Mortality rates at 28 and 90 days did not differ between groups : 22/66 ( 33 % ) of citrate-treated patients died versus 25/72 ( 35 % ) of heparin-treated patients at 28 days , and 27/65 ( 42 % ) of citrate-treated patients died versus 29/69 ( 42 % ) of heparin-treated patients at 90 days ( P = 1.00 for both ) .