Impaired adrenal vascular response to hemorrhagic hypotension by an adreno-femoral venous shunt.
We studied the influence of an adreno-femoral venous shunt on the regional blood flow in the dog adrenal gland during hemorrhagic hypotension. An adreno-femoral venous shunt was placed transperitoneally in the left adrenal gland while the animal was under pentobarbital anesthesia. The right adrenal gland was left intact. Hemorrhagic hypotension was induced at 50 mm Hg mean arterial blood pressure for 1 hr in six dogs and the other six dogs served as normotensive controls. Nonradioactive microspheres (2 X 10(6), 15 +/- 2 micron) were injected into the ventricle. The adrenal cortical and medullary blood flows were estimated by microscopic counting of the microspheres in the serially sectioned adrenal gland. The total adrenal blood flow (sum of the cortical and medullary blood flows) of two methods was compared; the microsphere method vs timed venous sampling through the shunt. In the intact right adrenal gland, the cortical blood flow was significantly decreased, but the medullary blood flow remained unchanged during hemorrhagic hypotension. Subsequently the total adrenal blood flow was not significantly decreased. In the cannulated left adrenal gland, both the cortical and medullary blood flows were significantly decreased and adrenal vascular autoregulation was inhibited. The total adrenal blood flow calculated by the microsphere method showed a significant correlation with that by timed venous sampling through the shunt. These results indicate that the adrenal medullary vasculature autoregulates during hemorrhagic hypotension and that an adreno-femoral venous shunt abolishes this vascular response.
D000302:Adrenal Cortex / Q000098:blood supply; D000311:Adrenal Glands / Q000098:blood supply* / Q000601:surgery; D000313:Adrenal Medulla / Q000098:blood supply; D000818:Animals; D001794:Blood Pressure; D004285:Dogs; D005260:Female; D005268:Femoral Vein / Q000601:surgery*; D006470:Hemorrhage / Q000503:physiopathology*; D007022:Hypotension / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D012039:Regional Blood Flow