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Evidence summaries

Use of Neuraminidase Inhibitors in Patients with 2009 Pandemic Influenza (H1n1)

Early use of neuraminidase inhibitors in patients with severe H1N1 pandemic influenza may decrease admissions to intensive care units and improve survival. Level of evidence: "C"

Summary

One study 1 collected data on patients hospitalized with 2009 H1N1 influenza in the United States (n=272). Of the patients, 45% were <18 years and 5% were HASH(0x2fcfe80)65 years; 73% had at least one underlying medical condition (asthma, diabetes, heart, lung, or neurologic diseases, or pregnancy); 25% were admitted to an intensive care unit and 7% died. Of the 268 patients for whom data were available regarding the use of antiviral drugs, such therapy was initiated in 200 patients (75%) at a median of 3 days after the onset of illness; 39% of patients received antiviral therapy within 48 hours after the onset of symptoms. Of the patients that were admitted to intensive care unit (ICU), 86% received antiviral drugs, and the median time from the onset of illness to the initiation of antiviral therapy was 6 days; 23% of patients received antiviral drugs within 48 hours after the onset of illness. Of the 19 patients who died, 90% received antiviral drugs, and the median time from the onset of illness to the initiation of antiviral therapy was 8 days; none of the patients who died received antiviral therapy within 48 hours after the onset of symptoms. In a multivariable model, the only variable that was significantly associated with a positive outcome was the receipt of antiviral drugs within 2 days after the onset of illness.

Another study 2 included reports on 788 pregnant women in the United States with 2009 influenza A(H1N1). Among those, 30 died. Among 509 hospitalized women, 22.6% were admitted to an ICU. Pregnant women with treatment more than 4 days after symptom onset were more likely to be admitted to an ICU (56.9% vs 9.4%; RR 6.0, 95% CI 3.5 to 10.6) than those treated within 2 days after symptom onset. Only 1 death occurred in a patient who received treatment within 2 days of symptom onset.

A cumulative case-control study 3 included all laboratory-confirmed cases of pandemic H1N1 influenza among residents of the province of Manitoba, Canada, for whom the final location of treatment was known (n=795). The median interval from onset of symptoms to initiation of antiviral therapy was 2 days (interquartile range, IQR 1-3) for community cases, 4 days (IQR 2-6) for patients admitted to hospital and 6 days (IQR 4-9) for those admitted to an ICU (p<0.001). In a multivariable logistic model, the interval from onset of symptoms to initiation of antiviral therapy (OR 8.24, 95% CI 2.82 to 24.1), First Nations ethnicity (OR 6.52, 95% CI 2.04 to 0.8) and presence of an underlying comorbidity (OR 3.19, 95% CI 1.07 to 9.52) were associated with increased odds of admission to the ICU (i.e., severe disease) relative to community cases.

An observational study 4 from Mexico included 899 patients admitted to the hospital with confirmed, probable, or suspected 2009 influenza (A)H1N1. Critical illness occurred in 58 of 899 patients (6.5%). Patients were young (median 44, range 10 to 83 years), few patients had comorbid respiratory disorders, but 21 (36%) were obese. Time from hospital to ICU admission was short (median 1 day, IQR 0 to 3 days), and all patients but 2 received mechanical ventilation for severe acute respiratory distress syndrome and refractory hypoxemia. By 60 days, 24 patients had died (41.4%). Patients who died had greater initial severity of illness, worse hypoxemia, higher creatine kinase levels, higher creatinine levels, and ongoing organ dysfunction. After adjusting for a reduced opportunity of patients dying early to receive neuraminidase inhibitors, neuraminidase inhibitor treatment (vs no treatment) was associated with improved survival (OR 8.5, 95% CI 1.2 to 62.8).

Clinical comments

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    References

    • Jain S, Kamimoto L, Bramley AM et al. Hospitalized patients with 2009 H1N1 influenza in the United States, April-June 2009. N Engl J Med 2009;361(20):1935-44. [PubMed]
    • Siston AM, Rasmussen SA, Honein MA et al. Pandemic 2009 influenza A(H1N1) virus illness among pregnant women in the United States. JAMA 2010;303(15):1517-25. [PubMed]
    • Zarychanski R, Stuart TL, Kumar A et al. Correlates of severe disease in patients with 2009 pandemic influenza (H1N1) virus infection. CMAJ 2010;182(3):257-64. [PubMed]
    • Domínguez-Cherit G, Lapinsky SE, Macias AE et al. Critically Ill patients with 2009 influenza A(H1N1) in Mexico. JAMA 2009;302(17):1880-7. [PubMed]

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