Eighteen cases of 2009 influenza A H1N1 associated with respiratory failure in adults

Abstract

Objective To investigate the clinical feature,treatment and outcome of respiratory failure in patients with 2009 influenza A H1N1 infection in critically ill adults.Methods A prospective observational study of 18 patients with respiratory failure suffering from 2009 influenza A H1N1 infection admitted between November 22,2009 and January 16,2010.Their clinical data were analyzed.Results Respiratory failure occurred in 18 patients with confirmed(n=9)or probable(n=9)2009 influenza A H1N1.Among the 18 patients 8 patients were male,10 patients were female(7 were pregnant or postpartum).Eight patients had pre-existing medical conditions.Twelve patients were between 20 and 40 years of age,the mean age was 37.1 years.Three were obese with body mass index over 30 kg/m2.The 28-day mortality was 33.3%(6/18)with 1 additional late death.The median duration from the onset of the illness to hospital admission was 4.1 days(1-5 days)and from the onset to first dose of oseltamivir was 5.5 days(2-12 days),from onset to mechanical ventilation initiation was 6.8 days(4-12 days).Seventeen patients had primary viral pneumonia and 1 patient had an asthma exacerbation and 3 patients experienced multiple organ dysfunction syndrome(MODS).Twelve patients received corticosteroids,10 patients required vasopressors.All patients were mechanically ventilated,1 patient underwent extracorporeal membrane oxygenation(ECMO).Patients who died had higher acute physiology and chronic health evaluation I score compared to survivors(29.2±7.3 vs.18.6±6.4,P=0.02).All deceased patients received high-level ventilation settings[peak inspiratory pressure ≥35 cm H2O(1 cm H2O=0.098 kPa)and positive end-expiratory pressure≥18 cm H2O]within the first 7 days of ventilation,and the hypoxemia[oxygenation index≤60 mm Hg(1 mm Hg=0.133 kPa)]lasted 24 hours.In contrast only 1 among survivors did(9.1%vs.100.0%,P＜0.01).Compared with survivors,acute kidney injury and barotrauma occurred more frequently in non-survivors(42.9% vs.27.3%,28.6% vs.9.1%,both P＜0.05).Whereas all deceased patients received vasopressors,only 4 survivors required vasopressor support(100.0% vs.36.4%,P ＜0.05).Conclusion Severe acute respiratory distress syndrome is the most common manifestation in critically ill patients with 2009 influenza A H1N1 infection in adult.Failure to obtain satisfactory oxygenation with high-level ventilation settings within the first 7-days,onset of acute kidney injury and barotrauma,and continuous need for vasopressors portend a poor prognosis. Key words: Influenza A H1N1 ; Respiratory failure ; Acute respiratory distress syndrome ; Treatment ; Prognosis ;