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Due to heparin-induced thrombocytopenia, patients receiving heparin >4 days should have a platelet count prior to neuraxial block.


Anesthetic considerations: Many women with cardiac disease The American Society of Regional Anesthesiology (ASRA) guide-
will be treated with anticoagulants to avoid thromboembolism. lines should be considered when performing any regional
anesthetic on a patient taking anticoagulants (Table 1.7).24 The
The decision to perform neuraxial anesthesia in a patient receiv-
ing thromboprophylaxis should be made on an individual basis. patient™s coagulation status should be optimized and level of



5
1 Cardiovascular and respiratory disorders


anticoagulation carefully monitored before spinal or epidural
Table 1.8 Hemodynamic advantages and disadvantages of
placement and at epidural catheter removal. In patients who
vaginal birth and elective cesarean section
have received neuraxial blocks, postprocedure neurological
monitoring needs to be carried out at regular intervals (<2 hours Vaginal birth Cesarean section
between neurologic checks). The epidural infusion should be
Advantages Minimize blood loss Predictable and planned
limited to dilute local anesthetics that minimize sensory and
Minimize surgical stress Timed delivery
motor block to aid neurological assessment.24
Quicker recovery All personnel
Hemodynamic stability immediately available
6. Uterotonic agents
Disadvantages Unpredictable timing Increased surgical stress
Care should be exercised when administering oxytocin to
Potentially prolonged Higher blood loss
patients with cardiac disease since a large bolus can cause
Painful and stressful Longer recovery
hypotension and tachycardia and has been shown to cause
Potentially ˜˜after-hours™™ Higher potential
increases in cardiac stress.27 A slow infusion of a dilute oxyto-
postoperative
cin solution is usually well tolerated. Other uterotonic agents
complications
such as ergometrine can induce systemic hypertension and
coronary vasoconstriction. Prostaglandin F2-alpha has the
potential to cause severe pulmonary hypertension if large phase and Valsalva maneuvers. Although induction of labor in
doses are injected directly into the circulation.28 pregnant patients with cardiac disease is safe,33 there are
7. Peripartum monitoring higher maternal and neonatal complications compared to
The level of monitoring, beyond standard American Society of healthy controls.
Anesthesiology guidelines, should be appropriate for the sever- 10. The critical postpartum period
ity of the cardiac lesion and the planned obstetric or anesthetic The immediate postpartum period is critical, especially if pul-
intervention. Invasive monitoring is advised in symptomatic monary hypertension is present. Most fatalities occur in the
patients with known cardiac defects. Monitoring of radial artery first week after delivery, but others occur as late as three to
pressure Æ central venous pressure (CVP) Æ pulmonary artery four weeks postpartum. For this reason invasive monitoring
catheter Æ transesophageal echocardiography (TEE) allows pre- should not be discontinued immediately after delivery, and full
cise, continuous measurement of hemodynamic variables and therapeutic and monitoring support in a critical care setting
guides appropriate use of fluid and drug therapy. When the should be provided. Postoperative pain management (e.g.,
pathophysiology of critically ill obstetric patients cannot be epidural analgesia) is useful in reducing the cardiovascular
explained by noninvasive hemodynamic monitoring and the stress response following C/S. In addition, a neuraxial-induced
patient fails to respond to conservative medical management, sympathectomy may improve microvascular flow and reduce
invasive hemodynamic monitoring may be helpful in guiding the risk of perioperative deep vein thrombosis.
further management.29 The benefits of additional hemody-
namic data provided by invasive monitoring should be weighed
Valvular lesions
against the risks associated with invasive line insertion.30,31
8. Basic hemodynamic goals Women with stenotic lesions do not tolerate the changes in HR or
Although care must be individualized to the cardiac lesion and increases in CO that occur during pregnancy. Any woman with a
patient condition, basic maintenance of hemodynamic goals symptomatic stenotic lesion warrants very close attention and
are applicable to most cases. possible correction before or during pregnancy.
 Avoid sudden alterations in HR and maintain normal sinus
rhythm.
Mitral stenosis
 Maintain preload and minimize sudden increases or decreases
Mitral stenosis (MS) accounts for 90% of rheumatic heart disease
in central blood volume. Pregnant patients with cardiac disease
in pregnancy, with 25% of patients developing symptoms for the
are at increased risk of developing pulmonary edema.
 Avoid sudden decreases in afterload and SVR. Decreases in first time during late pregnancy. Mitral stenosis is the most com-
mon cardiac pathology associated with acute pulmonary edema
SVR are compensated for by increasing HR, which can lead
in pregnancy, followed by aortic valve disease and primary myo-
to worsening cardiac function.
cardial disease. Symptoms depend on the severity and include
9. Vaginal versus cesarean delivery
fatigue and dyspnea on exertion initially, but may progress to
There are advantages and disadvantages of both vaginal and
paroxysmal nocturnal dyspnea, orthopnea, and shortness of
cesarean section (C/S) with no convincing evidence that either
option is clearly superior (Table 1.8).32 The delivery plan breath at rest. Mitral stenosis is considered severe when the
valve area is 1 cm2 or less. Overall mortality is around 1% in
should be individualized according to the woman™s condition.
mild disease or 5“15% in severe mitral valve disease.
Vaginal delivery may be preferable if obstetrically indicated,
Predictors of adverse events include:7,34,35
however, limits to the duration should be discussed and pre-
 mitral valve area <1.5 cm2
parations for a potential C/S considered. Assisted delivery is
 NYHA functional class >II
recommended to avoid prolonged pushing, a rapid expulsive



6
Chapter 1


 left ventricular ejection fraction (LVEF) <40%  The enlarged left atrium promotes thrombus formation and
 a previous cardiac event. anticoagulation prophylaxis should be used in patients with
atrial fibrillation or a prior embolic history.
 Bacterial endocarditis prophylaxis should be administered
Pathophysiology
although its role in an uncomplicated labor and delivery is
A small mitral valve area causes a decrease in left ventricular (LV) controversial.
 Beta-blockers may reduce the incidence of pulmonary edema.37
filling and LV output. There is a concomitant increase in left atrial
 Consider valvuloplasty or valve surgery. Valvuloplasty or valve
(LA) volume and pressure, with an increased pulmonary capillary
wedge pressure (PCWP). These result in irreversible elevation in surgery before pregnancy may reduce the complications dur-
ing delivery.38 Patients who develop severe symptoms during
pulmonary vascular resistance (PVR) over time so that pulmonary
edema and pulmonary hypertension can develop. Right ventri- early pregnancy may benefit from a second trimester valvulo-
plasty.39,40 Intractable heart failure or pulmonary edema are
cular hypertrophy, dilatation, and failure may then occur, causing
peripheral edema. indicators for urgent surgical intervention or balloon valvulo-
plasty.41,42 Balloon mitral valvuloplasty should be considered
Relative obstruction across the valve increases as pregnancy
for mitral valve areas <1.5 cm2 13 and for refractory pulmonary
advances because of the increase in blood volume, HR, and CO.
edema.43 However, appropriate radiation screening should
Increased obstruction leads to pulmonary venous congestion and
may produce pulmonary edema. be provided and plans made in case of sudden valve rupture.
Overall percutaneous balloon mitral valvuloplasty carries fewer
fetal and maternal risks than open surgical valvotomy and can
Management principles36
be performed under local anesthesia with light sedation (e.g.,
 Maintain sinus rhythm and prevent rapid ventricular rates. 0.5“1 mg i.v. midazolam).
Atrial fibrillation and tachycardia can also precipitate worsen-
ing cardiac function. Aggressively treat new onset atrial fibrilla-
Anesthetic options
tion pharmacologically or with direct cardioversion especially
in the hemodynamically compromised patient (see Chapter 2). Evidence-based data on the ideal anesthetic and analgesic for the
parturient with MS is lacking.44 Management must be individu-
 Avoid large, rapid falls in SVR. This is compensated for by
increasing HR, which can worsen cardiac function. alized to optimize patient outcome. The degree of monitoring
 Prevent increases in central blood volume. Careful fluid man- should be based on the severity of the disease and the woman™s
condition.44 The concomitant use of invasive hemodynamic
agement and diuresis may be necessary.
 Avoid factors that may increase pulmonary artery pressure monitors is recommended in symptomatic parturients with crit-
ical stenosis.45,46
(PAP) (see Table 1.9). Prostaglandins, which may be useful in
treating uterine atony, can precipitate increases in pulmonary It is important to minimize pain and catecholamine release
vascular pressure. during labor. A carefully titrated epidural for labor and delivery
addresses all the above mentioned hemodynamic goals. Epidural
analgesia during the first stage of labor can reduce PVR and SVR,
lower PAP, and decrease CO to baseline levels.45 Rapid prehydra-
Table 1.9 Factors affecting pulmonary vascular
resistance (PVR) tion should be avoided, and slow titration of local anesthetic
solution is recommended to minimize hemodynamic changes.
Factors decreasing PVR Factors increasing PVR
When treating hypotension, phenylephrine is preferred over
" PaO2 Hypoxia ephedrine, which may increase the HR. Epinephrine-containing
# PaCO2 " PaCO2 local anesthetic solutions are best avoided due to concerns about
Alkalemia Acidosis potential tachycardia. Combined spinal“epidural (CSE) analgesia
may be a good option for these patients.44,47 An intrathecal opioid
Medications: phosphodiesterase Medications: prostaglandin
III inhibitors (e.g. milrinone), F2-alpha, nitrous oxide. combined with a dilute epidural infusion minimizes sympathetic
prostaglandin E1 and I2, block and concomitant hypotension. Trendelenburg position
may help to improve cardiac index and PCWP,48 but may be
isoprenaline, inhaled nitric
oxide uncomfortable for the awake patient. Consider assisted delivery
Spontaneous ventilation Positive pressure ventilation to limit maternal Valsalva maneuvers and expulsive efforts.
and PEEP Both epidural and general anesthesia (GA) have been described
Hypothermia for C/S. Epidural anesthesia has an advantage over a subarachnoid
Sympathetic stimulation: pain, block in that it can be slowly titrated. Epidural anesthesia has
light anesthesia, anxiety been used successfully in women with severe MS undergoing
urgent C/S.48 If GA is required, avoid drugs that produce tachycar-
PEEP ¼ positive end-expiratory pressure
dia such as atropine, pancuronium, ketamine, and meperidine.
Adapted from: Lovell, A. T. Anaesthetic implications of grown-up
Although most anesthetic agents have a negative inotropic effect,
congenital heart disease. Br. J. Anaesth. 2004; 93: 129“39.
(see Table 1.1) patients with mild disease can tolerate a sodium



7
1 Cardiovascular and respiratory disorders


thiopental induction. Patients with more severe disease may bene- to increase their CO. In addition, the myocardium receives its
fit from a ˜˜cardiac™™ anesthetic induction with an intravenous (i.v.) oxygen supply during diastole and the thickened myocardium
opioid and a cardiostable induction agent (e.g. etomidate). is adversely affected by a reduced perfusion time associated
Although opioids (e.g. alfentanil, fentanyl) can provide hemody- with tachycardia.
 Avoid decreases in SVR. A drop in SVR cannot be compensated
namic stability, transplacental drug transfer may cause neonatal
respiratory depression.36 Remifentanil may be the preferred opioid for by an increase in SV because of the fixed outlet obstruction.
in the peripartum setting due to its short context-sensitive half-life. Patients with AS increase their HR to maintain CO, but this also
The lowest possible dose of uterotonic agent is recommended increases oxygen consumption and decreases diastolic filling.
 Avoid hypotension. Hypotension causes ischemia in the hyper-
as it may produce significant adverse cardiovascular effects. The
intrapartum and immediate postpartum periods are high risk as trophied ventricular muscle. Diastolic BP is important if cor-
onary blood flow is to be maintained.55
the PCWP increases in the presence of severe MS (functional class
III and IV).49 In the appropriate patient, C/S may be followed by  Consider valvuloplasty. In some cases, percutaneous balloon
immediate corrective surgery, for example closed mitral valvot- aortic valvuloplasty has been performed during pregnancy
omy.50 Postoperative ventilation and intensive care may be neces- with good maternal and fetal outcomes.56 Aortic balloon valvu-
sary. Patients may need inotropic support as well as a pulmonary loplasty in pregnancy may be performed in symptomatic
severe AS as a palliative procedure.57 Valvuloplasty is usually
vasodilator such as nitroglycerin or sodium nitroprusside.
reserved for cases of severe symptomatic AS when aortic valve
area is <1.0 cm2.13
Aortic stenosis
Symptomatic aortic stenosis (AS) is associated with higher neo-
Anesthetic options
natal and maternal mortality rates.51,52 Asymptomatic pregnant
patients tolerate pregnancy without complications.53 Valve area is Some anesthesiologists prefer GA in patients with AS.55 This is out
a better index of severity than gradient estimation, which is often of concern that sympathectomy from regional anesthesia will
exaggerated in pregnancy due to the high flows.54 Patients usually reduce SVR and induce tachycardia and hypotension. However,
become symptomatic (syncope, angina, and dyspnea on exertion) there are a number of case reports advocating carefully titrated
as the valve area decreases to 1 cm2 and a critical valve area is epidurals for labor and delivery in parturients with severe AS.27,53,58
<0.6 cm2. A systolic pressure gradient >50 mmHg between the LV More recently, continuous spinal analgesia and anesthesia have
been used successfully for labor and C/S.59,60 A continuous spinal
and aorta means severe stenosis; however, some patients may not
be able to generate large pressure gradients if they have LV dys- technique using incremental doses may minimize sympathectomy-
function. Transvalvular gradients increase progressively through- induced cardiovascular changes and provide a more controlled
hemodynamic profile.60 When using a regional technique, it is
out pregnancy, as a consequence of increased blood volume
and reduced SVR. Coexisting coarctation, symptomatic AS at the important to slowly titrate the local anesthetic and opioid
onset of pregnancy, and cardiac deterioration are considered with invasive monitoring appropriate for the severity of the AS.
important risk factors for the woman with AS in pregnancy.53 A single-shot spinal technique is not recommended.61 Regional
anesthesia avoids the tachycardia and stress response from intu-
bation and surgical stimuli associated with GA.
Pathophysiology
Pain and anxiety can increase SVR and afterload. A slow reduc-
A small aortic valve causes increased pressure and work for the LV. tion in SVR with an epidural technique may improve CO in the face
Left ventricular hypertrophy results and the thickened myocardial of a fixed SV, assuming that the filling pressures are adequate.
walls are more prone to ischemia. The higher the transvalvular Some authors recommend avoiding epinephrine-containing
gradient, the greater the risk of myocardial ischemia. These epidural local anesthetic solution, while others have used it in the
test dose in parturients with cardiac disease.27 Phenylephrine is the
patients have a fixed SV because of the decreased diameter of the
aortic valve. Eventually, the LV fails causing a decrease in CO. drug of choice to treat hypotension. Unlike ephedrine it improves
LV filling without causing tachycardia.62
There is no good evidence to show whether regional or GA is
Management principles
safer in patients with AS.63 If GA is required, an opioid-based
 Avoid sudden decreases in venous return and LV filling. anesthetic is useful when LV function is compromised and in
cases of severe AS.55,64 Remifentanil has been used to blunt the
Decreases in left ventricular end diastolic volume (LVEDV)
are poorly tolerated and will cause a decrease in SV and CO in hemodynamic response to intubation in patients with AS under-
going C/S under GA.65 In one report, remifentanil provided car-
a patient with limited reserve. Augmented preload with i.v.
fluids may be of benefit in maintaining a fixed SV. However, diovascular stability in conjunction with rapid emergence from
anesthesia with minimal neonatal side effects.65 A standard gen-
pulmonary congestion secondary to LV failure may be exacer-
bated by fluid loads in the presence of hypervolemia associated eral anesthetic rapid sequence induction with sodium thiopental
and succinyl choline may decrease CO.63 The use of etomidate as
with pregnancy.
 Maintain sinus rhythm. Bradycardia is poorly tolerated since an induction agent may be preferable to avoid myocardial
these patients have a fixed SV. Patients rely on increases in HR depression from sodium thiopental, and tachycardia associated



8
Chapter 1


with ketamine (see Table 1.1). It must be emphasized that a monitoring to guide fluid and drug therapy. Epidural analgesia
cautious anesthetic technique is necessary in conjunction with is favored for labor pain because it attenuates an increase in
invasive monitoring to guide appropriate therapy in the event of SVR from peripheral vasoconstriction secondary to the pain of
adverse hemodynamic changes. labor. Reducing SVR increases the forward flow component across
All uterotonic agents should be used cautiously as they may the valve.
produce significant cardiovascular effects. Postpartum monitor- If patients tolerate the supine position with left uterine tilt, then
ing is vital as mortality has been reported up to three to five days regional anesthesia is a good choice for C/S. If GA is necessary, try
following delivery.55 avoiding anesthetic agents with significant myocardial depres-
sant effects (see Table 1.1), especially in patients with LV dysfunc-
tion. Techniques that cause a slight increase in HR may be
Regurgitant valvular lesions
beneficial (e.g. ketamine).
Chronic mitral or aortic regurgitation is usually well tolerated
during pregnancy if the patient remains asymptomatic or only
Aortic regurgitation or insufficiency
mildly symptomatic.66 The physiological changes of pregnancy
with reduction in SVR and tachycardia favor forward flow and Most patients with aortic regurgitation (AR) tolerate the cardio-
limit the regurgitant back flow. However, clinical deterioration vascular demands of pregnancy, although patients with sig-
and heart failure are possible during pregnancy, particularly nificant LV enlargement and dysfunction may develop heart
in patients with LV dysfunction and a reduced ejection failure.
fraction.67

Pathophysiology
Mitral regurgitation or insufficiency
Left ventricular volume overload causes LV dilatation and
Mitral regurgitation (MR) is usually well tolerated and patients increased LV volume, work that eventually leads to LV dysfunc-
can be asymptomatic for many years. Left ventricle dysfunction tion. The regurgitant volume depends upon the diastolic pressure
and heart failure eventually develop if the condition is left gradient between the aorta and the LV, as well as the duration of
untreated. The increased intravascular volume associated with diastole. The decrease in SVR seen in pregnancy can improve AR
pregnancy and delivery may worsen LV volume overload. Patients by decreasing the regurgitant volume. However, the increase in
are also at risk for atrial fibrillation, pulmonary edema, emboli intravascular volume associated with pregnancy and uterine con-
formation, and endocarditis. tractions can lead to volume overload and LV dysfunction.


Pathophysiology Management principles and anesthetic options
Regurgitation of blood from the LV into the LA occurs during The management principles and anesthetic options for AR are the
systole. This causes LA enlargement with eventual increases in same as for patients with MR (see above).
LA pressure. This pressure is transmitted to the pulmonary circu-
lation causing elevations in pulmonary venous pressure and
Mixed valvular lesions
PCWP. This eventually causes pulmonary edema and may lead
to RV failure. The LV may also fail secondary to an increase in Mixed valvular lesions often present a dilemma as to which lesion
volume load. Pain and surgical stimulation can increase SVR, to treat and which hemodynamic goals to adopt. As a general rule,
which might decrease forward flow across the valve. therapy should be directed to the management of the dominant,
most severe valvular lesion. For example, if a woman presents
with severe MR and mild MS then management should be direc-
Management principles
ted to treat the regurgitant lesion, even if this conflicts with the
 Prevent increases in SVR, as an elevated SVR can impair for- usual treatment of MS.
ward flow. Treatment should be aimed at afterload reduction.
 Maintain a normal to slightly elevated HR, avoiding bradycar-
Management principles
dia. A slow HR prolongs diastole and allows for a longer period
of regurgitation. Ephedrine may be a good drug to use in this General management goals and monitoring outlined earlier in
setting to prevent and treat hypotension and avoid bradycardia the chapter should be followed and should be appropriate for
associated with alpha-agonists. Treat dysrhythmias aggres- the patient™s condition. Often a compromise is reached for
maintenance of hemodynamic objectives in mixed lesions.68
sively if they occur.
Importantly, avoid rapid HR and treat dysrhythmias aggressively.
Maintain preload, minimize sudden increases in central blood
Anesthetic options
volume and avoid sudden decreases in SVR. Use cardiovascular
Asymptomatic patients probably do not need invasive monitor- monitoring appropriate for the severity of the underlying lesion
ing, but severely compromised patients should have invasive and the patient™s clinical condition.



9
1 Cardiovascular and respiratory disorders


monthly and adjusted as necessary.77 Patients still on anticoagu-
Anesthetic options
lants are at risk for postpartum hemorrhage. If regional anesthe-
Refer to the anesthetic management options for specific valvular
sia is planned, allow an adequate time between anticoagulation
lesions discussed earlier. Treatment must be individualized and
administration and regional (epidural and/or spinal) anesthesia
no absolute recommendations can be made because evidence-
(see Table 1.7).
based data are lacking. However, there are a number of case reports
Regular assessment of signs and symptoms may help detect
describing the successful management of pregnant women with
any residual or new valve dysfunction. It is important to exclude
mixed valvular lesions. In one such case report, a woman with
residual myocardial dysfunction or pulmonary hypertension that
moderate to severe MR and mild MS was managed with epidural
may exist despite correction of the valvular lesion. Consider inva-
analgesia for induced labor and ventouse-assisted vaginal deliv-
sive monitoring where significant residual myocardial dysfunc-
ery.69 Other reports have described the use of epidural analgesia
tion or pulmonary hypertension exists. Patients with a valve
for labor and delivery in women with combined mitral and aortic
prosthesis are at higher risk for developing dysrhythmias, espe-
regurgitation,70 and combined MS and AS.71 More recently, a
cially atrial fibrillation. Management goals and anesthetic con-
parturient with mixed pulmonary stenosis and aortic incompe-
siderations should be individualized according to the lesion. (See
tence had a C/S under epidural anesthesia.68
specific valvular lesions.)


Valvulotomy and prosthetic valves Mitral valve prolapse
There have been many reports of successful pregnancy following Mitral valve prolapse (MVP) is the most common valvular lesion “
valvular surgery.72 Generally, women who are asymptomatic occurring in approximately 2“4% of the general population “ and
before pregnancy are able to tolerate pregnancy and delivery.67 is most prevalent in young women. A benign course can be
Symptomatic patients with underlying LV dysfunction and/or expected in 85% of patients with MVP,78 but 15% develop MR
pulmonary hypertension may not tolerate the stresses of preg- over time. Most patients progress uneventfully during pregnancy
nancy. Compared to pregnant women with prosthetic valves, and the peripartum period;79,80 however, some patients may sus-
patients with previous valvotomies have fewer complications tain cardiac dysrhythmias (e.g. supraventricular and ventricular
and less fetal morbidity.73 Women with prosthetic valves are tachydysrhythmias, bradydysrhythmias, and conduction blocks).
at higher risk of complications including valve infection, throm- The role of routine endocarditis prophylaxis for labor and delivery
boembolism, and bleeding due to anticoagulant therapy.74 is controversial.79 The current recommendation is that bacte-
Women with aortic valve replacement have a lower incidence rial endocarditis prophylaxis is only necessary in MVP with MR
of complications than those with a mitral valve prosthesis,75,76 and/or thickened leaflets (see Tables 1.5 and 1.6).
possibly due to better ventricular function and less stringent
anticoagulation compared to mitral valve lesions.73 All women
Management principles
with prosthetic valves are at risk for valvular infection and clini-
cians should consider bacterial endocarditis prophylaxis (see Avoid decreases in preload by providing adequate volume re-
Tables 1.5 and 1.6). Anticoagulation should be considered placement and left uterine displacement. Maintain afterload and
throughout pregnancy due to the high risk of thromboembolism. avoid increases in HR. Hypovolemia, venodilation, increased air-
American College of Cardiology (ACC) and American Heart way pressure, and tachycardia all decrease LV volume causing an
Association (AHA) Guidelines should be considered,21 although earlier prolapse of the valve leaflets and thus increasing MR.
they were produced before data regarding LMWH for pregnant Conditions that increase LV volume, such as bradycardia, after-
patients with prosthetic valves were available.77 load augmentation, hypervolemia, or negative inotropic agents,
cause later prolapse, with a delayed click.
Asymptomatic patients with MVP require only routine man-
ACC/AHA recommendations21
agement.73 Continue antidysrhythmic therapy and make provi-
From week 1 to week 36 of pregnancy, high-risk women (throm- sions for urgent management of dysrhythmias (see Chapter 2). In
boembolic history or older generation mechanical mitral valves) patients with MVP and associated symptomatic mitral regurgita-
should be maintained on warfarin (Æ low dose aspirin) to keep tion, the hemodynamic goals are similar to those for MR.
the INR between 2“3.21 After week 36, warfarin should be discon-
tinued. However, because of the risk of warfarin embryopathy
Anesthetic options
some women opt to use heparin as an alternative therapy during

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