In cardiac surgery, the establishment of Cardiopulmonary bypass (CPB) involves profound changes that can alter the pharmacokinetics and clinical response to drugs. Methadone has characteristics that make it attractive for the management of postoperative pain, however, to date there are no pharmacokinetic or pharmacodynamic studies that allow guidance on how to perform the dosage and dose adjustment of methadone in patients undergoing cardiopulmonary bypass. The main of this study is to describe the pharmacokinetics of methadone in adult patients undergoing cardiac surgery with extracorporeal circulation. A pharmacokinetic clinical study will be proposed. Drug concentrations will be measured at different times, estimating how plasma levels vary before, during and after CPB. For the plasma methadone analysis, 10 blood samples will be taken from each patient following a pre-established schedule. They will be analyzed using a high performance liquid chromatography (HPLC) spectrofluorometric method. Changes in volumes, clearance, and other covariates associated with CPB are not expected to significantly affect methadone plasma concentrations.
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Peak Plasma Concentration (Cmax)
Timeframe: Time Frame: 0, 5-10, 30, 60, 120, 240 minutes of operation of the CPB and 12 or 24 hours of CPB]
Describe the change of the levels of methadone plasmatic levels (ng/mL) measured by high pressure liquid chromatography (HPLC)
Timeframe: Time Frame: 0, 5-10, 30, 60, 120, 240 minutes of operation of the CPB and 12 or 24 hours of CPB]