Labour analgesia and anaesthetic management of a primigravida with uncorrected Pentology of Fallot.

Tetraology of Fallot is the most common congenital heart disease causing intracardiac right-left shunts. It is characterized by presence of ventricular septal defect, aortic overriding, pulmonary artery outflow obstruction and right ventricular hypertrophy. When these features are associated with atrial septal defect, it is often referred to as Pentology of Fallot (POF). If the lesions remain uncorrected, they can cause significant morbidity and mortality to the patient. Pregnancy and labour in such a patient present with significant haemodynamic changes, which can be challenging to the anaesthesiologist. Our patient with POF was managed with labour analgesia and subsequently epidural anaesthesia for drainage of vulval haematoma with successful outcome.

INTRODUCTION

Cyanotic congenital heart disease is still a common occurrence and many patients with uncorrected cardiac lesions present for various non-cardiac surgery. The haemodyanamic changes in these patients pose a significant challenge for the anaesthesiologist. This case report is aimed at presenting a case of labor epidural analgesia and subsequently epidural anaesthesia in a patient with uncorrected pentalogy of Fallot.

CASE REPORT

A 22-year-old primigravida was admitted to the labour ward with history of 8-months amenorrhoea. She was known to have cyanotic congenital heart disease since childhood, and was not on any regular medications or follow-up. There was no history of asthma, diabetes mellitus or hypertension. Family history did not reveal any significant information. The patient complained of joint pains and breathlessness for the last 8 days. Breathlessness was more prominent on exertion and was relieved on taking rest. She also gave a history of palpitations, giddiness and blurring of vision, which improved over the course of pregnancy. The patient had a normal obstetric history in all the trimesters. Echocardiogram [Figure 1] at the 4th month revealed Pentology of Fallot (POF) and hence she was advised therapeutic termination of pregnancy, for which she had refused.

Figure 1

Echocardiography image of the patient with Pentology of Fallot showing atrial and ventricular septal defect

On pre-anesthetic check up, grade II clubbing and peripheral cyanosis were present. There was no pedal oedema or raised jugular venous pulsations. A grade-3 pansystolic murmur was heard all over the precordium on auscultation. Electrocardiogram (ECG) showed normal sinus rhythm, right axis deviation and right bundle branch block. Echocardiography revealed malpositioned great vessels, double-outlet right ventricle with severe pulmonary stenosis, large subaortic ventricular septal defect with significant overriding of aorta, moderate-sized atrial septal defect with left–right shunt and severe tricuspid regurgitation. There was hypoplasia of middle pulmonary artery with pulmonary artery gradient of 107 mmHg. Chest X-ray was not ordered in view of the pregnancy. Arterial blood gas showed pH 7.38, PaO2 48 mmHg, PaCO2 34 mmHg and SaO2 of 84%. Her complete blood count showed haemoglobin of 12.3 gm% and platelets 2,10,000/mm3. Serum urea, creatinine, coagulation functions and electrolytes were within normal limits.

As the patient was getting frequent painful contractions that were associated with tachycardia, the obstetricians requested for labour analgesia. With a strict aseptic technique, in sitting posture at L3/4 interspace, 25 μg fentanyl was injected intrathecally using a 25G bevel cut spinal needle. This was followed by placement of an 18G epidural catheter at the L2/3 interspace. The patient had excellent pain relief immediately, with a visual analogue score of 0. Continuous electrocardiography (ECG), pulse oximetry and non-invasive blood pressure monitoring were performed during the labour. Heart rate settled from 140 bpm to 102 bpm. Blood pressures were stable. Labour progressed normally with an outlet forceps-assisted vaginal delivery of a healthy male baby within 2 h. Apgar at birth was 8/10 and 10/10 after 5 min. Total fluids throughout labour was normal saline 300 ml with 10 units of oxytocin. The patient received supplemental oxygen during the procedure and post-partum period. There was no requirement for subsequent epidural top-up.

Five hours following delivery, the patient started complaining of severe pain at the episiotomy site. Examination revealed a huge vulval haematoma that required immediate drainage. In the operating theatre, under full cardiac monitoring, epidural analgesia was provided with 10 mL of 0.125% bupivcaine and 50 μg of fentanyl. This was supplemented with pudendal nerve block using 0.25% bupivcaine. The patient was haemodynamically stable, with the oxygen saturation between 80 and 85% throughout the surgical procedure. The rest of the post-partum period was uneventful and the patient was discharged on the 7th day of admission to the hospital.

DISCUSSION

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart defect seen in around 5–6% of congenital heart malformations. The true incidence seems to be higher in the developing nations. It is characterized by anterior and superior infundibular septal displacement, ventricular septal defect, aortic override, infundibular obstruction and right ventricular hypertrophy.[12] When the TOF is associated with atrial septal defect, it is commonly referred to as POF. There is an association between TOF and chromosomal defects seen in 15% of the population, with the possibility of genetic transmission to the offsprings.[3] Normal pregnancy and delivery are associated with alterations in cardiovascular physiology. There is fall in systemic vascular resistance (SVR), increase in blood volume and increase in cardiac output secondary to increased heart rate and stroke volume, and a physiological left ventricular hypertrophy. These physiological changes are not very well tolerated in patients with congenital cardiac defects.

The pathophysiology of TOF depends on the level of right ventricular outflow obstruction. When the obstruction is mild, the patients present with increased pulmonary blood flow (acyanotic Fallot or Rose Tetrology). Acyanotic Fallot is more commonly seen in adults,[4] while children present with significant right ventricular outflow obstruction, right–left shunt and cyanosis. Pregnancy increases mortality and morbidity rates of uncorrected cyanotic heart disease patients.[1] Risk is increased when arterial oxygen saturation levels at rest are below 85%.[5] Maternal cyanotic cardiac lesions lead to an impaired uteroplacental perfusion and diminished foetal oxygenation, leading to a higher incidence of miscarriages, premature births and low birth weight babies.[5] Anaesthetic management for patients with cyanotic heart disease requires a thorough understanding of the pathophysiology, events and medications, which alters the magnitude of the right-to-left intracardiac shunt. Decreased SVR, increased pulmonary vascular resistance and increased myocardial contractility increase the magnitude of the right-to-left shunt.

The choice of anaeshetic technique is crucial in the management of patients with cyanotic heart disease. Sympathetic blockade seen in regional techniques may increase shunt by decreasing SVR, leading to decreased ventricular filling and cardiac output.[6] Pharmacological agents that decrease SVR increase the magnitude of the right-to-left shunt and accentuate arterial hypoxemia. Also, intermittent positive pressure ventilation and positive end expiratory pressure cause increases in pulmonary vascular resistance and decrease pulmonary blood flow. Providing adequate analgesia, maintenance of uterine–placental perfusion, preventing aortocaval compression and minimization of sympathetic block by maintaining intravascular volume are the goals of anaesthetic management.[7] In cyanotic congenital heart diseases (TOF, POF), administration of labour analgesia during early labour is advisable to limit increases in pulmonary vascular resistance and consequent right-to-left shunting. Small incremental doses of local anaesthetic drugs with opioids are preferred over large bolus doses to avoid abrupt reduction in SVR, which may cause reversal of shunt flow and hypoxemia. Intravenous fluids should be carefully monitored to prevent deficits or excesses, leading to shunt worsening and patient's decompensation.

Adequate pain relief with minor haemodynamic changes should be aimed when regional anaesthesia is considered. Shrivastava et al. reported administration of epidural block to a patient with uncorrected TOF for caesarean section.[8] Mendes et al. described a case where labour analgesia was administered in uncorrected TOF that was diagnosed during gestation.[9] As an institutional practice, we employ combined spinal epidural labour analgesia, which is an effective and safe technique. It allows the use of subarachnoid opioids, such as fentanyl or sufentanil, leading to faster analgesic effect, lower sympathetic and motor block. Placing an epidural catheter allows administration of low concentration of local anaesthetic with minimal haemodynamic changes. The same technique is described previously with good outcome.[10]

The pathophysiology and the haemodynamic derangements of POF are more or less similar to TOF, eventually depending on the magnitude of shunt. Perioperative management of these patients is essentially similar in both the cases. The anaesthetic management of patients with POF is not commonly reported in the literature owing to the rarity of occurrence. Recent advances in cardiac interventions and surgery have enabled more number of women with congenital heart disease to thrive well into their childbearing years. Although pregnant women with congenital heart disease are rarely reported around the world, a thorough understanding of the pathophysiology and anaesthetic management of these patients is essential.

CONCLUSION

Cyanotic congenital heart disease complicating pregnancy is still the leading cause of maternal deaths. The choice of anaesthesia in these patients requires thorough understanding of problems, careful titration of drugs and maintaining haemodynamic stability. Our patient with POF was managed with labour analgesia and subsequently epidural anaesthesia for drainage of vulval haematoma with successful outcome.