Comparison between preload with colloid versus preload with crystalloid before spinal anesthesia

Abstract

ypotension following spinal anaesthesia is mainly occurs due to sympathetic blockade leading to peripheral vasodilatation and venous pooling of blood. As a result, there is decreased venous return and cardiac output leading to hypotension (Williamson et al., 2009). The spectrum of morbidity associated with hypotension may include but is not limited to a higher incidence of nausea, vomiting, dizziness, aspiration, syncope and cardiac arrhythmias (Ngan Kee et al., 2005). One of the most commonly used methods to reduce spinal anaesthesia induced hypotension is administration of fluids before implementation of spinal anaesthesia, a technique named ‘pre loading’ first described by Wollman and Marx. This preloading with intravenous fluids offset the vasodilating effects of sympathetectomy caused by spinal anaesthesia thereby maintaining the venous return and thus the drop in blood pressure is prevented (Wollman and Marx, 1968). Crystalloids have shorter half life in the intravascular compartment and generally exit the intravascular space within 1 hour so that their ability to expand the intravascular volume is limited due to shorter duration of action. Pre loading with crystalloids has been found to be less effective due to the shorter half life as they are less successful in maintaining the