Chest
Volume 137, Issue 4, April 2010, Pages 752-758
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Original Research
Influenza A(H1N1) Infection
Clinical Findings and Demographic Factors Associated With ICU Admission in Utah Due to Novel 2009 Influenza A(H1N1) Infection

https://doi.org/10.1378/chest.09-2517Get rights and content

Background

Novel 2009 influenza A(H1N1) infection has significantly affected ICUs. We sought to characterize our region's clinical findings and demographic associations with ICU admission due to novel A(H1N1).

Methods

We conducted an observational study from May 19, 2009, to June 30, 2009, of descriptive clinical course, inpatient mortality, financial data, and demographic characteristics of an ICU cohort. A case-control study was used to compare the ICU cohort to Salt Lake County residents.

Results

The ICU cohort of 47 influenza patients had a median age of 34 years, Acute Physiology and Chronic Health Evaluation II score of 21, and BMI of 35 kg/m2. Mortality was 17% (8/47). All eight deaths occurred among the 64% of patients (n = 30) with ARDS, 26 (87%) of whom also developed multiorgan failure. Compared with the Salt Lake County population, patients with novel A(H1N1) were more likely to be obese (22% vs 74%; P < .001), medically uninsured (14% vs 45%; P < .001), and Hispanic (13% vs 23%; P < .01) or Pacific Islander (1% vs 26%; P < .001). Observed ICU admissions were 15-fold greater than expected for those with BMI ≥ 40 kg/m2 (standardized morbidity ratio 15.8, 95% CI, 8.3-23.4) and 1.5-fold greater than expected among those with BMI of 30 to 39 kg/m2 for age-adjusted and sex-adjusted rates for Salt Lake County.

Conclusions

Severe ARDS with multiorgan dysfunction in the absence of bacterial infection was a common clinical presentation. In this cohort, young nonwhites without medical insurance were disproportionately likely to require ICU care. Obese patients were particularly susceptible to critical illness due to novel A(H1N1) infection.

Section snippets

Materials and Methods

Individuals with confirmed novel A(H1N1) who were older than 15 years and treated in four ICUs at three academic hospitals in Salt Lake County, Utah, from May 19, 2009, to June 30, 2009, were included in this report. We identified patients concurrently and reviewed medical charts, radiologic and laboratory findings, hospital billing charges, length of stay, and in-hospital survival. The report was declared exempt by the institutional review boards of Intermountain Healthcare and the University

Clinical Data

Forty-seven patients with novel A(H1N1) infection were admitted to one of four adult ICUs among three academic hospitals between May 19, 2009, and June 30, 2009. The median age of patients was 34 years (range 15-62 years) (Table 1). Twenty (43%) were men. Most had typical influenza symptoms on illness presentation, including fever (100%), cough (89%), and shortness of breath (66%). Sixty-two percent had one or more risk factors for influenza-related complications as defined by the CDC.15 The

Discussion

This case series reveals the spectrum of critical illness among a young cohort with severe ARDS and multiorgan dysfunction solely attributable to novel A(H1N1) infection seen during a 6-week period in Salt Lake County. We also report demographic features in our ICU cohort (race/ethnicity, BMI, and medical insurance) compared with the Salt Lake County population.

Severe infection from influenza typically occurs in the elderly, the very young, and those with comorbid diseases.19 Consistent with

Conclusions

We report a critically ill cohort with unexpected numbers of nonwhite, obese, medically uninsured patients with novel A(H1N1) infection, most with severe lung injury and multiorgan dysfunction due to influenza without concomitant bacterial infection. Our findings suggest that demographic factors and obesity are associated with critical illness due to novel A(H1N1) infection.

Acknowledgments

Author contributions: Dr Miller: contributed to collecting data and drafting and revising the submitted manuscript.

Dr Markewitz: contributed to collecting data and drafting and revising the submitted manuscript.

Dr Rolfs: contributed to collecting data and drafting and revising the submitted manuscript.

Dr Brown: contributed to drafting and revising the submitted manuscript.

Dr Dascomb: contributed to drafting and revising the submitted manuscript.

Dr Grissom: contributed to drafting and revising

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