This prospective , double-blind , randomized , controlled study enrolled patients scheduled for primary hip replacement surgery , who were randomized to receive either an unbalanced crystalloid ( chloride : 155.5 mmol/l ) or a 1 : 1 mixture of a balanced crystalloid and a balanced colloid ( 6 % w/v hydroxyethyl starch 130/0 .42 ; chloride : 98 and 112 mmol/l , respectively ) .