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Severe H1N1 infection raises pulmonary embolism risk

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – Patients with severe cases of novel H1N1 influenza virus infection (swine flu) are at heightened risk for chest complications, including pulmonary emboli, Michigan researchers suggest.

The investigators, all from the University of Michigan in Ann Arbor, report on two groups – 14 patients who required mechanical ventilation in the ICU (group 1), and 52 who were treated either as outpatients or with brief hospitalization (group 2). Five patients in the first group died.

All patients had chest x-rays, and 15 patients had CT scans, including 10 patients from the ICU group.

As reported online October 14th in the American Journal of Roentgenology, five patients in the ICU group (36%) had pulmonary emboli.

The first radiograph was abnormal in 100% of group 1 patients and 27% of group 2 patients. Group 1 patients also presented with bilateral lung involvement. On initial imaging, three or more lung zones were involved in 93% of group 1 and in 9.6% of group 2.

Three patients on mechanical ventilation developed bacterial pneumonia, caused by one case each of Pseudomonas, Escherichia coli, and Citrobacter.

Lead author Dr. Prachi P. Agarwal and associates sum up, noting that the most ill patients tend to develop bilateral air-space disease, and that pulmonary embolism should be carefully sought on contrast-enhanced CT scans in these patients.

Am J Roentgenol 2009.