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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)
VII.
Perioperative Therapy
A.
Rationale for Surgical Coronary Revascularization and
Summary of Evidence
1. Preoperative
CABG
To date, no randomized or well-controlled trials have
assessed the overall benefit of prophylactic coronary
bypass surgery to lower perioperative cardiac risk of
noncardiac surgery. Ellis et al analyzed the coronary
angiograms of 63 patients undergoing major nonthoracic
vascular surgery in a case-control study that indirectly
supported benefit from preoperative coronary bypass
surgery (294).
These investigators found that a coronary occlusion
proximal to viable myocardium was associated with a
higher rate of perioperative MI and death, raising the
question of whether revascularizing coronary occlusions
might not reduce the frequency of these adverse events.
However, in this study, the number of milder, "nonobstructive"
lesions was also associated with MI and death. This
is consistent with studies that show that the most severe
stenoses may not always be responsible for MI, and that
coronary thrombosis frequently occurs at the site of
milder stenoses. Thus, preoperative revascularization
of severe stenoses may not reduce perioperative ischemic
complications.
A
study by Fleisher et al of a cohort of Medicare beneficiaries
undergoing infrainguinal or abdominal aortic reconstructive
surgery found that preoperative stress testing followed
by revascularization, when appropriate, was associated
with improved short- and long-term survival with the
higher-risk aortic surgery (261).
However, this association may be confounded by the fact
that the cohorts referred for preoperative stress testing
were "healthier" patients, as evidenced by the finding
that stress testing with or without coronary revascularization
was associated with greater short- and long-term survival.
On the other hand, a number of retrospective studies
have demonstrated that patients who previously have
successfully undergone coronary bypass have a low perioperative
mortality rate in association with noncardiac procedures
and that their mortality rate is comparable to the surgical
risk for other patients who have no clinical indications
of CAD (170-173).
In
1984, results of preoperative coronary angiography were
reported in a larger series of 1,001 patients under
consideration for elective vascular surgical procedures
at the Cleveland Clinic (174).
Severe CAD that met contemporary indications for coronary
bypass surgery at that time was identified by routine
coronary angiography in 251 patients, including 188
(34%) of 554 patients with clinical evidence of CAD
and 63 (14%) of 446 patients without clinical manifestations
of CAD (p less than 0.001). Of these, 216 underwent
coronary bypass surgery (before vascular surgery) with
a related mortality rate of 5.3%, followed by a mortality
rate of 1.5% for vascular surgery. Operative deaths
with vascular surgery occurred in 1 (1.4%) of 74 patients
with normal coronary arteries, in 5 (1.8%) of 278 with
mild to moderate CAD, in 9 (3.6%) of 250 with advanced
but compensated CAD, and in 6 (14%) of 44 with severe,
uncorrected, or inoperable CAD (175).
Studies such as these have generated interest in the
possible protective influence of coronary bypass surgery
on subsequent surgical risk, even though interpretation
of most retrospective studies is limited by failure
to define the criteria for nonfatal MIs and to indicate
whether or not serial ECGs and cardiac enzymes were
obtained perioperatively.
Eagle
et al analyzed 3,368 patients in the CASS database who
underwent noncardiac surgery during more than 10 years
following entry in the CASS study (260).
Patients undergoing urologic, orthopedic, breast, and
skin operations had a very low mortality rate, less
than 1%, regardless of whether they had undergone prior
CABG for CAD. However, patients undergoing thoracic,
abdominal, vascular, and head and neck surgery had a
much higher risk of death and MI in the 30 days after
the surgical procedure. When patients undergoing these
higher-risk surgical procedures who had undergone prior
CABG were compared with those who had not, patients
who had undergone prior CABG had a lower risk of death
(1.7% vs. 3.3%, p=0.03) and nonfatal MI (0.8% vs. 2.7%,
p=0.002) than patients without prior CABG. Prior CABG
was most protective among patients with multivessel
CAD and those with more severe angina. These data indicate
that patients undergoing low-risk procedures are unlikely
to derive early benefit from revascularization before
low-risk surgery, but suggest that patients with multivessel
disease and severe angina undergoing high-risk surgery
might well benefit from revascularization before noncardiac
surgery.
In attempting to balance the potential risks vs. benefits
of CABG before noncardiac surgery, the additional short-term
risks and long-term benefits should be understood. Long-term
benefits of such strategies were not incorporated into
two recent decision models (168,169).
If the long-term benefits had been included, the value
of preoperative coronary revascularization would have
been increased. For instance, the European Coronary
Surgery Study Group (176)
has reported interesting findings in a small subset
of 58 patients with peripheral vascular disease within
a much larger series of 768 men who were randomly assigned
to receive either coronary bypass surgery or medical
management for angina pectoris. Although the presence
of incidental peripheral vascular disease was associated
with reductions in the 8-year survival rates for either
surgical or medical management of CAD, its influence
was especially unfavorable in patients who received
medical therapy alone. That is, the long-term survival
rate was 85% after coronary bypass surgery, compared
with 57% for nonsurgical treatment (p=0.02). Rihal and
colleagues (166)
have reported similar findings in more than 2,000 patients
enrolled in the CASS study. Compared with coronary bypass
surgery in patients with both CHD and peripheral vascular
disease, surgically treated patients with three-vessel
disease had significantly better long-term survival
than those treated medically after adjustment for all
covariates, including clinical measures of disease stability,
stress test results, and left ventricular function.
In a study at the Cleveland Clinic Foundation, the cumulative
5-year survival rate for the 216 patients who received
coronary bypass was 72% (81% in nondiabetic men) compared
with 43% (p=0.001) for 35 patients in whom coronary
bypass was indicated but never performed (175,177).
Fatal cardiac events occurred within a mean of 4.6 years
in 12% and 26% of these two subsets, respectively (p=0.033).
These later studies illustrate the importance of both
perioperative and long-term cardiac risk when considering
whether to recommend coronary bypass surgery before
noncardiac surgery. The indications for surgical coronary
revascularization in this group, therefore, are essentially
identical to those recommended by the ACC/AHA Task Force
and the accumulated data on which those conclusions
were based (178).
Examples include patients with the following conditions:
acceptable coronary revascularization risk and suitable
viable myocardium with left main stenosis, three-vessel
CAD in conjunction with left ventricular dysfunction,
two-vessel disease involving severe proximal left anterior
descending artery obstruction, and intractable coronary
ischemia despite maximal medical therapy.
In
patients in whom coronary revascularization is indicated,
timing of the procedure depends on the urgency of the
noncardiac surgical procedure balanced against stability
of the underlying CAD. The decision to perform revascularization
on a patient before noncardiac surgery to "get them
through" the noncardiac procedure is appropriate only
in a small subset of very-high-risk patients. Patients
undergoing elective noncardiac procedures who are found
to have prognostic high-risk coronary anatomy and in
whom long-term outcome would likely be improved by coronary
bypass grafting (178)
should generally undergo revascularization before a
noncardiac elective surgical procedure of high or intermediate
risk (Table 3).
2.
Preoperative PCI
Summary of Evidence
The role of prophylactic preoperative coronary intervention
in reducing untoward perioperative cardiac complications
remains unclear. No randomized clinical trials have
documented whether prophylactic PCI with balloon angioplasty,
stents, or other devices before noncardiac surgery reduces
perioperative ischemia or MI. There is an ongoing trial
designed to determine whether patients who require elective
surgery, specifically elective vascular surgery, would
benefit from prior preoperative coronary artery revascularization
(295).
Several retrospective series have been reported. In
a 50-patient series reported from Mayo Clinic (179),
percutaneous transluminal coronary angioplasty (PTCA)
using balloons without stents was performed before noncardiac
surgery (52% vascular procedures) in patients at high
risk for perioperative complications (62% were classified
higher than Canadian class III, 76% had multivessel
disease, and all had abnormal noninvasive tests).
Ten percent required urgent coronary bypass surgery
after angioplasty. The noncardiac procedure was performed
a median of 9 days after PCI, the perioperative MI rate
was 5.6%, and the mortality rate 1.9%. Whether this
result differs from what might have occurred without
PTCA is uncertain.
Elmore
et al (180)
compared the results of preoperative coronary angioplasty
and coronary bypass surgery in patients identified for
elective abdominal aortic aneursymorrhaphy. This study
retrospectively analyzed the records of 2,452 patients
who underwent abdominal aortic surgery between 1980
and 1990. Only 100 (4.1%) had revascularization before
aortic surgery, and 95% of these had symptomatic CAD.
Eighty-six had coronary bypass surgery and 14 had angioplasty.
There were no perioperative deaths in this group at
the time of aortic surgery, compared with 2.9% perioperative
mortality for the entire group (n=2,452). The patients
having angioplasty had significantly more one- and two-vessel
disease and less three-vessel disease than did the bypass
group. Late cardiac events were more frequent in the
angioplasty group. The small numbers in the angioplasty
group and the retrospective analysis over a long period
of time make interpretation of the results of this study
difficult. It appears, however, that candidates for
elective abdominal aortic aneurysmorrhaphy with symptomatic
disease (CAD) have a low operative mortality when revascularization
is performed before surgery by either angioplasty or
bypass surgery.
Allen
et al (181)
performed a retrospective analysis of 148 patients who
underwent angioplasty before noncardiac surgery (abdominal
35%, vascular 33%, and orthopedic 13%). Surgery occurred
within 90 days after angioplasty in 72. There were four
operative deaths (one cardiac), and 16 patients experienced
cardiac complications during the noncardiac surgery.
Cardiac complications were more common in patients older
than 60 years. Little information can be gleaned from
this small retrospective study except to note the low
incidence of cardiac death in patients who had coronary
angioplasty sometime before their noncardiac surgery.
Gottlieb
et al studied 194 patients who underwent PTCA followed
by aortic abdominal, carotid endarterectomy, or peripheral
vascular surgery. The median interval between PTCA and
surgery was 11 days (interquartile ranges 3 and 49 days)
(296).
Twenty-six (13.4%) of the patients had a cardiac complication,
but only one patient died, and one had a nonfatal MI.
The long time interval over which PTCA was performed
before surgery and the inability to know whether the
clinical outcome of these patients would have been different
had a prior PTCA procedure not been performed limit
the conclusions that can be drawn from this study.
Massie
et al performed a case-control study of 140 patients
with abnormal dipyridamole thallium scans in two or
more segments; 70 underwent coronary angiography (of
whom 25 were referred for revascularization) and 70
(matched for age, gender, type of vascular surgery,
and number of myocardial segments suggesting ischemia
on thallium scanning) did not (297).
A trend toward late benefit associated with preoperative
revascularization was offset by a trend toward an early
hazard from the risk of the preoperative invasive cardiac
evaluation and treatment. There were no significant
differences between the angiography group and matched
control subjects with respect to the frequency of perioperative
nonfatal MI (13% vs. 9%) or fatal MI (4% vs. 3%) or
the frequency of late nonfatal MI (16% vs. 19%) or late
cardiac death (10% vs. 13%).
In
a retrospective cohort study by Posner et al, adverse
events in the 30 days after noncardiac surgery were
compared among patients who had undergone preoperative
PTCA at any time, patients with coronary disease who
had not undergone a percutaneous revascularization procedure,
and patients without known coronary disease ("normal
controls") (298).
Patients with coronary disease had twice the risk of
cardiac events as normal controls; however, the risk
among patients who had undergone PTCA was half that
of patients who had coronary disease but not undergone
PTCA. The benefit was limited to a reduction in angina
and HF; there was no reduction in early postoperative
MI or death associated with prior PTCA. The investigators
did not control for the severity of coronary disease,
comorbid illness, or the medical management used in
the PTCA and no PTCA groups. No benefit was seen in
patients undergoing revascularization less than 90 days
before noncardiac surgery. The long time frame
in which PTCA had been performed preoperatively limits
the conclusions that can be drawn from this study.
Given
these limited data, For
patients who undergo successful coronary intervention
with or without stent placement
before planned noncardiac surgery, there is uncertainty
regarding how much time should pass before the noncardiac
procedure is performed. Delaying noncardiac surgery
for more than 6 to 8 weeks increases the chance
that restenosis at the angioplasty site will have occurred
and thus theoretically increases the chances of perioperative
ischemia or MI. However, performing the surgical procedure
too soon after the PCI procedure might also be hazardous.
Arterial recoil and/or acute thrombosis
at the site of balloon angioplasty is most likely to
occur within hours to days after coronary angioplasty.
Therefore, delaying surgery for at least a week after
balloon angioplasty to allow for healing of the vessel
injury at the balloon treatment site has theoretical
benefits. If a coronary stent is used in the revascularization
procedure (as they are currently in the majority of
percutaneous revascularization procedures), further
delay may be beneficial. Stent thrombosis is most common
in the first 2 weeks after stent placement and is exceedingly
rare (less than 0.1% of most cases) more than 2 and
certainly more than 4 weeks after stent placement (299,300).
Given that stent thrombosis remains a very morbid event,
resulting in Q-wave MI or death in the majority of patients
in whom it occurs, and given that the risk of stent
thrombosis diminishes after endothelialization of the
stent has occurred (which generally takes 4 to 8 weeks),
it appears reasonable to
delay elective noncardiac surgery for 2 weeks and ideally
4 weeks to allow for at least partial endothelialization
of the stent, but not for more than 6 weeks or 8 weeks,
when restenosis begins to occur (if it is to occur).
A retrospective study indicates that the frequency
of stent thrombosis when elective noncardiac surgery
is performed within two weeks of stent placement is
very high, as is the frequency of MI and death (301).
A thienopyridine (ticlopidine or clopidogrel) is generally
administered to stent patients (with aspirin) for 2
to 4 weeks because these drugs reduce stent thrombosis.
The thienopyridines (and aspirin as well) inhibit platelet
aggregation and therefore increase the risk of bleeding.
These medications may increase risk of perioperative
surgical bleeding but decrease the risk of stent thrombosis.
For this reason, delaying surgery 2 to 4 weeks after
stent placement allows their use to reduce coronary
thrombosis. Then, after stoppage, the noncardiac
surgery can be performed. Consistent with this notion,
the ongoing Veterans Administration trial investigating
the role of PCI before vascular surgery has stipulated
that a minimum of 2 weeks elapse after stent placement
before surgery is performed (295).
Once the antiplatelet agents are stopped, their effects
do not diminish immediately. It is for this reason that
some surgical teams request a week's delay before proceeding
to surgery.
Similarly,
there is little evidence to show how long a more distant
PCI (e.g., months to years before
noncardiac surgery) protects against perioperative MI
or death. Because coronary restenosis is unlikely to
occur more than 8 to 12 months after There
are data that permit comparison of the protective effects
of revascularization with CABG and balloon angioplasty
before noncardiac surgery. In the Bypass Angioplasty
Revascularization Investigation (BARI), patients with
multivessel coronary disease were randomly assigned
to undergo balloon angioplasty or CABG (302).
In an ancillary study of BARI, the results of 1049 surgeries
performed in 501 patients subsequent to their enrollment
and revascularization procedure in BARI were analyzed;
250 patients had undergone CABG and 251 had undergone
angioplasty (303).
The median time from the most recent coronary revascularization
procedure to noncardiac surgery was 29 months. The results
of the study reveal that the frequency of death or MI
was low in patients with multivessel disease who had
undergone balloon angioplasty or CABG (1.6% in both
groups), and there was no difference in the length of
hospitalization or hospital cost. The risk of death
or MI was lower when the noncardiac surgery was performed
less than 4 years after coronary revascularization (0.8%
vs. 3.6% in patients undergoing surgery 4 or more years
after coronary revascularization). These data do not
provide insight into which patients require preoperative
coronary revascularization, but they do suggest that
the risk of perioperative infarction or death is approximately
equal in patients who have undergone angioplasty or
CABG
if they had been amenable to either type of coronary
revascularization procedure.
B.
Perioperative Medical Therapy
Summary of Evidence
Several randomized trials have examined the impact of
medical therapy begun just before surgery on reducing
cardiac events. Most are single-center trials with relatively
small numbers of subjects. These studies have evaluated
beta blockers, nitroglycerin, the calcium channel blocker
diltiazem, as well as alpha agonists (Table
10).
Two
recent randomized, double-blinded trials looked at the
effect of perioperative beta blockers on cardiac events
surrounding surgery. Poldermans et al examined the effect
of bisoprolol on patients at high risk for perioperative
cardiac complications (252).
Of 846 patients with risk factors for cardiac disease
and scheduled for vascular surgery, 173 were found to
have an abnormal dobutamine stress echocardiogram (DSE).
Of these patients, 61 were excluded from further study
owing to marked abnormalities on DSE or because they
were already taking beta blockers. The remaining 112
patients were randomized to bisoprolol or placebo perioperatively.
The rates of cardiac death (3.4% vs. 17%; p=0.02) and
nonfatal MI (0% vs. 17%; p less than 0.001) were lower
for the bisoprolol vs. placebo groups, respectively.
Generalizability of this study is limited by the unblinded
design and the exclusion of all but the highest-risk
patients. Also, patients began taking bisoprolol a mean
of 37 days before surgery, with adjustments made based
on heart rate.
Boersma
et al subsequently reanalyzed the total cohort of 1351
consecutive patients enrolled in this randomized trial
of bisoprolol (304).
Forty-five patients had perioperative cardiac death
or nonfatal MI. Eighty-three percent of patients had
fewer than 3 clinical risk factors. Among this subgroup,
patients receiving beta blockers had a lower risk of
cardiac complications (0.8% [2/263]) than those not
receiving beta blockers (2.3% [20/855]). In patients
with 3 or more risk factors (15%), those taking beta
blockers who had a DSE demonstrating 4 or fewer segments
of new wall-motion abnormalities had a significantly
lower incidence of cardiac complications (2.3% [2/86])
compared with those not receiving beta-blocker therapy
(10.6% [12/121]) . Moreover, among patients with more
extensive ischemia on DSE (five or more segments), there
was no difference in the incidence of cardiac events
(4 of 11 for those taking beta blockers vs. 5 of 15
for those not taking beta blockers). Therefore, beta-blocker
therapy was beneficial in all but the subset of patients
with more extensive ischemia.
One
must also be cautious about inferring a class effect
from this observation about bisoprolol and be mindful
of the course of therapy used. The Multicenter Study
of Perioperative Ischemia Research Group (251,305)
randomized 200 patients undergoing general surgery to
a combination of intravenous and oral atenolol vs. placebo
for seven days. Although they found no difference in
perioperative MI or death, they reported significantly
fewer episodes of ischemia by continuous monitoring
(24% vs. 39%; p= 0.03) in the atenolol and placebo groups,
respectively. They then followed up these patients after
discharge and documented fewer deaths in the atenolol
group over the subsequent 6 months (1% vs. 10%; p less
than 0.001). It is not clear why such a brief course
of therapy could exert such delayed effect, and the
study did not control for other medications given either
before or after surgery. ACE inhibitor and beta-blocker
use preoperatively differed significantly between the
study groups.
More
limited studies have also examined the use of perioperative
beta blockers. Stone et al (55)
gave oral beta blockers two hours before
surgery to a randomized group of patients with mild
hypertension who had predominantly (58%) vascular surgery.
Control subjects had a higher frequency (28%) of ST-segment
depression than treated patients (2%). In a nonrandomized
study, Pasternack et al (186)
gave oral metoprolol immediately before surgery, followed
by intravenous drug during abdominal aortic aneurysm
repair. Only 3% suffered an acute MI compared with 18%
for matched controls. In a later report, the same authors
reported less intraoperative ischemia in patients treated
with oral metoprolol before peripheral vascular surgery
(58).
Yeager et al (306)
reported a case-control analysis of their experience
with perioperative MI during vascular surgery, comparing
53 index cases of perioperative MI with 106 matched
controls. They found a strong association of beta-blocker
use with a decreased likelihood of MI (odds ratio 0.43;
p=0.01). Raby et al (307)
demonstrated in 26 vascular surgery patients
randomized to a protocol of heart rate suppression with
intravenous esmolol that the esmolol group had fewer
episodes of ischemia than controls (33% vs. 72%; p=0.055).
Several recent studies examined the role of alpha-agonists
(clonidine and mivazerol) in perioperative cardiac protection.
Mivazerol (4 mcg per kg) was given during
the first 10 minutes followed by infusion. Oliver
et al (308)
reported a large, randomized, placebo-controlled,
multicenter trial of the alpha2-agonist mivazerol in
perioperative use. They randomized 2854 patients with
known CAD or significant risk factors who were undergoing
noncardiac surgery to a 1.5 mcg per kg per h infusion
of mivazerol or placebo. Among patients with an established
history of CAD who were undergoing general surgical
procedures, the rate of MI was no different between
the mivazerol and placebo groups, but the cardiac death
rate was reduced (13/946 vs. 25/941; p=0.04). Among
patients undergoing vascular procedures, both cardiac
death rate (6/454 vs. 18/450; p=0.017) and the combined
end point of death or MI (44/454 vs. 64/450; P=0.037)
were significantly reduced. The Multicenter Study of
Perioperative Ischemia Research Group (309)
also reported the results of a placebo-controlled, randomized,
double-blind study of perioperative mivazerol. Three
hundred patients with known CAD undergoing noncardiac
surgery were randomized to high-dose (1.5 mcg per kg
per h) or low-dose (0.75 mcg per kg per h) mivazerol
or placebo. No differences in perioperative death or
MI were observed, but the high-dose group had significantly
less myocardial ischemia than the placebo group (20/98
vs. 35/103; p=0.026). Finally, two randomized, placebo-controlled
studies of clonidine for perioperative myocardial protection
were performed in 297 patients undergoing vascular surgery
(310)
and 61 patients undergoing general surgery (311).
Both demonstrated a significant decrease in the incidence
of myocardial ischemia (35/145 vs. 59/152, p less than
0.01 and 1/28 vs. 5/24, p=0.05 respectively).
There
have been only two studies examining the role of calcium
channel blockers in this situation. These studies
are too
small to allow definitive conclusions (Table
10).
The
use of nitrates is discussed in the section on intraoperative
management (Section VIII).
Recommendations
There are still very few randomized trials of medical
therapy before noncardiac surgery to prevent perioperative
cardiac complications, and they do not provide enough
data from which to draw firm conclusions or recommendations.
Most are insufficiently powered to address the effect
on outcome of MI or cardiac death and rely on the surrogate
end point of ECG ischemia to show effect. Current studies,
however, suggest that appropriately administered beta
blockers reduce perioperative ischemia and may reduce
the risk of MI and death in high-risk patients. When
possible, beta blockers should be started days or weeks
before elective surgery, with the dose titrated to achieve
a resting heart rate between 50 and 60 beats per minute.
Perioperative treatment with alpha2-agonists may have
similar effects on myocardial ischemia, MI, and cardiac
death. Clearly, this is an area where further research
would be valuable.
Recommendations
for Perioperative Medical Therapy
Class I
1.
Beta blockers required in the recent past to control
symptoms of angina or patients with symptomatic arrhythmias
or hypertension.
2. Beta blockers: patients at high cardiac risk owing
to the finding of ischemia on preoperative testing who
are undergoing vascular surgery.
Class
IIa
Beta blockers: preoperative assessment identifies untreated
hypertension, known coronary disease, or major risk
factors for coronary disease.
Class
IIb
Alpha 2-agonists: perioperative control of hypertension,
or known CAD or major risk factors for CAD.
Class
III
1. Beta blockers: contraindication
to beta blockade.
2. Alpha 2-agonists: contraindication to alpha2-agonists.
C. Valve Surgery
There
is little information about the appropriateness of valvular
repair or replacement before a noncardiac surgical procedure
is undertaken. Clinical experience indicates that patients
with valvular heart disease severe enough to warrant
surgical treatment should have valve surgery before
elective noncardiac surgery. Recently it has been suggested
that patients with severe mitral or aortic stenosis
who require urgent noncardiac surgery, such as intestinal
resection for lesions causing serious gastrointestinal
bleeding, may benefit from catheter balloon valvuloplasty
at least as a temporizing step to reduce the operative
risk of noncardiac surgery (187,188).
Unfortunately, there are no controlled studies, and
the risks of balloon aortic valvuloplasty in older patients
are significant (187).
Experience
with managing valvular heart disease during labor and
delivery provides insights into the approach to management
of the patient for noncardiac surgery. The vast majority
of women with regurgitant valvular heart disease can
be managed medically during the course of pregnancy,
including labor and delivery, because the decrease in
peripheral vascular resistance that occurs with pregnancy
tends to decrease regurgitant lesions (189).
Increased arterial impedance is not well tolerated in
patients with aortic and mitral regurgitation. Therefore,
increases in blood pressure should be prevented, and
left ventricular afterload should be optimized with
vasodilators. In contrast, patients with significant
aortic or mitral stenosis often do not do well with
the increased hemodynamic burden of pregnancy. If the
stenosis is severe, percutaneous catheter balloon valvotomy
should be considered as definitive therapy or as a bridge
to care for the patient through pregnancy, labor, and
surgical delivery. Excessive changes in intravascular
volume should be avoided (see also Section
III, "Valvular Heart Disease").
D.
Arrhythmia and Conduction Disturbances
In
the perioperative setting, cardiac arrhythmias or conduction
disturbances often reflect the presence of underlying
cardiopulmonary disease, drug toxicity, or metabolic
derangements. In patients with documented hemodynamically
significant or symptomatic arrhythmias, electrophysiologic
testing and catheter ablation, particularly for supraventricular
arrhythmias, may be indicated
to prevent arrhythmia recurrence (190,191,312).
Supraventricular arrhythmias may require either electrical
or pharmacological cardioversion if they produce symptoms
or hemodynamic compromise. If cardioversion is not possible,
satisfactory heart rate control should be accomplished
with oral or intravenous digitalis, beta-adrenergic
blockers, or calcium channel blockers. Among these three
types of medications, digitalis is the least effective
agent, and beta blockers are the most effective agent
for controlling the ventricular response during atrial
fibrillation (313).
An additional benefit of beta blockers is that they
have been shown to accelerate the conversion of postoperative
supraventricular arrhythmias to sinus rhythm as compared
with diltiazem (314).
In patients with atrial fibrillation who are taking
oral anticoagulation therapy, it may be necessary to
discontinue the anticoagulant several days before surgery.
If time does not allow and it is important that the
patient not be on anticoagulants, the effect of warfarin
can be reversed by parenteral vitamin K or fresh frozen
plasma (66).
Ventricular arrhythmias, whether simple premature ventricular
contractions, complex ventricular ectopy, or nonsustained
tachycardia, usually do not require therapy unless they
are associated with hemodynamic compromise or occur
in the presence of ongoing
or threatened myocardial ischemia or left ventricular
dysfunction. Studies have
shown that although nearly half of high-risk patients
undergoing noncardiac surgery have frequent premature
ventricular contractions or asymptomatic nonsustained
ventricular tachycardia, the presence of these ventricular
arrhythmias is not associated with an increase in nonfatal
MI or cardiac death (240,241).
Nevertheless, the presence of an arrhythmia in the preoperative
setting should provoke a search for underlying cardiopulmonary
disease, ongoing myocardial ischemia or infarction,
drug toxicity, or metabolic derangements. Physicians
should also have a low threshold at which they
institute prophylactic beta-blocker therapy in patients
at increased risk of developing a perioperative or postoperative
arrhythmia (including those in whom arrhythmias are
present during the preoperative evaluation). Several
recent studies have demonstrated that beta-blocker therapy
can reduce the incidence of arrhythmias during the perioperative
period (250,259).
Sustained
or symptomatic ventricular tachycardia should be suppressed
preoperatively with intravenous lidocaine, procainamide,
or amiodarone, and a thorough search should be conducted
for underlying causes and appropriate short- and long-term
therapy. The indications for temporary pacemakers are
almost identical to those previously stated for long-term
permanent cardiac pacing (192).
Patients with intraventricular conduction delays, bifascicular
block (right bundle-branch block with left anterior
or posterior hemiblock), or left bundle-branch block
with or without first-degree atrioventricular block
do not require temporary pacemaker implantation in the
absence of a history of syncope or more advanced atrioventricular
block (71).
E.
Implanted Pacemakers and ICDs
It
is important to be aware of the many potential adverse
interactions between electrical/magnetic activity and
pacemaker or ICD function that may occur during the
operative period (see Section
II). These interactions result from electrical current
generated by electrocautery or cardioversion, as well
as the impact of metabolic derangements, antiarrhythmic
agents, and anesthetic agents on pacing and sensing
thresholds. The probability of these adverse interactions
can be minimized if certain precautions are taken. Although
this topic has been analyzed in a number of review articles
and book chapters, no formal guidelines have been developed
(315-318).
Electrocautery
involves the use of radiofrequency current to cut or
coagulate tissues. It is usually applied in a unipolar
fashion between the cautery device and an indifferent
plate attached to the patient's skin. The potential
for electrical magnetic interference with an implanted
device is related to the amount of generated current
in the vicinity of the pacemaker or ICD device. In general,
high current is generated if the cautery device is close
to the pacemaker, particularly if the current path of
the cautery lies along the axis of the pacemaker or
ICD lead. The electrical current generated by electrocautery
can cause a variety of responses by the implanted device,
including the following: 1) temporary or permanent resetting
to a backup, reset, or noise-reversion pacing mode (i.e.,
a dual-chamber pacemaker may be reset to VVI pacing
at a fixed rate); 2) temporary or permanent inhibition
of pacemaker output; 3) an increase in pacing rate due
to activation of the rate-responsive sensor; 4) ICD
firing due to activation by electrical noise; or 5)
myocardial injury at the lead tip that may cause failure
to sense and/or capture. Cardioversion can have similar
effects on pacemaker or ICD function. Although the probability
of any of these adverse interactions occurring has fallen
owing to the almost universal use of bipolar leads (which
reduces the probability of electrical-magnetic interference)
and improved pacemaker and ICD design, they still do
occur (315-318).
The
likelihood and potential clinical impact of adverse
interactions occurring in patients with ICDs and pacemaker
devices will be influenced by a number of factors, including
whether the pacemaker has unipolar or bipolar leads,
whether the electrocautery is bipolar or unipolar, the
relative distance from and orientation of the electrocautery
relative to the pacemaker and pacemaker lead, and whether
the patient is pacemaker dependent. These factors, combined
with the urgency of surgery and the availability of
expertise in pacing and/or ICDs, will ultimately determine
the type and extent of evaluation that is performed.
However, under optimal circumstances, several general
recommendations can be made. Patients with implanted
ICDs or pacemakers should have their device evaluated
before and after surgical procedures. This evaluation
should include determination of the patient's underlying
rhythm and interrogation of the device to determine
its programmed settings and battery status. If the pacemaker
is programmed in a rate-responsive mode, this feature
should be inactivated during surgery. If a patient is
pacemaker dependent, pacing thresholds should be determined
if the patient has not been evaluated recently in a
pacemaker clinic. ICD devices should be programmed off
immediately before surgery and then on again
postoperatively to prevent unwanted discharge due to
spurious signals that the device might interpret as
ventricular tachycardia or fibrillation. If QRS complexes
cannot be seen during electrocautery, other methods
of determining heart rate should be monitored to be
certain device inhibition is not present. Finally, if
emergent cardioversion is required, the paddles should
be placed as far from the implanted device as possible
and in an orientation likely to be perpendicular to
the orientation of the device leads (i.e., anterior-posterior
paddle position is preferred).
F.
Preoperative Intensive Care
1. General Considerations
Preoperative invasive monitoring in an intensive care
setting can be used to optimize and even augment oxygen
delivery in patients at high risk. It has been proposed
that indexes derived from the pulmonary artery catheter
and invasive blood pressure monitoring can be used to
maximize oxygen delivery which will lead to a reduction
in organ dysfunction.
2.
Summary of Evidence
Only two studies have prospectively evaluated the efficacy
of preoperative pulmonary artery catheter utilization
and optimization of hemodynamics in a randomized trial
with cardiac complications as a major outcome. Berlauk
et al randomly assigned 89 patients undergoing infrainguinal
arterial bypass procedures to groups that received a
pulmonary artery catheter and (1) preoperative hemodynamic
optimization overnight in the intensive care unit, (2)
hemodynamic optimization for 3 hours preoperatively
by the anesthesia care team, or (3) intraoperative monitoring
based solely on clinical indications (193).
When MI or nonarrhythmogenic cardiac death was used
as the outcome, no significant differences were demonstrated.
Similarly, Ziegler et al found no differences in intraoperative
or perioperative cardiac complications between vascular
surgery patients randomly assigned to preoperative pulmonary
catheter-guided hemodynamic optimization vs. routine
care (319).
3.
Recommendations
Although no benefit has been shown, some experienced
clinicians believe that preoperative preparation in
an intensive care unit may benefit certain high-risk
patients, particularly those with decompensated HF.
Preparation of such patients should occur under close
supervision.
G.
Venothromboembolism/Peripheral Arterial Disease
Two
peripheral vascular disorders that merit attention preoperatively
are venous thromboembolism and, in the elderly, chronic
occlusive peripheral arterial disease.
Prophylactic
measures need to be planned and in some cases started
preoperatively for persons with clinical circumstances
associated with postoperative venous thromboembolism.
These correlates of thromboembolic risk include advanced
age, prolonged immobility, or paralysis; prior venous
thromboembolism; malignancy; major surgery, particularly
operations involving the abdomen, pelvis, or lower extremities;
obesity; varicose veins; HF; MI; stroke; fractures of
the pelvis, hip, or leg; congenital or acquired aberrations
in hemostatic mechanisms (hypercoagulable states); and
possibly, high-dose estrogen use as determined by the
recent consensus conference of the American College
of Chest Physicians (320).
The choice of prophylactic measure or agent—graded-compression
elastic stockings, low-dose subcutaneous heparin, low-molecular-weight
heparin, warfarin, or intermittent pneumatic compression—will
depend on the risk of venous thromboembolism and the
type of surgery planned. Table
11 provides published recommendations for various
types of surgical procedures (320).
The
noninvasive techniques—impedance plethysmography
and real-time compression ultrasonography—are
effective objective tests to exclude clinically suspected
deep venous thrombosis and are best used for this purpose
(197,198).
Routine screening of all postoperative patients with
a noninvasive technique is not as cost-effective or
efficient as appropriate antithrombotic prophylaxis
for moderate- and high-risk patients (195,199).
The
prevalence of chronic occlusive peripheral arterial
disease rises with increasing age, affecting more than
10% of the general population older than 65 years (200)
and as many as half of persons with CAD (201).
Patients with this condition may be at increased risk
of perioperative cardiac complications, even for a given
degree of coronary disease (321).
This may warrant particular attention to the preoperative
evaluation and intraoperative therapy of such patients.
Protection of the limbs from trauma during and after
surgery is as important for those with asymptomatic
arterial disease as for those with claudication.
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