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Indian J. Anaesth. 2004; 48 (4) : 259-263 : PREGNANCY AND CP BYPASS REVIEW ARTICLE
PREGNANCY AND CARDIOPULMONARY BYPASS
Dr. R. C. Agarwal1 Dr. P. K. Bhattacharya2 Dr. Lata Bhattacharya3 Dr. R. K. Jain4
SUMMARY
The physiology of the female is substantially altered during pregnancy. Pregnant patients may also present with various kinds of
cardiac diseases and the manifestations of these diseases may get worsened, and can be deleterious for both mother and fetus. Cardiac
surgery with extra corporeal support during pregnancy has been associated with elevated fetal morbidity and mortality. Maternal
morbidity and mortality seem more related to the subjacent cardiac disease and is not affected by cardiopulmonary bypass (CPB).
Fetal mortality remains elevated as a consequence of CPB factors that stimulate uterine activity and contractions and reduce placental
perfusion. Sub optimal gas exchange at the placental interface seems to be the main substrate for fetal bradycardia and distress.
Monitoring uterine activity and fetal heart rate is of paramount importance in the prevention of fetal bradycardia. Adjusting the
perfusion flow, perfusion pressure and FiO can contribute to improve placental blood flow and allow for better exchange with fetal
blood. Tocolytic agents may contribute to block uterine contractions and improve placental perfusion. This article reviews the influence
of CPB factors on the mother, the influence of CPB on the fetoplacental unit and the principal aspects of CPB that can be associated
with lower fetal and maternal morbidity and mortality.
Keywords : Pregnancy, Heart diseases, Cardiovascular surgery, Cardiopulmonary bypass, Open-heart surgery,
Maternal outcome, Fetal-neonatal outcome.
Introduction
incidence of cardiac disease in pregnant women varies in Cardiac surgery with extra corporeal support in a different countries, it is more prevalent in developing than pregnant patient constitute a complex endeavor, as it in developed countries. Most specialists agree that the heart represents the sum of anaesthetic, surgical and CPB effects disease is the leading cause of death during pregnancy and on two individuals under biologically distinct situation. It is generally agreed that only emergency surgical procedures Medical therapy is not always sufficient to drive a should be performed during pregnancy. Although maternal heart with a reduced functional reserve or acute morbidity and mortality depends more on the pre existing complications in pregnant women. Despite maximal medical cardiac disease and is not affected by CPB, fetal morbidity therapy, whenever the clinical condition of a pregnant woman and mortality is high with extra corporeal support and with cardiac disease deteriorates, surgical correction is the only alternative to restore cardiovascular function and create The concern of anaesthesiologist in such cases is conditions for the pregnancy to evolve normally.
that hormonal secretions from the corpus luteum and the Percutaneous balloon valvuloplasty may be promising placenta, as well as mechanical effects of the gravid uterus in future when adequate imaging can be performed with in a compromised cardiac status causes major physiological safe or no radiation exposure, but presently it is prohibited alterations in every organ system of the body. These effects in view of the radiation hazards associated with it to the can create serious problems to either of the two organisms.
fetus. Closed mitral valvotomy has been frequently performed There is a 1-4% incidence of cardiac disease in with success to carry the mother through the pregnancy, pregnancy as reported in united states1,2 and rheumatic heart disease accounts for 60% of the total.3 Although the The earliest reports of cardiac surgery during 1. D.A., M.D., Prof. and Head2. Asst. Prof.
pregnancy appeared in 1952, when Brock,7 Cooley and Chapman,8 Logan and Turner9 and Mason10 accomplished a total of eleven mitral commissurotomies with one maternal 1,2,4. Dept. of Anaesthesiology and Critical Care, death and one premature delivery. In 1957 Daley et al11 Bhopal Memorial Hospital and Research Centre combined hypothermia with three minutes of cardio circulatory arrest to perform a pulmonary valvotomy under direct vision, on which successful termination of pregnancy Correspond to :
Dr. R. C. Agarwal
was attained. In 1959 Dubourg et al4 performed a pulmonary commissurotomy and repaired an atrial septal defect at (Accepted for publication on 14-05-2004) 6 weeks gestation, using extracorporeal circulation (ECC), INDIAN JOURNAL OF ANAESTHESIA, AUGUST 2004 the patient survived the operation but had a spontaneous Effects of Cardiopulmonary bypass
Adverse effects of CPB include changes in coagulation, alteration in the function of cellular and protein components 10 years later, Zitnick et al12 summarized 20 cases of the blood, release of vasoactive substances from leukocytes, of open-heart surgery during pregnancy and reported complement activation, particulate and air embolism, non an overall maternal mortality of 5% and fetal mortality of pulsatile flow, hypothermia and hypotension.15 All these 33%. In 1983, Becker5 reviewed 55 cases of open heart factors can compromise the delicate biological equilibrium surgery done with ECC during pregnancy and found that between the fetus and the placenta. During prolonged although maternal mortality has decreased to 1.8%, operations such as valve replacement or repair of aneurysms, fetal mortality had only slightly improved at 21.8%.
the deleterious effects of CPB act longer and their injury Almost all the operations were performed during the second trimester of pregnancy where universal indication wasprogressive congestive heart failure unresponsive to medical Effect of Anaesthesia
The concern over the effects of anaesthetic agents on the fetal development and teratogenicity during cardiac Born et al13 has reported a single center study of surgery and CPB for pregnant patients exists whenever any 30 cases and documented a maternal mortality of 13% and drug is administered to a pregnant women, especially during a fetal mortality of 33% among patients with rheumatic the first trimester when fetal organogenesis occurs, but it valvular disease operated during pregnancy in the period appears that most anaesthetic agents, intravenous, 1981-1992. Weiss and co-workers14 reviewed the outcome of inhalatory, and paralyzing agents are devoid of teratogenic cardiovascular operations under CPB during pregnancy at effects and can be safely employed in a pregnant patient.16 delivery and post partum from 161 cases reported between Hypocarbia as a result of mechanical hyperventilation leads 1984 and 1996. Surgery during pregnancy resulted in to a decrease in uterine blood flow by 25%. Although the fetal-neonatal morbidity and mortality of 9% and 30% blood pressure remains unchanged during hyperventilation, respectively. The maternal morbidity and mortality were adverse effect on uterine blood flow was attributed to a decrease in venous return and cardiac output.15,17 Physiologic changes during pregnancy and their
Cardiopulmonary bypass and fetal response
implications for CPB
There are only few studies regarding the effects of It is of paramount importance to understand the maternal CPB on the fetus. Since the first report of the use physiologic changes that occur in mothers during pregnancy of fetal heart recording during bypass by Koh and and the physiology of feto placental unit. From 12th to 36th Co-workers18 in 1975, it has been known that fetal weeks of pregnancy cardiac output gradually increases to a bradycardia occurs almost invariably at the onset of maternal peak of 50% above resting levels. This rise in cardiac CPB.19 What causes bradycardia at the beginning of the output is secondary to rise in intravascular volume. Oxygen bypass is unknown, but it may be related to a decreased consumption rises by 25% to 30% above non-pregnant levels.
fetal oxygenation secondary to placental hypotension or to Rise in intra vascular volume along with oxygen consumption acid base changes. It has been postulated that starting a leads to a rise in cardiac preload causing an increase in normothermic CPB with a high perfusion flow avoids the stroke volume and heart rate, which finally leads to a high Uterine contractions occurring on a background of a Mean red cell mass increases in pregnancy, but this decreased perfusion and relative hypotension associated with is out weighed by an increase in blood volume, which leads CPB may produce inadequate placental perfusion with the to a fall in haematocrit level. Systemic and pulmonary resulting fetal response of bradycardia. A rate of 70 to 80 vascular resistance decreases in pregnancy, which beats per minute represents a considerable degree of fetal particularly affects the patients with right to left shunts.
distress. Elevating the perfusion flow and increasing the Thrombotic event increases during pregnancy because maternal PO to 300 to 400 mmHg can correct it. Hence, of a relative state of hypercoagulability. Uterine blood flow Oxygen exchange at placental interface is favored by which is approximately 3% of total cardiac output increases increasing both, the perfusion flow and arterial PO .
Both maternal and fetal catecholamines elevate due All these changes are necessary to allow the mother to stress, which increases the peripheral vascular resistance, to cope with the new and increased metabolic demands which is not tolerated by the immature fetal myocardium.
Anaesthetic agents produce maternal and fetal anaesthesia AGARWAL, BHATTACHARYA, LATA, JAIN : PREGNANCY AND CP BYPASS but fail to block the fetal response to the excess of circulatory of contractions, so that they can be adequately treated catecholamines and other vasoactive agents.
before the development of fetal hypoxia and bradycardia.14 Monitoring fetal heart rate and uterine activity can Uterine and fetal monitoring during CPB
offer valuable information to the perfusionist regarding the Monitoring uterine activity and fetal heart rate can placental blood flow and perfusion. At present, the best use offer valuable information regarding placental blood flow of fetal heart rate monitoring is to allow adjustment of flow and perfusion,19 so, it is a good recommendation to add both rates, should fetal bradycardia occur.
these monitoring to CPB monitoring protocol of pregnant Fetoplacental unit response to cardiopulmonary bypass
Thirty to sixty minutes after the fetus is removed Cardiotocography
from the bypass a severe progressive respiratory acidosis It is based on the surface detection of electrical develops.21 The underlying cause is probably activation of activity, much like the conventional electrocardiography.
Eicosanoids products. The experiments have shown that An abdominal belt contains two sets of electrodes, one to inactivation of these products like prostaglandin E and monitor the uterine activity and the other to monitor the Thromboxane22, 23 using indomethacin and corticosteroids can prevent this respiratory acidosis.
Ultrasonography and Doppler monitor
A more intractable metabolic acidosis develops six Doppler transducers are available to monitor fetal to eight hours. after bypass is discontinued. This late heart beats from the surface of maternal abdominal wall.
metabolic acidocis is due to low cardiac output secondary These probes are difficult to maintain in place during the to an increase in systemic vascular resistance because of procedure. Smaller probes have also been used transvaginally an increase in catecholamine levels, and is a part of fetal to monitor fetal heart beats and umbilical cord flow, but they have not gained wide popularity.
In the experimental setting of fetal CPB a spinal Conduct of Cardiopulmonary Bypass
anaesthetic to the fetus has been shown to prevent this stress CPB effects on the fetoplacental unit can contribute response and subsequent metabolic acidosis,24 but this is to interrupt pregnancy and, to determine fetal death. During clearly impractical in the clinical setting of maternal CPB.
CPB the perfusionist’s attention should be directed at the Although both indomethacin and steroids have been placental blood flow, which can be optimized to offer the shown to be beneficial in the experimental settings, the fetus the best conditions for oxygen exchange and, thus detrimental effects of indomethacin on platelet function maintain its viability. In case of any indication of fetal with subsequent risk of bleeding may place the mother at distress, it should be treated aggressively. An obstetrician unreasonable risk, particularly in the perinatal period.
should be available in the operating room to monitor and Steroids would therefore be preferable in this context.
adjust uterine and fetal parameters.
CPB effect on pregnant uterus
Positioning in the operating table
It has been suggested that the dilutional effect of A 30 to 60 degrees pelvic tilt should be applied in bypass causes a decrease in hormonal levels; particularly the form of a wedge on the right side to avoid compression progesterone, which produces, increased uterine excitability.
by the gravid and relaxed uterus over the inferior vena Uterine contractions are particularly common during the cava, particularly during the third trimester of pregnancy, rewarming phase after moderate or profound hypothermia5 to avoid hypotension after the induction of anaesthesia.
and are considered to be the most important predictor of Anticoagulation
fetal death.25 They occur more frequently with increasing There is a small potential risk of placental gestational age. Progesterone supplementation has been haemorrhage, fetal abortion or premature labor with the successfully used to stabilize the uterus around the time of use of heparin, although it does not cross the fetoplacental the bypass.26 b agonists27 have also been tried with good barrier. Recommendation for CPB on a pregnant patient is that ACT should be maintained between 480 to 600 seconds.
Uterine contractions in association with non pulsatile flow of CPB can produce insufficient irrigation of the As a part of physiologic changes certain degree of placenta and determine the development of fetal hypoxia.
anaemia always exist in pregnant patients. Plasma oncotic Monitoring is therefore essential to allow early identification pressure is also 10 to 20% less than normal. Crystalloids, INDIAN JOURNAL OF ANAESTHESIA, AUGUST 2004 haemodilution although successful, has been reported to cause fetal distress with low haematocrit. Perfusate volume Blood flow to the uterus is under a strong alpha- should be minimum necessary to initiate bypass because of adrenergic control. Vasopressor with alpha adrenergic low oncotic pressure. A haematocrit of 25% obtain a better receptor effects can reduce uterine and placental blood environment for the fetus, but the ideal haematocrit is 30 flow. Whenever a peripheral vasodilatory effect is required to 34%. Plasma albumin or colloids can favor tissue during CPB an infusion of hydralazine can be administered perfusion and contribute to avoid interstitial edema.
without any untoward effects. Ephedrine and low dosedopamine does not appear to influence the uterine blood Diuretics should not be a part of routine protocol, flow. Isoproterenol has been recommended as the inotrope but can be used to stimulate maternal diuresis if necessary.
of choice soon after bypass, it has got a positive effect on Furosemide is preferred to mannitol. Mannitol crosses the placental barrier and can stimulate fetal diuresis.28 Anoncotically adjusted prime makes addition of mannitol or Acid base management
furosemide unnecessary and can avoid untoward effects of Significant changes in acid base balance are less diuretics on the fetus. Before starting bypass, perfusate pH likely to occur under normothermic CPB. The only changes and temperature should be adjusted, to preserve fetal seen are metabolic acidosis, as a consequence of reduced tissue perfusion and respiratory alkalosis because of excess Pump flow
gas flow in the oxygenator. Adjusting the perfusion and gas Arterial flow should be 20 to 40% higher than flows flows without the use of any drug can easily control both used for routine CPB in non pregnant patients, to sustain adequate fetoplacental gas exchange during non pulsatile During hypothermic CPB acid base disturbances can be more pronounced and there is no consensus regarding Mean arterial pressure
pH management during pregnancy. It is a good practice The best demonstration of an adequate arterial to manage pH according to alpha stat protocol. No pressure is the fetal response to CPB, and the pump flow recommendation has been found to add CO to the ventilating should be sufficient to maintain a mean arterial pressure above 70 mmHg (70 to 90 mmHg). During CPB on pregnant Myocardial protection
patients, high perfusion flow, high mean arterial pressureand a normal cardiotocography usually present a clear During long procedures and with the use of continuous cardioplegia, high potassium level in the maternal blooddiffuses to fetal blood and originates fetal hyperkalemia.
Gas flows
The hyperkalemia secondary to cardioplegia infusion affects To achieve a better perfusion and gas exchange of the fetal myocardium and produces bradycardia, conduction placental tissue and fetoplacental unit, CPB during pregnancy disturbances or cardiac arrest. Regardless of the type of has to be conducted with a higher FiO to produce an cardioplegia, the effluent should be aspirated from the right arterial PO of at least 200 mmHg. If fetal bradycardia atrium or coronary ostia to avoid its mixing to the perfusate.
occurs, PO should be elevated to about 400 mmHg along Management of fetal bradycardia
with other measures such as, increasing perfusion flow andpressure15. High maternal arterial PO does not affect fetal Fetal bradycardia indicates fetal distress, increasing organs and will not contribute to produce any ill effects.
pump flow and FiO are the usual measures taken to correct fetal bradycardia. If despite these measures fetal heart rate Hypothermia
remains low, a small drip of ephedrine may be required.
Gas exchange during hypothermia is reduced at the In few cases, it has been found that despite all management, placental level. Hypothermia can increase uterine tone and fetal bradycardia persists for entire duration of CPB and contractions, and elevate uterine vascular resistance.
reverts when normal circulation is resumed. When Maternal bradycardia, ventricular arrhythmias and fibrillation bradycardia prolongs to the postoperative period the risk of are more common during hypothermia. Fetal mortality is fetal death is substantially increased.
higher when CPB is conducted with hypothermia. Significanthypothermia should be avoided unless extended aortic clamp Management of uterine contractions
time is anticipated or a circulatory arrest period is required.
Most commonly, increased uterine contractions are Rewarming produces uterine contractions and increases associated with arterial hypotension, hypothermia, rewarming and dilution of pregnancy hormones such as progesterone.
AGARWAL, BHATTACHARYA, LATA, JAIN : PREGNANCY AND CP BYPASS Prolonged and intense contractions are associated with a 13. Born D, Massonetto JC, de Almeida PA et al. Heart surgery higher incidence of fetal death. Beta agonist drugs can with extra corporeal circulation in pregnant woman: analysis cease uterine contractions. Effective agents are terbutaline of materno fetal outcome. Arq Bras Cardiol 1995; 64: and ritodirine. Terbutaline can be given in the dose of 10 mgmin-1, which can be increased as necessary to 14. Weiss BM, Von Segesser LK, Alon E, Seifert B, Turina MI.
80 mgmin-1, and should be continued for four hours. Ritodirine Outcome of cardiovascular surgery and pregnancy: a systematic is given at a dose of 50 to 150 mgmin-1 and should be review of the period 1984-1996. Am J Obstet Gynecol 1998;179: 1643-53.
15. Hammon JW Jr, Edmunds LH Jr. Extracorporeal circulation: Conclusion
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A high risk of fetal morbidity and mortality is associated with CPB during pregnancy. Avoidance of sudden 16. Duncan PG, Pope WDB, Cohen MM, Greer N. Fetal risk of change in placental blood flow, maintenance of physiology anaesthesia and surgery during pregnancy. Anesthesiology1986; 64: 790-4.
of placenta to the normal as possible, managing the arterialoxygen tension along with the perfusion flow and pressure 17. Levinson G, Shnider SM, deLorimier AA, Steffenson JL.
Effects of maternal hyperventilation on uterine blood flow are the key determinants in the management of patient and fetal oxygenation and acid base status. Anesthesiology under CPB. Fetal bradycardia and increased uterine contractions need immediate attention and management.
18. Koh KS, Friesen RM, Livingstone RA, Peddle LJ. Fetal monitoring With the optimal care provided by the modern neonatal during maternal cardiac surgery with cardiopulmonary bypass.
care units and considering caesarian section as an option, the deleterious effects of CPB can be avoided when the 19. Trimakos AP, Maxwell KD, Berkay S, Gardner TJ, Achuff SC.
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