e3 86 Zierer A, El Sayed Ahmad A, Papadopoulos N, et al Selective an tegrade cerebral perfusion and mild (28°C–30°C) systemic hypo thermic circulatory arrest for aortic arch replacement results from 1[.]
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an-tegrade cerebral perfusion and mild (28°C–30°C) systemic
hypo-thermic circulatory arrest for aortic arch replacement: results from
1002 patients J Thorac Cardiovasc Surg 2012;144:1042-1049.
87 Corno AF, Bostock C, Chiles SD, et al Comparison of Early
Out-comes for Normothermic and Hypothermic Cardiopulmonary
Bypass in Children Undergoing Congenital Heart Surgery
Fron-tiers in pediatrics 2018;6:219.
88 Xiong Y, Sun Y, Ji B, Liu J, Wang G, Zheng Z Systematic Review
and Meta-Analysis of benefits and risks between normothermia and
hypothermia during cardiopulmonary bypass in pediatric cardiac
surgery Paediatric anaesthesia 2015;25(2):135-142.
89 Murkin JM, Farrar JK, Tweed WA, et al Cerebral autoregulation
and flow/metabolism coupling during cardiopulmonary bypass: the
influence of PaCO 2 Anesth Analg 1987;66:825-832.
90 Abdul Aziz KA, Meduoye A Is pH-stat or alpha-stat the best
tech-nique to follow in patients undergoing deep hypothermic
circula-tory arrest? Interact Cardiovasc Thorac Surg 2010;10:271-282.
91 Melrose DG, Dreyer B, Bentall HH, Baker JB Elective cardiac
arrest Lancet 1955;269:21-22.
92 Shiroishi MS Myocardial protection: the rebirth of
potassium-based cardioplegia Tex Heart Inst J 1999;26:71-86.
93 Follette DM, Mulder DG, Maloney JV, Buckberg GD Advantages
of blood cardioplegia over continuous coronary perfusion or
inter-mittent ischemia Experimental and clinical study J Thorac
Cardio-vasc Surg 1978;76:604-619.
94 Barner HB Blood cardioplegia: a review and comparison with
crystalloid cardioplegia Ann Thorac Surg 1991;52:1354-1367.
95 Bartels C, Gerdes A, Babin-Ebell J, et al Cardiopulmonary bypass:
evi-dence or experience based? J Thorac Cardiovasc Surg 2002;124:20-27.
96 Kotani Y, Tweddell J, Gruber P, et al Current cardioplegia practice
in pediatric cardiac surgery: a North American multiinstitutional
survey Ann Thorac Surg 2013;96:923-929.
97 Chambers DJ, Fallouh HB Cardioplegia and cardiac surgery:
pharmacological arrest and cardioprotection during global ischemia
and reperfusion Pharmacol Ther 2010;127:41-52.
98 Matte GS, del Nido PJ History and use of del Nido cardioplegia
solution at Boston Children’s Hospital J Extra Corpor Technol
2012;44:98-103.
99 Ginther RM Jr, Gorney R, Forbess JM Use of del Nido
cardiople-gia solution and a low-prime recirculating cardioplecardiople-gia circuit in
pediatrics J Extra Corpor Technol 2013;45:46-50.
100 Allen BS, Barth MJ, Ilbawi MN Pediatric myocardial protection:
an overview Semin Thorac Cardiovasc Surg 2001;13:56-72.
101 Butler J, Rocker GM, Westaby S Inflammatory response to
cardio-pulmonary bypass Ann Thorac Surg 1993;55:552-559.
102 Levy JH, Tanaka KA Inflammatory response to cardiopulmonary
bypass Ann Thorac Surg 2003;75:S715-S720.
103 Wan S, LeClerc JL, Vincent JL Inflammatory response to cardio-pulmonary bypass: mechanisms involved and possible therapeutic
strategies Chest 1997;112:676-692.
104 Allan CK, Newburger JW, McGrath E, et al The relationship be-tween inflammatory activation and clinical outcome after infant
cardiopulmonary bypass Anesth Analg 2010;111:1244-1251.
105 Hovels-Gurich HH, Vazquez-Jimenez JF, Silvestri A, et al Produc-tion of proinflammatory cytokines and myocardial dysfuncProduc-tion af-ter araf-terial switch operation in neonates with transposition of the
great arteries J Thorac Cardiovasc Surg 2002;124:811-820.
106 Appachi E, Mossad E, Mee RB, Bokesch P Perioperative serum interleukins in neonates with hypoplastic left-heart syndrome and
transposition of the great arteries J Cardiothorac Vasc Anesth
2007;21:184-190.
107 Graham EM, Atz AM, McHugh KE, et al Preoperative steroid treatment does not improve markers of inflammation after cardiac
surgery in neonates: results from a randomized trial J Thorac Car-diovasc Surg 2014;147:902-908.
108 Scrascia G, Rotunno C, Guida P, et al Perioperative steroids administration in pediatric cardiac surgery: a meta-analysis of
randomized controlled trials Pediatr Crit Care Med 2014;15:
435-442.
109 Fudulu DP, Gibbison B, Upton T, et al Corticosteroids in Pediatric Heart Surgery: Myth or Reality Frontiers in pediatrics 2018;6:112.
110 Dreher M, Glatz AC, Kennedy A, Rosenthal T, Gaynor JW A Single-Center Analysis of Methylprednisolone Use during Pediatric Cardiopulmonary Bypass The Journal of extra-corporeal technol-ogy 2015;47(3):155-159.
111 Darling E, Searles B, Nasrallah F, et al High-volume, zero balanced ultrafiltration improves pulmonary function in a model of
post-pump syndrome J Extra Corpor Technol 2002;34:254-259.
112 Huang H, Yao T, Wang W, et al Continuous ultrafiltration attenu-ates the pulmonary injury that follows open heart surgery with
cardiopulmonary bypass Ann Thorac Surg 2003;76:136-140.
113 Sever K, Tansel T, Basaran M, et al The benefits of continuous
ul-trafiltration in pediatric cardiac surgery Scand Cardiovasc J 2004;
38:307-311.
114 Song LO, Yinglong LI, Jinping LI Effects of zero-balanced ultrafil-tration on procalcitonin and respiratory function after
cardiopul-monary bypass Perfusion 2007;22:339.
Trang 2Abstract: Cardiopulmonary bypass (CPB), which originated in
the mid-twentieth century, was designed to allow for the repair of
congenital heart defects Its history has since been characterized
by perpetual technological advancements that have been
instru-mental in sustaining the momentum of clinical progress of this
field The current guidelines for use of CPB to treat congenital
heart defects are designed to meet the metabolic demands of the
patient throughout the repair while minimizing the impact of
as-sociated nonphysiologic effects The progress of CPB in repair of
Key words: Cardiopulmonary bypass, perfusionist, congenital heart defect, oxygenation, anticoagulation, ultrafiltration, hypo-thermia, myocardial protection, systemic inflammatory response
congenital heart defects has played a major role in the steady re-duction of morbidity and mortality associated with cardiac sur-gery in children Pediatric mortality rates are now comparable to those in adult patients
Trang 336
Critical Care After Surgery for
Congenital Cardiac Disease
PAULA HOLINSKI, JENNIFER TURI, VEERAJALANDHAR ALLAREDDY,
V BEN SIVARAJAN, AND ALEXANDRE T ROTTA
• The neonatal myocardium is less compliant than that of the
older child, less tolerant of increases in afterload, and less
re-sponsive to increases in preload A predictable decrease in
car-diac index typically occurs 6 to 12 hours after separation from
cardiopulmonary bypass, but milrinone administration during
the early postoperative period may attenuate this phenomenon.
• Patients with postoperative low cardiac output (CO) require
careful evaluation for unanticipated residual lesions.
• Patients with restrictive physiology from hypertrophy and
diastolic dysfunction of the right ventricle may require high
right-sided filling pressures to achieve adequate cardiac output,
making them prone to hepatic congestion, anasarca, pleural
effusions, and ascites.
• Inhaled nitric oxide plays an important role in the management
of postoperative pulmonary hypertension in the cardiac
inten-sive care unit.
• Hypoxemia after bidirectional cavopulmonary anastomosis
generally is a sign of decreased pulmonary blood flow related
to reduced cardiac output.
PEARLS
• Liberation from positive-pressure mechanical ventilation should be accomplished as soon as feasible, particularly in patients after a cavopulmonary anastomosis (bidirectional Glenn) or Fontan operation because spontaneous breathing improves pulmonary blood flow, arterial oxygen saturation, and ventricular preload.
• Ventricular ectopy and elevated atrial pressures after the arterial switch operation should raise suspicion of myocardial ischemia from insufficient coronary blood flow.
• Postoperative care of the patient with hypoplastic left heart syndrome after stage I palliation (Norwood procedure) may require delicate balancing of the pulmonary and systemic blood flows A high arterial oxygen saturation denotes excessive pulmonary blood flow and in patients with impaired ventricular output is generally accompanied by inadequate systemic blood flow, acidosis, and end-organ dysfunction.
Congenital anomalies account for the largest diagnostic category
among causes of infant mortality in the United States.1 Structural
heart disease leads the list of congenital malformations Of the
more than 4 million children born each year in the United States,
nearly 40,000 have some form of congenital heart disease (CHD)
Approximately half of these children appear for therapeutic
inter-vention within the first year of life; the majority require critical
care expertise in pediatric intensive care units (PICUs) We
recog-nize that many centers have developed separate specialized
pediat-ric cardiac intensive care units to care for these patients, while
some continue to cohort cardiac patients within a general PICU
In this chapter, the PICU designation is used interchangeably to
denote the unit caring for critically ill patients necessitating care
following surgery or procedures to treat congenital cardiac
condi-tions These patients now represent a major diagnostic category for
admissions in large PICUs across the country, accounting for 30%
to 40% or more of PICU admissions in many centers In addition
to the traditional pediatric-age patients, many PICUs now also care for young adult survivors of congenital heart disease, since these patients now outnumber children with congenital heart dis-ease in the general population.2
Neonatal Considerations
Care of the critically ill neonate requires an appreciation of the special structural and functional features of immature organs, the
interactions of the transitional neonatal circulation, and the
sec-ondary effects of the congenital heart lesion on other organ sys-tems.3–5 The neonate responds more quickly and profoundly to physiologically stressful circumstances, such as rapid changes in
pH, lactic acid, blood glucose, and temperature Neonates have diminished fat and carbohydrate reserves compared with older children; however, they have a higher metabolic rate Immaturity
of the liver and kidney may be associated with reduced protein
Trang 4CHAPTER 36 Critical Care After Surgery for Congenital Cardiac Disease
synthesis and glomerular filtration such that drug metabolism is
altered and hepatic synthetic function is reduced These issues
may be compounded by the normal increased total body water of
the neonate compared with the older patient, along with the
pro-pensity for capillary leakage This is especially prominent in the
immature lung of the neonate, in which the pulmonary vascular
bed is nearly fully recruited at rest, and the lymphatic recruitment
required to handle elevated mean capillary pressures associated
with increases in pulmonary blood flow may be suboptimal.5 The
neonatal myocardium is less compliant than that of the older
child, less tolerant of increases in afterload, and less responsive to
increases in preload Younger age also predisposes the
myocar-dium to the adverse effects of cardiopulmonary bypass (CPB) and
hypothermic ischemia implicit in support techniques used during
cardiac surgery These factors do not preclude intervention in the
neonate but rather simply dictate that extraordinary vigilance
be applied to the care of these children and that intensive care
management plans account for the immature physiology
The observed benefits of neonatal reparative operations in
pa-tients with two ventricles are numerous (Box 36.1) Elimination
of cyanosis and congestive heart failure (CHF) early in life
opti-mizes conditions for normal growth and development Palliative
procedures such as pulmonary artery banding and creation of
systemic-to-pulmonary artery shunts do not fully address cyanosis
or CHF and may introduce their own set of physiologic and
ana-tomic complications Examples of improved outcomes with a
single reparative operation rather than staged palliation as a
new-born are well known and evoke little controversy Approaches that
have been abandoned include banding the pulmonary arteries in
truncus arteriosus,6 staging repair of type B interrupted aortic
arch (IAA),7 and staging repair of transposition of the great
arter-ies with IAA.8 In other conditions (e.g., severely cyanotic
new-born with tetralogy of Fallot [TOF]), the risks and benefits of
neonatal repair versus a palliative shunt are debatable.9
Whereas the neonate may be more labile than the older child,
there is ample evidence that this age group is more resilient in its
response to various forms of stress, including metabolic or ischemic
injury Tolerance of hypoxemia in the neonate is characteristic of
many species,10 and the plasticity of the neurologic system in the
neonate is well known.11 It is the rule rather than the exception
that neonates presenting with shock secondary to obstructive left
heart lesions can be effectively resuscitated without persistent
end-organ impairment The pliability and mobility of vascular
struc-tures in the neonate improve the technical aspects of surgery
Reparative operations in neonates take advantage of normal
post-natal changes, allowing more normal growth and development in
crucial areas such as myocardial muscle, pulmonary parenchyma,
and coronary and pulmonary angiogenesis
Postoperative pulmonary hypertensive events are more
com-mon in the infant who has been exposed to weeks or com-months of
high pulmonary pressure and flow.6 This is especially true for such
lesions as truncus arteriosus, complete atrioventricular (AV) canal defects, and transposition of the great arteries (TGA) with ven-tricular septal defects (VSDs) Finally, cognitive and psychomotor abnormalities associated with months of hypoxemia or abnormal hemodynamics may be diminished or eliminated by early repair However, if early reparative surgery results in more exposures
to CPB (e.g., repeated conduit changes) and associated adverse effects on cognitive or motor function, then the risk-to-benefit assessment must be modified accordingly
Preoperative Care
Optimal preoperative care involves (1) initial stabilization, airway management, and establishment of adequate vascular access; (2) complete and thorough noninvasive delineation of the ana-tomic defect(s); (3) initiation/termination of prostaglandin therapy, as appropriate; (4) evaluation and treatment of secondary organ dysfunction, particularly the brain, kidneys, and liver; and (5) cardiac catheterization if necessary, typically for (a) physiologic assessment (e.g., vascular response to oxygen or another pulmo-nary vasodilator), (b) interventions such as balloon atrial septos-tomy or valvoseptos-tomy, or (c) anatomic definition not possible by echocardiography (e.g., coronary artery distribution in pulmonary atresia with intact ventricular septum or delineation of aorticopul-monary collaterals in TOF with pulaorticopul-monary atresia) Magnetic resonance imaging (MRI) and magnetic resonance angiography have emerged as important adjuvant diagnostic modalities in the evaluation of the cardiovascular system, including qualitative as-sessments of valve and ventricular function, and quantification of flow, ventricular volume, mass, and ejection fraction.12 , 13
Congenital heart defects can be complex and difficult to cate-gorize or conceptualize Rather than trying to determine the management for each individual anatomic defect, a physiologic approach can be taken The following questions should be asked:
1 How does the systemic venous return reach the systemic arte-rial circulation to maintain cardiac output?
2 What, if any, intracardiac mixing, shunting, or outflow obstruction exists?
3 Are the pulmonary and systemic circulations in series or paral-lel?
4 Are the defects amenable to a two-ventricle or single-ventricle repair?
5 Is pulmonary blood flow increased or decreased?
6 Is there a volume load or pressure load on the ventricles? Appropriate organization of preoperative data, patient prepa-ration, and decisions about monitoring, anesthetic agents, and postoperative care are best accomplished by focusing on a few major pathophysiologic problems, beginning with whether the patient is cyanotic, is in CHF, or both Most pathophysiologic mechanisms that are pertinent to optimal patient preparation and
to the perioperative plan focus on one of the following major problems: severe hypoxemia, excessive pulmonary blood flow, CHF, obstruction of blood flow from the left heart, and poor ventricular function Although some patients with congenital heart disease present with only one of these problems, many have multiple interrelated issues
Severe Hypoxemia
In the first few days of life, many of the cyanotic forms of CHD present with severe hypoxemia (Pao2 ,50 mm Hg) in the absence
of respiratory distress Infusion of prostaglandin E1 (PGE1) in
• BOX 36.1 Advantage of Neonatal Repair
Early elimination of cyanosis
Early elimination of congestive heart failure
Optimal circulation for growth and development
Reduced anatomic distortion from palliative procedures
Reduced hospital admissions while awaiting repair
Reduced parental anxiety while awaiting repair
Trang 5382 SECTION IV Pediatric Critical Care: Cardiovascular
patients with decreased pulmonary blood flow maintains or
rees-tablishes pulmonary flow through the ductus arteriosus This may
also improve mixing of venous and arterial blood at the atrial level
in patients with transposition of the great arteries.14
Conse-quently, neonates rarely require surgery while severely hypoxemic
PGE1 dilates the ductus arteriosus of the neonate with
life-threatening ductus-dependent cardiac lesions and improves the
patient’s condition before surgery PGE1 can reopen a functionally
closed ductus arteriosus even several days after birth, or it can be
used to maintain patency of the ductus arteriosus for several
months postnatally.14 , 15 The common side effects of PGE1
infusion—apnea, hypotension, fever, central nervous system
(CNS) excitation—are easily managed in the neonate when
nor-mal therapeutic doses of the drug (0.01–0.05 mg/kg per minute)
are used.16 However, PGE1 is a potent vasodilator; thus,
intravas-cular volume may require augmentation at higher doses Patients
with intermittent apnea resulting from administration of PGE1
may require mechanical ventilation preoperatively, although
apnea can resolve with the concomitant administration of
amino-phylline or caffeine.17 PGE1 usually improves the arterial
oxygen-ation of hypoxemic neonates who have poor pulmonary perfusion
as a result of obstructed pulmonary flow (critical pulmonic
steno-sis or pulmonary atresia) by providing pulmonary blood flow
from the aorta via the ductus arteriosus The improved
oxygen-ation reverses the lactic acidosis that often develops during
epi-sodes of severe hypoxia, and clinical improvement is seen in a
matter of minutes to hours.18
Excessive Pulmonary Blood Flow
Excessive pulmonary blood flow is frequently the primary
prob-lem of patients with CHD The intensivist must carefully evaluate
the hemodynamic and respiratory impact of left-to-right shunts
and the extent to which it contributes to the perioperative course
in the ICU Children with left-to-right shunts may have chronic
low-grade pulmonary infection and congestion that cannot be
eliminated despite optimal preoperative preparation If so, surgery
should not be postponed further Respiratory syncytial viral
infec-tions are particularly prevalent in this population, but advances in
intensive care have markedly improved outcomes with this and
other viral pneumonias.19
Aside from the respiratory impairment caused by increased
pulmonary blood flow, the left heart must dilate to accept
pulmo-nary venous return that might be several times normal If the
body requires more systemic blood flow, the neonatal heart
re-sponds inefficiently, as most of the increment in cardiac output is
recirculated to the lungs Eventually, symptoms of CHF appear
Medical management with inotropes, systemic vasodilators, and
diuretics may improve the patient’s condition, but the diuretics
may induce profound hypochloremic alkalosis and potassium
depletion that often persist after surgery
Obstruction of Left Heart Outflow
Patients who require surgery to relieve obstruction to outflow
from the left heart are among the most critically ill children in the
ICU These lesions include interruption of the aortic arch, critical
coarctation of the aorta, aortic stenosis (AS), and mitral stenosis
or atresia as part of the hypoplastic left heart syndrome (HLHS)
spectrum These neonates present with inadequate systemic
perfu-sion and profound metabolic acidosis The initial pH may be
be-low 7 despite a be-low partial pressure of arterial carbon dioxide
(Paco2) Systemic blood flow is largely or completely dependent
on blood flow into the aorta from the ductus arteriosus; thus, its closure causes a dramatic worsening of the patient’s condition The patient suddenly becomes critically ill, and survival requires PGE1 infusion to allow blood flow into the aorta from the pulmo-nary artery.18 , 20 PGE1 infusion improves perfusion and metabo-lism in neonates with acidosis, metabolic derangements, and renal failure because of inadequate systemic perfusion so that surgery generally can be deferred until stability is achieved Ventilatory and inotropic support and correction of metabolic acidosis— along with calcium, glucose, and electrolyte abnormalities— should occur preoperatively Adequacy of stabilization, rather than severity of illness at presentation, appears to influence post-operative outcome the most.21
Ventricular Dysfunction
Ideally, the intensivist should participate in the preoperative care of all patients who are expected to recover in the ICU after surgery Understanding the extent of ventricular dysfunction preoperatively provides considerable insight into intraoperative and postoperative events Although patients with large shunts may have only mild-to-moderate hypoxemia as a result of ex-cessive pulmonary blood flow, the price paid for near-normal arterial oxygen saturation is chronic ventricular dilation and dysfunction and pulmonary vascular obstructive disease Older patients with CHD and poor ventricular function as a result of chronic ventricular volume overload (aortic or mitral valve regurgitation or longstanding systemic-to-pulmonary arterial shunts) present a different challenge, mitigated to some extent
by afterload reduction However, great care must be exercised
in hearts with chronic volume overload as there is a propensity for ventricular fibrillation during sedation, anesthesia, or intu-bation of the airway For patients with significantly increased pulmonary-to-systemic flow ratio (Qp/Qs), systemic blood flow should be optimized without further augmenting pulmo-nary flow during induction of anesthesia in the ICU or in the operating room
Postoperative Care
Assessment
When the clinical course of patients after cardiac surgery deviates from the usual expectation of uncomplicated recovery, our first responsibility is to verify the accuracy of the preoperative diagno-sis and the adequacy of surgical repair For example, a young in-fant who is acidotic, hypotensive, and cyanotic after surgical re-pair of TOF may tempt us to ascribe these findings to the vagaries
of ischemia/reperfusion injury caused by CPB or transient, post-operative stiffness of the right ventricle However, the real culprit may be an additional VSD undetected preoperatively and there-fore not closed, a significant surgical patch leak, or residual right ventricle (RV) outflow obstruction Correct postoperative assess-ment is imperative, and treatassess-ment follows accordingly Evaluation
of the postoperative patient relies on examination, monitoring, interpretation of vital signs, and imaging Only when the accu-racy of the diagnosis and adequacy of the repair are established can a CPB-related low–cardiac output state be presumed and treatment optimized Treating low–cardiac output states and pre-venting cardiovascular collapse often are the central features of pediatric cardiac intensive care and are the focus of this chapter