Treatment with neuraminidase inhibitors for critically ill patients with influenza A(H1N1)pdm09

Abstract
Backgound. Neuraminidase inhibitor (NAI) antiviral drugs can shorten the duration of uncomplicated influenza illness when administered early (<48 hours after illness onset) to otherwise healthy outpatients, but the optimal timing of effective therapy for critically-ill patients is not well established.

Methods. 
We analyzed California surveillance data to characterize the outcomes of patients in intensive care units (ICU) treated with NAIs for influenza A(H1N1)pdm09 [pH1N1]. Demographic and clinical data were abstracted from medical records using standardized case report forms.

Results. 
From April 3, 2009 – August 10, 2010, 1950 pH1N1 cases hospitalized in ICUs were reported. Of 1859 (95%) with information available, 1676 (90%) received NAI treatment and 183 (10%) did not. The median age was 37 years (range: 1 week - 93 years), 1473 (79%) had ≥1 co-morbidity, and 492 (26%) died. The median time from symptom onset to starting NAI treatment was 4 days (range 0-52). NAI treatment was associated with survival: 107 of 183 (58%) untreated cases survived, compared to 1260 of 1676 (75%) treated cases (p≤.0001). There was a trend towards improved survival for those treated earliest (p <.0001). Treatment initiated within 5 days after symptom onset was associated with improved survival compared to those never treated (p<0.05).

Conclusions. 
NAI treatment of critically ill pH1N1 patients improves survival. While earlier treatment conveyed the most benefit, patients started on treatment up to 5 days from symptom onset also had increased survival. Further research is needed on whether starting NAI treatment later than 5 days may also convey benefit.