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Management of coarctation of the aorta during pregnancy
Management of coarctation of the aorta during pregnancy In this report, we shall describe the instantaneous electronic monitoring of the fetal heart rate at 24 weeks' gestation. The mother was undergoing resection of coarctation of the aorta. Because the fetal heart rate reflects physiological and pharmacologic events, monitoring this rate enabled the anesthesiologists and surgeons to make therapeutic intervention sooner and on a more rational basis.
Paul G. Barash, M.D., John C. Hobbins, M.D., Robert Hook, M.D., H. C. Stansel, Jr., M.D., Ruth Whittemore, M.D., and Frederick W. Hehre, M.D., New Haven, Conn.
Ihe incidence of coarctation of the aorta in the female population has been estimated between 1:1000 to 1:3000. Most patients born with coarctation have corrective surgery in their pre-teen years. However, a small proportion eludes either recognition or surgical correction. The literature contains numerous case reports describing surgical correction during pregnancy, but detailed information regarding perioperative and anesthetic management is often lacking. Case report A 24-year-old primigravida in the fifth month of pregnancy was admitted for evaluation of an uncorrected coarctation of the thoracic aorta. Past medical history revealed that a murmur had been noted in infancy but was not investigated. When she was 10 years of age, although asymtomatic, her physical findings were as follows: The blood pressure was 130/70 mm. Hg in the left arm and 94/70 in the left leg. A venous hum was heard bilaterally in the parasternal region at the second intercostal space. A Grade 2/6 to 4/6 harsh systolic murmur was heard over the entire From the Departments of Anesthesiology, Obstetrics and Gynecology, Surgery, and Pediatrics, Yale University School of Medicine and Yale-New Haven Hospital, New Haven, Conn. Received for publication Nov. 15, 1974. Address for reprints: 'Paul G. Barash, M.D., Department of Anesthesiology, 333 Cedar Street, New Haven, Conn. 06510.
precordium. Electrocardiography revealed left ventricular hypertrophy with S-T segment elevation in Leads V.-, and V„. No rib notching was seen on the chest x-ray film. Since she was asymptomatic, definitive surgery was deferred until such time as the aorta would be of adult size. Surgery was advised when the girl was 16 years old, but her parents refused the operation. At the age of 24 years, in the twentieth week of pregnancy, she was referred for obstetric care. The blood pressure was 160/76 mm. Hg in the right arm, 142/76 mm. Hg in the left arm, and 110/76 mm. Hg in the left leg. Physical examination revealed a left ventricular heave and no change in the murmur. Findings from the electrocardiogram and chest x-ray film were within normal limits. She refused to allow termination of pregnancy but did undergo cardiac catheterization. The ascending aortic pressure was 140/70 mm. Hg (mean 85 to 105) and the descending aortic pressure 110/70 mm. Hg (mean 9 0 ) . Good collateral circulation was noted. Sonar evaluation revealed that the condition of the fetus and placenta was compatible with 20 weeks' gestation, and there were no apparent fetal deformities. Laboratory studies were within normal limits. When the risks of operation and continuing pregnancy were explained, the patient consented to resection of the coarctation. She was premedicated with meperidine, 50 mg., and hydroxyzine, 100 mg. intramuscularly, at 8:45 A.M. Intravenous catheters, a central venous pressure catheter, a radial artery catheter, and an external fetal heart rate monitor were placed prior to induction of anesthesia. Thiopental, 300 mg. intravenously, was used for anesthesia, and
78 1
The Journal of
782
Barash et al.
Thoracic and Cardiovascular Surgery
MaBP'90' nwiHo
Fig. 1. The placement of retractors in the chest caused obstruction of the maternal venous return. The initial rise in fetal heart rate following placement is thought to be compensatory, after which the fetal heart rate falls for the next 1 minute, 30 seconds. Removal of the retractors returned the fetal heart rate to normal levels in 45 seconds. MaBP, Maternal arterial blood pressure. FHR, Fetal heart rate.
MaBP mniHg1
N'3300
Fig. 2. The effect of the initial attempt to cross-clamp the maternal aorta. During crossclamping, the fetal heart rate remained in the normal range but reflected the fall in maternal blood pressure when the clamp was removed 1 minute, 30 seconds later. Since fetal heart rate was normal during cross-clamping, we decided to complete the resection. MaBP, Maternal arterial blood pressure. FHR, Fetal heart rate.
intubation was facilitated with succinylcholine, 100 mg. intravenously. The patient was positioned in the right lateral decubitus position with no change in vital signs. Anesthesia was maintained with halothane and nitrous oxide-oxygen (50:50). The patient was placed on an Ohio volumelimited respirator and was ventilated 8 times per minute at a tidal volume of 900 ml. with an inspiratory pressure of 30 cm. of water. After an incision was made through the fourth intercostal space, the thoracic aorta was mobilized and the coarctation excised and repaired by primary endto-end anastomosis. During dissection of the coarcted segment, the fetal heart rate averaged 110 to 115 beats per minute but occasionally fell below 100 with surgi-
cal manipulation. At one point when retractors obstructed the venous return to the heart, the fetal heart rate fell to 66 beats per minute, concomitant with the decrease in maternal blood pressure (Fig. 1). When the retractors were repositioned, the fetal heart rate returned to normal. At other times, the depth of halothane anesthesia was considered to be the cause of borderline decreases in fetal heart rate; decreasing the concentration of halothane prompted the fetal heart rate to return again to normal. Further, when the aorta was cross-clamped (Fig. 2 ) , the fetal heart rate was satisfactorily maintained until the clamp was removed and the maternal blood pressure fell. The decrease in blood pressure caused a temporary drop in fetal heart rate. Reapplication
Volume 69 Number 5
Coarctation of aorta re pregnancy
783
May, 1975
of the aortic clamp returned both maternal blood pressure and fetal heart rate to normal. Removal of the clamp at the completion of the aortic anastomosis caused neither maternal blood pressure nor fetal heart rate to change. Despite our efforts to maintain the Pa,v>, in the 30 to 35 mm. Hg range (normal ~ 32 mm. Hg at 24 weeks' gestation), the Pa
son, but his motor development has been normal. Lack of adequate stimulation in the home environment is thought to be the source of some of the inadequacy.
Discussion The decision to resect the coarctation at 20 weeks' gestation was made for the following reasons: 1. Goodwin1 reported an over-all 9.5 per cent mortality rate in individual pregnancies with uncorrected coarctation. 2. Mortensen2 has shown that fewer than 10 per cent of pregnancies were uncomplicated in patients with unresected coarctation. However, 85 per cent of pregnancies were considered normal in patients with previously resected coarctation. Furthermore, 50 per cent of patients with unresected coarctation had cardiovascular-renal complications, whereas only 5 per cent of the group with previous resection had these problems. Since this patient refused termination of pregnancy, the operative risk of resection of the coarctation appeared less than the expected risk of maternal death, and the probability of an uncomplicated pregnancy improved with correction of the coarctation. Halothane was chosen as the primary anesthetic agent because the woman's cardiovascular responses could be modulated and because, as a myometrial depressant, the drug would also decrease the risk of premature labor. High concentrations of oxygen could be given. Since the patient was in the second trimester of pregnancy, the risk of birth defects from commonly used anesthetic agents was quite small.' Reduction of uterine blood flow interferring with placental gas exchange may cause changes in fetal heart rate. Since the relationship between maternal hypotension, uterine blood flow, and fetal heart rate patterns are well established, careful monitoring of the fetal heart rate during surgery provided an indication of fetal welfare.4 As may be seen from Figs. 1 and 2, the fetal heart rate was an exquisite reflection of the maternal blood pressure and maternal cardiac
The Journal of
7 84
Barash et al.
Thoracic and Cardiovascular Surgery
output: Decreases in blood pressure were almost instantly mirrored in accelerations and decelerations in fetal heart rate, presumably reflecting decreases in oxygenation. The management of hypertension in this patient deserves special consideration, because halothane was used to control intraoperative variation in blood pressure. Halothane exerts its action on the cardiovascular system"' by (1) vasomotor center depression, (2) vagal simulation, (3) negative chronotropism, (4) negative ionotropism, (5) ganglionic blockade, and (6) peripheral vasodilation. Although no one effect is predominant, judicious use of this agent can modulate the patient's cardiovascular responses. Dilute intravenous-drip trimethaphan was utilized in the immediate postoperative period because of its rapid action, evanescence, and ease of control. Trimethaphan probably does not cross the placenta because of the high degree of ionization. Although reserpine may cause depletion of fetal catecholamines, the risk was acceptable because of the advantages of its use. This patient exhibited paradoxical postoperative hypertension; hence, some depletion of norepinephrine stores facilitated the return to normotension. She was placed on a regimen of methyldopa to maintain normotension during the remainder of the pregnancy. The indications for induction of labor
were as follows: (1) favorable condition of the cervix (2 cm. dilated); (2) full term by both dates and physical examination; (3) fetal pulmonary maturity, as indicated by the lecithin/sphingomyelin ratio. Continuous lumbar peridural analgesia was chosen to control the discomfort of labor and, possibly, any hypertension which ■might occur during the first stage of labor. Although peridural anesthesia is not a recognized means of controlling hypertension during labor, Bonica'' states that it may be used cautiously. Since a large degree of obstetric hypotension is related to aortocaval compression, electronic monitoring of the fetus provided an indication of fetal well being. REFERENCES 1 Goodwin, J. F.: Pregnancy and Coarctation of the Aorta, Lancet 1: 16, 1958. 2 Mortensen, J. D., and Joelsson, I.: Coarctation of the Aorta and Pregnancy, J. A. M. A. 191: 596, 1965. 3 Adamsons, K., and Joelsson, I.: The Effects of Pharmacologic Agents Upon the Fetus and Newborn, Am. J. Obstet. Gynecol. 96: 437, 1966. 4 Hon, E. H.: An Atlas of Fetal Heart Rate Patterns, New Haven, Conn. 1968, Hardy Press, Inc. 5 Price, H. L., and Price, M. L.: Has Halothane a Predominant Circulatory Action? Anesthesiology 27: 764. 1966. 6 Bonica, J. J.: Principles and Practice of Obstetric Analgesia and Anesthesia, Philadelphia, Pa., 1969, F. A. Davis Company, p. 981.
Paul G. Barash, M.D., John C. Hobbins, M.D., Robert Hook, M.D., H. C. Stansel, Jr., M.D., Ruth Whittemore, M.D., and Frederick W. Hehre, M.D., New Haven, Conn.
Ihe incidence of coarctation of the aorta in the female population has been estimated between 1:1000 to 1:3000. Most patients born with coarctation have corrective surgery in their pre-teen years. However, a small proportion eludes either recognition or surgical correction. The literature contains numerous case reports describing surgical correction during pregnancy, but detailed information regarding perioperative and anesthetic management is often lacking. Case report A 24-year-old primigravida in the fifth month of pregnancy was admitted for evaluation of an uncorrected coarctation of the thoracic aorta. Past medical history revealed that a murmur had been noted in infancy but was not investigated. When she was 10 years of age, although asymtomatic, her physical findings were as follows: The blood pressure was 130/70 mm. Hg in the left arm and 94/70 in the left leg. A venous hum was heard bilaterally in the parasternal region at the second intercostal space. A Grade 2/6 to 4/6 harsh systolic murmur was heard over the entire From the Departments of Anesthesiology, Obstetrics and Gynecology, Surgery, and Pediatrics, Yale University School of Medicine and Yale-New Haven Hospital, New Haven, Conn. Received for publication Nov. 15, 1974. Address for reprints: 'Paul G. Barash, M.D., Department of Anesthesiology, 333 Cedar Street, New Haven, Conn. 06510.
precordium. Electrocardiography revealed left ventricular hypertrophy with S-T segment elevation in Leads V.-, and V„. No rib notching was seen on the chest x-ray film. Since she was asymptomatic, definitive surgery was deferred until such time as the aorta would be of adult size. Surgery was advised when the girl was 16 years old, but her parents refused the operation. At the age of 24 years, in the twentieth week of pregnancy, she was referred for obstetric care. The blood pressure was 160/76 mm. Hg in the right arm, 142/76 mm. Hg in the left arm, and 110/76 mm. Hg in the left leg. Physical examination revealed a left ventricular heave and no change in the murmur. Findings from the electrocardiogram and chest x-ray film were within normal limits. She refused to allow termination of pregnancy but did undergo cardiac catheterization. The ascending aortic pressure was 140/70 mm. Hg (mean 85 to 105) and the descending aortic pressure 110/70 mm. Hg (mean 9 0 ) . Good collateral circulation was noted. Sonar evaluation revealed that the condition of the fetus and placenta was compatible with 20 weeks' gestation, and there were no apparent fetal deformities. Laboratory studies were within normal limits. When the risks of operation and continuing pregnancy were explained, the patient consented to resection of the coarctation. She was premedicated with meperidine, 50 mg., and hydroxyzine, 100 mg. intramuscularly, at 8:45 A.M. Intravenous catheters, a central venous pressure catheter, a radial artery catheter, and an external fetal heart rate monitor were placed prior to induction of anesthesia. Thiopental, 300 mg. intravenously, was used for anesthesia, and
78 1
The Journal of
782
Barash et al.
Thoracic and Cardiovascular Surgery
MaBP'90' nwiHo
Fig. 1. The placement of retractors in the chest caused obstruction of the maternal venous return. The initial rise in fetal heart rate following placement is thought to be compensatory, after which the fetal heart rate falls for the next 1 minute, 30 seconds. Removal of the retractors returned the fetal heart rate to normal levels in 45 seconds. MaBP, Maternal arterial blood pressure. FHR, Fetal heart rate.
MaBP mniHg1
N'3300
Fig. 2. The effect of the initial attempt to cross-clamp the maternal aorta. During crossclamping, the fetal heart rate remained in the normal range but reflected the fall in maternal blood pressure when the clamp was removed 1 minute, 30 seconds later. Since fetal heart rate was normal during cross-clamping, we decided to complete the resection. MaBP, Maternal arterial blood pressure. FHR, Fetal heart rate.
intubation was facilitated with succinylcholine, 100 mg. intravenously. The patient was positioned in the right lateral decubitus position with no change in vital signs. Anesthesia was maintained with halothane and nitrous oxide-oxygen (50:50). The patient was placed on an Ohio volumelimited respirator and was ventilated 8 times per minute at a tidal volume of 900 ml. with an inspiratory pressure of 30 cm. of water. After an incision was made through the fourth intercostal space, the thoracic aorta was mobilized and the coarctation excised and repaired by primary endto-end anastomosis. During dissection of the coarcted segment, the fetal heart rate averaged 110 to 115 beats per minute but occasionally fell below 100 with surgi-
cal manipulation. At one point when retractors obstructed the venous return to the heart, the fetal heart rate fell to 66 beats per minute, concomitant with the decrease in maternal blood pressure (Fig. 1). When the retractors were repositioned, the fetal heart rate returned to normal. At other times, the depth of halothane anesthesia was considered to be the cause of borderline decreases in fetal heart rate; decreasing the concentration of halothane prompted the fetal heart rate to return again to normal. Further, when the aorta was cross-clamped (Fig. 2 ) , the fetal heart rate was satisfactorily maintained until the clamp was removed and the maternal blood pressure fell. The decrease in blood pressure caused a temporary drop in fetal heart rate. Reapplication
Volume 69 Number 5
Coarctation of aorta re pregnancy
783
May, 1975
of the aortic clamp returned both maternal blood pressure and fetal heart rate to normal. Removal of the clamp at the completion of the aortic anastomosis caused neither maternal blood pressure nor fetal heart rate to change. Despite our efforts to maintain the Pa,v>, in the 30 to 35 mm. Hg range (normal ~ 32 mm. Hg at 24 weeks' gestation), the Pa
son, but his motor development has been normal. Lack of adequate stimulation in the home environment is thought to be the source of some of the inadequacy.
Discussion The decision to resect the coarctation at 20 weeks' gestation was made for the following reasons: 1. Goodwin1 reported an over-all 9.5 per cent mortality rate in individual pregnancies with uncorrected coarctation. 2. Mortensen2 has shown that fewer than 10 per cent of pregnancies were uncomplicated in patients with unresected coarctation. However, 85 per cent of pregnancies were considered normal in patients with previously resected coarctation. Furthermore, 50 per cent of patients with unresected coarctation had cardiovascular-renal complications, whereas only 5 per cent of the group with previous resection had these problems. Since this patient refused termination of pregnancy, the operative risk of resection of the coarctation appeared less than the expected risk of maternal death, and the probability of an uncomplicated pregnancy improved with correction of the coarctation. Halothane was chosen as the primary anesthetic agent because the woman's cardiovascular responses could be modulated and because, as a myometrial depressant, the drug would also decrease the risk of premature labor. High concentrations of oxygen could be given. Since the patient was in the second trimester of pregnancy, the risk of birth defects from commonly used anesthetic agents was quite small.' Reduction of uterine blood flow interferring with placental gas exchange may cause changes in fetal heart rate. Since the relationship between maternal hypotension, uterine blood flow, and fetal heart rate patterns are well established, careful monitoring of the fetal heart rate during surgery provided an indication of fetal welfare.4 As may be seen from Figs. 1 and 2, the fetal heart rate was an exquisite reflection of the maternal blood pressure and maternal cardiac
The Journal of
7 84
Barash et al.
Thoracic and Cardiovascular Surgery
output: Decreases in blood pressure were almost instantly mirrored in accelerations and decelerations in fetal heart rate, presumably reflecting decreases in oxygenation. The management of hypertension in this patient deserves special consideration, because halothane was used to control intraoperative variation in blood pressure. Halothane exerts its action on the cardiovascular system"' by (1) vasomotor center depression, (2) vagal simulation, (3) negative chronotropism, (4) negative ionotropism, (5) ganglionic blockade, and (6) peripheral vasodilation. Although no one effect is predominant, judicious use of this agent can modulate the patient's cardiovascular responses. Dilute intravenous-drip trimethaphan was utilized in the immediate postoperative period because of its rapid action, evanescence, and ease of control. Trimethaphan probably does not cross the placenta because of the high degree of ionization. Although reserpine may cause depletion of fetal catecholamines, the risk was acceptable because of the advantages of its use. This patient exhibited paradoxical postoperative hypertension; hence, some depletion of norepinephrine stores facilitated the return to normotension. She was placed on a regimen of methyldopa to maintain normotension during the remainder of the pregnancy. The indications for induction of labor
were as follows: (1) favorable condition of the cervix (2 cm. dilated); (2) full term by both dates and physical examination; (3) fetal pulmonary maturity, as indicated by the lecithin/sphingomyelin ratio. Continuous lumbar peridural analgesia was chosen to control the discomfort of labor and, possibly, any hypertension which ■might occur during the first stage of labor. Although peridural anesthesia is not a recognized means of controlling hypertension during labor, Bonica'' states that it may be used cautiously. Since a large degree of obstetric hypotension is related to aortocaval compression, electronic monitoring of the fetus provided an indication of fetal well being. REFERENCES 1 Goodwin, J. F.: Pregnancy and Coarctation of the Aorta, Lancet 1: 16, 1958. 2 Mortensen, J. D., and Joelsson, I.: Coarctation of the Aorta and Pregnancy, J. A. M. A. 191: 596, 1965. 3 Adamsons, K., and Joelsson, I.: The Effects of Pharmacologic Agents Upon the Fetus and Newborn, Am. J. Obstet. Gynecol. 96: 437, 1966. 4 Hon, E. H.: An Atlas of Fetal Heart Rate Patterns, New Haven, Conn. 1968, Hardy Press, Inc. 5 Price, H. L., and Price, M. L.: Has Halothane a Predominant Circulatory Action? Anesthesiology 27: 764. 1966. 6 Bonica, J. J.: Principles and Practice of Obstetric Analgesia and Anesthesia, Philadelphia, Pa., 1969, F. A. Davis Company, p. 981.