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Indian J. Anaesth. 2004
; 48 (4) : 259-263 : PREGNANCY AND CP BYPASS
PREGNANCY AND CARDIOPULMONARY BYPASS
Dr. R. C. Agarwal1 Dr. P. K. Bhattacharya2 Dr. Lata Bhattacharya3 Dr. R. K. Jain4
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.
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
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
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
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
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.
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
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
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cease uterine contractions. Effective agents are terbutaline
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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
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TOM TOUR 2004 NOTES Abbreviations AK – Andrew Keites CH – Chris Huelin DO – David Oliver GG – Guy Gothard HJ – Hugo Jacques IM – Iain McInnes JB – James Birch JJ – Justin Jouan JK – Julian Kett MV – Matthew Vincent RL – Rob Leader SB – Steven Bowen Pre Tour Odds – (Jof the bookie) 6/4 Guy “I look over 50 (waist)” Gothard Chris “I’ll take on the r
PROVINCIA DI SONDRIO ________________________________ PROCESSO VERBALE DI DELIBERAZIONE DELLA GIUNTA PROVINCIALE Oggetto: DETERMINAZIONE DELLE SPESE D’ISTRUTTORIA IN MATERIA DI ACQUE MINERALI, TERMALI, DI SORGENTE E IN MATERIA DI AUTORIZZAZIONI ALLO SCARICO L’anno 2004 (duemilaquattro), addì 6 (sei) del mese di dicembre, alle ore 14 (quattordici), nella sala delle