Wednesday, October 14, 2009

Severely Ill H1N1 Patients At Risk Of PE



# 3833




One of the remarkable findings over the summer regarding the novel H1N1 Swine flu virus has been that, in a very small subset of patients, it can produce absolutely devastating symptoms.  


Not only are some patients experiencing ARDS (Acute respiratory distress syndrome), and requiring ventilator or ECMO support (see The ECMO Option), others are experiencing multi-organ failure and lung damage comparable to what has normally been associated with the H5N1 `bird flu’ virus.


Very early on we began hearing reports of some H1N1 cases involving  Pulmonary Emboli.   Pulmonary embolism (PE) is a blockage of a major artery in the lung by a thrombus (blot clot), or commonly, by an air or fat emboli.

PE can frequently produce a fatal outcome, particularly if untreated.  Diagnosing PE, particularly in patients already experiencing severe respiratory distress from a viral infection, can be difficult.


The July 10, 2009 / 58(Dispatch);1-4  MMWR (Morbidity & Mortality Weekly Report) of the CDC  described 5 such cases observed in Michigan in: Intensive-Care Patients With Severe Novel Influenza A (H1N1) Virus Infection --- Michigan, June 2009


Today, we get a pair of follow up studies in American Journal of Roentgenology, which describe (in detail of most interest to pulmonologists and radiologists) computed tomography (CT) scans of patients with severe H1N1 infection. 

First the press release, where the authors warn clinicians to be watchful for signs of PE in H1N1 patients, and then links to the two studies.


A hat tip to Dutchy on FluTrackers for Posting this link.


American Roentgen Ray Society


CT scans show patients with severe cases of H1N1 are at risk for developing acute pulmonary emboli

Researchers utilizing computed tomography (CT) scans have found that patients with severe cases of the H1N1 virus are at risk for developing severe complications, including pulmonary emboli (PE), according to a study to be published online Oct. 14, 2009, in the American Journal of Roentgenology. The study will be published in the December issue of the AJR.


A pulmonary embolism occurs when one or more arteries in the lungs become blocked. The condition can be life-threatening. However, if treated aggressively, anti-coagulants (blood thinners) can reduce the risk of death.


The study, performed at the University of Michigan Health Service, included 66 patients diagnosed with the H1N1 flu. Two study groups were formed. Group one consisted of 14 patients who were severely ill and required Intensive Care Unit (ICU) admission. Group two consisted of 52 patients who were not severely ill and did not require ICU admission.


All 66 patients underwent chest X-rays for the detection of H1N1 abnormalities. Ten patients from the ICU group and five patients from the largely outpatient group, underwent CT scans. "Pulmonary Emboli were seen on CT in five of 14 ICU patients," said Prachi P. Agarwal, M.D., lead author of the study.


"Our study suggests that patients who are severely ill with H1N1 are also at risk for developing PE, which should be carefully sought for on contrast-enhanced CT scans," she said.


"With the upcoming annual influenza season in the United States, knowledge of the radiologic features of H1N1 is important, as well as the virus's potential complications.The majority of patients undergoing chest X-rays with H1N1 have normal radiographs.

CT scans proved valuable in identifying those patients at risk of developing more serious complications as a possible result of the H1N1 virus, and for identifying a greater extent of disease than is appreciated on chest radiographs," said Dr. Agarwal.



Both articles are available online today, at the links below.

Imaging Findings in a Fatal Case of Pandemic Swine-Origin Influenza A (H1N1)

Chest Radiographic and CT Findings in Novel Swine-Origin Influenza A (H1N1) Virus (S-OIV) Infection