Washington, Oct 13 : H1N1 infection hits young patients the hardest as they often suffer from severely low levels of oxygen in the blood and multi-system organ failure, says a new study.

The study showed that the condition of young patients with H1N1 worsened significantly after hospital admission and they had to be put on prolonged mechanical ventilation, and frequent use of rescue therapies.

Lead researcher Dr Anand Kumar, of the Health Sciences Centre and St. Boniface Hospital, Winnipeg, Manitoba, Canada, and colleagues with the Canadian Critical Care Trials Group H1N1 Collaborative examined critically ill patients with 2009 influenza A(H1N1) in 38 adult and paediatric intensive care units

They focused on the death rate at 28 and 90 days, as well as the frequency and duration of mechanical ventilation and the duration of ICU stay.

A total of 168 patients had confirmed or probable 2009 H1N1 infection and became critically ill during this time period, and 24 died within the first 28 days from the onset of critical illness. Five more patients died within 90 days.

The study showed that patients with 2009 influenza A(H1N1) infection-related critical illness experienced symptoms before entering the hospital, but worsened rapidly and required care in the ICU within one or two days.

Shock and multi-system organ failure were common, and 136 patients received mechanical ventilation. Lung rescue therapies included neuromuscular blockade, inhaled nitric oxide and high-frequency oscillatory ventilation.

"In conclusion, we have demonstrated that 2009 influenza A(H1N1) infection-related critical illness predominantly affects young patients with few major comorbidities and is associated with severe hypoxemic respiratory failure, often requiring prolonged mechanical ventilation and rescue therapies," said the authors.

"With such therapy, we found that most patients can be supported through their critical illness."

The study appears Journal of American Medical Association (JAMA). (ANI)