Delirium and Pulmonary Embolism in the Elderly

To the Editor: Delirium, an acute confusional state, is a common, complex medical disorder associated with substantial morbidity and mortality among persons 65 years or older.¹ This potentially reversible cognitive disturbance is increasingly recognized as a sign of serious underlying illness.¹ Despite the fact that hypoxia is a well-known precipitating factor for delirium and that pulmonary embolism (PE) is a common cause of hypoxia, neither customary medical practice nor recent reviews^1-4 specifically consider delirium as a possible presentation of PE. We describe 5 elderly patients with delirium in whom PE was subsequently diagnosed. We suggest a causal relationship between both entities.

From January 2003 to December 2007, 215 consecutive adult patients at our hospital were diagnosed as having PE. Of these 215 patients, 5 presented with clinical features of delirium (Table). These 5 patients were all older than 72 years and had 1 or more predisposing factors for delirium, including older age, cognitive impairment, severe illness, fracture, and surgery. No metabolic or electrolyte disturbances were evident, and intravascular volume appeared normal. Moreover, none of the admission medications were discontinued during hospitalization. After ruling out common causes of delirium, we suspected PE as a precipitating factor because of chest pain and left calf swelling (patient 1), acute dyspnea (patient 2), sudden worsening dyspnea (patient 3), and otherwise unexplained d-dimer level increase (patients 4 and 5). In addition, PE was suspected in one patient (patient 4) because of the clinicians' recent experience with the first 3 patients. High-probability ventilation-perfusion lung scans were obtained in patients 1 through 4 (bilateral findings in patients 1, 3, and 4 and right-sided alterations in patient 2). Specifically, the lung scan performed in patient 3 was regarded as high probability even in light of the patient's prior lung disease. Chest computed tomography revealed signs of bilateral pulmonary embolic disease in patient 5. All 5 patients received sequential therapy with subcutaneous dalteparin (100 UI/kg every 12 hours) and warfarin. Delirium resolved within 2 to 5 days after anticoagulation was initiated. No new episodes of delirium or PE developed after these patients were discharged.

TABLE.

Characteristics of the Patients^a

Elderly patients can experience delirium secondary to almost any acute condition, including simple conditions like untreated urinary tract infection, urinary retention, constipation, colds, and undermanaged pain, and more serious causes including a variety of vascular conditions such as myocardial infarction, cerebral ischemia, and PE. Delirium may complicate PE in patients with other evidence of the disease but occasionally may be the sole evidence (other than increased d-dimer level) of PE, as occurred in 2 of our patients. Moreover, the diagnosis of PE “is missed more often than it is made,”² in part because of its frequent atypical presentations.^2,5 We believe that delirium in the elderly should be regarded as an atypical presentation of PE. Consequently, when clinicians search for the underlying cause of delirium, they should remember that PE is one of the many acute conditions that can cause delirium in the elderly. Although PE-related hypoxemia, acute ventricular impairment, hypotension, and/or paradoxical embolism could work to explain this “lung-brain connection,” the mechanisms remain unknown.