• H Masuda, T Ogata, and K Kikuchi.
• Second Department of Surgery, National Defense Medical College, Saitama, Japan.
• Ann. Thorac. Surg. 1989 Jun 1; 47 (6): 890-6.

AbstractTo evaluate the physiological changes that occur after temporary occlusion of the superior vena cava, we clamped the vena cava for one hour in 6 cynomolgus monkeys, monkeys with a venous system most resembling that of humans. The data from arterial blood gas analysis, ie, pH, arterial oxygen tension, arterial carbon dioxide tension, and HCO3-, were within normal limits during and after occlusion of the superior vena cava. Intracranial pressure was 8.6 +/- 0.8 mm Hg (mean +/- standard error) before occlusion and rose to 22.1 +/- 2.2 mm Hg during clamping. It decreased significantly to 17.7 +/- 1.9 mm Hg just before removal of the clamp and recovered to 8.6 +/- 0.9 mm Hg after the clamp was removed. Regional cerebral blood flow was 45 +/- 9 mL/min/100 g before clamping and decreased to 37 +/- 3 mL/min/100 g during clamping. It recovered to 47 +/- 5 mL/min/100 g after removal of the clamp. Cerebral perfusion pressure was within the margin of safety during clamping. Histological findings in the brain showed the effect of congestion in 1 monkey, but the change was slight. The electroencephalogram and electrocardiogram showed no abnormalities in this experiment. In conclusion, one-hour clamping of the superior vena cava with the azygos vein ligated was safe in 6 cynomolgus monkeys. We believe that in the clinical setting, one-hour occlusion of the superior vena cava would result in findings similar to those in this study, unless particular complications, such as arteriosclerosis or a cerebrovascular disorder, exist.

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