Spiral Computed Tomography for the Diagnosis of Pulmonary Embolism in Critically Ill Surgical Patients

HYPOTHESIS: Spiral computed tomographic pulmonary angiography (CTPA) is sensitive and specific in diagnosing pulmonary embolism (PE) in critically ill surgical patients. DESIGN: Prospective study comparing CTPA with the criterion standard, pulmonary angiography (PA). SETTING: Surgical intensive care unit of an academic hospital. PATIENTS: Twenty-two critically ill surgical patients with clinical suspicion of PE. The CTPAs and PAs were independently read by 4 radiologists (2 for each test) blinded to each other's interpretation. Clinical suspicion was classified as high, intermediate, or low according to predetermined criteria. All but 2 patients had marked pulmonary parenchymal disease at the time of the event that triggered evaluation for PE. INTERVENTIONS: Computed tomographic pulmonary angiography and PA in 22 patients, venous duplex scan in 19. RESULTS: Eleven patients (50%) had evidence of PE on PA, 5 in central and 6 in peripheral pulmonary arteries. The sensitivity and specificity of CTPA was, respectively, 45% and 82% for all PEs, 60% and 100% for central PEs, and 33% and 82% for peripheral PEs. Duplex scanning was 40% sensitive and 100% specific in diagnosing PE. The independent reviewers disagreed only in 14% of CTPA and 14% of PA interpretations. There were no differences in risk factors or clinical characteristics between patients with and without PE. The level of clinical suspicion was identical in the 2 groups. CONCLUSIONS: Pulmonary angiography remains the gold standard for the diagnosis of PE in critically ill surgical patients. Computed tomographic pulmonary angiography needs further evaluation in this population.