This very interesting experimental study in lambs deals with the controversial issue of the adverse effects of the transfusion of stored blood in the setting of hemorrhagic shock (HS) and the potentially beneficial role of inhaled nitric oxide (NO) in reducing these detrimental effects.

The results of study by Baron et al. appear to demonstrate that resuscitation after 2 hours of experimentally induced HS (obtained by the acute withdrawal of 50% of the blood volume) with blood stored for a mean of 39 ± 2 days produces transient pulmonary hypertension, increases circulating markers of tissue injury (aspartate aminotransferase and creatine phosphokinase) and pulmonary myeloperoxidase activity while resuscitation with fresh blood does not affect these variables.

Moreover, the authors showed that, in lambs transfused with stored blood, inhalation of NO during and after resuscitation prevents the increase in the mean pulmonary arterial pressure and in pulmonary vascular resistance and attenuates tissue injury.

Although it must always be kept in mind that data obtained in animals may not apply to patients, the results of this rigorous study could be of help in clarifying the mechanisms and the processes responsible for the adverse effects of stored blood. The trial also supports the opportunity of testing NO inhalation as a strategy to prevent these adverse effects.

– Giovanni Inghilleri