HEMODYNAMIC-EFFECTS OF AORTIC OCCLUSION DURING HEMORRHAGIC - SHOCK AND CARDIAC-ARREST

Objective: To determine the hemodynamic consequences of aortic occlusi on during controlled hemorrhagic arrest. Methods: Ten anesthetized, he modynamically monitored swine were subjected to a 40 mL/kg hemorrhage over 10 minutes, followed by a 5-minute period of apnea. At this time (T15), they were randomized into an UP group (n = 5) in which the thor acic aorta was occluded or a DOWN group (n = 5) in which the aorta was not occluded. Simultaneously, volume resuscitation with shed blood pl us 20 mL/kg of normal saline was performed over a 10-minute period. Ca rdiac massage was performed until return of spontaneous circulation (R OSC), which was defined as a sustained systolic blood pressure > 60 mm Hg. After 30 minutes of occlusion (T45), the aortic occlusion was rel eased. Parameters measured include mixed venous and arterial blood gas es, serum lactic acid levels, cardiac index, mean arterial pressure (M AP), mean pulmonary artery pressure (MPAP), coronary perfusion pressur e (CoPP), and left ventricular stroke work index (LVSWI). Oxygen deliv ery index (DO2I) was measured using a pulmonary artery catheter, and o xygen consumption index (VO2I) was measured by direct calorimetry (Del ta Trac metabolic monitor). Results: Four animals in each group achiev ed ROSC after 3.0 +/- 1.8 and 2.2 +/- 1.8 minutes in the occluded and nonoccluded groups, respectively, During cardiac compressions and volu me resuscitation, the CoPP, MAP, and MPAP were greater in the UP group , although the differences did not achieve statistical significance. A fter volume resuscitation was complete and during the period of aortic occlusion (T25-T45), the UP group had significantly greater MAP (mm H g), with a difference of 42.5 a 29.75 mm Hg at T25 and 44.7 +/- 19 mm Hg at T35 (p < 0.03), Despite no difference in DO2I, VO2I (mL/min/kg) was significantly lower in the UP group than in the DOWN group, 4.28 /- 0.48 versus 8.33 +/- 0.85 at T25 (p = 0.0002) and 4.62 +/- 0.9 vers us 7.09 +/- 0.72 at T35 (p = 0.0005). After release of aortic occlusio n at T45, the UP group had significantly lower CoPP (mm Hg) than the D OWN group (20.5 +/- 17.3 versus 66.5 +/- 28.2 at T45, p = 0.03), LVSWI (g/kg) was also lower in the UP than in the DOWN group (18.6 +/- 8.28 versus 36.5 +/- 10.2 at T60 [p = 0.03] and 23.6 +/- 6.48 versus 48.8 +/- 15.3 at T240 [p = 0.02]). After release of the occlusion, there we re trends toward increased acidosis and lactic acid levels in the UP g roup. Conclusion: Aortic occlusion in this controlled hemorrhagic arre st model does not result in improved salvage but is associated with im paired left ventricular function, systemic oxygen utilization, and cor onary perfusion pressure in the postresuscitation period.