Cardiac Catheterization
Placement of transvenous and transarterial catheters into the
heart and great vessels (cardiac catheterization) allows determination of cardiac
anatomy, ventricular function, valvular anatomy, and pulmonary vascular anatomy.
Pressure measurements in cardiac chambers and vascular structures may be made with
these catheters. Injection of contrast medium allows radiologic visualization of
various structures, and indicator injection with distal sampling allows determination
of flow according to the Fick principle. In addition, blood samples may be withdrawn
from various areas for determination of oxygen saturation to detect the presence
and location of shunts. Although much (but by no means all) of this information
can be obtained with echocardiography, cardiac catheterization remains the "gold
standard" for detailed diagnosis of complex cardiac anatomic anomalies. It must
be noted that because multiple measurements and samples are necessary for the complete
cardiac catheterization procedure, the measurements cannot be performed simultaneously.
For the hemodynamic and shunt calculations to be valid, a relatively constant cardiovascular
and respiratory state is necessary.[111]
[112]
Arterial pressures of oxygen (PaO2
) and
CO2
(PaCO2
) must be "normal"
for the patient being studied and must remain so during the measurement periods.
The anesthetic techniques used in a given institution should be consistent so that
the cardiologist does not have to account for differences in anesthetic techniques
when interpreting diagnostic data. These constraints can make anesthetic management
of these patients extremely difficult.
Cardiac catheterization in adults is frequently performed in conjunction
with coronary angiography. Access to the right side of the heart (pulmonary circulation)
is through the venous system and usually involves catheter placement in the femoral
vein. The left side of the heart (systemic circulation) is accessed as the coronary
arteries are accessed, through the brachial, radial, or more commonly, the femoral
arteries. Complications related to vascular access are similar to those outlined
for coronary angiography. Because catheters are placed within the cardiac chambers,
supraventricular and ventricular arrhythmias are common during this procedure. The
procedure is usually performed under local anesthesia, but patients benefit from
systemic analgesia and sedation. Medications frequently used for this purpose include
fentanyl and midazolam, sometimes supplemented with propofol. Oxygen is administered
as needed, but care must be taken to maintain "normal" (for the patient) arterial
blood gas values if pulmonary hemodynamics is to be measured during the procedure.
As with coronary angiography, the anesthesiologist must be prepared to deal with
acute hemodynamic and respiratory instability in patients who may have severe valvular
and myocardial dysfunction.
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