The hemodynamic effects of deliberated hypotension induced by PGE1 or SNP on 14 dogs anesthetized by ketamine were studied separately.MAP was decreased by 30%~40% after infusing PGE,or SNP Hemodynamic variables were measured before and 15 min 30 min after hypotension and 15 min after the discontinuation of infusion.The results indicated that SVRI, PVRI, MPAP, LVSWI and RVSWI all decreased significantly during PGE1-or SNP-induced hypotension. CVP decreased and HR increased significantly during SNP-induced hypotension, but with no significant change during PGE1-induced hypotension and with SVI. CI. PCWP remained unchanged in these two groups throughout the experiments.