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ACC/AHA
Guideline Update for Perioperative Cardiovascular Evaluation
for Noncardiac Surgery
A
Report of the American College of Cardiology/American
Heart Association Task Force on Practice Guidelines
(Committee to Update the 1996 Guidelines on Perioperative
Cardiovascular Evaluation for Noncardiac Surgery)
VIII.
Anesthetic Considerations and
Intraoperative Management
The
pathophysiological events that occur with the trauma
of surgery and the perioperative administration of anesthetic
and pain-relieving drugs often affect the physiology
of cardiac function and dysfunction to great degrees.
Specific integration of these changes with the consultative
evaluation is a field unto itself and beyond the scope
of these guidelines. The information provided by the
cardiovascular consultant needs to be integrated by
the anesthesiologist, surgeon, and postoperative caregivers
in preparing an individualized perioperative management
plan.
There
are many different approaches to the details of the
anesthetic care of the cardiac patient. Each has implications
regarding anesthetic and intraoperative monitoring.
In addition, no study has clearly demonstrated a change
in outcome from the use of the following techniques:
a pulmonary artery catheter, ST-segment monitor, transesophageal
echocardiography (TEE), or intravenous nitroglycerin.
Therefore, the choice of anesthetic and intraoperative
monitors is best left to the discretion of the anesthesia
care team. Intraoperative management may be influenced
by the perioperative plan, including need for postoperative
monitoring, ventilation, and analgesia. Therefore, a
discussion of these issues before the planned surgery
will allow for a smooth transition through the perioperative
period.
A.
Choice of Anesthetic Technique and Agent
Multiple
studies have examined the influence of anesthetic drugs
and techniques on cardiac morbidity. In a large-scale
study of unselected patients, coexisting disease and
surgical procedure were the most important determinants
of outcome (202).
It appears there is no one best myocardium-protective
anesthetic technique (203-207).
All anesthetic techniques and drugs are associated with
known effects that should be considered in the perioperative
plan. Opioid-based anesthetics have become popular because
of the cardiovascular stability associated with their
use. The use of high doses, however, is associated with
the need for postoperative ventilation. Because weaning
from the ventilator in an intensive care setting has
been associated with myocardial ischemia, this feature
is important in the overall risk-benefit equation.
All
inhalational agents have cardiovascular effects, including
depression of myocardial contractility and afterload
reduction, their similarities being greater than their
differences. The choice of agent among the most common
agents—halothane, enflurane, isoflurane, and sevoflurane—did
not influence outcome in randomized trials (206).
Desflurane, one of the newer inhalational agents, has
been associated with an increased incidence of myocardial
ischemia compared with a narcotic-based anesthetic in
patients undergoing CABG, although the incidence of
MI was not different (322).
Neuraxial
anesthetic techniques include spinal and epidural approaches.
Both techniques can result in sympathetic blockade,
resulting in decreases in both preload and afterload.
The decision to use neuraxial anesthesia for the high-risk
cardiac patient may be influenced by the dermatomal
level of the surgical procedure. Infrainguinal procedures
can be performed under spinal or epidural anesthesia
with minimal hemodynamic changes if neuraxial blockade
is limited to those dermatomes. Abdominal procedures
can also be performed using neuraxial techniques; however,
high dermatomal levels of anesthesia may be required
and may be associated with significant hemodynamic effects.
High dermatomal levels can potentially result in hypotension
and reflex tachycardia if preload becomes compromised
or blockade of the cardioaccelerators occurs. A total
of 5 studies have been published (203-207)
that evaluate regional vs. general anesthesia for high-risk
patients undergoing noncardiac surgery. No difference
in outcome was detected in any of these studies.
Monitored
anesthesia care by an anesthesia caregiver includes
the use of local anesthesia supplemented with intravenous
sedation/analgesia and is believed by some to be associated
with the greatest safety margin. In a large-scale study,
however, monitored anesthesia care was associated with
the highest incidence of 30-day mortality (202).
This finding may reflect a strong selection bias in
which the patients with significant coexisting disease
were selected for surgery with monitored anesthesia
care rather than other anesthetic techniques. Although
this technique can eliminate some of the undesirable
effects of general or neuraxial anesthesia, it provides
poor blockade of the stress response unless the local
anesthetic provides profound anesthesia of the affected
area. If the local anesthetic block is less than satisfactory
or cannot be used at all, monitored anesthesia care
could result in an increased incidence of myocardial
ischemia and cardiac dysfunction compared with general
or regional anesthesia. To achieve the desired effect,
excess sedation can occur. Therefore, there may be no
significant difference in overall safety with monitored
anesthesia care, and general or regional anesthesia
may be preferable.
B.
Perioperative Pain Management
From
the cardiac perspective, pain management may be a crucial
aspect of perioperative care. Because the majority of
cardiac events in noncardiac surgical patients occur
postoperatively, the postoperative period may be the
time during which ablation of stress, adverse hemodynamics,
and hypercoagulable responses is most critical. Although
no randomized, controlled study specifically addressing
analgesic regimens has demonstrated improvement in outcome,
patient-controlled analgesia techniques are associated
with greater patient satisfaction and lower pain scores.
Epidural or spinal opiates are becoming more popular
and have several theoretic advantages. Several studies
have evaluated differing combinations of general and
epidural anesthesia and intravenous and epidural analgesia
(323-327).
The patients having epidural anesthesia/analgesia have
demonstrated lower opiate dosages, better ablation of
the catecholamine response, and a less hypercoagulable
state (328,329).
In one study of patients undergoing lower extremity
vascular bypass procedures, the use of epidural anesthesia/analgesia
was associated with a lower incidence of cardiac morbidity;
however, this finding was not confirmed in two other
studies (205,207,327).
In a study of 124 patients undergoing aortic surgery,
there was no difference in the incidence of myocardial
ischemia in patients randomized to postoperative intravenous
analgesia vs. epidural analgesia (326).
Most important, an effective analgesic (i.e., one that
blunts the stress response) regimen must be included
in the perioperative plan.
C.
Intraoperative Nitroglycerin
1.
General Considerations
Nitroglycerin has been shown to reverse myocardial ischemia
intraoperatively. Intraoperative prophylactic use of
nitroglycerin in patients at high risk may have no effects,
however, or may actually lead to cardiovascular decompensation
through decreases in preload. Additionally, nitroglycerin
paste or patch may have uneven absorption intraoperatively.
Accordingly, nitroglycerin should usually be administered
in the intravenous formulation, if required.
The
venodilating and arterial dilating effects of nitroglycerin
are mimicked by some anesthetic agents, so that the
combination of agents may lead to significant hypotension
and myocardial ischemia. Therefore, nitroglycerin should
be used only when the hemodynamic effects of other agents
being used are considered.
2.
Summary of Evidence
Four controlled studies have evaluated the value of
prophylactic nitroglycerin infusions for high-risk patients,
including two studies in noncardiac surgery patients
(Table 11) (183,184,208,209).
Only one study, performed in patients with stable angina
undergoing carotid endarterectomy, demonstrated a reduced
incidence of intraoperative myocardial ischemia in the
group receiving 1 mcg per kg per minute of nitroglycerin.
Neither of the two small studies demonstrated any reduction
in the incidence of MI or cardiac death.
Recommendations
for Intraoperative Nitroglycerin
Class I
High-risk patients previously taking nitroglycerin who
have active signs of myocardial ischemia without hypotension.
Class
IIb
As a prophylactic agent for high-risk patients to prevent
myocardial ischemia and cardiac morbidity, particularly
in those who have required nitrate therapy to control
angina. The recommendation for prophylactic use of nitroglycerin
must take into account the anesthetic plan and patient
hemodynamics and must recognize that vasodilation and
hypovolemia can readily occur during anesthesia and
surgery.
Class
III
Patients with signs of hypovolemia or hypotension.
D.
Use of TEE
1. General Considerations
The use of TEE has become increasingly common in the
operating room for cardiac surgery but is less frequently
used in noncardiac surgery. Multiple investigations
have documented the improved sensitivity of TEE for
detection of myocardial ischemia compared with electrocardiography
or pulmonary capillary wedge pressure measurements.
Most studies have used off-line analysis of the TEE
images, however, and automated, on-line detection may
increase its value.
2.
Summary of Evidence
There are few data regarding the value of TEE-detected
wall-motion abnormalities to predict cardiac morbidity
in noncardiac surgical patients. In two recent studies
from the same group, intraoperative wall-motion abnormalities
were poor predictors of cardiac morbidity (210,211).
In one study involving 322 men undergoing noncardiac
surgeries, TEE demonstrated an odds ratio of 2.6 (95%
CI, 1.2 to 5.7) for predicting perioperative cardiac
events (210).
3.
Analysis and Interpretation
Interpretation of TEE requires additional training.
At present there are no commercially available real-time
monitors of quantitative wall motion. Although regional
wall-motion abnormalities in a high-risk patient suggest
myocardial ischemia, resolution of myocardial ischemia
may not result in improvement of wall motion.
4.
Recommendations
Currently there is insufficient evidence to determine
cost-effectiveness of TEE for its use as a diagnostic
monitor or to guide therapy during noncardiac surgery;
however, the routine use of TEE in noncardiac surgery
does not appear warranted. Guidelines for the appropriate
use of TEE have been developed by the American Society
of Anesthesiologists and the Society of Cardiovascular
Anesthesiologists (330).
E.
Maintenance of Body Temperature
Hypothermia
is common during the perioperative period in the absence
of active warming of patients. In a retrospective analysis
of a prospective randomized trial comparing two different
anesthetic techniques for infrainguinal revascularization
surgery, hypothermia was associated with an increased
risk of myocardial ischemia compared with patients who
had a core temperature greater than 35.5 degrees C in
the postanesthesia care unit (331).
Several methods of maintaining normothermia are available
in clinical practice, the most widely studied being
forced-air warming.
1.
Summary of Evidence
One randomized clinical trial has been performed in
300 high-risk patients undergoing noncardiac surgery
in which patients were randomized to active warming
via forced air (normothermic group) vs. routine care
(332).
Perioperative morbid cardiac events occurred less frequently
in the normothermic group than in the hypothermic group
(1.4% vs. 6.3%; p=0.02). Hypothermia was an independent
predictor of morbid cardiac events by multivariate analysis
(relative risk, 2.2; 95% CI, 1.1 to 4.7; p=0.04), indicating
a 55% reduction in risk when normothermia was maintained.
F.
Intra-Aortic Balloon Counterpulsation Device
Placement
of an intra-aortic balloon counterpulsation device has
been suggested as a means of reducing perioperative
cardiac risk in noncardiac surgery. Several case reports
have documented its use in patients with unstable coronary
syndromes or severe CAD undergoing urgent noncardiac
surgery (212,213,333,334).
Although the rate of cardiac complications is low compared
with other series of patients at similarly high risk,
there are no randomized trials to assess its true effectiveness.
Additionally, the use of intra-aortic balloon counterpulsation
is associated with complications, particularly in patients
with peripheral vascular disease.
1.
Recommendations
There is currently insufficient evidence to determine
the benefits vs. risks of prophylactic placement of
an intra-aortic balloon counterpulsation device for
high-risk noncardiac surgery.
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