Multi-center, double-blind, randomized, placebo-controlled. Randomization and data entry is internet based (htpp://www.webnaif.com). Patients will be randomized through a computer-generated random-number table and stratified by center in blocs of 6. Sample size, by group 120 patients. The study is powered to detect a 20% reduction in mortality, from 50% to 30% in 100 patients per study group at the 5% significance level with a power of 80%. An additional 20% (n=20) per group have been planned to compensate for losses.