case study
Aquapheresis™ in
a Patient That Suffered a Perioperative Myocardial Infarction with
Depressed Ejection Fraction and Pulmonary Edema
Introduction
In the postoperative period, fluid shifts in patients on cardiopulmonary
bypass are common. These can often be treated with vigorous diuresis,
but when patients have depressed myocardial function or acute injury,
diuretic refracturiness may occur as the response to loop diuretics
and is related to cardiac output and renal perfusion. This report
describes the use of aquapheresis/ultrafiltration in a patient that
suffered a perioperative myocardial infarction with depressed ejection
fraction and pulmonary edema.
Case Report
A 71-year-old diabetic male presented with unstable angina pectoris
and after cardiac catheterization, was found to have left main coronary
disease and an associated high-grade anterior descending coronary
lesion. The patient underwent three-vessel bypass surgery the day
following angiography with saphenous vein graft to the LAD diagonal
branch and the obtuse marginal branch, as well as an internal mammary
artery bypass to the LAD. At the time of surgery, when the anterior
descending artery was opened, thrombus was noted in the artery.
The patient was readily weaned from cardiopulmonary bypass; but
required significant inotropic support on the first postoperative
night. Electrocardiography the morning following surgery showed
a new Q wave in V-2, 3 and 4 and troponins were as high as 400.
He was extubated the day following surgery. On the evening of the
second postoperative day, the patient developed marked tachypnea,
decreasing oxygen saturations, and respiratory fatigue. His pulmonary
artery diastolic pressure went from 20 to 33 mmHg and required re-intubation.
On the fourth postoperative day, the patient was hemodynamically
stable and had decreasing oxygen needs on the ventilator. He was
awake and alert and responding well to diuresis. On the fifth postoperative
day, however, the patient had decreasing urinary responses to diuretics.
The PAD was 21 mmHg. The CVP was 16 torr. The BUN had risen to 36
mg% and the creatinine to 1.7 mg% from a baseline 22 mg% and 1.4
mg%. He also had hypochloremic, hypokalemic, metabolic alkalosis
related to loop diuretic utilization. Aquapheresis was prescribed
at a fluid removal rate of 300 to 500 cc per hour for a period of
up to eight (8) hours. A total of 2 liters of free water was removed
over 4.4 hours. The patient’s oxygenation improved and he
was extubated on the following day.
Comment
Over diuresis occurs commonly, manifested by arteriolar intravascular
volume contraction, increased systemic vascular resistance, and
decreased renal perfusion particularly in the case of myocardial
damage in which the cardiac output may be diminished or fixed. Intravascular
volume as measured by the central venous pressure will remain increased.
Pulmonary edema will then be refractory. Patients develop problems
with electrolyte imbalance, induced arrythmias, particularly atrial
fibrillation and enhanced activity of the neurohormonal axis. The
use of aquapheresis, a form of veno-venous ultrafiltration, reduces
this fixed preload without impacting hemodynamics or electrolyte
concentrations. Pulmonary edema can readily resolve and patients
can be more easily removed from mechanical ventilatory support.
Case history courtesy of:
Arlen Holter, M.D.
Co-Director of Cardiac Surgery
St. Joseph’s Hospital
St. Paul, Minnesota
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