Anesth Analg 2002;94:1673
© 2002 International Anesthesia Research Society
LETTERS TO THE EDITOR
Evidence-Based EACA Dosing?
John C. Lundell, MD
Department of Anesthesiology, Wilford Hall USAF Medical Center, San Antonio, TX
To the Editor: I read with great interest the clinical investigation by Butterworth et al. (1) as well as the previous article by the same investigators (2). These articles are have begun to address the paucity of scientific evidence to guide dosing of  -aminocaproic acid (EACA) for cardiac surgery with cardiopulmonary bypass. I wondered why the authors give EACA after heparinization rather than before incision, as is common practice. Is there any science behind this decision? What would the predicted levels be in the Butterworth et al. model if the initial dose of EACA were given prior to incision? Would this change the load and infusion recommended to achieve the desired blood concentration of the drug?
References
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Butterworth J, James RL, Lin Y, et al. Gender does not influence epsilon-aminocaproic acid concentrations in adults undergoing cardiopulmonary bypass. Anesth Analg 2001; 92: 1384–90.[Abstract/Free Full Text]
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Butterworth J, James RL, Lin Y, et al. Pharmacokinetics of e-aminocaproic acid in patients undergoing aortocoronary bypass surgery. Anesthesiology 1999; 90: 1624–35.[Web of Science][Medline]
Response
John Butterworth, MD, and
Robert James, MS MStat
Wake Forest University Medical Center, Winston-Salem, NC
In Response: We thank Major Lundell for his query. It does make a difference in the blood concentrations of -aminocaproic acid (EACA) when the loading dose is initiated at a time other than the one described in our protocol (1). Clinicians who wish to begin administration of EACA at the time of induction of anesthesia have two convenient options if they wish to maintain blood EACA concentrations at or above 260 mg/L. The first would be to administer a loading dose of 80 mg/kg over 20 min and a maintenance infusion of 30 mg · kg-1 · h-1. A simulation of this dosing scheme is provided in Figure 1. A second option would be to administer a 60 mg/kg loading dose over 20 min, a 30 mg · kg-1 · h-1 maintenance infusion, and a 10 mg/kg dose in the priming solution of the cardiopulmonary bypass pump. This dosing scheme is simulated in Figure 2. We assumed an 80-kg patient, a 45-min time interval before extracorporeal circulation, a 2-h bypass run, and termination of the EACA infusion 4 h after induction of anesthesia in both of the simulations.
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Figure 1. Simulation of -aminocaproic acid concentrations in blood after a loading dose of 80 mg/kg given over 20 min and a maintenance infusion of 30 mg · kg-1 · h-1 given for 4 h.
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Figure 2. Simulation of -aminocaproic acid concentrations in blood after administration of a 60 mg/kg loading dose over 20 min, a 30 mg · kg-1 · h-1 maintenance infusion given for 4 h, and a 10 mg/kg dose in the priming solution of the cardiopulmonary bypass pump.
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References
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Butterworth J, James RL, Lin YA, et al. Gender does not influence epsilon-aminocaproic acid concentrations in adults undergoing cardiopulmonary bypass. Anesth Analg 2001; 92: 1384–90.
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