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May
1998
Factors that predict the use of positive inotropic drug support after
cardiac valve surgery.
Butterworth JF, Legault C, Royster RL, Hammon JW; Anesth Analg
1998; 86:461-7.
[ see abstract below ]
Factors predictive of the requirement for positive inotropic agents after
cardiopulmonary bypass (CPB) for coronary artery bypass grafting (CABG)
have been previously defined as advanced age, female gender, decreased
left ventricular ejection fraction and prolonged CPB or aortic cross clamp
time1. The same group of authors recently postulated that valve
surgery presents a quite different, and valve specific, set of predictive
factors, which they examine in a study published in the March issue of
Anesthesia and Analgesia.
For example, after aortic valve replacement for aortic stenosis, contractility
may manifest as excessive as a result of the abrupt reduction in afterload,
but left ventricular hypertrophy and impaired diastolic compliance remain.
In contrast, with aortic regurgitation, the left ventricle remains dilated
and benefits from inotropic support. With mitral stenosis, chronic atrial
fibrillation and pulmonary hypertension are the major postoperative impediments,
with little or no requirement for inotropic support of the left ventricle.
With mitral regurgitation, pharmacologic afterload reduction assumes great
importance after the valve is replaced, because the left ventricle no
longer decompresses into the left atrium and impedance to outflow is actually
much greater with the prosthetic valve in place.
The study is an ancillary analysis of a randomized double-blind trial
of nimodipine neuroprotection for cardiac valve surgery, which was actually
terminated because of an excessive number of deaths in the treatment group.
This resulted in a number of exclusions that might have a bearing on extrapolation
of the results to the general population. Notably, patients were excluded
who had preexisting class 4 congestive heart failure (CHF), a transmural
myocardial infarction within the prior 30 days, and previous therapy with
calcium channel blockade. CPB was provided with a membrane oxygenator
with moderate hypothermia (28°C), with intermittent hypothermic blood
or crystalloid cardioplegia to achieve electrical silence during aortic
cross-clamping. Inotropic support was not administered routinely, but
only when specifically indicated.
Dopamine (> 5 mcg/kg/min), dobutamine and epinephrine were considered
to be inotropic infusions, and were administered for decreased cardiac
contractility observed during weaning from CPB, low cardiac index (CI
< 2.2 L/min/m2), or both. Amrinone was added when CI was inadequate
despite epinephrine > 60 ng/kg/min.
About 52% of the patients required inotropic support, a frequency similar
to that of patients undergoing CABG. Of these, 73% received epinephrine
alone, 5% received dobutamine or amrinone alone, and 22% received a combination
of epinephrine and amrinone. There was no difference in the requirement
for inotropic support whether patients received nimodipine or not, or
based on the nature of the valvular lesion (the latter could be attributable
to inadequate study power). "Risk" factors for administration of inotropic
support that emerged from univariate analysis included advanced age, CHF,
the anesthesiologist (but not the surgeon), concurrent ABG, long CPB time
(but not aortic cross-clamp time). Multivariate analysis eliminated most
of these, except age > 60 yr, CHF, decreased left ventricular ejection
fraction (in patents without mitral regurgitation) and the attending anesthesiologist.
The authors pointed out that clinician variability would vary by institution,
but could be accounted for by careful multivariate analysis.
Patients who received inotropic support did not have a worse outcome at
six months, which the authors believe attests to the transient nature
of left ventricular dysfunction after valve surgery.
As discussed, this study has a number of limitations in interpretation
and design, and the data could simply represent current clinical practice
at the authors' institution. Nonetheless, it serves as a useful paradigm
for evaluation of many of our approaches to clinical management, which
are so often arbitrary and based upon individual "experience" rather than
careful, systematic analysis of outcome.
1 Royster RL, Butterworth JF, Prough DS et al. Preoperative
and intraoperative predictors of inotropic support and long term outcome
in patients having coronary artery bypass grafting. Anesth Analg
1991; 72:729-36
Return to the Current Literature Review Front
Page , or read the abstract:
ABSTRACT
Left ventricular dysfunction is common after cardiac surgery and is often
treated with positive inotropic drugs (PIDs). We hypothesized that the use
of PIDs after cardiac valve surgery would have significant associations
with the valvular pathophysiology and surgical procedure, and unlike the
case for patients undergoing coronary artery surgery, would be unrelated
to duration of cardiopulmonary bypass (CPB) or of aortic clamping.
One hundred forty-nine consenting patients undergoing cardiac valve surgery
were studied. Patients with hepatic or renal failure, or New York Heart
Association class IV cardiac symptoms, were excluded. Patients were considered
to have received PIDs if they received an infusion of amrinone, dobutamine,
epinephrine, or dopamine (> or = 5 microg x kg[-1 x min[-1 ). PIDs were
received by 78 patients (52%).
In a univariate model, older age, history of congestive heart failure, decreasing
left ventricular ejection fraction, longer durations of CPB, and concurrent
coronary artery surgery significantly increased the likelihood of PID support.
There was also significant variation by anesthesiologist in the administration
of PIDs. The specific diseased valve and valvular stenosis or insufficiency
did not influence the likelihood of receiving PID support.
In a multivariable model, age, history of congestive heart failure, decreasing
left ventricular ejection fraction, and anesthesiologist were significantly
associated with the likelihood of PID support, but duration of CPB and concurrent
coronary artery surgery were not.
In conclusion, patient age and ventricular function, as well as physician
preferences, predicted the need for inotropic drug support; however, neither
the specific valvular lesion, nor duration of CPB were strongly predictive
in a multivariable model.
IMPLICATIONS: We evaluated factors related to use of positive inotropic
drugs after cardiac valve surgery. The likelihood of a patient receiving
these drugs increases with advancing age and with more severe preoperative
left ventricular dysfunction, but was not influenced by the specific diseased
valve or the duration of cardiopulmonary bypass.
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