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Anesthesia, Cardiopulmonary Bypass, and the Pregnant Patient

1991; Elsevier BV; Volume: 66; Issue: 4 Linguagem: Inglês

10.1016/s0025-6196(12)60666-1

1942-5546

Robert A. Strickland, William C. Oliver, Robert C. Chantigian, Judith A. Ney, Gordon K. Danielson,

Airway Management and Intubation Techniques

For the perioperative management of pregnant patients with severe cardiac or aortic disease who require a cardiac surgical procedure and cardiopulmonary bypass, a close, cohesive, working relationship must exist among several medical and surgical specialties. For appropriate management, the well-being of both the mother and the fetus must be considered. The best interests of the mother and the fetus may not coincide, and optimal therapy for one may be inappropriate for the other. We present 10 cases of severe cardiac or aortic disease in pregnant women who required surgical intervention. Eight patients underwent cardiopulmonary bypass during pregnancy, and two patients had cesarean section performed immediately before cardiopulmonary bypass. We also discuss the pertinent pharmacologic aspects related to the perioperative period and the management of cardiopulmonary bypass for the pregnant patient. For the perioperative management of pregnant patients with severe cardiac or aortic disease who require a cardiac surgical procedure and cardiopulmonary bypass, a close, cohesive, working relationship must exist among several medical and surgical specialties. For appropriate management, the well-being of both the mother and the fetus must be considered. The best interests of the mother and the fetus may not coincide, and optimal therapy for one may be inappropriate for the other. We present 10 cases of severe cardiac or aortic disease in pregnant women who required surgical intervention. Eight patients underwent cardiopulmonary bypass during pregnancy, and two patients had cesarean section performed immediately before cardiopulmonary bypass. We also discuss the pertinent pharmacologic aspects related to the perioperative period and the management of cardiopulmonary bypass for the pregnant patient. Cardiac disease occurs in fewer than 2% of pregnant women;1Otterson WN Dunnihoo DR Cardiac disease.in: Pauerstein CJ Clinical Obstetrics. John Wiley & Sons, New York1987: 627-644Google Scholar therefore, most clinicians are rarely concerned with this problem. The care of the pregnant patient with heart disease can be challenging, inasmuch as two lives are involved. The patient with cardiovascular disease who is well compensated in the nonpregnant state may have acute cardiac decompensation as the demand on the cardiorespiratory system increases substantially during pregnancy. During labor and delivery, the cardiac output may be twice that of the nonpregnant state, and a patient who has severe cardiac impairment, whether it is the result of congenital, rheumatic, or coronary artery disease, may have an increased risk for decompensation. Fetal mortality may exceed 50% in women with severe, untreated congenital heart disease.2McAnulty JH Metcalfe J Ueland K Heart disease and pregnancy.in: Hurst JW Schlant RC Rackley CE Sonnenblick EH Wenger NK The Heart: Arteries and Veins. Seventh edition. McGraw-Hill Information Services, New York1990: 1465-1478Google Scholar Although studies of outcome have suggested no increase in maternal mortality associated with cardiopulmonary bypass (CPB), the related fetal mortality is high.3Bernal JM Miralles PJ Cardiac surgery with cardiopulmonary bypass during pregnancy.Obstet Gynecol Surv. 1986; 41: 1-6Crossref PubMed Google Scholar Even though profound hypothermic bypass may be correct for the nonpregnant patient, it can be hazardous for the fetus. Nonpulsatile blood flow and hypotension associated with CPB may adversely affect placental blood flow. Recent reviews of cardiac disease during pregnancy1Otterson WN Dunnihoo DR Cardiac disease.in: Pauerstein CJ Clinical Obstetrics. John Wiley & Sons, New York1987: 627-644Google Scholar, 2McAnulty JH Metcalfe J Ueland K Heart disease and pregnancy.in: Hurst JW Schlant RC Rackley CE Sonnenblick EH Wenger NK The Heart: Arteries and Veins. Seventh edition. McGraw-Hill Information Services, New York1990: 1465-1478Google Scholar have not dealt in depth with the dramatic maternal and fetal physiologic alterations that occur during CPB and general anesthesia. In this report, we present eight cases at our institution of CPB during pregnancy for the correction or palliation of life-threatening cardiac or aortic lesions. For comparison, we also present two cases in which cesarean section was performed before the initiation of CPB. Pertinent aspects about the physiologic features of pregnancy, perioperative pharmacologic therapy, and CPB will be discussed. The Mayo Clinic experience with pregnant patients who required cardiac or aortic surgical procedures is summarized in Table 1. Maternal age ranged from 17 to 43 years, and gestational age varied from 7 to 35 weeks.Table 1Summary of 10 Mayo Clinic Cases of Cardiac or Aortic Surgical Procedures in Pregnant Patients (1965 Through 1989)*The fetal heart tones were monitored in three patients (cases 8, 9, and 10), and fetal distress as indicated by fetal bradycardia was detected in two (preoperatively in case 8 and during induction of anesthesia in case 10, which prompted performance of a cesarean). CPB = cardiopulmonary bypass; CPR = cardiopulmonary resuscitation; EGA = estimated gestational age; hypn = hypertension; L = left; mod = moderate; neuro = neurologic; PA = pulmonary artery; R = right; RDS = respiratory distress syndrome; RV = right ventricular; SV = supraventricular; temp = temperature; TI = tricuspid insufficiency; VSD = ventricular septal defect; WPW = Wolff-Parkinson-White.CaseAge (yr)Gestation (wk)†At time of operation.DiagnosisIndication for operationSurgical procedureCPB time (min)‡CPB flows ranged from 2.0 to 2.4 liters/min per m2.Lowest tempType of deliveryEGAOutcome1288Tetralogy of Fallot, Pott's shuntCardiac failureTetralogy repair10124°C§This patient had circulatory arrest for 16 minutes.Cesarean35 wkNormal baby24314Calcific aortic stenosisCardiac failureAortic valve replacement6436°CCesareanTermNormal baby32117Severe aortic stenosis, mitral regurgitation and stenosisSyncope and paroxysmal SV tachycardiaAortic and mitral valve replacements7332°CVaginalTermStillborn41720Aneurysm of descending thoracic aortaExpanding aneurysmResection of aneurysm, insertion of graft3935°CVaginalTermSmall baby with VSD5187Ebstein's anomaly, WPW syndromeRefractory arrhythmias, TIAccessory pathway ablation, tricuspid annuloplasty10223°CCesarean32 wkNormal baby62215Mitral regurgitation, cleft mitral valvePulmonary edemaMitral valve repair4732°CCesarean36 wkMultiple congenital defects72735Thrombosed mechanical aortic valveSevere cardiac failure, pulmonary edemaDébridement of aortic valve15428°CElective cesarean before CPB35 wkMaternal death82425Severe mitral stenosis, mod tricuspid regurgitation, increased RV and PA pressures, severe pregnancy-induced hypnSevere mitral stenosisMitral valve replacement5328°CFetus died intraoperatively25 wkApgar scores of 0 and 4, CPR needed, RDS, developmental delay93525Patent foramen ovaleNeuro deficit after R-L embolusClosure of patent foramen1836°CVaginal38 wkNormal baby103030Biscuspid aortic valve, severe stenosisSevere aortic stenosis, cardiac failureAortic valve replacement12820°CEmergency cesarean before CPB30 wkPrematurity and RDS* The fetal heart tones were monitored in three patients (cases 8, 9, and 10), and fetal distress as indicated by fetal bradycardia was detected in two (preoperatively in case 8 and during induction of anesthesia in case 10, which prompted performance of a cesarean). CPB = cardiopulmonary bypass; CPR = cardiopulmonary resuscitation; EGA = estimated gestational age; hypn = hypertension; L = left; mod = moderate; neuro = neurologic; PA = pulmonary artery; R = right; RDS = respiratory distress syndrome; RV = right ventricular; SV = supraventricular; temp = temperature; TI = tricuspid insufficiency; VSD = ventricular septal defect; WPW = Wolff-Parkinson-White.† At time of operation.‡ CPB flows ranged from 2.0 to 2.4 liters/min per m2.§ This patient had circulatory arrest for 16 minutes. Open table in a new tab Six patients had severe aortic or mitral valve disease (or both), and one patient each had tetralogy of Fallot, an aneurysm of the descending thoracic aorta, Wolff-Parkinson-White syndrome and Ebstein's anomaly, and a patent foramen ovale. Indications for surgical treatment were related to cardiac complications associated with the increased demands that pregnancy placed on the heart, an expanding aortic aneurysm, intractable arrhythmias, and the need to prevent further central nervous system embolic injury from right-to-left shunting associated with a patent foramen ovale. Two patients (cases 7 and 10) underwent cesarean section before CPB. The total CPB time for the pregnant patients ranged from 18 to 102 minutes. Of considerable interest, one patient (case 1) had circulatory arrest for 16 minutes at a core temperature of 24°C. Another patient (case 5) denied the possibility of being pregnant and was cooled to 23°C, without circulatory arrest. In the other pregnant patients on CPB, the temperature ranged from 28°C to 36°C. Various primary anesthetic techniques were used: a combination of isoflurane and fentanyl citrate in four cases (cases 6, 8, 9, and 10), halothane alone in three (cases 1, 2, and 4) and with meperidine hydrochloride in one (case 5), ketamine hydrochloride and fentanyl citrate in one (case 7), and meperidine hydrochloride and nitrous oxide in one (case 3). In addition, three patients (cases 7, 8, and 10) had post-CPB inotropic or vasodilator therapy. Postoperative premature labor developed in only one patient (case 9) and resolved after intravenous administration of magnesium sulfate. One fetus, at 25 weeks of gestation, died intraoperatively. Three fetuses were delivered 4 to 8 weeks preterm after premature labor. One baby delivered at term was stillborn, and another had multiple congenital abnormalities. It is important to emphasize the management dilemma involved with these types of patients. Sometimes determining the best therapeutic choice and deciding whether the mother or the fetus should receive priority are difficult challenges. In one patient (case 7) in the 35th week of gestation, the baby was delivered by cesarean section before the cardiac procedure. After delivery of the baby, the mother sustained a cardiac arrest, and CPB was instituted emergently. After the initial attempt to discontinue CPB, the hemodynamics deteriorated after administration of protamine sulfate, and CPB had to be resumed. Subsequently, the patient could not be weaned from CPB. Another patient (case 10), who had severe aortic stenosis and acute cardiac decompensation at 30 weeks of gestation, was to undergo aortic valve replacement in an effort to allow the baby a few more weeks to mature. During the induction of anesthesia, fetal bradycardia suggestive of fetal distress occurred. The baby was delivered by cesarean section, and the mother tolerated the delivery and subsequent cardiac operation without major problems. Physiologic changes that occur during pregnancy frequently alter the management of anesthesia and cardiac surgical procedures. The adverse consequences of these changes can usually be minimized if they are understood and appreciated. We will review the pertinent aspects of physiologic changes during pregnancy, and further details may be found in several recent publications.1Otterson WN Dunnihoo DR Cardiac disease.in: Pauerstein CJ Clinical Obstetrics. John Wiley & Sons, New York1987: 627-644Google Scholar, 2McAnulty JH Metcalfe J Ueland K Heart disease and pregnancy.in: Hurst JW Schlant RC Rackley CE Sonnenblick EH Wenger NK The Heart: Arteries and Veins. Seventh edition. McGraw-Hill Information Services, New York1990: 1465-1478Google Scholar, 4Cheek TG Gutsche BB Maternal physiologic alterations during pregnancy.in: Shnider SM Levinson G Anesthesia for Obstetrics. Second edition. Williams & Wilkins, Baltimore1987: 3-13Google Scholar Uterine blood flow (UBF) is approximately 3% of the total cardiac output during the first trimester and increases to approximately 10 to 15% during the third trimester. This change, in addition to a decrease in systemic vascular resistance, results in an increased cardiac output that reaches a level approximately 30 to 40% above the nonpregnant level by the 30th week of gestation. The blood pressure (BP) normally remains unchanged or decreases slightly despite the increase in cardiac output. During the second and third trimesters, the enlarging uterus can mechanically produce compression of the inferior vena cava against the spine, especially when the pregnant patient is in the supine position. This situation will decrease venous return and cardiac output and may substantially diminish uteroplacental perfusion. Compression of the aorta by the gravid uterus can also decrease uteroplacental perfusion. Thus, after the first trimester, the supine position must be avoided intraoperatively if possible, either by placing a wedge or blanket roll beneath the right hip or by rotating the operating table to the left. Such measures should displace the gravid uterus off the major abdominal vessels without appreciably altering the operative field. Mechanical ventilation can profoundly affect uterine blood and the fetus. In nonanesthetized pregnant ewes, mechanical hyperventilation resulted in a decrease in UBF of 25% during hypocarbia and, with the addition of carbon dioxide to the respiratory gases, during normocarbia and hypercarbia.5Levinson G Shnider SM deLorimier AA Steffenson JL Effects of maternal hyperventilation on uterine blood flow and fetal oxygenation and acid-base status.Anesthesiology. 1974; 40: 340-347Crossref PubMed Google Scholar Maternal BP remained unchanged during hyperventilation, and the adverse effect on UBF was thought to be the result of the mechanical effects of positive-pressure ventilation—that is, a decrease in venous return and cardiac output.5Levinson G Shnider SM deLorimier AA Steffenson JL Effects of maternal hyperventilation on uterine blood flow and fetal oxygenation and acid-base status.Anesthesiology. 1974; 40: 340-347Crossref PubMed Google Scholar In a similar study, UBF decreased with the production of respiratory alkalemia by hyperventilation in anesthetized pregnant ewes.6Motoyama EK Rivard G Acheson F Cook CD The effect of changes in maternal pH and Pco2 on the Po2 of fetal lambs.Anesthesiology. 1967; 28: 891-903Crossref PubMed Google Scholar Maternal hyperventilation and respiratory alkalemia also decrease fetal arterial oxygen tension and oxygen content despite increases in maternal oxygenation.5Levinson G Shnider SM deLorimier AA Steffenson JL Effects of maternal hyperventilation on uterine blood flow and fetal oxygenation and acid-base status.Anesthesiology. 1974; 40: 340-347Crossref PubMed Google Scholar, 6Motoyama EK Rivard G Acheson F Cook CD The effect of changes in maternal pH and Pco2 on the Po2 of fetal lambs.Anesthesiology. 1967; 28: 891-903Crossref PubMed Google Scholar Maternal metabolic alkalemia produced by the administration of sodium bicarbonate similarly results in a decreased fetal arterial oxygen tension and oxygen content.6Motoyama EK Rivard G Acheson F Cook CD The effect of changes in maternal pH and Pco2 on the Po2 of fetal lambs.Anesthesiology. 1967; 28: 891-903Crossref PubMed Google Scholar, 7Ralston DH Shnider SM deLorimier AA Uterine blood flow and fetal acid-base changes after bicarbonate administration to the pregnant ewe.Anesthesiology. 1974; 40: 348-353Crossref PubMed Google Scholar This diminished fetal arterial oxygen tension is probably attributable to a left shift of the maternal oxygen-hemoglobin dissociation curve. Because fetal mortality is increased in pregnant women who undergo a surgical procedure and CPB,3Bernal JM Miralles PJ Cardiac surgery with cardiopulmonary bypass during pregnancy.Obstet Gynecol Surv. 1986; 41: 1-6Crossref PubMed Google Scholar an understanding of potential problems and how to treat them may improve fetal outcome. The baseline fetal heart rate (FHR) normally varies from 120 to 160 beats/min. It can be reliably monitored transabdominally by Doppler techniques as early as the 12th week of gestation. FHR, variability of FHR, and uterine activity may be useful in evaluating the fetal status during anesthesia and a surgical procedure. Intraoperative fetal tachycardia may occur because of placental transfer after maternal administration of drugs such as sympathomimetics (for example, ritodrine hydrochloride and terbutaline sulfate) or parasympatholytics (for example, atropine sulfate). Fetal bradycardia may be due to fetal hypoxia or acidosis, maternal hypothermia, or the placental transfer of maternally administered drugs such as propranolol hydrochloride. Fetal hypoxia that produces bradycardia may result from a decrease in the oxygen content of maternal blood, a decrease in uterine perfusion pressure, or an increase in uterine artery resistance. The last two factors decrease the delivery of oxygen to the placenta by decreasing UBF. Variability in FHR is considered a measure of fetal well-being. Maternal factors such as hypoxemia, fever, and the administration of various medications, including local and general anesthetics, benzodiazepines, narcotics, and atropine, decrease the variability of the FHR. Although general anesthesia reduces the variability, the FHR usually remains in the normal range. The variability of the FHR reverts to normal when use of anesthetics or other drugs is discontinued.8Liu PL Warren TM Ostheimer GW Weiss JB Liu LMP Foetal monitoring in parturients undergoing surgery unrelated to pregnancy.Can Anaesth Soc J. 1985; 32: 525-532Crossref PubMed Scopus (12) Google Scholar Fetal factors that reduce the variability include acidosis, immaturity, and sleep cycles. The effects of uterine contractions on FHR are beyond the scope of this article but can be reviewed in appropriate obstetric textbooks. Risks to the fetus and the potential for premature labor necessitating delivery need to be discussed preoperatively with the patient. Fetal morbidity and mortality are substantial if delivery occurs at 24 to 26 weeks of gestation, and long-term neurologic sequelae occur in at least 20% of these premature fetuses. After 26 weeks of gestation, most tertiary-care centers achieve 80% survival, and the outcome is good. Cesarean section during CPB has been reported,9Martin MC Pernoll ML Boruszak AN Jones JW LoCicero III, J Cesarean section while on cardiac bypass: report of a case.Obstet Gynecol. 1981; 57: 41S-45SPubMed Google Scholar and emergency cesarean section should be seriously considered at this gestational age if severe fetal bradycardia occurs, even if the patient is on CPB. At 30 weeks of gestation, more than 99% of fetuses will survive if delivered, and prebypass cesarean section should be considered. Fetuses after 34 weeks of gestational age should be delivered before a maternal bypass procedure if the maternal status allows. Another perinatal consideration in mothers who require surgical treatment of congenital heart disease is the increased incidence of fetal congenital heart disease.1Otterson WN Dunnihoo DR Cardiac disease.in: Pauerstein CJ Clinical Obstetrics. John Wiley & Sons, New York1987: 627-644Google Scholar, 10Whittemore R Hobbins JC Engle MA Pregnancy and its outcome in women with and without surgical treatment of congenital heart disease.Am J Cardiol. 1982; 50: 641-651Abstract Full Text PDF PubMed Google Scholar At 16 weeks of gestation and later, fetal echocardiography can be performed, and those fetuses with severe cardiac lesions can be managed appropriately. Detailed high-resolution ultrasound examination of the fetus can also be performed to evaluate noncardiac anatomy; thus, appropriate decisions can be made if other severe fetal abnormalities are identified. Reportedly, 0.4 to 2.2% of women undergo anesthesia and surgical treatment while pregnant.11Brodsky JB Cohen EN Brown Jr, BW Wu ML Whitcher C Surgery during pregnancy and fetal outcome.Am J Obstet Gynecol. 1980; 138: 1165-1167Abstract Full Text PDF PubMed Google Scholar, 12Shnider SM Webster GM Maternal and fetal hazards of surgery during pregnancy.Am J Obstet Gynecol. 1965; 92: 891-900Abstract Full Text PDF PubMed Google Scholar, 13Smith BE Fetal prognosis after anesthesia during gestation.Anesth Analg. 1963; 42: 521-526Crossref PubMed Google Scholar Concerns about fetal development and teratogenicity exist whenever any drug is administered to pregnant women, especially during the first trimester when fetal organogenesis is occurring. The effects of isolated exposures to various anesthetics in pregnant humans have not, for the most part, been elucidated. Randomized clinical trials to assess the effects of drugs on the pregnant human female, the uteroplacental unit, and the fetus are neither ethical nor feasible. Thus, the information published about the effects of anesthetics and other drugs used during cardiac operations has been obtained from human studies limited by these restrictions and from animal studies that frequently have not simulated clinical situations. As a result, many aspects about the effects of drugs on the maternofetal unit are uncertain or unknown. Drugs used for anesthesia do not seem to cause fetal abnormalities.11Brodsky JB Cohen EN Brown Jr, BW Wu ML Whitcher C Surgery during pregnancy and fetal outcome.Am J Obstet Gynecol. 1980; 138: 1165-1167Abstract Full Text PDF PubMed Google Scholar, 12Shnider SM Webster GM Maternal and fetal hazards of surgery during pregnancy.Am J Obstet Gynecol. 1965; 92: 891-900Abstract Full Text PDF PubMed Google Scholar, 13Smith BE Fetal prognosis after anesthesia during gestation.Anesth Analg. 1963; 42: 521-526Crossref PubMed Google Scholar, 14Duncan PG Pope WDB Cohen MM Greer N Fetal risk of anesthesia and surgery during pregnancy.Anesthesiology. 1986; 64: 790-794Crossref PubMed Google Scholar In one study, premature labor and delivery were found to occur primarily as a result of the disorder that necessitated the surgical procedure and not as a result of the anesthetic agent, and no specific anesthetic technique or agent was superior to others.12Shnider SM Webster GM Maternal and fetal hazards of surgery during pregnancy.Am J Obstet Gynecol. 1965; 92: 891-900Abstract Full Text PDF PubMed Google Scholar In another study, in which 2,565 pregnant women who required surgical treatment during the first and second trimesters were compared with the same number of matched control subjects,14Duncan PG Pope WDB Cohen MM Greer N Fetal risk of anesthesia and surgery during pregnancy.Anesthesiology. 1986; 64: 790-794Crossref PubMed Google Scholar operative intervention, especially gynecologic procedures performed under general anesthesia, resulted in an increased rate of abortion, although no increase was noted in congenital malformations. The authors were unable to determine whether the operation or the effects of anesthesia on the uterus and UBF caused the increased rate of abortions. The commonly used nonnarcotic induction agents include thiopental sodium, ketamine, etomidate, and benzodiazepines such as diazepam and midazolam hydrochloride. As familiarity with propofol increases, this agent may also assume a more prominent role for induction of anesthesia for cardiac surgical procedures. Thiopental administered to parturients at cesarean section has been shown to have a larger apparent and steady-state volume of distribution when compared with that in nonpregnant women, and the elimination half-life for thiopental is also longer.15Morgan DJ Blackman GL Paull JD Wolf LJ Pharmacokinetics and plasma binding of thiopental. II. Studies at cesarean section.Anesthesiology. 1981; 54: 474-480Crossref PubMed Google Scholar A rapid transfer of thiopental from the human maternal circulation into placental tissue and amniotic fluid occurs during the first trimester of pregnancy16Jørgensen NP Walstad RA Molne K The concentrations of ceftazidime and thiopental in maternal plasma, placental tissue and amniotic fluid in early pregnancy.Acta Obstet Gynecol Scand. 1987; 66: 29-33Crossref PubMed Google Scholar and at term.17Bakke OM Haram K Lygre T Wallem G Comparison of the placental transfer of thiopental and diazepam in caesarean section.Eur J Clin Pharmacol. 1981; 21: 221-227Crossref PubMed Google Scholar In pregnant ewes, UBF has been shown to decrease 20% without a substantial decline in maternal BP after induction of anesthesia with thiopental and succinylcholine, intubation, and use of nitrous oxide in oxygen for maintenance anesthesia.18Palahniuk RJ Cumming M Foetal deterioration following thiopentone-nitrous oxide anaesthesia in the pregnant ewe.Can Anaesth Soc J. 1977; 24: 361-370Crossref PubMed Google Scholar In that study, fetal oxygen saturation and pH also declined concurrently. This adverse effect on the fetus may have been caused by a light depth of anesthesia, sympathetic stimulation, and uterine vasoconstriction. Cosmi and Shnider19Cosmi EV Shnider SM Obstetric anesthesia and uterine blood flow.in: Shnider SM Levinson G Anesthesia for Obstetrics. Second edition. Williams & Wilkins, Baltimore1987: 22-40Google Scholar also reported that clinical doses of thiopental reduce maternal BP and UBF in pregnant ewes. Ketamine has also been extensively studied in pregnant ewes and does not seem to affect the fetus or UBF adversely.20Craft Jr, JB Coaldrake LA Yonekura ML Dao SD Co EG Roizen MF Mazel P Gilman R Shokes L Trevor AJ Ketamine, catecholamines, and uterine tone in pregnant ewes.Am J Obstet Gynecol. 1983; 146: 429-434Abstract Full Text PDF PubMed Google Scholar, 21Levinson G Shnider SM Gildea JE deLorimier AA Maternal and foetal cardiovascular and acid-base changes during ketamine anaesthesia in pregnant ewes.Br J Anaesth. 1973; 45: 1111-1115Crossref PubMed Google Scholar, 22Swartz J Cumming M Biehl D The effect of ketamine anaesthesia on the acidotic fetal lamb.Can J Anaesth. 1987; 34: 233-237Crossref PubMed Google Scholar In pregnant ewes20Craft Jr, JB Coaldrake LA Yonekura ML Dao SD Co EG Roizen MF Mazel P Gilman R Shokes L Trevor AJ Ketamine, catecholamines, and uterine tone in pregnant ewes.Am J Obstet Gynecol. 1983; 146: 429-434Abstract Full Text PDF PubMed Google Scholar and humans,23Ellingson A Haram K Sagen N Solheim E Transplacental passage of ketamine after intravenous administration.Acta Anaesthesiol Scand. 1977; 21: 41-44Crossref PubMed Google Scholar placental transfer from mother to fetus is rapid. Appreciable adverse effects on UBF in pregnant ewes did not occur with 0.7 mg/kg20Craft Jr, JB Coaldrake LA Yonekura ML Dao SD Co EG Roizen MF Mazel P Gilman R Shokes L Trevor AJ Ketamine, catecholamines, and uterine tone in pregnant ewes.Am J Obstet Gynecol. 1983; 146: 429-434Abstract Full Text PDF PubMed Google Scholar or 5 mg/kg21Levinson G Shnider SM Gildea JE deLorimier AA Maternal and foetal cardiovascular and acid-base changes during ketamine anaesthesia in pregnant ewes.Br J Anaesth. 1973; 45: 1111-1115Crossref PubMed Google Scholar of ketamine. In one study, fetal hypertension and bradycardia were abolished by use of ketamine in fetal sheep made acidotic by partial occlusion of the umbilical cord, which restricted blood flow; however, fetal blood flows to the heart, brain, and kidneys were not altered considerably.22Swartz J Cumming M Biehl D The effect of ketamine anaesthesia on the acidotic fetal lamb.Can J Anaesth. 1987; 34: 233-237Crossref PubMed Google Scholar Etomidate is a safe and effective induction agent for both mother and newborn during cesarean section24Ionescu T, Besse TC, Smalhout B: Etomidate during caesarian section (abstract). Excerpta Medica International Congress Series No. 533, 1980, pp 318–319Google Scholar, 25Downing JW Buley RJR Brock-Utne JG Houlton PC Etomidate for induction of anaesthesia at caesarean section: comparison with thiopentone.Br J Anaesth. 1979; 51: 135-139Crossref PubMed Google Scholar and provides a hemodynamically stable induction of anesthesia in cardiac patients.26Warner MA Warner ME Anesthetic agents for cardiac surgery.in: Tarhan S Cardiovascular Anesthesia and Postoperative Care. Second edition. Year Book Medical Publishers, Chicago1989: 41-79Google Scholar Propofol rapidly and substantially crosses the human placenta at the time of cesarean section, without producing subsequent adverse effects on the newly delivered infant;27Dailland P Cockshott ID Lirzin JD Jacquinot P Jorrot JC Devery J Harmey JL Conseiller C Intravenous propofol during cesarean section: placental transfer, concentrations in breast milk, and neonatal effects; a preliminary study.Anesthesiology. 1989; 71: 827-834Crossref PubMed Scopus (62) Google Scholar however, its place in cardiac anesthesia has yet to be determined. Benzodiazepines such as diazepam and midazolam are frequently used during the induction and maintenance of cardiac anesthesia.26Warner MA Warner ME Anesthetic agents for cardiac surgery.in: Tarhan S Cardiovascular Anesthesia and Postoperative Care. Second edition. Year Book Medical Publishers, Chicago1989: 41-79Google Scholar Both drugs readily cross the placenta into the fetal circulation.17Bakke OM Haram K Lygre T Wallem G Comparison of the placental transfer of thiopental and diazepam in caesarean section.Eur J Clin Pharmacol. 1981; 21: 221-227Crossref PubMed Google Scholar, 28Cavanagh D Condo CS Diazepam—a pilot study of drug concentrations in maternal blood, amniotic fluid and cord blood.Curr Ther Res. 1964; 6: 122-126PubMed Google Scholar, 29Bach V Carl P Ravlo O Crawford ME Jensen AG Mikkelsen BO Crevoisier C Heizmann P Fattinger K A randomized comparison between midazolam and thiopental for elective cesarean section anesthesia. III. Placental transfer and elimination i