Background In the hospital setting, inadequate engagement between healthcare professionals and seriously ill patients and their families regarding end-of-life decisions is common. This problem may lead to medical orders for life-sustaining treatments that are inconsistent with patient preferences. The prevalence of this patient safety problem has not been previously described.

Methods Using data from a multi-institutional audit, we quantified the mismatch between patients’ and family members’ expressed preferences for care and orders for life-sustaining treatments. We recruited seriously ill, elderly medical patients and/or their family members to participate in this audit. We considered it a medical error if a patient preferred not to be resuscitated and there were orders to undergo resuscitation (overtreatment), or if a patient preferred resuscitation (cardiopulmonary resuscitation, CPR) and there were orders not to be resuscitated (undertreatment).

Results From 16 hospitals in Canada, 808 patients and 631 family members were included in this study. When comparing expressed preferences and documented orders for use of CPR, 37% of patients experienced a medical error. Very few patients (8, 2%) expressed a preference for CPR and had CPR withheld in their documented medical orders (Undertreatment). Of patients who preferred not to have CPR, 174 (35%) had orders to receive it (Overtreatment). There was considerable variability in overtreatment rates across sites (range: 14–82%). Patients who were frail were less likely to be overtreated; patients who did not have a participating family member were more likely to be overtreated.

Conclusions Medical errors related to the use of life-sustaining treatments are very common in internal medicine wards. Many patients are at risk of receiving inappropriate end-of-life care.