Death during patient-controlled analgesia: piritramide overdose and tissue distribution of the drug

We report about a fatality during patient-controlled analgesia (PCA). Piritramide peripheral blood concentration was measured with 0.1 mg/l and exceeded the normal therapeutic range. Therefore, a fatal overdose was considered as the cause of death with respiratory depression as the underlying pathophysiological mechanism. The tissue distribution was studied; highest concentrations of piritramide were measured in kidney, bile and urine. Due to a large volume of distribution a difference in the drug concentration found in heart and peripheral bloods the phenomenon of drug redistribution was observed. Confronted with toxicological results, investigations revealed, that the PCA pump had been changed during a previous servicing from displaying mg/h to ml/h, therefore, the anesthetist had entered “1.5” assuming mg/h, but actually applying 1.5 ml/h (which was therefore equivalent to 2.25 mg/h, given a concentration in the cartridge of 1.5 mg piritramide/ml). In total, 61.5 ml (instead of 61.5 mg) had been infused, equivalent to 92.25 mg piritramide. This case report is a further example that human errors can play a crucial role in the safety of medical equipment. Experts in anesthesia recommended human factors engineering design principles to improve the safety of medical devices.