Regional blood flow during cross-clamping of the thoracic aorta and infusion of sodium nitroprusside.
Labeled microspheres, 15 microns in diameter, were used to determine cardiac output and regional blood flow response to cross-clamping of the midthoracic aorta and subsequent sodium nitroprusside (SNP) infusion in 11 dogs. During aortic cross-clamping, mean arterial pressure above the occlusion (MAPa) increased 30% to 35%, mean arterial pressure below the occlusion (MAPb) decreased 87%, cardiac index decreased 12% to 14%, left atrial pressure (LAP) doubled, and renal and spinal cord (lower part) blood flows decreased substantially (85% to 94%). SNP infusion returned MAPa to baseline values, decreased MAPb by half, and substantially and further decreased renal blood flow (to 3% to 5% of baseline values). Myocardial and cerebral blood flows increased substantially (up to 250% to 400%). An increase in preload (fluid load) was accompanied by an increase in LAP, cardiac index, and myocardial blood flow only but not in renal or spinal cord flow. There was a strong association between cortical renal blood flow and MAPb (r2 = 0.92; p less than 0.0001), which suggests that blood flow through organs and tissues below the occlusion is pressure dependent. The data show that SNP infusion during thoracic aortic cross-clamping improves systemic and regional circulation above the occlusion but decreases MAPb and therefore blood flow below the occlusion. SNP infusion should be used with caution during aortic cross-clamping, since arterial hypotension of any degree may be deleterious to organs below the cross-clamp.
D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology*; D001775:Blood Circulation / Q000187:drug effects*; D001810:Blood Volume; D002560:Cerebrovascular Circulation / Q000187:drug effects; D003250:Constriction; D003326:Coronary Circulation / Q000187:drug effects; D004285:Dogs; D005292:Ferricyanides / Q000008:administration & dosage*; D007263:Infusions, Parenteral; D009599:Nitroprusside / Q000008:administration & dosage* / Q000494:pharmacology; D012039:Regional Blood Flow; D012079:Renal Circulation / Q000187:drug effects; D013116:Spinal Cord / Q000098:blood supply
D005292:Ferricyanides; D009599:Nitroprusside