Investigación Científica y Tecnológica

Fernando Aguilera Castro*, Paola Diaz**, Juan Carlos Calderon**, Iovan Gutierrez***.

* Médico, anestesiólogo. Director del posgrado de Anestesiología y Reanimación. Universidad el Bosque, Hospital Simón Bolívar. Profesor asociado de la Universidad El Bosque, Bogotá, Colombia. Correspondencia: Carrera 17 No. 146-62 casa 4, Bogotá, Colombia. Correo electrónico: ofaguilerac@gmail.com
** Residente III, posgrado de Anestesiología y Reanimación, Universidad El Bosque, Hospital Simón Bolívar, Bogotá, Colombia. Correo electrónico: diaz_paola@hotmail.com, juankvla@hotmail.com
*** Médico, anestesiólogo, Hospital Simón Bolívar, Bogotá, Colombia. Correo electrónico: iovanguti@hotmail.com

Recibido: septiembre 19 de 2010. Enviado para modificaciones: diciembre 13 de 2010. Aceptado: enero 13 de 2011.

We report our experience managing pregnant patients with heart disease at the Simón Bolívar Hospital in Bogotá. The report includes three patients seen between January and December, 2009.

The first case is a 28-year old patient with tetralogy of Fallot and 38.3 weeks of gestation. The second case is a 20-year old patient in labor with an Ebstein's anomaly and 38.6 weeks of gestation. The third case is a 21-year old patient with severe aortic stenosis in week 39 of pregnancy.

The outcome in all three cases was favorable. Knowledge of the different heart diseases enables safe anesthetic management. The choice of the anesthetic technique requires assessment of the following parameters: cardiac reserve, ventricular function, pulmonary hypertension, pulmonary or duct stenosis, conduction defects and arrhythmias.

Cardiovascular diseases may cause complications in 0.2 to 3 per cent of pregnancies and are an important cause of maternal mortality (1,2). Pregnancy and labor are well tolerated in patients with uncomplicated congenital heart disease (CHD), atrial septal defect (ASD), ventricular septal defect (VSD), patent ductus arteriosus and Ebstein's anomaly (3). This is not true in women with cyanotic CHD like Eisenmenger's and tetralogy of Fallot (TOF) (4). Eisenmenger's and primary pulmonary hypertension account for 50 % of maternal mortality from CHD (5). TOF accounts for 10 % of deaths, while mortality due to aortic stenosis depends on the functional area of the valve. In CHD, poor prognostic signs include a hematocrit of > 60 %, an SaO₂ < 80 %, right ventricular hypertension and episodes of syncope (6).

Review of the clinical records of three pregnant patients with CHD in the moderate-to-severe risk range, seen between January and December 2009 at the Simón Bolívar Hospital.

CASE 1

Twenty-eight-year old patient in week 38.3 of pregnancy, with a diagnosis of TOF, admitted for iterative C-section. The patient complained of multiple episodes of angina associated with a functional class III/IV.

History: G3, P1, C1, A1. Previous C-section and amputation of the right lower extremity due to popliteal artery obstruction. Fracture of the left lower limb. Use of low-molecular weight heparin (LMWH) 40 mg every 12 hours. BP 96/60, HR 62, RR 12, weight 70 kg, height 155 cm, SaO₂ 74 % with an FIO2 of 21 %, central and peripheral cyanosis, Mallampati 3, pansystolic murmur IV/VI, predominantly in the lung; FHR 142; upper limbs with clubbing of fingers. Hb 17 g/dl; hematocrit 52, %. Blood gases: pH 7.32, pCO₂ 42, pO₂ 52, HCO₃, 17. EKG: HR 65, right axis, right bundle branch block with right ventricular hypertrophy (RVH), left ventricular hypertrophy (LVH), presence of subepicardial ischemia.

Echocardiogram: Preserved left ventricular systolic function, RVH, right ventricular outflow tract obstruction, 30 % overriding aorta and a peak gradient of 137 mmHg. Prophylaxis with LMWH was interrupted and the operation was performed under general anesthesia. Standard monitoring was used with right subclavian central catheter and left radial arterial line. Vital signs at the start were: BP 160/100, HR 100, RR 17, SaO₂ 74 % with an FIO₂ of 21 %. Saturation increased to 90 % after three minutes of pre-oxygenation. Induction was performed with etomidate 20 mg, remifentanil 0,25 µg/kg/min continuous infusion, rocuronium 40 mg, sevoflurane at 1 MAC. Intubation with a No. 7 endotracheal tube, mechanical ventilation with 8 ml/kg tidal volume (tv), HR 12. A male baby was born five minutes after the incision, with an APGAR test of 8, 9, 9. Oxytocin was infused at a dose of 10 IU, leading to a slight drop in blood pressure (90/60) and saturation (88 %). Remifentanil was decreased to 0.15 µ/kg/min. At the end of surgery, blood gases were pH 7.26, pCO₂ 36, pO₂ 82, HCO₃ 16.8, SaO₂ 93.8 %, with an FIO2 of 100 %. Total crystalloid administration was 2.000 ml, urinary output was 2.5 cc/kg/h and intra-operative blood loss was 500 ml.

The patient was transferred to the intensive care unit (ICU), did not require hemodynamic support, was managed with an FIO₂ of 35 %, and asked for voluntary discharge.

CASE 2

Twenty-year old patient in labor at 38.6 weeks of pregnancy with an Ebstein's anomaly, functional class II/IV. G1, P0, A0. TA 88/53, HR 101, RR 20, weight 64 kg, height 163 cm, SaO2 89 % at 21 %, peripheral cyanosis. Mallam-pati 2, pansystolic murmur III/VI, FHR 136, clubbing of fingers; Hb 16 g/dl, hematocrit 48.9 %. Blood gases: pH 7.42, pCO₂ 30, pO₂ 59.5, HCO₃ 20, SaO₂ 90 % with an FIO2 of 21 %, PaFi 118. EKG: HR 95, right axis, incomplete right bundle branch block, anteroseptal subepicardial ischemia.

Using basic pulse oxymetry, non-invasive blood pressure monitoring and continuous DII EKG, lumbar peridural anesthesia was given with a cephalad epidural catheter, after the test dose was negative. A titrated dose of levobupivacaine 22.5 mg (3 cc) plus fentanyl 50 µg in saline solution up to 12 ml (0.125 %) was administered. After the procedure, values were as follows: BP 90/69, HR 90, RR 12. The intra-partum echocardiogram revealed a small left ventricle with normal wall thickness and contractility; left ventricular ejection fraction (LVEF) was 38 %; the right ventricle appeared deformed as a result of low-riding tricuspid leaflets, ventricular atrialization, grade 1-2 tricuspid regurgitation with a 42 mmHg gradient, and mild pulmonary hypertension.

Uterine activity increased and the patient went into the expulsive phase of labor. At that point a boost was given with levobupivacaine 0.125 % and fentanyl 50 µg (10 ml). A female baby was born weighing 2,490 g and measuring 48 cm in length after an instrumental delivery using spatulas, while the following values were maintained: BP 130/90-120/80, HR 90-100 and SaO₂ 88 % - 94 %. The mother remained under monitoring for 24 hours in the ICU and was discharged with a referral for management by cardiology.

CASE 3

Twenty-one year-old patient in week 39 of pregnancy and severe aortic stenosis. History: G1, P0, A0; non-studied heart murmur since childhood with diminished functional class III/IV, but no episodes of syncope or angina. BP was 140/90, with no symptoms of vasospasm. The chest X-ray showed cardiomegaly at the expense of the left ventricle. Hb 12.9 g/dl, Hct 40 %, platelets 203,000, uric acid 6,6 mg/dl, creatinine 0.74, LDH 274 U/L, TGO 22 U/L, TGP 14 U/L, proteinuria 10.06 mg/dl. The transthoracic echocardiogram showed a displastic aortic valve with severe stenosis and a pressure gradient of 170-180 mmHg across the valve. The decision was made to deliver the baby by C-section. Monitoring was performed under sedation with midazolam 1 mg and fentanyl 50 µg: right radial arterial line and right subclavian catheter, EKG, SaO₂, EtCO₂, and urine output.

Induction was performed with the patient in supine decubitus and right wedge, with 100 % oxygenation through a 16 G peripheral venous access, using remifentanil 0.15 µg/kg/min, fentanyl 50 µg, vecuronium 1 mg, ketamine 75 mg and succinylcholine 100 mg. The surgical procedure was initiated simultaneously with oro-tracheal intubation. The baby was delivered 3 minutes later with APGAR values of 7, 9 and 10. Anesthesia was maintained with remifentanil 0.12 µg/kg/min, 1 % sevoflurane, vecuronium 2 mg, midazolam 2 mg. Volume-controlled ventilation with 500 ml tv, RR 12, FiO2 100 %. Six IU of oxytocin were passed slowly in dilution. Total blood loss amounted to 600 cc approximately and there was lowering of the blood pressure down to 105/50 mmHg. 100 µg of phenyleph-rine were given. The procedure was completed with no complications. The patient received 2,000 ml of Ringer's lactate and urine output was 200 ml.

DISCUSSION

Tetralogy of Fallot. Is found in 5 % of pregnant women and includes ventricular septal defect, RVH, pulmonary stenosis with outflow tract obstruction and overriding aorta. It is the CHD with more right-to-left shunting that becomes exacerbated with pregnancy, giving rise to cyanosis and syncope (7). This usually happens during labor and delivery due to increased cardiac output and systemic vascular resistance (8). Full repair is recommended before delivery if the pulmonary output/systemic output ratio (Qp/Qs) is > 1.5 and right ventricular systolic pressure > 60 mmHg (9).

Ebstein's anomaly. Prognosis depends on the severity of the tricuspid regurgitation, the right ventricular dysfunction and the cyanosis resulting from the right-to-left shunting. Cyanosis may manifest itself for the first time during pregnancy, due to the rise in right ventricular filling pressure. Connolly et al. (10) reported 111 pregnancies in patients with Ebstein's anomaly, with complications ocurring in cyanotic mothers.

In patients with uncorrected heart disease, early epidural analgesia must be initiated in order to avoid hypotension and aorto-caval compression that may revert shunting (11). In the event of hypotension, diluted and titrated phenylephrine is preferred. The decision to perform a C-section must be based on obstetrical reasons, in which case continuous epidural anesthesia with titrated doses and standard monitoring is useful.

The following are the hemodynamic goals for the management of TOF and Ebstein's anomaly: avoid a drop in systemic vascular resistance; maintain intravascular volume and venous return; prevent hypoxemia, hypercapnea and acidosis, as well as myocardial depression during anesthesia (12).

Spinal anesthesia is not indicated because of the sharp reduction in SVR, shunt reversion and hypoxemia (13).

In CHD with right-to-left shunting, the reduced dilutional effect in the lungs shortens pharmacologial action times and, consequently, smaller doses are required.

Aortic stenosis (AS). Although the course of pregnancy in patients with congenital AS may be satisfactory, mortality is high in cases of valve areas under 0.75 cm² (14). Aortic stenosis leads to left ventricular flow obstructions in the valvular, subvalvular or supravalvular spaces. Patients become symptomatic when the valve area is reduced by 70 %, or when the left ventricle/ aortic valve gradient is greater than 50 mmHg.

The increased ventricular pressure required for ejecting volume through the stenotic valve gives rise to LVH, reduced compliance, and fixed stroke volume. There is a poor balance between O₂ delivery and consumption because a lower systemic vascular resistance, even if it does not increase cardiac output, may reduce coronary flow. Atrial systole is critical for left ventricular filling and ejection. A drop in heart rate leads to a drop in cardiac output, while an increase in heart rate increases oxygen consumption.

When blood pressure is normal or slightly elevated it helps maintain adequate perfusion of the hypertrophic left ventricle. A sharp decrease in systemic vascular resistance will result in profound hypotension and tachycardia (15). Pregnant patients with aortic stenosis are unable to increase cardiac output sufficiently in order to meet the demands associated with pregnancy. A gradient of >100 mmHg across the valve increases the risk of complications (16).

The hemodynamic goals are to maintain normal cardiac rate and rhythm, systemic vascular resistance, intravascular volume and venous return, and to avoid myocardial depression and shivering.

Some authors contraindicate the use of neural axis anesthesia; however, others advocate the use of titrated doses of local epidural anesthetics that allow enough time for adaptation to the hemodynamic changes (17).

When general anesthesia is used, it is important to avoid reduced venous return due to positive pressure ventilation, myocardial depression due to the anesthetic agents, and the autonomic stress response due to shallow anesthesia.

Despite advances in the management of high-risk pregnant patients with heart disease in specialized centers, in our country the most vulnerable population has no access to centers where high technology is available. Therefore, they have to resort to the public hospital network where no high-technology obstetric centers are available. Referral of these patients is extremely difficult and, for this reason, in a public hospital like ours we have to provide care with the scarce resources available. Pregnant patients with heart disease require treatment based on hemodynamic goals, and large centers that provide care for cardiovascular diseases usually do not have an obstetrics service.

In the three cases discussed in this report, early epidural analgesia with levobupivacaine and fentanyl, and general anesthesia with etomidate, remifentanil and sevoflurane, enabled us to achieve a satisfactory outcome for the mothers as well as for the newborns.

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Conflicto de intereses: Ninguno declarado.
Financiación: Recursos propios de los autores.