Intravenous infusion of nitroprusside: effects upon cardiovascular dynamics and regional blood flow distribution in conscious dogs.
Intravenous infusion of nitroprusside (5 micrograms/kg/min) was carried out in conscious dogs over a 15-min period in order to describe changes in both central and peripheral vascular areas. Dogs were prepared with an electromagnetic flow probe positioned at the root of the aorta, and microspheres (9 microns) were used to measure regional blood flow distribution before and after 15 min of infusion. Controlled hypotension (-15 to -20 mmHg) was maintained throughout the infusion period and this hypotensive state was associated with a significant decrease in stroke volume (-16%), left ventricular power (-25%) and work (-40%) while cardiac index was not significantly affected. Those values were almost back to control levels 5 min following the end of infusion. Regional blood flow studies showed that at the fifteenth min of infusion, nitroprusside induced a significant decrease in blood perfusion to all areas of the myocardium (range -10% to -25%) while their local vascular resistances were not affected significantly. Blood perfusion to liver (hepatic artery), spleen and intestine was also modified significantly (-17%, -12% and -16%, respectively) while their vascular resistances remained close to control values. By the time measurements were made, blood flow to cerebral and renal tissues remained normal while their vascular resistances fell significantly (15% for brain and 20% for kidneys). For each organ studies, blood perfusion was uniform. These results indicate that nitroprusside elicits both central and peripheral hemodynamic changes and that reflex adjustments modify the vasodilator effect of the drug in most vascular beds that we have studied.
D000818:Animals; D001784:Blood Gas Analysis; D004285:Dogs; D005292:Ferricyanides / Q000494:pharmacology*; D006439:Hemodynamics / Q000187:drug effects*; D007263:Infusions, Parenteral; D009599:Nitroprusside / Q000494:pharmacology*; D012039:Regional Blood Flow / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects
D005292:Ferricyanides; D009599:Nitroprusside