Pharmacokinetics of Morphine and Oxycodone in Frail Elderly Undergoing Cardiac Surgery

Postoperative pain after cardiac surgery in elderly patients is common and leads to postoperative complications. Opioids play an important role in treatment of postoperative pain after cardiac surgery. In frail elderly after cardiac surgery however dosing schemes for opioids are still unknown, potentially leading to inadequate treatment of pain and/or safety issues. * Single center observational cohort study * The study population includes frail patients ≥70 years undergoing elective cardiac surgery. * Primary endpoints of this study is the concentration of morphine, oxycodone and metabolites in blood over time on behalf of pharmacokinetic modelling. * Secondary endpoints of this study are the pharmacodynamic parameters of morphine, oxycodone and metabolites (M3G, M6G, noroxycodone and oxymorphone) in blood in frail patients; such as pain scores, postoperative opioid consumption, vital signs, side effects of opioids and the influence of covariates such as frailty, serum creatinine, Glomerular Filtration Rate (GFR) on the pharmacokinetics and pharmacodynamics of morphine and oxycodone.