American Society of Regional Anesthesia and Pain Medicine November 2017 - 47
Neuraxial Analgesia for Cardiac Surgery
A
nesthesiologists have long debated the utility of neuraxial
techniques in cardiac surgery. This approach continues to be
explored as the field of cardiac anesthesia trends away from
high-dose opioid regimens and toward balanced techniques that
allow for expedited recoveries.1 Increasing data support the efficacy
of thoracic epidural analgesia (TEA) and intrathecal analgesia as
beneficial components of these fast-track approaches. However,
unique considerations in cardiac surgery patients, such as the
requirement for full anticoagulation to facilitate cardiopulmonary
bypass, continue to limit their application in this area. The risks
associated with neuraxial techniques in this setting have potentially
devastating consequences, but at the same time, they occur
infrequently enough that an accurate incidence remains difficult to
establish. As discussed in this review, such uncertainty is a defining
feature in the debate about the application of neuraxial analgesia in
cardiac surgery.
The pathophysiologies encountered in cardiac surgery offer a
variety of potential mechanisms for neuraxial analgesia to exert
beneficial effects. Multifactorial inflammatory responses have
been correlated with a variety of adverse outcomes, including
cardiovascular, pulmonary, renal, hematologic, and neurologic
dysfunction, and can be attenuated in cardiac surgery patients with
neuraxial analgesia.2-4 High spinal analgesia (45-mg hyperbaric
bupivacaine), as a supplement to general anesthesia (GA) in
patients undergoing coronary artery bypass graft (CABG) and/or
aortic valve replacement, favorably alters the net inflammatory
response based on measurements of serum biomarkers.5 High
spinal analgesia (37.5-mg hyperbaric bupivacaine) also decreases
serum concentrations of epinephrine, norepinephrine, and cortisol
in the post-cardiopulmonary bypass (CPB) period for CABG
surgery.6
Benjamin A. Abrams, MD
Cardiothoracic Fellow
Nathaen S. Weitzel, MD
Associate Professor
Department of Anesthesiology
University of Colorado Anschutz Medical Campus
Aurora, Colorado
Section Editor: Kristopher Schroeder, MD
(CAD). In patients with multivessel CAD, TEA improves myocardial
perfusion in response to sympathetic activation as demonstrated
by nuclear medicine imaging.8 Conversely, sympathectomy can
potentially impair myocardial perfusion if systemic vasodilation
reduces coronary perfusion pressure.
The improvements in myocardial oxygen balance may extend
beyond sympathectomy and may also result from the excellent
pain control afforded by neuraxial analgesia. Improvements in
postoperative pain scores and opioid requirements have been
demonstrated with TEA over GA alone.9,10 Improved analgesia
likely contributes
to reductions in
mechanical ventilation
time and respiratory
complications as
well.7,10,11
"Despite growing evidence for the efficacy of
neuraxial analgesia, many anesthesiologists
remain hesitant to use these approaches
based on some unique considerations in the
cardiac surgery population."
In addition to attenuating
the inflammatory
response, neuraxial
analgesia provides
reliable sympatholysis.
Neuraxial blockade
for many cardiac
procedures requires at
least a T1 dermatome
level, which results in
complete sympathectomy. Blockade of cardiac accelerator fibers
(T1-T4) combined with dense analgesia reduces the sympathetic
response to surgical stimulation and limits myocardial oxygen
demand. Additionally, TEA has been shown to reduce the incidence
of supraventricular tachyarrhythmias (SVTs) in cardiac surgery
when compared to GA alone, further reducing myocardial oxygen
demand.7 With respect to myocardial oxygen supply, coronary
vasodilation secondary to sympathectomy can improve myocardial
perfusion, particularly in the setting of coronary artery disease
The extreme
application of
neuraxial analgesia
in this context is
to perform cardiac
surgery without general anesthesia.12,13 Until recently, most of the
reported cases were for single-vessel, off-pump CABG surgeries
because of the limited options for graft harvesting sites under
neuraxial anesthesia. However, Watanabe et al14 published data
from a large series of awake patients undergoing off-pump CABG
for which multiple vessels could be grafted through advancements
in surgical technique and regional anesthesia. For example, radial
artery grafts were harvested by either extending neuraxial blockade
to a C5 level or through brachial plexus nerve blocks. Additionally,
American Society of Regional Anesthesia and Pain Medicine
2017
47
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