Nitroglycerin and nitroprusside induced changes in cerebral hemodynamics

In dogs both nitroglycerin and nitroprusside are capable of elevating cerebral spinal fluid presssure (Pcsf), lowering cerebral perfusion pressure, and decreasing CBF. The increase in Pcsf appears to be independent of changes in CBF since marked increases in Pcsf occurred with no changes in CBF in the normal Pcsf group. This suggests the possibility that these drugs may increase cerebral blood volume and Pcsf via changes in cerebral venous capacitance. From a clinical perspective these studies confirm that both nitroglycerin and nitroprusside, in the presence of an initially elevated Pcsf, may lower cerebral blood flow. Since the patients most likely to receive these drugs often have marginal cerebral perfusion pressure to start, special attention must be paid to the cerebral hemodynamic effects of these agents. Finally, while producing less systemic hypotension, at any given dose range administered nitroglycerin appeared to elevate Pcsf more than did nitroprusside.