient, opioid alone may be administered through epidural/intrathecal route. Adequate perineal and segmental analgesia reduce stress-induced increase in HR and potentiate the urge to push. This allows foetal descent to be accomplished by uterine contractions and avoiding the deleterious effects of Valsalva maneuver during the second stage of labour. Low SA (when EA is not used) may be administered for a controlled second stage and delivery.

Management of caesarian delivery

In moderate to severe disease, SA is avoided due to acute fall in SVR following the block. EA with titrated dose of LA is preferred over SA as the former results in better control of haemodynamic state due to slower onset of blockade. Prophylactic use of vasopressors and intravascular volume loading are best avoided. A careful titration of anaesthetic and analgesic dose allows judicious and appropriate volume supplementation in a critical parturient. These parturients are prone to hypotension not only because of EA, but also due to venous pooling, prior beta-adrenergic blockade, and diuretic therapy. About 50–100 μg of phenylephrine or 20–40 μg of metaraminol is used in case of hypotension with little or no untoward effect on uteroplacental circulation. Caution use of oxytocin is warranted.

Few details about the anticipated changes during neuraxial block in parturients with other cardiovascular disease, anaesthetic goals, and neuraxial block of choice that anaesthesiologists should know are described in Table 5.

Table 5

Physiologic changes during neuraxial block, anaesthetic goal, and neuraxial block of choice

SPECIAL GROUPS

Congenital cardiac lesions with a palliative surgery

Successful palliative repair for a cardiac lesion before pregnancy is associated with some degree of maternal foetal risk even in best of hands. There are few reports available describing the successful use of EA or combined spinal epidural anaesthesia in these lesions. Table 6 represents the most common palliative intracardiac shunt in which successful pregnancy and delivery happened.[29303132]

Table 6

Palliative cardiac shunt lesions

Prosthetic heart valve and anticoagulation

Parturient receives anticoagulation for several reasons, of which prosthetic heart valve is one. Chronic use of anticoagulation may give rise to thrombocytopaenia. The ideal level of platelets before neuraxial block should be more than 100,000/mm−3 according to different studies. There are some suggested durations for discontinuation of anticoagulant administration before and after neuraxial block and epidural catheter [Table 7].[33343536]

Table 7

Duration to discontinue/continue anticoagulant before/after neuraxial block

Postoperative analgesia in these cases is usually with an opioid or α-agonist or a combination of opioid and nonsteroidal anti-inflammatory drugs intravenously. Patient-controlled analgesia is an alternative mode of analgesia in these group of patients.

SUMMARY

Optimal management during neuraxial anaesthesia requires a thorough assessment of the anatomic and functional capacity of the diseased heart along with an analysis of how the described major physiologic changes are likely to affect the specific limitations imposed by the intrinsic disease, patient's tolerance to pain during labour or surgery, impact of uterine contraction-induced autotransfusion, postpartum changes induced by relief of vena caval obstruction, potential for postpartum haemorrhage, and use of uterine oxytocic agents.

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Conflicts of interest

There are no conflicts of interest.