Management of a parturient with uncorrected tetralogy of Fallot in shock: an anesthetic challenge

Abstract

Tetralogy of Fallot (TOF) is the most common form of cyanotic congenital heart disease. The survival of patients with uncorrected TOF till the fourth decade of life is rare (around 3%). Pregnancy in a patient with uncorrected TOF requires a multidisciplinary approach. A confluence of pregnancy, uncorrected TOF and shock is infrequent. The state of hypovolaemia and a decrease in systemic vascular resistance due to anaesthetic agents increase the right to left shunt. The decrease in pulmonary blood flow provokes a ‘hypercyanotic spell’. We report the successful management of 30-year-old pregnant (G3P2A2L0) with uncorrected TOF, presenting to the emergency department with incomplete abortion in shock.

Background

Tetralogy of Fallot (TOF), first described in the literature by a French physician Arthur Fallot in 1888, is assumed to be a consequence of incomplete rotation and inaccurate partition of the conotruncus. Four components of TOF include an unrestricted ventricular septal defect (VSD), right ventricular outflow tract (RVOT) obstruction, overriding of the aorta and right ventricular hypertrophy. The right to left shunt decreases the pulmonary blood flow (PBF) and hence the oxygenation of blood. The RVOT obstruction increases the pressures in the right ventricle, which, in association with overriding of aorta, promotes the deoxygenated blood to flow through the aorta.¹ Pregnancy in patients with uncorrected TOF increases maternal morbidity and mortality with significant effects on fetal outcome.^{2 3} We report the successful management of 30-year-old pregnant (G3P2A2L0) with uncorrected TOF, presenting to the emergency department with incomplete abortion in shock for surgical management of uterine bleed.

Case presentation

A 30-year-old (weight 50 kg and height 150 cm) G3P2A2L0 (G = gravida, P = para, A = abortion and L = live) presented to the emergency with bleeding per vagina (blood loss not assessable) and haemodynamic instability. She was a known case of uncorrected ‘classic’ TOF on tablet torsemide 10 mg+spironolactone 25 mg once daily (OD) and tablet metoprolol 12.5 mg OD for 2 years. Her previous abortions (all in first trimester) were spontaneous without any intervention. Clinically, she had central cyanosis with clubbing of grade 3 and was dyspneic (New York Heart Association (NYHA) grade 3). On auscultation, S1 was normal, S2 was loud and single, and the pulmonary area had a systolic murmur. Chest X-ray posterior–anterior view shows a boot-shaped heart (figure 1). Electrocardiograph revealed a right axis deviation and p wave of >1.5 mm length and a biphasic pattern in lead V1, indicating a right atrial enlargement (figure 2). Her previous two-dimensional echocardiography commented a VSD of 18 mm with a right to left shunt, right ventricular dilatation with hypertrophy, severe pulmonary stenosis with the gradient of 60 mm Hg and overriding of the aorta. She was diagnosed with TOF during her visit to antenatal clinic for her poor obstetric history. Before the event, her oxygen saturation (SpO2) was 75%, and non-invasive blood pressure (NIBP) was 100/55 mm Hg in the previous antenatal record. Her NIBP at admission (19:30) was 70/30 mm Hg, pulse was feeble with a rate of 136/min, SpO2 was 57% on room air and peripheries were cold and clammy. She was conscious but irritable. Wide bore intravenous access was secured, and blood was sent for cross-matching and investigations. Fluid resuscitation was done with crystalloids keeping in view her cardiac status. The external jugular vein (19:45) was cannulated, and intravenous norepinephrine was started at 0.5–1 µg/kg/min. Her vitals started improving. But, as she continued to bleed profusely (20:00), she was started on blood transfusion (250 mL packed red blood cells (PRBC)) as well as crystalloid resuscitation (90 mL/hour). Crystalloids were used as maintenance fluid, and the losses were replaced with PRBC. Misoprostol 800 µg was placed per vaginum. She was brought to the operating room (OR) for uterine suction and evacuation and to proceed after giving antibiotic prophylaxis for infective endocarditis.

Figure 1.

Chest X-ray posterior–anterior view depicting a boot-shaped heart.

Figure 2.

Electrocardiograph depicting a right axis deviation and p wave of >1.5 mm length and a biphasic pattern in lead V1, indicating a right atrial enlargement.

The patient was received in the OR with an NIBP of 69/35 mm Hg measured in the right upper limb, pulse rate of 132 beats/min and SpO2 of 68%. The blood continued to go through the 16G intravenous cannula. The American Society of Anesthesiologists standard monitoring was attached. As the patient had food 2 hours before the presentation, rapid sequence intubation was done with intravenous ketamine 100 mg and intravenous succinylcholine 75 mg. Later, intravenous fentanyl 50 µg and intravenous vecuronium 5 mg were supplemented. Anaesthesia was maintained with a titrated dose of sevoflurane+O2. Right radial artery was cannulated with ultrasound guidance after multiple attempts. Postinduction the SpO2 decreased to 30%, the invasive blood pressure dropped to 34/20 mm Hg, and pulse rate was 145 beats/min. With the suspicion of ‘hypercyanotic spell’, both the femoral arteries were occluded by manual external compression, intravenous phenylephrine 250 µg and intravenous esmolol 2.5 mg were given. The fraction of oxygen concentration was increased to 1. Second unit PRBC was infused at a faster rate. On other intravenous line, 300 mL bolus of crystalloid was administered. The saturation increased gradually and was maintained at 72%–75%, and blood pressure improved to 90/60 mm Hg. Her heart rate now was 120 beats/min. She was hyperventilated to maintain slight alkalosis. The surgical team proceeded with the suction evacuation. The bleeding was controlled after the evacuation of placental products. Methylergometrine 0.2 mg was administered intramuscularly. The arterial blood gas analysis showed pH 7.45, pCO₂ 26.8 mm Hg, pO₂ 40.3 mm Hg, haematocrit 41%, haemoglobin (Hb) 135 g/L, HCO₃−18.7 mmol/L, base excess (BE) −5.6 mmol/L, SO% 79%, Na+ 138 mmol/L, K+ 4.38 mmol/L, lactate 1.1 mmol/L and Ca2+ 1 mmol/L. Her investigations, which were sent on admission, also showed low Hb of 125 g/L prior to transfusion, which was very low for a patient with cyanotic heart disease. Intraoperatively she received three units of PRBC (third unit PRBC continued in the postoperative period). Intravenous calciumgluconate 2 g was administered. Renal and liver function tests were within the normal range (table 1). She was extubated successfully and shifted to the high dependency unit (HDU) for further management. Further blood transfusion was advised according to the postoperative hemogram and cardiac status. Intravenous paracetamol and fentanyl were advised for pain relief. She stayed in HDU for observation and then was shifted to obstetric ward after 2 days. She was counselled against pregnancy and advised to use temporary contraception measures until surgical correction of TOF. She was referred to the Department of Cardiothoracic Surgery.

Table 1.

Depicting postoperative investigations.

Haemoglobin	Preoperative 12.5 g/dL; postoperative 12 g/dL
Platelet count; PT/INR	150x109/L; 12 s
Serum urea; creatinine; sodium; potassium; chloride	20 mg/dL; 1 mg/dL; 145 mEq/L; 5 mEq/L; 111 mEq/L
Serum AST; ALT; ALP; albumin; total bilirubin	41 IU/L; 26 IU/L; 130 IU/L; 3.5 g/dL ; 1 mg/dL

ALP, alkaline phosphatase; ALT, alanine transaminase; AST, aspartate aminotransferase; PT/INR, prothrombin time/international normalised ratio.

Outcome and follow-up

The patient stayed in HDU for observation and then was shifted to obstetric ward after 2 days. She was counselled against pregnancy and advised to use temporary contraception measures until surgical correction of TOF. She was referred to the Department of Cardiothoracic Surgery.

Discussion

The prevalence of heart disease in pregnancy ranges from 1% to 4%. The fetal complications in a pregnancy with heart disease range from intrauterine growth retardation to miscarriages.³

The critical lesion in TOF is infundibular obstruction of the right ventricular tract accounting for the pathology and symptoms. Cyanosis, dyspnea, secondary polycythaemia and easy fatigability are the common presenting symptoms of patients with TOF. Right to left shunt, decreased PBF and changes in the pulmonary vasculature contribute to hypoxaemia. This results in adaptive changes such as secondary polycythaemia, increased blood viscosity and vasodilation to improve tissue oxygenation. But these adaptive changes increase the risk of thromboembolism. Hyperventilation leads to chronic respiratory alkalosis and thus decreases the delivery of oxygen to the tissues.

In pregnancy, additional demand is imposed on the already decompensated heart. Due to the physiological changes during pregnancy (decrease in systemic vascular resistance (SVR)), there is an increase in right to left shunt, and symptoms become severe during pregnancy. Polycythaemia decreases the placental perfusion. Polycythaemia, along with hypoxaemia may cause intrauterine fetal growth retardation, abortions and stillbirths. Good antenatal care involving an anaesthesiologist, obstetrician and cardiologist is essential for successful management of a patient with uncorrected TOF. The patient should be evaluated for NYHA functional status, ventricular function, arrhythmias, pulmonary hypertension, severe RVOT obstruction, cyanosis and need for anticoagulation, as these form the main predictors for maternal morbidity.^{2 4}

Patient, with uncorrected TOF, without an antenatal check-up, presenting in shock is rare. The anaesthetic grid includes maintaining a fine balance between hypovolaemia and volume overload, preventing the increase in heart rate as it increases the RVOT obstruction, maintaining SVR and decreasing pulmonary vascular resistance (PVR) by avoiding hypoxia, hypercarbia and acidosis and maintaining the contractile function of the ventricle (figure 3). An expected complication in this patient population is a ‘hypercyanotic spell’ due to hypovolaemia and decrease in SVR caused by anaesthetic agents. This causes a decrease in PBF by increasing the right to left shunt and hence the desaturation. Primary goals for correction of ‘hypercyanotic spell’ includes relieving the infundibular spasm and decreasing the shunt. Treatment includes increasing the SVR by mechanical methods like external pressure on aorta or occlusion of femoral arteries (manual external compression), pharmacological methods like intravenous phenylephrine 5–10 µg/kg, administering oxygen to decrease the hypoxic pulmonary vasoconstriction, increasing the preload to RV by volume infusion, which supports the blood pressure and reduces RVOT obstruction, β-blocker for negative ionotropic effect and reduction in heart rate that decreases the infundibular spasm. The depth of anaesthesia needs to be increased to decrease the contractility and hence the infundibular spasm. Despite the fact that intravenous morphine is recommended in awake patients for treatment of ‘hypercyanotic spells’, it produces excess vasodilation under anaesthesia and hence not recommended. Ketamine is the induction agent of choice, as it maintains SVR. Among all the inhalational agents, sevoflurane has minimal effect on SVR and hence reduces the shunt fraction.⁵

Figure 3.

Flowchart depicting the mechanism for hypercyanotic spell and intervention done in the patient (out of box). HPV, hypoxic pulmonary vasoconstriction; HR, heart rate; PRBC, packed red blood cells; SVR, systemic vascular resistance.

Anaesthesia in pregnancy with TOF has been reported, but this presentation as an emergency in shock is rare. Tawfik et al and Parker et al presented the successful management of caesarean section in pregnant patients with uncorrected TOF.^{6 7} The blood transfusion strategy in patients with congenital heart disease is not well defined.⁸ According to our institutional protocol, the trigger for blood transfusion is Hb of less than 120 g/L with haemodynamic instability. Our goal was to maintain Hb of 150 g/L.

An unbooked pregnant patient with uncorrected TOF in shock requires meticulous management of fluid and blood transfusion and strict vigilance to avoid hypothermia, hypoxia, hypercarbia and acidosis. During anaesthesia, maintenance of SVR and preventing the increase in PVR and heart rate are the cornerstones to avoid the increase in right to left shunt. The probability of ‘hypercyanotic spell’ is high in these patients and should be diligently managed by decreasing the shunt and decreasing the infundibular spasm. Pregnancy should be planned after surgical correction of TOF, with multidisciplinary management, for a better fetal and maternal outcome.

Learning points.

• Parturient with uncorrected tetralogy of Fallot in shock is a rare presentation.

• It requires a multidisciplinary approach.

• Maintaining systemic vascular resistance and adequate volume status is important for minimising right to left shunt.

• The threshold for ‘hypercyanotic spell’ is low.