PREOPERATIVE MANAGEMENT
Preoperative Evaluation
Caring for children with congenital heart disease presents the
anesthesiologist with a wide spectrum of anatomic and
physiologic abnormalities. Patients range from young, healthy, asymptomatic children
who are having a small ASD closed to the newborn infant with hypoplastic left heart
syndrome requiring aggressive perioperative hemodynamic and ventilatory support.
Intertwined with the medical diversity of these patients are the psychological factors
affecting both the patient and the parents. Preparation of the patient and the family
is time-consuming, but omitting or compromising this aspect of patient care is a
major deterrent to a successful outcome and patient/parental satisfaction. This
approach mandates that cardiac surgeons, cardiologists, anesthesiologists, intensivists,
and nurses work as a team in preparing the patient and the family for surgery and
postoperative recovery. This team-oriented approach also serves as a safeguard to
prevent errors and omissions in the exacting perioperative care necessitated by the
complexity of cardiac surgery for congenital heart disease. The preoperative visit
offers the family the opportunity to meet the surgeon and anesthesiologist.
The preoperative evaluation should always start with a careful
history and physical examination. The history should concentrate on the cardiopulmonary
system. Parents should be questioned about the general health and activity of their
child. Fundamentally, a child's general health and activity will reflect cardiorespiratory
reserve. Deficiencies may point toward cardiovascular or other systems that may
influence anesthetic or surgical risk. It is important to determine whether the
child has normal or impaired exercise tolerance. Is he or she gaining weight appropriately
or exhibiting signs of failure to thrive on the basis of cardiac cachexia? Does
the child exhibit signs of congestive heart failure (diaphoresis, tachypnea, poor
feeding, recurrent respiratory infections)? Is there progressive cyanosis or new
onset of cyanotic spells? Any intercurrent illness such as a recent upper respiratory
tract infection or pneumonia must be ascertained. Lower respiratory tract infections
may require a delay in proposed surgery, based on the negative impact that airway
reactivity and elevations in PVR may have on surgical outcome. Recurrent pneumonia
is frequently associated with pulmonary overcirculation altered lung compliance in
patients with increased pulmonary blood flow.
A good history must delineate previous surgical and cardiologic
interventions. These may have an impact on both surgical and anesthetic plans for
the current procedure. Patients who have had their subclavian artery sacrificed
for a subclavian flap angioplasty to correct coarctation or a Blalock-Taussig shunt
will not accurately display systemic arterial pressure or perhaps even pulse oximetry
when the monitoring is applied to the left arm. Likewise, children who have femoral
venous occlusion following catheterization are not candidates for femoral venous
access, particularly for femoral CPB should sternotomy prove impossible. It is equally
important to ascertain current medications, previous anesthetic problems, or family
history of anesthetic difficulties.
In the modern era of echocardiography and cardiac catheterization,
physical examination rarely contributes additional anatomic information about the
underlying cardiac lesion. However, it is extremely useful in assessing the overall
clinical condition of the child. For example, an ill-appearing, cachectic child
in respiratory distress has limited cardiorespiratory reserve, and the use of excessive
premedication or a prolonged inhalational induction could result in significant hemodynamic
instability.
Laboratory evaluation should include analysis of hemoglobin, hematocrit,
pulse oximetry, and, in selected patients (e.g., those on diuretics or with renal
impairment), serum electrolytes. An elevated hematocrit in a normovolemic child
gives an indication of the magnitude and chronicity of their hypoxemia. Levels above
60% may predispose to capillary sludging and secondary end organ damage, including
stroke.[37]
Despite these risks, liberalized nothing-by-mouth
guidelines that permit children to consume clear liquids up to 2 hours before anesthetic
induction have virtually eliminated the need to admit these patients for preoperative
intravenous hydration.[38]
[39]
Echocardiography with Doppler color flow imaging (echo-Doppler)
is an invaluable tool that provides a noninvasive means of assessing intracardiac
anatomy, blood flow patterns, and estimates of physiologic data.[40]
For many cardiac defects, more invasive studies are generally not required if a
good echocardiographic assessment is made. Echo-Doppler is especially helpful for
defining intracardiac abnormalities. Extracardiac abnormalities, such as pulmonary
artery or vein stenosis, are more difficult to define by echo-Doppler and often require
cardiac catheterization. The ability to interpret anatomy and physiology accurately
requires a skilled echocardiographer, reaffirming the need for a well-integrated
interactive team. Although the complexities posed by extreme anatomic variation
and changing loading conditions render intraoperative echo-Doppler challenging even
for experienced echocardiographers, the pediatric cardiac anesthesiologist should
develop some familiarity with its capabilities and limitations in order to participate
in critical intraoperative management decisions.
Cardiac catheterization remains the gold standard for assessing
anatomy and physiologic function in congenital heart disease. Although many anatomic
questions can now be reliably answered noninvasively, cases that present complex
anatomic questions or those for which physiologic data are required, catheterization
remains a vital tool. Important catheterization data for the anesthesiologist include
the following:
- Child's response to sedative medications
- Pressure and oxygen saturation in all chambers and great vessels
- Location and magnitude of intra- and extracardiac shunt (
p:s)
- Pulmonary vascular resistance, systemic vascular resistance
- Chamber size and function
- Valvular anatomy and function
- Distortion of systemic or pulmonary arteries related to prior surgery
- Coronary artery anatomy
- Anatomy, location, and function of previously created shunts
- Acquired or congenital anatomic variants that might have an impact on planned
vascular access or surgery
Careful review of the cardiac catheterization data and an understanding
of their potential impact on the operative and anesthetic plan are essential. Not
all the medical problems can be evaluated and corrected preoperatively; the surgeon,
cardiologist, and anesthesiologist must discuss the potential management problems
and any need for further evaluation or intervention before arrival in the operating
room. Appropriate communication and cooperation between the two physicians will
optimize patient care and facilitate perioperative clinical management. Typically,
institutions have a regularly scheduled combined cardiology/cardiac surgery meeting
to discuss candidates for surgery, during which all essential information is displayed
and discussed. Such a meeting provides an invaluable opportunity for learning about
specific patients proposed for surgery as well as a continuing educational forum
that promotes an interdisciplinary exchange directed at contemporary concepts in
congenital heart disease and its treatment, both medical and surgical.
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