Hemodynamic effects of Dextran 40 on hemorrhagic shock during hyperbaria and hyperbaric hyperoxia

Three groups of six dogs each were instrumented with an electromagnetic flow-meter around the pulmonary artery, and indwelling silastic cannulas in the pulmonary artery, the left ventricle, the ascending aorta and the right atrium. After 7-10 d, dogs were studied under normobaric conditions, breathing air, at 2.8 atmospheres absolute (ATA) breathing 100% oxygen (PO2 approximately equal to 2128 mm Hg), and at 6 ATA breathing air (PO2 approximately equal to 960 mm Hg). Baseline recordings were made at 1 ATA and repeated after arrival at depth. The dogs were hemorrhaged until the mean aortic pressure fell to 40 mm Hg. Pressure was maintained between 40-50 mm Hg for 30 min. Enough Dextran 40 was then infused to stabilize the aortic pressure to within 90% of its original 1 ATA baseline value. Hemodynamic parameters were measured or calculated at eight different times. More than twice the amount of Dextran 40 was required at depth than at 1 ATA. There were statistically significant differences due to the effects of hemorrhage but no differences between the three groups attributable to either of the hyperbaric conditions or the effects of Dextran 40.