Minimum effective fluid volume of colloid to prevent hypotension during caesarean section under spinal anesthesia using a prophylactic phenylephrine infusion: An up-down sequential allocation study

Our study is the first to investigate variable fluid loading volumes in this population. A HES preload of approximatively 700 mL prevented maternal hypotension in 50% of the parturients under the conditions of this study. We suggest that up-down sequential allocation design is a useful tool to compare different fluid loading regimens in this setting.