Hypotension following spinal anaesthesia for caesarean Section can occur In up to 80% without pro -Phylactic measures(1). For many years, this was believed to Arise primarily as a result of
venous vasodilation. How-Ever, studies that have utilised cardiac output monitoring Have demonstrated that arterial vasodilation is more Likely to be responsible for the decrease in blood pressure Following spinal anaesthesia, at least initiall (2) The focus of attention for prophylaxis and management has there-Fore shifted from fluid-loading strategies to the extensive Investigation of the role of vasopressors(3). Currently, the Alpha-agonist phenylephrine, which directly counteracts The sympatholysis-induced decrease in arterial resistance And is associated with a lower incidence of foetal acidosis, Has become the preferred agent.(4) A phenylephrine Infusion commencing at the time of the spinal injection currently recommended as the most effective approach To prevent hypotension, although phenylephrine Boluses given prophylactically or noradrenaline infusion May be at least as effective.(5) However, fluid loading strategies remain another part of An antihypotensive strategy, as they can counteract the Relative hypovolaemia due to venodilation and, by Increasing the venous return, help to maintain haemo-Dynamic stability.(6)