Cardiac effects of splanchnic and non‐splanchnic blood volume redistribution during aortic occlusions in dogs

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Abstract
Translocation of blood from the lower body dilates the left ventricle during occlusion of the descending thoracic aorta and by increased activation of the Frank-Starling mechanism, stroke volume is maintained despite raised aortic blood pressure. The contributions from the splanchnic and non-splanchnic blood volumes to the left ventricular dilation were examined by ultrasonic measurements of myocardial chord length (MCL) in atropinized open-chest dogs. End-diastolic MCL rose by 2.5 .+-. 0.9% during abdominal suprarenal aortic occlusion, draining blood from the non-splanchnic region, and by 7.4 .+-. 1.7% during thoracic aortic occlusion draining blood from both splanchnic and non-splanchnic regions. Systolic left ventricular pressure rose by 16 .+-. 3 mmHg and 76 .+-. 12 mmHg, respectively. End-diastolic MCL rose by 6.0 .+-. 1.2% during combined thoracic aortic and abdominal infrahepatic vena cava occlusion draining blood solely from the splanchnic region and further by blood drained from the non-splanchnic region after release of the vena cava occlusion. Similar results were obtained using a shunt permitting selective drainage first from the non-splanchnic region during thoracic aortic occlusion. Blood translocation from the non-splanchnic region maintains cardiac output during abdominal aortic occlusion. During occlusion of the thoracic aorta, drainage from the splanchnic region accounts for about 70% of the increase in end-diastolic MCL.