Ans. A: Sodium Nitroprusside Antihypeensive therapy in acute aoic dissection aims specifically to lessen pulsatile load or aoic stress, in order to retard the propagation of the dissection and prevent aoic rupture. The goals of treatment are to prevent myocardial ischemia, decrease left ventricular afterload, decrease myocardial oxygen consumption, and prevent rupture and bleeding from suture lines Nitroprusside is a potent direct aerial and venous dilator, acting through release of nitric oxide. It has a rapid onset of action, and a shoer half-life and thus is given in the form of continuous infusion. The hypotensive effects of nitroprusside can be unpredictable because it simultaneously causes potent venodilatation and peripheral aerial vasodilatation. This is especially the case for patients with severe left ventricular hyperophy and preload-dependent diastolic dysfunction. It has been shown to cause coronary steal; it can cause a significant reflex tachycardia, and it can decrease oxygen circulation. It is photosensitive, so it requires special handling. Its most serious adverse effect is in the form of cyanide toxicity, which occurs due to accumulation of its metabolites thiocyanate/ cyanide and its clinical presentation may vary leading to difficulty in diagnosis. Thus, it is recommended that this drug be used only when other intravenous antihypeensive agents are not available