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On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.57 no.6 Campinas Nov./Dec. 2007
Anesthesia for cesarean section in a patient with familiar hypertrophic cardiomyopathy. Case report*
Anestesia para cesária en paciente portadora de cardiomiopatía hipertrófica familiar. Relato de caso
Renato Mestriner Stocche, TSAI; Luis Vicente Garcia, TSAII; Jyrson Guilherme Klamt, TSAII
Assistente do Serviço de Anestesiologia do HC/FMRP-USP; Doutor em Ciências
Médicas pela FMRP-USP
IIProfessor-Assistente Doutor da Disciplina de Anestesiologia da FMRP-USP
OBJECTIVES: Familiar Hypertrophic cardiomyopathy (FHC) is a rare hereditary
cardiac disorder characterized by hypertrophy of the ventricular septum and
variable degrees of subvalvular aortic stenosis. In this disease, the increase
in myocardial contractility and reduction in peripheral vascular resistance
can aggravate left ventricular outlet obstruction, leading to arrhythmias and
cardiac ischemia. The objective of this report was to discuss the anesthetic
management of cesarean section in a patient with FHC.
CASE REPORT: A patient in the 33rd week of pregnancy and prior diagnosis of FHC presented, on the 24-hour Holter monitor, 22 episodes of non-sustained ventricular tachycardia (NSVT) and 2 episodes of sustained ventricular tachycardia (SVT). She complained of episodes of palpitation, dyspnea, and chest pain of short duration. The patient was medicated with atenolol, with control of symptoms and cardiac arrhythmias. Within 38 weeks and 5 days of gestation, the patient underwent elective cesarean section. Besides the usual monitoring, analysis of the ST segment and invasive blood pressure were also instituted. Anesthesia consisted of combined spinal-epidural technique with subarachnoidal administration of 5 µg of sufentanil followed by the administration of increasing doses of 0.375% bupivacaine until it reached the level of T6 (total of 16 mL). Metaraminol was used as a vasopressor. Perioperative maternal hypotension or other complications were not observed.
CONCLUSIONS: General anesthesia is often used for cesarean sections in patients with FHC. Spinal-epidural anesthesia with slow installation of the blockade was a safe alternative. In those patients, one should avoid an increase in myocardial contractility and, if necessary, a a-agonist should be used to treat maternal hypotension.
Key Words: ANESTHETIC TECHNIQUES, Regional: epidural, spinal block; DISEASES, Cardiac: familiar hypertrophic cardiomyopathy; SURGERY, Obstetric: cesarean section.
Y OBJETIVOS: La cardiomiopatía hipertrófica familiar (CHF)
es una enfermedad cardiaca rara con transmisión hereditaria caracterizada
por hipertrofia del septo ventricular y grado variable de estenosis aórtica
subvalvar. En esa enfermedad, el aumento de la contratilidad del miocardio y
la disminución de la resistencia vascular periférica pueden agravar
la obstrucción de la vía de salida del VE, produciendo arritmia
e isquemia cardiaca. Este relato quiso discutir el manoseo anestésico
para cesárea en paciente con CHF.
RELATO DEL CASO: Paciente con 33 semanas de embarazo y diagnóstico previo de CHF presentó en el holter de 24 horas 22 episodios de taquicardia ventricular no sustentada (TVNS) y 2 episodios de taquicardia ventricular sustentada (TVS). Refería episodios de palpitación, disnea y dolor precordial de corta duración. La paciente fue medicada con atenolol y presentó control de los síntomas y de las arritmias cardiacas. Con 38 semanas y 5 días de embarazo la paciente fue sometida a la cesárea electiva. Además de la habitual monitorización contó con el análisis de segmento ST y presión arterial invasiva. Se utilizó anestesia intradural-epidural con inyección de 5 µg de sunfentanil en la raqui seguida de administración de bupivacaína a 0,375% en dosis de incremento hasta alcanzar una altura de T6 (total de 16 mL). Se usó metaraminol como vasopresor. No hubo hipotensión arterial materna u otras complicaciones en el perioperatorio.
CONCLUSIONES: La anestesia general se usa con frecuencia para cesáreas de pacientes con CHF. La anestesia intradural-epidural con instalación lenta del bloqueo fue una alternativa segura. En esas pacientes, el aumento de la contratilidad miocárdica debe ser evitado, y si fuere necesario se debe utilizar un a-agonista para la corrección de hipotensión arterial materna.
Familiar hypertrophic cardiomyopathy (FHC), also known as asymmetric septal hypertrophy, idiopathic hypertrophic subaortic stenosis, hereditary hypertrophic cardiomyopathy, or idiopathic subaortic stenosis, is a hereditary disorder with characteristics of autosomal inheritance. Left ventricular hypertrophy develops, especially in the septum, as a consequence of structural changes in cardiac contractile cells. Changes in the cardiac conduction system can also be present 1.
Symptoms usually include dyspnea, fatigue, palpitations, angina, and syncope, which begin after the adolescence. The clinical picture may vary from minimal symptoms to acute myocardial infarction or sudden death 2.
The pathophysiology of FHC is complex and the physiologic changes of pregnancy and anesthesia for cesarean section or analgesia during delivery have a great impact in the hemodynamic status of those patients that can even lead to maternal death 3.
This report presents the case of a pregnant woman with FHC who underwent cesarean section. We discuss the pathophysiology of this disorder, the implications in pregnancy, as well as the objectives and anesthetic conduction.
A 34-year old pregnant woman, in her second pregnancy, diagnosed with FHC 20 years before this presentation. The patient had a history of angina and palpitations before the pregnancy, and was not taking any medications. Past anesthetic history revealed that she underwent simple epidural block for a cesarean section three years before this presentation. At that time she developed chest pain and cardiac arrhythmia, which improved after the end of the anesthesia and evolved without other problems.
In the current pregnancy, at the 33rd week she was referred to the high-risk prenatal service of the Hospital das Clínicas de Ribeirão Preto. She reported that during the pregnancy she had several episodes of palpitation, dyspnea, and chest pain of short duration. An electrocardiography showed overload of the left atrium and ventricle. The echocardiogram was compatible with familiar hypertrophic cardiomyopathy without left outlet obstruction at rest. On the 24-hour Holter monitor she presented 22 episodes of non-sustained ventricular tachycardia (NSVT), with up to six consecutive beats, and two episodes of sustained ventricular tachycardia (SVT) with more than 25 consecutive beats.
The patient was medicated with 25 mg of atenolol once a day to control cardiac arrhythmias. There was improvement of the palpitation and chest pain after the introduction of the medication. On the 24-hour Holter monitor it was observed that the arrhythmias were under control. However, the dose had to be readjusted to 12.5 mg/day due to symptomatic hypotension (80 ´ 50 mmHg). Prenatal follow-up consisted of two weekly appointments, and atenolol was maintained.
Fetal vitality and development were evaluated regularly with weekly fetal biophysical profile, by-weekly ultrasound, and morphological ultrasound. Malformation or delayed fetal development was not detected.
After the initial pre-anesthetic evaluation, the Gynecology, Anesthesiology, and Pediatric teams met and decided for an elective cesarean section under regional anesthesia. The patient signed an informed consent and, when she had 38 weeks and 5 days of pregnancy, the cesarean section was performed.
After an 8-hour fasting period, the patient was medicated with oral metochlopramide, 10 mg, and ranitidine, 50 mg, with a small amount of water. Before admission to the operating room, we made sure a cardioverter/defibrillator and a multiparameter monitor with invasive measurement of the blood pressure (Dixtal 2210) were available.
The anti-arrhythmic medication was also prepared (lidocaine, esmolol, and amiodarone), as well as the vasoactive medications (metaraminol, adrenaline, and nitroglycerine). Metaraminol was prepared for continuous infusion with 10 µg.mL-1 and for a bolus administration of 250 µg.mL-1. Besides the medications and material for general anesthesia, the equipment for cardiorespiratory and cerebral resuscitation were also available.
In the operating room, venoclysis was done with a short 18G catheter (30 mm) for fast infusion of fluids and 20G for continuous infusion of medications, followed by catheterization of the radial artery for continuous monitoring of the blood pressure. Monitoring also included a cardioscope on DII, AVF, and V5 derivations with analysis of the ST segment, analysis of arrhythmias, and pulse oximetry.
Three hundred milliliters of Ringer's lactate were infused before the blockade. This was followed by combined spinal-epidural block with the patient in the sitting position, with the subarachnoid administration of 5 µg of sufentanil, and introduction of an epidural catheter. With the patient in the left lateral decubitus and receiving oxygen via a nasal cannula, fractioned administration of 0.375% bupivacaine through the epidural catheter was instituted. Initially, 8 mL of the solution of local anesthetic were injected, and after 5 minutes another 4 mL, which were followed by two consecutive doses of 2 mL 5 minutes apart, for a total of 16 mL (60 mg) in 25 minutes.
Anesthesia was satisfactory, with a level at T6. Hemodynamic changes were discrete and an infusion of 5 mL per minute of metaraminol solution was started 5 minutes after the first dose of bupivacaine via the epidural catheter. The infusion was maintained with variable rates in order to maintain maternal blood pressure at pre-epidural block levels until delivery of the fetus. The newborn had Apgar scores in the first and fifth minutes of 9 and 10, respectively. During the procedure, maternal hydration consisted of the infusion of 1,350 mL of fluids. Urine output during the procedure totaled 60 mL and blood loss was not measured, but it was considered normal for an elective cesarean section. Postoperative hydration totaled 2,000 mL of fluids in the first 24 hours and the urine output in the first 12 hours was 420 mL.
The procedure was uneventful, without maternal or fetal intercurrences, and both mother and child where transferred to intensive care units, where they remained for 12 hours. They were both discharged in the third postoperative day in good conditions.
In familiar hypertrophic cardiomyopathy, the anterior cuspid of the mitral valve approximates the hypertrophied septum during systole, causing a left ventricular outlet obstruction (subaortic stenosis). The obstruction varies according to the degree of septal hypertrophy (anatomic changes), as well as to the dynamic changes of each cardiac cycle.
The main factors that promote an increase in left ventricular outlet obstruction are: 1) Increase in contractile strength; 2) Reduction in end-systolic volume of the left ventricle, which occurs with increased heart rate or reduction in venous return; and 3) Reduction in peripheral vascular resistance. Besides those pathophysiological changes, one should also consider the elevated risk of subendocardic ischemia secondary to ventricular hypertrophy, increased oxygen consumption, and reduction in ventricular compliance. The last one also decreases the capacity to accommodate significant increases in blood volume. All those changes, associated or not with an accessory pathway in the cardiac conduction system, increase the possibility of arrhythmias 1,4.
Physiological changes of pregnancy cause overload of the cardiorespiratory system. Some of those changes, such as blood volume, are favorable for patients with FHC, since they reduce the degree of obstruction. However, other changes, such as increase in cardiac output, heart rate, levels of catecholamines, and reduction in peripheral vascular resistance, usually result in worse symptoms, and at least two cases of sudden death during pregnancy have been reported 3,5.
Beta-blockers are widely used for the control of symptoms because they reduce the degree of left ventricular obstruction along with its anti-arrhythmic and anti-angina properties 1. However, the use of beta-blockers during pregnancy may be associated with a reduction in the rhythm of fetal growth and development, justifying a rigid follow-up, with fetal biophysical profile and fetal development with serial ultrasounds 6.
At the end of pregnancy, aorta-cava compression might result in large hemodynamic changes, and one should avoid the horizontal dorsal decubitus. The approach to the type of delivery should be based on the obstetric indication 7. In this case, we decided for a cesarean section because the patient wanted this type of delivery and she was very anxious, and it was possible that she would not cooperate with a normal delivery.
Based on the pathophysiology of the disease, the anesthetic objectives were to maintain or reduce myocardial contractility and heart rate, maintain pre- and postload, and avoid hypotension secondary to peripheral vasodilation. For the cesarean section, those objectives could be achieved with balanced general anesthesia, which is frequently used. However, regional anesthesia with slow installation of the blockade was another option 8. In this case, we chose Spinal-Epidural block with low dose of subarachnoid sufentanil (5 µg) and fractioned doses of continuous epidural bupivacaine diluted. Thus, the installation of the sympathetic blockade was gradual and without important hemodynamic repercussions. Prior hydration and vigorous hydration until the delivery of the fetus, to decrease the incidence of hypotension, should be avoided in those cases. Vigorous hydration, with more than 2,000 mL of crystalloid, associated with increased blood volume due to uterine involution and decompression of the vena cava, might cause volume overload in the immediate postoperative period that can lead to cardiac decompensation in a patient with cardiac problems. In this case, prevention and correction of hypotension should be done with predominantly a-agonist drugs; in the case presented here, metaraminol was used, since b-agonists are contraindicated because they increase cardiac contractility and heart rate and, consequently, the degree of left ventricular outlet obstruction9. Concern on maintaining pre-load without fast crystalloid infusion and, consequently, avoid sudden hemodynamic changes led to the use of continuous infusion of the vasopressor. Continuous infusion of vasopressors and metaraminol is one of them can also be done to minimize the changes in maternal blood pressure and, consequently, maintain placental perfusion 10.
Monitoring concentrated on the possibilities of subendocardic ischemia, cardiac arrhythmias, and early diagnosis of maternal hypotension. In those patients, the use of pulmonary artery catheter is controversial. On the other hand, transesophageal echocardiogram, which is mildly invasive and provides important information on the degree of left ventricular outlet obstruction, can be used, if available, when the patient is undergoing general anesthesia 11. During vaginal deliveries, transthoracic Doppler echocardiogram can also be used 12.
Close understanding among anesthesiology, obstetric, and neonatology teams, and anticipated preparation of anesthesia, are fundamental. For this reason we held a meeting with the different teams and made sure monitors, drugs, defibrillator/cardioverter were available for immediate use 13.
Intensive and prolonged monitoring during recovery from anesthesia is fundamental, since the increased blood volume after the delivery, associated with intraoperative hydration and end of the sympathetic block, might result in cardiac decompensation and pulmonary edema during this period 14,15. In the case presented here, the patient remained in intensive care for 12 hours with the same intraoperative monitoring. Epidural analgesia was also maintained with 0.125% bupivacaine associated with epidural morphine to decrease the neuro-endocrine and metabolic response to the surgical trauma. Intensive monitoring of the newborn was also important because the beta-blocker used by the mother predisposes the newborn to hypotonia, hypoglycemia, hypotension, bradycardia, and respiratory depression 16.
To conclude, simple measures, such as anesthetic planning according to the pathophysiology of the disease, preparing the medications before hand, intensive intra- and postoperative monitoring, and cooperation among the different medical teams are important for the anesthetic success of pregnant women with cardiopathies.
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Dr. Renato Mestriner Stocche
Rua Dr. João Gomes da Rocha, 835/181 Irajá
14020-550 Ribeirão Preto, SP
Submitted em 15
de dezembro de 2006
Accepted para publicação em 21 de agosto de 2007
* Received from Serviço de Anestesiologia do Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto (HC-FMRP) da Universidade de São Paulo (USP), Ribeirão Preto, SP