Central and regional haemodynamics during controlled hypotension produced by adenosine, sodium nitroprusside and nitroglycerin. Studies in the pig.

Controlled hypotension was induced in pigs by the infusion of adenosine, sodium nitroprusside (SNP) or nitroglycerin (TNG). Central and regional haemodynamics were studied using the microsphere technique during control and hypotensive periods. All three drugs produced decreases in mean arterial pressure (MAP), but it was very difficult to maintain stable values of hypotension with TNG, and it was necessary to increase continuously the dose of SNP to produce stable hypotension. Adenosine produced an increase in cardiac output (CO), maintained blood flow to the cerebrum, cerebellum, heart, kidneys and adrenal glands and increased blood flow to the spinal cord and splanchnic organs, except the spleen. SNP and TNG decreased CO, but blood flow to the aforementioned organs (except the spleen) was maintained. Urine flow was greatly impaired during the infusion of adenosine.