SALUTARY CONSEQUENCES OF OXYGEN-THERAPY ON THE LONG-TERM OUTCOME OF HEMORRHAGIC-SHOCK IN AWAKE, UNRESTRAINED RATS

Decreased oxygen delivery and cellular hypoxia are major factors in th e pathophysiology of shock. We studied the effects of 100% O-2 at 0.1 and 0.3 MPa (1 and 3 atm abs) in severe hemorrhagic shock in awake, un restrained rats. Shock was induced by withdrawing 50% of the total blo od volume within 120 min. Blood pressure, heart rate, and the electroe ncephalogram (EEG) were recorded during the first 6 h of the protocol. The animals were observed for 7 days. The shock protocol resulted in 60 and 90 % mortality after 1 day and at the end of 7 days, respective ly. A single 90-min exposure to O-2 at 0.1 and 0.3 MPa, which was star ted 30 min after bleeding, maintained mean arterial blood pressure at significantly higher values compared to untreated controls throughout the exposure period (P < 0.05). Oxygen therapy at both doses also impr oved the long-term survival rate and survival time significantly (P <0 .01). No clinical or EEG sign of CNS O-2 toxicity was detected in O-2- treated animals. Our results indicate that O-2 given alone after sever e bleeding exerts a beneficial effect on the long-term outcome of hemo rrhagic shock in awake, unrestrained rats.