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J Thorac Cardiovasc Surg 1997;113:1126-1127
© 1997 Mosby, Inc.
LETTERS TO THE EDITOR |
Department of Surgery
University of Massachusetts Medical Center
55 Lake Ave., N.
Worcester, MA 01655-0304
Reply to the Editor:
As Lemmer points out, correctly, our recent paper documented a reduction in chest tube drainage during the first 24 hours of about 200 ml after the use of epsilon-aminocaproic acid (EACA).
1In that same series of patients, we did not observe a reduction in blood product administration.
We disagree, however, with his characterization of the reduction in blood as "essentially negative results." In fact, the 200 ml incremental blood loss in the control group represents a 30% increase (p = 0.002). One reason for the difference of (only) about 200 ml between the control and EACA groups is that the patients operated on by surgeon 1 in the study had significantly less bleeding than the other patients, and surgeon 1 operated on a disproportionately large number of patients in the control group: 65% of the control patients were operated on by surgeon 1, and 56% of surgeon 1's patients were control patients. The second reason is that the overall blood loss in the series was low: 647 ml and 839 ml at 24 hours in the EACA and control groups, respectively. After reading Lemmer's criticisms, we almost feel obliged to apologize for our institution's good results. Had we a higher rate of blood loss, the difference between the control and EACA groups might have been greater, and a significant difference in blood product administration might also have been observed.
Except for the comparison of the cost of the two drugs, we did not compare EACA with aprotinin. Because Lemmer suggests that we drew conclusions regarding the relative efficacy of EACA and aprotinin (we did not), it may be of some use now to compare the results in our recent study with those of the excellent and conclusive multiinstitutional study of aprotinin reported by Lemmer and colleagues. 2 Our 24-hour cumulative blood losses were 647 ml in the EACA group and 839 ml in the control group. In Lemmer's report, the blood losses in primary coronary artery bypass graft (CABG) cohort at the time of chest tube removal were 855 ml and 1503 ml in the aprotinin and control groups, respectively. Inasmuch as the chest tubes in the Lemmer series were removed earlier (20.9 hours and 17.3 hours in the aprotinin and control groups, respectively) than in our patients (postoperative day 2), the hourly drainage rate in our series (calculated at 24 hours) is considerably less than in the Lemmer series (Table I). In their redo CABG cohort, the losses were 1225 ml and 1979 ml in the aprotinin and control groups, respectively. The results we reported are for all types of cardiac operations, including valve operations and redo operations. Thus, in this group of patients expected to be at higher risk of bleeding than were the patients reported on by Lemmer, our control patients had about as much bleeding as did the aprotinin-treated patients in Lemmer's series, and our treatment (with EACA) patients has less bleeding.
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3 the number of patients receiving transfusions was significantly less in the EACA-treated patients (4.8%) than in those in the control group (26.3%). Lemmer points out that we did not compare aprotinin against EACA. He is correct. We did not intend to do so. We only wished to ask whether EACA reduces blood loss when compared with a control series not receiving EACA. The only comparison of EACA with aprotinin made in our paper was of the cost of the two drugs. We did not claim that EACA more effectively reduces bleeding than does aprotinin, only that it does so less expensively. In fact, we are currently engaged in a Bayer-supported study of aprotinin to ascertain whether its documented reduction of bleeding reduces transfusion costs and other intensive care unit costs (such as ventilator support) sufficiently to offset the high cost of the drug.
We are embarrassed to realize that our paper contains an egregious numerical error—as Lemmer noticed and we did not. In the original manuscript, the cost of aprotinin was based on the (correct) volume use of the high-dose regimen: 200 ml before institution of cardiopulmonary bypass, 200 ml in the heart-lung pump prime, and an infusion rate during the operation of 50 ml/hr. When the final manuscript was submitted, the aprotinin dose was converted from milliliters to kallikrein inactivator units (kIU) and a tenfold error was introduced. None of the authors noticed the error. The correct doses are 2 x 106 kIU before cardiopulmonary bypass, 2 x 106 kIU in the pump prime, and 0.5 x 106 kIU/hr infusion—not ten times that dose, as was published. However, since the cost calculation was based on the volume dose used, the cost calculation of $785 per patient is correct as published, and the comparison with the $6.96 per-patient EACA cost remains rather striking. We apologize for the error, which, fortunately, did not affect the cost calculation in our paper. When we use aprotinin, we use the standard high-dose regimen as described above and in the package insert.
Although Lemmer is critical of our conclusions, we suspect that we both have nearly identical indications for the use of aprotinin. As does he, we use it only in operations expected to carry a high bleeding risk. We probably differ in that we do not use the drug routinely in redo operations because we do not consider those to carry a high bleeding risk.
12/8/80545
References
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