Capillary blood flow and arteriolovenular shunt in various organs in hypotensive states induced by nitroglycerine,nitroprusside, and nicardipine

The capillary blood flow of 14 organs was measured in dogs using the microsphere (9μm diameter) trapping method under hypotension induced by administration of either nitroglycerin (NTG), nitroprusside (SNP), or nicardipine (NIC). Simultaneously, blood flow through the arteriolovenular shunt in the brain, kidney, liver, mesenteric organs, skeletal muscles of the pelvic limb, and all organs in the body, except the lungs, were measured by collecting venous blood drained from the organs at 4.8 ml·min⁻¹ for 2 min. Capillary blood flow remained unchanged in most organs under hypotension with either NTG or SNP, but in increased in most organs, together with an increase in cardiac output, under hypotension with NIC. Arteriolovenular shunt tended to increase in four organs, with the exception of the liver, and increased in the whole body under hypotension with NTG. However, arteriolovenular shunt remained unchanged under hypotension with SNP. Arteriolovenular shunt increased in the mesenteric organs under hypotension with NIC, but decreased in the skeletal muscles of the pelvic limb. These results indicated that none of these hypotensive drugs impairs the nutrient supply to organs; further, NIC protects it much more since it does not increase the shunt flow through major organs.