Pulmonary embolism in critically ill patients receiving antithrombotic prophylaxis: a clinical-pathologic study

Purpose The true incidence of pulmonary embolism (PE) in critically ill adult patients receiving antithrombotic prophylaxis is unknown, as well as the impact on the outcome. The aim of this study was to assess the incidence of PE in a surgical and medical intensive care unit and to evaluate the presence of risk factors that could be helpful in identifying patients at higher risk of missed diagnosis. Materials and Methods We retrospectively reviewed the autopsies and clinical data of all patients who died in our intensive care unit from 1996 to 2007. All patients received prophylaxis with subcutaneous low–molecular weight heparin. Results Among the 600 autopsies, the clinical diagnosis of PE was confirmed in 13 patients (true positives) and not confirmed in 20 patients; in 73 patients, the PE was discovered only at the autopsy (false negatives [FNs]). The overall incidence of PE in our patients was 14.3%. Pulmonary embolism was considered the cause of death in 45% of FNs and 77% of true positives. Among all comorbidities, only a recent abdominal surgery and the presence of acute renal failure were associated with a higher risk of missed diagnosis. In the FN group, there was a significantly higher frequency of cases of septic shock. Conclusions Despite thromboprophylaxis, critically ill patients remain at risk for PE; and because of the difficulty in diagnosing it clinically, the death certificate diagnosis of PE underestimates the problem.