Crystalloids Versus Colloids Versus Hypertonic Saline as a Co-load During Spinal Anesthesia.

Spinal anesthesia is commonly accompanied by hypotension due to vasodilation that follows sympathetic blockade and decreased systemic vascular resistance. Prevention of hypotension is usually achieved through administration of fluids and vasopressors . Fluids are either administrated before initiation of spinal anesthesia which is defined as fluid pre-loading or at time of initiation of spinal anesthesia which is defined as fluid co-loading .There is an ongoing debate concerning both the proper fluid timing, pre-load against co-load and fluid type crystalloids against colloids. Fluid preloading with colloids appears to have superior effect on that of crystalloids as the later shows a shorter intravascular half-life. While both colloid and crystalloid co-loading show comparable results .Although crystalloid preloading has been the traditional regimen for long time, it failed to reduce the incidence of hypotension. This is because crystalloids rapidly distribute out of the intravascular compartment to the interstitial space. Superiority of fluid co-loading might be explained by decrease of the extravascular crystalloid redistribution secondary to the simultaneous vasodilatation response to sympathetic block.This study aims at comparing the effectiveness of co-loading of crystalloids versus colloids versus hypertonic saline 3% in preventing hypotension induced by spinal anesthesia.