Survival curves. (A) Kaplan-Meier plot over the 96 hours study comparing animals challenged with intrapulmonary S aureus and exchange transfused 42- (solid circle, solid line) or 7-day-old stored blood (open circle, dashed line). (B) Serial measures of lung injury. Arterial-alveolar oxygen gradient shows lung damage was significantly worse (higher) in the animals with pneumonia receiving 42- (solid circle, solid line) versus 7-day-old (open circle, dashed line) stored blood at 24 hours (P = .005) and 48 hours (P = .01) after bacterial challenge. (C) Degree of shock after exchange transfusion. Shock reversal score accounts for the level of vasopressor support (norepinephrine) needed to maintain the mean arterial pressure at a preset normal level for canines (mean 80 mmHg). Only after 48 hours did bacterial challenge and transfusion of 42-day-old blood produce a significantly worse (lower) shock reversal score (P = .01). (Inset) Degree of shock during exchange transfusion. In contrast, the shock reversal score was improved (higher) in the 42 compared with 7-day-old stored blood (P = .02) during the period of transfusion (7-16 hours). (D) Pulmonary artery pressures during transfusions. Mean pulmonary artery pressures (mPAP) immediately before (circle) and after (triangle) each of the 4 exchange transfusions of 20 mL/kg-stored blood. The difference between pre- and post-mPAP (thick line) was greater with transfusion of 42- (solid symbol, black line) compared with 7-day-old (open symbol, gray line) blood (P = .005, the 4 exchanges averaged). Data presented as mean ± SE.