Outcomes of Patients Hospitalized in Denver With 2009 Influenza A(H1N1): An Inner City Experience

Background: By October 2009, pandemic 2009 influenza A(H1N1) had become widespread in at least 49 states and stressed the capacity of several healthcare systems across the US.  Urban safety-net hospitals serve large numbers of chronically ill, indigent patients and services are frequently overburdened. The impact of the H1N1 epidemic on public safety net hospital capacity to care for these patients has not been reported.

Objective: To describe baseline characteristics, treatment, resource utilization, and outcomes of patients with laboratory confirmed 2009 influenza A(H1N1) who were hospitalized at an academic safety-net hospital in Denver, CO. 

Methods:  Observational study of 135 hospitalized patients with PCR-confirmed 2009 influenza A(H1N1) 5/6-11/2, 2009. Demographic data, presenting symptoms, comorbid conditions, critical illness characteristics, treatments, length of stay, and mortality were collected by electronic abstraction from the institution’s data warehouse.  Where applicable, data were compared with that for the 2008-9 season from 12/19/2008- 3/23/2009, when H1N1 was not in circulation.

Results: 135 patients were hospitalized with 2009 H1N1 influenza, a 9-fold increase over the 16 hospitalized during 2008-9 seasonal influenza. Patients were young (median, 31.0 [range, 0-87] years); 129 (95.6%) were under 65; and 36 (26.7%) were under 18 years of age.  71 (52.6%) were female.  7 (5.2%) were pregnant; 16 (11.9%) were homeless. Of 130 evaluable patients, 101 (77.7%) were admitted for fever and/or respiratory symptoms. The majority of the 135 patients (64%) had comorbid respiratory disorders; 8 (5.9%) had congestive heart failure; 24 (17.8%) had diabetes; 11 (8.1%) had an underlying malignancy; 5 (3.7%) had rheumatologic disease; 3 (2.2%) had underlying HIV infection.  1 patient (0.7%) had renal failure.  No patients had underlying neuromuscular disorders. Oseltamivir treatment was given to 110 (81.5%). Intensive Care admission was comparable to 2008-9 seasonal influenza (37.5%)-- with 2009 H1N1 influenza, critical illness occurred in 44 of 135 patients (33%). 28/44 patients (64%) were admitted directly to the ICU upon presentation. 13 of 44 (30%) required mechanical ventilation (MV) for acute hypoxemic respiratory failure (AHRF), compared with 1 patient(16.7%) in 2008-9. Of the 589 hospital bed days occupied by influenza patients during the study period, 189 were ICU bed days, 170 (90%) of which were concentrated in the last 60 days of the study period. Only 6 of 44 (13.6%) critically ill were under age 18.  2 patients, both adults, died (1.5%). 

Conclusions: The 2009 H1N1 pandemic resulted in a substantial increase in the number of influenza hospitalizations.  Although the proportion of patients requiring critical care similar to seasonal influenza those admitted to the ICU for H1N1 frequently required MV for AHRF, resulting in major resource and staffing challenges.